ABSOLUTE
P~ESSURE-Ihe
sum
of
gauge pressure
plj.,js
atmospheric pressure. Absolute pressure can
be
zero only in a perlect vacuum.
ACTUAL
BODY
RATING-see
VALVE BODY RATING.
ACTWATOR-a
controlled molar, relay
or
solenoid
In
which the electric energy is converted into a rolary, lin-
ear. or switching action.
An actuator can effect a
change in the controlled variable
by operating the final
control elements a number
of
times. Valves
aM
damp'
ers are examples of mechanisms which can
be
controlled

by
actuators. Also see PROPOR-
TIONAL, SPRING RETURN, and TWO-POSITION
ACTUATORS.
AI
R
-the
elastic, invisible mixture
of
gases
that surrounds
lr,e eanh; atmosphere. Also see AMBIENT, ATOMIZ-
ING. COMBUSTION. COMPRESSED. EXCESS, IN-
DUCED. PREHEATED. PRIMARY, SEAL,
SECONDARY, AND VENTILATION AIR.
AIR-ATOMIZING OIL
BURNER-see
ATOMIZING
OIL
BURNER.
AIR
CHANGE-a
complete replacement
of
all the air in
the combusllon chamber and breaChing
of
a furnace or
boiler.
AIRFLOW SWITCH

-a
conlrollerused
to
prove proper air
movement through a corrbustlon chamber
by measur-
ing
wirdlox
or
breeching pressure
or
by measuring air
velocity (sail switCh). Also
see LOCKOUT
and
RUN·
NING INTERLOCKS.
AI
R·FUEL RATIO - the ratio
of
the weight, or volume
of
air
to fuel measured
in
Ihe same unils under the same con-
ditions.
The
cptimum air-fuel ratio
is

the minimum ratio
that will provide complete cOlTtlusllon
of
the fuel with
enough excess
air
10
maintain a stable flame envelope.
Also see STOICHIOMETRIC AIR-FUEL RATIO.
AIR
HEATER-an
IndirecHired. venled appliance in-
lended
to supply heated air for space neating and other
purposes,
but
not
Intended for permanent installation.
AIR
REGISTER-a
burner mounting which may admit
secondary
air
to
the corrouslion space.
AIR RICH
-the
air-fuel ratio supplied to a furnace that pro-
vide:s
more air than the optimum ratio.

AlA
SHUTTER-an
adjustable device
for
varying the size
of Ihe air inlet
or
Inlets regulating primary and/or secon-
dary air.
An
air shutler may
be
automatically or manu-
aUy
operated.
ALARM-an
audible device
or
visible signal indicating a
malfunction
Of
off-normal condition.
ALARM CIRCUIT
-an
electrical circuit that includes a
bell. horn, or similar device to signal an unsafe
condition.
ALTERNATING CURRENT
(ac)-a
flow

of
eleclriclty
which reaches maximum in one direction, decreases to
zero, then reverses itself
and
reaches maximum
in
the
opposite direction. The cycle
is
repeated continuously.
The
number
of
such cyCles
per
second
is
the
frElQJency
in hertz
(HZ).
The average value
of
voltage during any
cycle
is
zero.
AMBIENT AIR
-generally

speaking, the air surrounding
t/1e
equipment.
AMBIENT
TEMPERATURE-the
temperature
of
tne air
surrounding tne eqUipment.
AMPUFIER-a
device
used
to increase the magnitude at
a small input signal to proportions sufficient to perform
some desirable function. Also see FLAME SIGNAL
AMPUFtER.
AMPUFIER
SATURATION-the
point at
whiCh
an
in-
creased input signal no longer increases the amplifier
output.
ANGSTROM UNIT
(.&.)
-a
unil
of
measurement of a wave-

length
of
lilflt
and
other electromagnetic radiation,
eqJalto
one len-thousandth (1/10,000)
at
a micron.
ANNUNCIATOR-a
device which indicates an
off-
standard or abnormal condition by visual and/or audi-
ble
sig'lals.
ANTIFLOODING DEVICE
-a
primary control which
causes the
fuel flow to
be
shul
off
LPQn
a rise in fuel
level
or
~
receivingexC8SS fuel,
and

which operates
before the hazardous diSCharge
of
fuel
can
occur.
APERTURE
DISC-a
thin, flat, cIrcular plate
of
any mate-
rial with an
~nlng
or
hole (orifice)
of
predetermined
diameter to restrict
the
area viewed through
it.
AOUADAG
TUBE-an
electron
tlbe
sensitive to ultravio-
let radial ion,
used
in
the C7012 Purple Peeper Ultravio-

let Flame Detectors. When saturated with Ultraviolet
radiation. this tube delivers
less
than'
microwallto
the
flame $lg'lal amplifier.
ARC GAP
PROTECTOR-a
devIce which cord.Jcls at
high vollage levels
10
bypass
an eleclronic network,
thus protecting tne network
agaj~t
damage
from
hlgl
voltage Int9lference ~ch as thai generatac:l by a
sp<Irk
ignilion system).
331
71·91558-1
ARMATURE-the
moving
eJementln an electrClllleChani-
cal device, such
as
the movable iron core in a solenoid,

Ihe rotaling part
of
a generator
or
motor, the movable
pirt'of
a relay,
or
lhe spring-mounted, iron portion
of
a
bell or
buner.
ARTIFICIAL
FUELS-man-made
fuels, Including all
manufactured and byiJroduct fuels.
ARTIST
CAP
- a fabricated hood, usually
of
sheetmelal,
placEld
on tq:)
of
a stack
to
prevent downdrafts or erratic
draffs becauSe
of

the direcliOl'l8( wind effecls.
ASH - the noncombustible mailer that remains after a fuel
is burned.
ASPU?Al1NG
BURNER-a
burner
in
which the fuel in a
gasElCIU&
or
finely
divided
form is burned in suspension.
the air for combustion
being
su~lied
by bringing into
contact
With
the fuel, air drawn
thrClUQh
one
or more
openings by
lhe
lower stalic pressure created by the
velocity
of
the fuel stream. Also
see

VENTURI and
ZERO·GOVERNOR BURNER.
ASPIRATOR
MIXER-a
gas-air ptoportioning device thaI
causes the flow
01
cOmbuslion air to induce the proper
amount
of
gas
inlo
the airstream. It is used with low
pressure air
and
zero gas. Also called a Suction Type
Mixer. Also
see
ZERO·GOVERNOR BURNER.
ATMOSPHERE-the
invisible mixture
01
gasas (air) sur-
rounding the earth: a unit
of
pressure defined
'as
lhe
pressure
of

760 millimelers
01
mercury at
sea
level and
at
0 C [32
Fl,
which
is equal to 14.6969
p::lUncts
per
square inch
(PSi),
or
29.92' inchas
of
mercury.
ATMOSPHERJC
BURNER-a
gas
burner relying
on
at-
mospheric pressure to
bring
in combustion air.
It
si~
permits Ihe air required

for
combustion to enter the
CO!T1:lustion
'Chamber,
or
It draws air
into
the
combus-
lion chamber from
the
area surrounding the burner.
Two methods are
used
10
draw
air into the combustion
space.
Natural·Draft Burner the natural draft produced by
the product!>
of
combvstion moving L.p Ihrough
Ihe
chimney,
or
staCK,
draws air in
atlhe
bottom
of

the
burner.
InliQiratlng Burner the fuel gas Is allowed
10
es-
cape at
high
velocity
into
the throal
of
a venturi
tLbe,
creating a lower static pressure which
draws In the air. Also called
an
Injection
or
Ven-
turi Mixing Burner.
A typical atmospheriC burner draws In
pari
Of
the
c:om-
bustion air
by
venturi action and the rast
by
a natural

draft.
ATMOSPHERIC
PRESSURE-the
prBSSUre
exerled
on
lhe
earlh's
surface
by
the weight
of
lhe
air and moislure
above it; a
unit
of
pressure equal
10
about 14.7 psi (see
ATMOSPHERE).
Also
called
~rometfrc
Pressure.
ATMOSPHERIC REGULATOR
see ZERO
GOVERNOR.
ATOMIZE-Io
reduce a liquid into a multitude

of
liny
drop-
1e1.9
or a fine spray.
ATOMIZER-a
device which breaks liquid fuel into a fine
spray.
It may require the assistancs
of
an atomizing
medium such as steam
or
air. Also
sea
MECHANICAL
ATOMIZER.
ATOMJZING
AIR-the
air
su~IiBd
10
an air·atomizing oil
burll8r
(usually about 10 percent) which
IS
used to
break the oil stream into tiny droplets.
Ths
atomizing air

is also later used
10r
combustion.
ATOMiZING
MEDIUM-a
supplementary fluid, such
as
sleam
or
air,
which
assists
in
breaKing oil into a finely
divided stale.
ATOMIZING OIL
BURNER-an
oil burner which delivers
fuel oil to the combustion
ZOIl8 in the form 01 tiny drop-
leis.
It
uses some form at nozzle
or
ori1ice to spray the
oil into the combustion charrCer.
An
atomizing oil
burner
is

classified
by
the medium used to breaK
up
the
oil into fine particles.
Air-Atomizing
Oil Burner compressed air.
Steam-Atomizing
QII
Burner-steam
at pressuras
greater Ihan
25 pounds per square inch (psig).
MeC,l',anical-A\Omizinq Oil Burner
no
mBdium; the
oil is p mped at hig'l pressures
(50 to 300 psig)
through
a suitabie burner nozzle orifice which
breaks
il
into a fine mist. Synonymous
with fressure-Atomizina Oil Burner. (Also
see PRESSURE-ATOMIZJNG GUN
TYPE
BURNER.)
Air· and Steam-Atomizing Oil Burners can
be

further
classified by the location at which
the atomization takas
place.
External·Mix Oil
Burner-the
high velocity air
or
steam strikas
lhe
oil after it has left the nozzle.
Internal-Mix Oil Burner the
high
velocity air
or
steam striKes jets
of
incoming oil in atomizing
cha/Ttler,
and
the oil is discharged from the noz-
zle in completely atomized 10rm.
AUTO-shan
for automatic;
lhe
firing rate position (on a
programmer)
lhat
provides a period during Which
lhe

firing fate
motor
is operating frem an external Control-
ler. Also see MODULATE.
AUTOMATIC-self·ragJlaling
or
self-acting; Capable
of
responding to
cMain
predetermined Conditions.
AUTOMAl1CAl1.Y IGNITED BURNER - burner
In
which
fuel
10
the main burner
is
aulonalically
turned
on and
i~iled.
AUTOMATIC BURNER
-a
burner that
stMs
and stops
automalically.
AUTOMAl1C
CONTROL-ij

sy6Iem thai reacts to a
change
or
unbalance in
one
of
its variables
by
adjusting
the other variables
10
restore the system to the desired
balance. For example, a 6y8Iem for control
01
air-fuel
ratio can
be
set
up
so
lhat a change in the selling
of
the
combustion air valve results in a corresponding change
in the
fueJ
input.
AUTOMATIC CONTROL
VALVE-an
electrically oper-

ated valve which combines a valve
l::lc.dy
and a valve ac·
tuator
or
motor. A signal from some remote point can
.e(lergize the actuator
or
motor to
qJen
or
close the
valve,
or
10 proportion
lhe
rate
of
flow through the valve.
Also see CONSTANT·LEVEL, FIRING RATE, MODU-
LATING, MOTORIZED, and SAFETY SHUTOFF
VALVES.
AUTOMATIC
IGNITION-a
system in which a burner is ig-
nited
direttly,
without manual intervention, by an aulo-
.matically supervised ig1ltion spark
or

pilot.
AUTOMATIC SAFETY SHUTOFF
VALVE-see
SAFETY
SHUTOFF VALVE.
AUTOMATIC
SYSTEM-a
system which regJlates itself
, and requires
no
manual operations: a system in which
the burner is cycled completely automatically under
control
of
an automatic temperature or pressure
controller.
AUXIUARY
POTENTIOMETER-a
potentiometer
mounted in or on a modulating motor, which is used to
control an external device in response to movements
of
the motor.
AVAILABLE HEAT
-the
quantlly
of
heat released in a
combustion chamber that is available for useful pur-
poses.

II
is
the total quantity
of
heat released minus
both the dry flue
gas loss and the moisture loss.
BAFFLE-a
metal or refractory plate
or
wall used to de-
flect the flow
of
gases
or
liquids or to minimize the ef-
fects
of
flame, heal,
or
flue gases.
BAG ASSEMBLY - closely related parts grouped together
in a single
packaQEl,
purchased as 1 unit.
BALANCING RELAY
-a
relay with an armature pivoted
between 2 etectromagnelic coils.
The

armature con-
trols the position
of
the
Wiper
on a feEKDack potenti.
ometer
In
the electrical circuit.
If
the currents through
the 2 coils differ, the armature moves toward the coil
with the most current (strongest electrornagnetit
force).
As the armature moves, the potentiometer wiper
changes the resistance in series with both coils unlil
the currents are equal. The armature stops when the
circuit is balanced. Besides the electromechanical
type
just dBscribed, there is also a solid slate type which per·
forms tile same functions electronically. A balancing
relay
is
used in a Modutrol motor to position it. Also
called a
"mouse
trap. "
BAR CHART
-a
representalion

of
the
~raling
se-
quence 01 a flame safeguard programming control us-
ing bars
shaded
to show the times when various
circuits are energiZed.
BAROMETER-an
instrument used to measure atmos-
pheric pressure.
BAROMETRIC PRESSURE - see ATMOSPHERIC
PRESSURE.
BASE
-the
main
s~rting
frame or structure
of
an
as-
sembly, excluding the legs.
BATCH TYPE
FURNACE-a
furnace
thai
Is
shul down
periodically to remove

lhe
old
charQEI
and add a
new
charQEl;
as dlsllngulshed
from
a ContinUJUS Furnace.
BELLOWS-a
metallic accordian-like
box
which can
be
compressed mechanically or with
fluid
pressure
Oike
a
spring}, and which will return to its normal shape when
Ihe pressure is released.
BENT-TUBE
BOILER-see
WATER-TUBE BOiLER.
BlAST
FURNACE
GAS-a
gas
of
low Btu content result-

ing from
burnirg
coke with a defiCiency 01 air in a blast
furnace.
BLEEDER-an
intentional leak, usually used to
rectJce
pressure
in
an impulse line.
BLEEDING-intentional
leak3Qe (usually
of
gas). Leak·
age that mi'lt't occur during shutdown
In
a safety shut-
off
valve "block-and-bleed- arrangement. Gas bleeds
off
10 the atmosphere through a normally
qJen
vent
valve. When the safely shutoff valve(s) is opened,
the
venl
or
bleed valve closes
and
"bleecjing" slq:lS. Also

see DOUBLE-BLOCK-AND-BLEED.
BLOCK-AND·BlEED see DOUBLE-BLOCK·AND-
BLEED.
BLOWER
-a
fan used to deliver air under pressure to the
desired space. Also see BURNER MOTOR.
BODY
RATING-see
VALVE
BODY
RATING.
BOILER
-a
closed vessel
in
which a liquid
is
heated or
va-
porized; used to s'-W1y hot waler or steam for heating,
processing, or power purposes. Also see CAST IRON
SECTIONAL, DRYBACK, FIREBOX, FIRE-lUBE,
HIGH PRESSURE, HIGH TEMPERATURE, LOW
PRESSURE, PACKAGED, SCOTCH,
WATER·lUB~
and WETBACK BOiLERS.
BOiLER HORSEPOWER
(BoHP)-the
EQJivalent of

the
heat
rElQJired
to evaporate 34.5
Ib
[15.648
kC]
of
waler
per hour lrom a temperature
of
212 F [100 Cl into dry,
saluraled steam al the same temperature.
~i\/a'enl
to 33,472 Bluh, 9.803 kilowalls, or 40
poundS
of steam
per hour.
BONNET
-see
VALVE BONNET.
BOOSTER
HEAlER-a
heater used
10
raise the tempera·
ture
of
oil from thai tEQJired for pumping
10

thai
re-
quired for atomization.
BOTTLED
GAS-see
UQUEFIED-PETROLEUM
GAS.
BOURDON
TIJBE-a
lube thai responds
10
pressure
changes.
The ILbe, with elliptical cross section,
i6
33J
71-97558-1
shaped into an
arc
or
spiral witl"l 1
end
attached
to
an
irdcatlng,
ret01ding,
Of
controlling deliice. A pressure
wltl"lln the

tlbe
makes It less elliptical and more nearly
circular, thus actuating
Il"Ie
attached device.
BOX·HEADER
BOILER-see
WATER·TUBE BOILER.
BRAKE-WINDING
-the
winding
in
an electric motor which
floId9
lhe
armature againsl a brake
SilOE!
to
hold
the
lTDIor In Its
open
posllion
after the mOior limit swllc;h
opens;'
When
both
the motor winding and the brake
wtr1dir1g
are energiZed.

I,"""
streng1h o1lhe motor wjnd-
Ing O\Iercomes the
brake
Winding.
BRANDi
CIRCUIT
-a
secondary cJn;uillaading
from
the
mainoil
circulating
Ic:q::>
10 a burner
or
gfOl.q:l ofbUmers.
BREAKDOWN
(VOLTAGE}-that
volla~
et
which an In-
sulator or dielectric
r~lures.
BREECHING - a passageway
to
condJc\ flue gases from
tne /umace
or
bOiler

10
Il"Ie
chimney. Also caffed
1!l.Ii
~
Of
vanl connector.
BRIDGE CIRCUJT
~an
eJectrical nalwol1c arranged
so
lhat the
volta~
at a given
poinl
in the circuit
lOan
be
z&-
roed by adjusling the electrical paramelers (resistance.
inciJctance, and capacitance) in the branchas until
the
currents balance.
BRING·UP
TlME-lhe
time required
to
raise a cold fur·
nace
and

its
char~.
if
any,
to
operating temperature.
BRITISH THERMAL UNIT
(Btu)-tl"le
quantity
of
heat
ra-
q.Jir9d 10 raise the temperature
of
t
pound
of
water
from'
degree
F.
BTU
(8tu)-sae
BRJTISH
THERMAL
UNIT
BTUI-!
(BrUhl-one
Btu per
hour;

1
million
Btuh is eq.;iva-
lent
to
7 gallons of oil per hour, 800 pounds
of
steam p&r
ho.Jr,
or
a
boiler
inpul
of
20
boiler
horsepower (Be
HPJ.
BUCKET BRIGADE - a colloquial term, for the elec\(onic
setf-checking Circuitry in the flame signal amplifier
of
scme
flame sa1egUard controls.
The
term refers
10
lhe
periodiC
"dumping"
(discharQlngj

of
one
capacitor
in
the circuil
info
anolher.
11
this
dumping
steps, due
to
a
failure in
Ihe
flame
delection
system. the control shuts
d:lwn the burnElr.
BUNKER
~C~
Otl-a
term
for
heavy
oil
(No.6
fuel oil).
S8IB
HEAVY FUEL Oll_

BURNER-a
device which introduces fuel
and
air into a
furnace at
lhe
oasireo velocities.
11 'rt:x;lence,
and
can.
centration
to
eslablish
and
mainlain proper ignition and
combustion
of
the
fust
Also
see
ATMOSPHERIC. AT·
OMIZING OIL, AUTOMATlCALL
Y IGNITED. AUTO·
MATIC, COMBINATION. INSHOT, LONG FLAME.
MAIN, MANUALLY IGNITED, MULTI PORT. NOZZLE-
MIXING, PARTJAL-PAEMIX,
POWER, PREMIX. RAW
GAS,
ROTARY OIL, SEMIAUTOMATiC. UPSHOT,

and WARMUP BURNERS.
BURNER
CONTROlLER-an
aulomatlc lemperalure
or
pl"9SSU¥9 sensing device
connected
In the
il'lpJl
Circuit
01
a flame safeguard control. 1Ilndirectly acts
to
tum
a
bUrner
on
or
off
in order
to
maintain pressure, air tem-
pe,ralUTe,
waler temperalure,
or
liq.Jid level wJlhin the
desired limits.
BURNER
HEAD-that
end

of
a burner beyond the nozzle
or
portS.
BURNER-INPUT CONTROL
VALVE-see
FIRING RATE
VALVE.
BURNER
MOTOR-
fhe motor which
ctives
the blOWer
or
fan
thai
delivers air
at
proper velocity
into
the corrt>us-
tion chamber.
BURNER
REFRACTORY-see
REFRACTORY,
BURNING VELOCITY -
see
FLAME PROPAGATION
RATE.
BUSHING

-a
usually removable lining
or
sleeve
of
melal
or
other malerial
lhal
isc
inserted or ecrewed into
an
q:Jening
to
Ifmillts
size.
resl81
wear or erosion, ser\fe as
a guide,
or
protect wires from abrasion
and
lX'SSib!e
shOrt
circuit;
an
internally
an:::J
exlernally threaded
plug

fOi
connecting a pipe
or
titling with another
of
different
size. FO(exarnpls.
lhepart
at
the C7015A
Intrared(lead
sulfide) Flame Detector which Includes the viewing
window
Of
magnifying lens;
it1ils
over Ihe plug-in lead
sulfide cell.
ard
Is
held
in place
by
the mounting collar.
BUTANE:
- a gaseous hydrocarbon fuel; a mixture
of
eas-
ily
liquefiable hydrocarbon gases, principally butane.

Bulane is one
01
tne
cCll1ll=Of'l8nts
of
raw natural
gas.
and is also derived
from
pe:roleum refini"lQ
proces.se:s
BUTTERFLY
DAMPER-a
single blade damper, pivoted
abOut ils center; Ihe blade somewhat
~esembles
Ihe
opened wings of a bullerfly.
BUTIERFLY
VALVE-a
throttling valva tor a pipe, con-
sisting
of a rotating hinged plate thaI somewhal resem-
bles
the opened
wir1gS
of
a butterfly; ol1en used as a
firint;;l
rale valve.

lhe
Honeywell V51E Bullerfly Valve
~
excellent
hi~'<Olume
floYl
characteristics, makinQ
il
useful
for
close mocIulation
of
the supply
of
air
or
fuel
gases to
lar~
furnaces. This type
of
~alve
cbes
not
cloSEl
:ightly. so a separate safety shutoff valve
musl
be
US&d
wilh it for final closeoff.

CAD
cal-see
CADMIUM SULFIDE CELL.
CADMIUM
SULfiDE
CELL-a
ph'>Io.condJclive devlea
that responds
10
the visible light
emilledby
an oil flame.
In the presence
01
~isible
lighl, the
eleclrkal
resistance
o11ha
cadmium
sulfide {CdS) becomes very low and
the cell conducts
current
The
cad cell is used In flame
detectors
10r
Oil
burner Systems.
334

CAGE
VALVE-a
single-seated valve containing a frame
or box (cage) Inside which Ihe
plug
slides, cpening the
ports.
CALL
FOR
HEAT-when
the controlled lemperature
or
pressure drops below the cperallng set p:linl, Ihe
burner
controller contacts make to iniliale burner
cperation.
CALQRIE-Ihe
quanllty or heat required to raise the tern-
. peralure
o~
1 gram
of
waler 1 degree C.
CA~pLlNG.
(CANDLEUGHTING}-the
deterioration or
the pilot to an unsatisfactory condition, characterized
by
a lazy, yellow 1lame; usually caused
by

a high ambi·
ent temperature
or
an excessively large pilot burner
orifice.
CAflACInVE
LOAD-a
leading load; a load that
is
pre-
oominantly capacitive, so that the alternating current
leads
the
alternating voltage, I.e., the voltage doeS not
change direction until
afler
the corresponding current
does.
CAPACITY INDEX
(Cvl-the
quantity or waler, in gallons
per
minute at
60
F,
thatllows through a given valvewilh
a pressure drop or , psi.
The
flow or
a.ny

fluid through
the same valve can
be
calculated from the C
v
. Also
ca.lled the Flow Coefficient.
CASlNG-l)
a.
covering
of
sheets
of
metal or other mate-
rial such as a 1ire resistanl comJXlSition
l::::oard
l.lSed
10
enclose all or a portion or a steam generating plant;
2)
an enclosure torming the outside
of
a.n
appliance, no
parts
01
which are likely to be subjected
10
intense heat.
CAST IRON SECTIONAL

BOILER-a
OOPer
comJX)S9d
or
a.
number
of
separale sections 1a.stened together,
re-
sulting in a large heal transfer area. It can
be
fired
by
an
LPShot or :nshol
gas burner, or
by
a pressure atomizing
oil burner. Sizes range
up to 4 million Btuh (about
80
BoHP). . ,
CELL - a single unit that produces voltage
Of
currEW11
by
converting radiant energy into electrica.l energy. Also
see CADMIUM SULFIDE
and
LEAD SULFIDE CELLS.

CENTRAL
FURNACE-a
seI1-contained, indirect-fired
furnace designed to supply heated
air
through ducts to
spaces remole 1rom or
adjacenllo
the furnace location.
CENTRAL
HEATER-a
stationary. indirect-fired, vented
awliance
in
one
of
these classes: boilers, cenlral fur-
naces,
1100r
furnaces, recessed healers,
and
floor-
mounted unit heaters connecled to a ducl system.
CENTRIFUGAL ATOMIZING OIL BURNER - see
ROTARY
OiL
BURNER.
CHARACTERIZED
GUIDE-a
valve guide with notches

or
V's
cui
inlo
il
to determine the valve flow characteris·
tic; also
known
as a skirted guide.
CHARGE-a.
load; the maximum or necessary QJNItity
thaI a conla.iner or
awaratus
is buill to accommodate;
e.g., fuel in a furnace. In electricity, the elsclricat
energy stored in a capacilor
or
ba!tery or held on an
insulated object.
CHASSIS-a
sheetmelal
bOx,
frame,
or
single plate
on
which the components of a device are mounted; the
asserrbled
frame and parts.
CHATTER-see

RELAY CHATTER.
CHECKING RELAY
-a
relay iri the selt-checklng circuit or
some flame safeguard controls which makes
ard
breaks periodically
(~Checking~
or
~peCking·
action)
when the flame signal
is
strong enough. While check-
ing, it trans1ers energy to
hold in the
11ame
relay.
It
slops
MChecking
M
it
the flame signal becomes too weak
or disappears.
CHIMNEY-a
brick, metal, or concrete stack enclosing 1
or more
11ues
for conveying

11ue
gases to !he ouIside
atmosphere.
CHIMNEY
CONNECTOR-the
pipe
which connects a
fuel burning appliance to the chimney;
a.lso
called a
smoke pipe.
CIRCUIT-see
ELECTRICAL CIRCUIT.
CIRCULATING LOOP- themain loop
in
which oil
is
circu-
lated from the storage tanks to
1M branch circuilsand
then back to the storage tanks.
CLOSED CIRCUIT OIL
SYSTEM-a
system in which oil
may
be
pu~
completely through the circulating
loop and back into the oil storage tank.
CLOSED

IMPELLER-see
IMPELlER.
CLOSE-OFF RATING
-the
maximum allowable pressure
drop to which a valve may
be subjected while fully
closed.
It
is a function
of
the
JXlWer
available from the
valve actuator for holding the valve closed, and is
ll'k:ie-
pendenl of the actual valve
l:xxtf
raling.
COCK-a
manually operaled faucet
or
valve tor shutting
oft
or throttling down
the~ow
or a
li~id
or gas.
usua.11y

by means of a tapered plug. Also see PETCOCK
ard
SUPERVISORY FUEL COCK.
COMBINATlON
BURNER-a
burner
by
means
of
which
more than 1 fuel can be burned.
eilher
separa.lety or si·
multaneously. Also called a Mullifuel Burner. A
C1.lil!:.
Fuel Burner uses , prime fuel,
but
can switch
to
a
stanchy
1ue1
under peak load conditions. A
.Gas:Ol!
~
is capable
of
burning either gas or
oil-some.
types can burn

OOlh
at the same time.
Ex~les
of
a
Combination Burner:
Pressure-Atomizing Oil/Gas Ring
BuOl9f'.
Horizontal Rotary Oil/Gas Ring Burner.
Combination of 2 burners (under separate
Sl.4l9r-
vision)
in
1 asserrbly.
COMBUSTlBLE
MATERIAL-material
that will
iglile
and
bum.
k3
pertaining to materIals ad}acent to
Of
in
con-
tact with heal-prodJcing
Wiances,
chimney connec·
tors, vent connectors, steam
and

hoi
water pipes, m
warm air
wcts,
II
is material
made
or or surfacedwilh
335
71-97558-1
wood.
COlTpfElSsacI
paper, plant fibers, or other mate-
rtalthat wlllignite and burn. Such material shall
be
con-
sidaTEld
as combustible even lhough flameproofed,
fire-retardant treated, or plastered
COMBUSTION-the
act
or
process
ofbutning;
the rapid
oxidation
of
fuel accompanied by the production at
heat, or heat and light. Complete col'1'bustlon req.Jires
an

adequate suppl)l
of
oxygen. Also
se&
COM
PI.ETE,
INCOMPLETE,
and PERFECT COMBUSTION.
COMBUSTION
AIR-the
air
r&q Jired
tor clJl'l'lllele and
sanSfactory combustion of the fuel;
ooes
nol
inclUde
the air
used
for atomization. Also called main air. The
actual amounl of air supplied
Is
usually expressed as a
percentage
of
the lheoretical amount required for
can-
p1ete
combustion.
,


,.
COMBUSTION AIR
SWITCH-se&
AIRFLOW SWITCH.
COMBUSTION
CHAMBER-the
panion
of
the heating
or
prcx:ess equipment where fuel is burned. Also called
the~.
COMBUSTION
CONTROL-see
FIRING RATE
CONTROLLER.
COMBUSTION CONTROL VALVE-5ElEl FIRING RATE
VALVE.
COMBUSTION
DETECTOR-see
FLAME DETECTOR.
COMBUSTION
PRODUCTS-
mailer resulting from
COITI-
bUstion. such as flue Qi!S8S, water,vapor, and ash; but
excluding excess air.
COMBUSTION
RATE-se&

FIRING RATE.
COMBUSTION
SAFEGUARD-see
FLAME SAFE-
GUARD
CONTROL
COMMON-a
terminal, connection. leadwire, circuit, or
other part
of
an
eleClricj;l1
networ'K which
is
shared
by
olher parts of tho networ'K. On a flame safeguard
co~
trol, the terminal and leadwire which are in lhe circuit
for all JXlSitions
01
the firing rate swllching
circuit
COMPlETE
COMBUSTION-burning
with stoichiometric
P'C90rtions
of
air
and

fuel pllAi a rncderale excess
of
air
10
ensure Ihal all
of
the fuel
is
burned.
COMPRESSED
AIR-air
al a pressure of 5
or
more
jX)Unds per
SQ,Jare
inch above atmospheriC pressure.
COMPRESSED-AIR-ATOMIZING OIL
BURNER-see
ATOMIZING OIL BURNER.
COMPRESSIBLE
FLOW-flow
of
hiQh
pressure gas or air
which undergoes a pressure drop sufficient to resull in
a
siglificant
reduction
01

its density.
CONDENSATE-condensed
water resulting from the
removal of lalent heal from steam.
CONDUCTION-the
transfer
of
heat or transmission
of
electricity through a materia!
(cal/eel
a condUclor) by
passing
II
from molecule to molecule.
CONDUCTIVITY CiRCUIT
-a
flame proving circuit which
operates on
an
ac flame aignal
and
utilizes the electri-
cal corOJction
of
a flame, as d1sllnculsheci
fran
rectlfi-
calion. Also
5ElEl

CONDUCTIVITY FLAME
ROD
SYSTEM
and
FLAME CONDUCTIVITY.
CONDUCTIVITY FLAME ROD
SYSTEM-a
flame
roo
deteclioo system
based
on the ability
of
the flame
10
conClucl
a currant; conducts the same amount of cur-
rent in
eUher
dlrectioo, as distinguished tram flame
reeliflCatioo.
CONDUIT
-a
tlbe
or trOlJl;;flfor carrying
and
protecting
electrical wires.
CONSTANT-lEVEL
VALVE-an

automatic control valve
for maintainIng, within a reservoir, a constant level
of
fuel for delivery
10
the bumer.
CONSTANT PILOT
-se&
CONTINUOUS PILOT,
CONTlNUOUS CHECK
RELAY-see
DYNAMIC SELF
CHECK.
CONTlNUOUS COMPONENT
CHECK-5ElEl DYNAMIC
SElF
CHECK.
CONTINUOUS
FURNACE-a
furnace
~rated
on
an
un·
intern pted
cyCle,
In
which the charge
iEi
being

con-
stantly added to, moved thrOUgh,
and
removed from
the furnaCe;
as diSIlngulsheel
from
a Batch Type
Fumace.
CONTlNUOUS
IGNlTlON-ignition
by
an
energ,o
source
which is continuously maintaineelthroughout
the
time
the burner
is
in service, whether the main burner is
tiring or not.
CONTINUOUS PILOT
-a
pilot that
burns
without
turndown throughout the entire time the burner assem·
bly is in service, whether lhe main
butner

is firing or not.
The pilot ignites fuel which may leak into the corrbus·
tion chamber whan the burner is off, thus prevenling a
hazarcbus
cordilioo
at stanup.
(~Gontinuous
Pilol"
is
Underwriters
laboratories
Inc. term for the
old
term
"Standing PlIot )
CONTROL-a
device which
dir&crJy
operates a system to
reg.Jlate the fuel, air, waler,
or
electrical
Eiul=Ply
to the
controlled equipment.
It may
bEl
automatic, semiauto-
malic, or manual. Also see AUTOMATIC. FLAME
SAFEGUARD, MODULATING, NONRECYClING,

ON-QFF, OPERATING, PRIMARY, PROGRAMMING.
RECYClING, AND SAFETY CONTROLS.
CONTROL AGENT
-the
meellum which is manipulated
by the control syslem
10
cause a change in the con-
trolled medium. For ellample, suppose a heating coil
thrClllgh which steam is flowing
Is
used to heat a room.
The rcom thermostat is placeel so that it measures tem-
perature (conl(olleel variable)
in
the room air (conlrolleel
medium), and operates a valve which regulates Ihe
flow jmanipulateel variable} of the steam (control agent)
thrOlJl;;fl
the heating coil. Heal from the coHls thus fur-
nished to the room air.
CONTROL
POINT
-the
value
0:
the controlled variable
which the controller operates to maintain. Also see SET
POINT.
CONTROL

SYSTEM-the
entire system, including the
controlled system
And
the automatic conlrol eq.Jip-
ment.
see
CONTROLLED SYSTEM.
CONTROL
VALVE-see
AUTOMATlC CONTROL
VALVE.
CONTROL
lONE-
the section
of
a furnace
In
which tem-
perature'is controlled
by
the throllling action
of
a single
valve. Also see VALVE ZONE.
CONTROLLED
MEDIUM-the
substance (usually aIr,
water, or steam) whose characteristics (such as lem-
I perature, pressure, flaw rate, volume, level, or concen·

tration) are
being
controlled.
CONTROLLED
SPACE-
the volume
of
the controlled me-
dium. For example, a room in which the air temperature
is
being
cootrolled.
CONTROLLED
SYSTEM-the
system made up of all
equipment
In
which the controlled variable exists,
but
which does not include the automatic control
eqUipment.
CONTROLLED
VARIABLE~that
quantity or condition of a
controlled medium which
is
measured and controlled.
For example, temperature, pressure. flow rate, vol-
ume, level, or concentration.
CONTROLLER-a

device which senses and measures
changes in the controlled variable
and
indireCtly acts to
maintain the controlled variable within preset limits.
It
direCtly affects the operation
of
a flame safeguard con-
trol. Also
S99
LIMIT; and BURNER, FIRING RATE,
MODULATING, PRESSURE, PROPORTIONING,
SAFET'(, !lind VACUUM CONTROLLERS.
CONVECTION-transfer
of
heat
by
moving masses
of
mailer. Convection currents are set
l4>
in a fluid
by
me-
chanical agitation or because
of
differences in elensity
al different temperatures.
CRACKING-the

process
of
breaking
c:bwn
hydrocar-
bons
by
heat
and
pressure into simpler compounds or
elements: e.g., the breaking down
of
petroleum Into
gasoiine.
CRITICAL PRESSURE
DROP-see
PRESSURE DROP.
CROSS'CONNECTED-two
pipes or systems
of
flow
connected to each other, usually to proviele an equali.
zation or interplay
of
pressures.
CROSS·DRUM
BOILER-see
WATER-TUBE BOILER.
CRUDE
OlL-unrefined

oil in its natural stale as it comes
tram the ground. Also called petrgleum
or
!<II.!Q!i.
CURTAIN TYPE
DAMPER-a
damper composed
of
flex-
ible material, which moves
in
a venical plane as
it
is
rolled.
337
CUTOFF - immediate shutdown
of
a system atter loss of
the main
burner
flame,
wilh
no
attempt to
recyCle
or to
relight the burner.
Cv-see
CAPACITY INDEX.

DAMPER
-a
elevice for introducing a variable resistance
for regulating {he volumetrIc
flow
of
gas
or air. Also sea
BUTTERFLY, CURTAIN, FLAP, LOUVER, andSLJDE
TYPE DAMPERS: and OPPOSED and PARALLEL
BLADE DAMPERS.
DAMPER
MOTOR-see
FIRING RATE MOTOA.
DEAD END
LJNElSYSTEM-the
end
of
a pipe line which
does not lead back
10
an
oil Slorage tank, so
the
oil
in
that
end
of
the line cannot

be
recirculated. A system
which does not contain a return line
10
an all storage
lank, so the oil cannot
be
recirculated in a closed
circuit.
DEFICIENCY OF AIR
-a
supply
of
air which is inadequate
lor complete combustion
of
a fuel. (This is [he same
as
an excess
of
fuel.) Also see FUEL RICH.
DELAYED
MIXING-a
process in which the fuet and air
leave Ihe
burner
nozzle unmixed and, thereafter, mix
relatively slowly, largely through diffusion. This results
in
a long, luminous 1lame. called a diffusion flame, long

Ilame, luminous flame,
or
yellow
11ame.
Also see LONG
FLAME BURNER.
DETECTOR
-a
elevice that produces an electrical
OOlput
that
Is
a measure of the radiation incielent on the
device. Also see FLAME DETECTOR, SMOKE
DETECTOR,
and
SENSOR.
DEVIATlON-the
difference between the sel point and
the value
of
the controlled variable at
any
inslant.
DIAPHRAGM
VALVE-a
SOlenoid-operated. gas valve
in
which a membrane or partilion separates lhe inlat and
outlet. When the solenoid

is
d&-energlzed, the main
gas supply applies pressure to the top
oflhe
dlaphragn
10
help hold the valve closed. When the solenoid is an·
ergized, a plunger
opens
a bleed
pon
in
the
I~
side of
Ihe valve.
As
the gas bleeds off the
I~
of
lhe dia-
phragm, main
gas pressure
on
lhe
underside
of
the dia·
phragm
cpens

the valve. Honeywell
V4B
and V88
Diaphragm Valves are generalty used on atrra;pheric
type
gas
burners tor
srTlOClth
lightoff.
Thej
fealure vari-
able, slow q::lefling times
and
fast closing
1IrTeS.
Also
see SOLENOID.
DIFFERENTlAL-the
sroallesl range through which the
controller variable must
pass
in
oreler to move the final
control element
'rom
one
10
the other
of
il~

2 possible
positions, such as from ON
10
OFF.
DIFFUSION FLAME
BU
RNER
-see
LONG FLAME
BURNER.
71·97558-1
DIRECT CURRENT
(de)
-an
essentially ccnstanl-value
curr&/\! lhat flows
In
ally
one direction.
DIRECT·FIRED HEATER
-a
heater In whie"
thepnxiJclS
01
e6iTb.istlon (l'lue gases) are
Inlerm1xec:l
with the
medium being "eatec:l (e.g.,
ail1.
Also see DIRECT-

FIRED EXTERNAL
and
DIRECT-FIRED INTERNAL
HEATERS.
DIRECT·~IRED
EXTERNAL
HEATER-any
oven healing
SyStEll!"
in whiCh
'he
products
of
cootlusUon frem the
burnel'\,l!\rs discharged
into
the oven chamber
by
a cir·
culating fan
or
blower,
and
in which the
bul'119r'S
are in a
cOlTbJstion chamber ellectively separalec:l frem Ihe
oven chamber. ll"Jere are 2 types:
1. Nonreclrculating-prodJCIS
of

combusllon are
''discharged into the oven cl'\arrt)er and are nat
returned
to
the combustion charrtler.
2.
ReCirculating - oven chamber atmosphere is
recirculated to the combustion chamber and
Is
In
conlact
wit"
the burner flame.
DIRECT-FIRED INTERNAL
HEATER-any
oven healilll;l
system in which Ihe burners
are
within the oven
cham
ber, and the products
of
combustion are in contact with
the oven atmosphere.
DIRECT SPARK
IGNIllON~use
of
an Ignition spal1l.
generated
by

a high voltage transformer,
10
lir,tll lhe
main burner; aw1ies
10
burners not using a pilot,
usually small oil burners. Also see PROVED SPARK
iGNITION.
DISCONNECT SWITCH -
see MASTER SWITCH.
DISSOCIATION-the
process
by
which a chemical com·
pound breaks c:bwn inlo sil"llJler
cCllTPJl1enl.6.
For ex·
al"llJle. breaking
up
CombUSliQi"l
products into
cOl'Tbustibles and oxygen,
aCCot'T'flanied
by
an
absorp-
tion
of
heal.
Thi.6

·usually occurs at high tefTC)9ralures,
and
Ills
one
of
the factors limiting the maximum tem-
peralure ot a flame.
DJS11UATE
OIL-light
fraction of oil separated frem
cru&
oil
by
fractional distillation.
DIVER11NG
VALVE-a
three-way valve with
linlel
and 2
oullels. A
fluid
entering the Inlel
por1
Is
diverted to
either
of
the 2 outlet ports in any prq:lOrtion desirec:l by
moving Ihe valve stem. A diverting valve
is

doLble-
seeted with a aisc tor each seat, so
It can generally
be
used
in
mixing
~lications
also.
DOUBLE-BLOCK·AND·BLEED-a valve arrangement
In
which a normally open vent valve just c:bwnstream from
an automatic safety Shutoff valve
(SSOV)
allows any
gas
that leaks past the SSOV during shutc:bwn to
es-
cape to the outside atmosphere. A second SSOV lust
c:bwnsUearn from the vent valve blocks any
gas which
is
not
ventec:l.
When the
$SOV's
are open, the vent
valve is closed. Also see BLEEDING.
DOUBLE-SEATED
VALVE-a

valve with 2 seats and
discs arranged
so
thai
in
Ihe closed posilion there is
very
Uttle
fluid pressure forCing the stem toward the
open or closed position; rEQJlres less power to operate
than a single-sealed valve the same size; ofIen
has a
larger port area
tor
a given pipe size; cbes
not
have
tir,tlt shuloff.
(Do not contuse lhis valve with the type
01
valve with a second seal
used
in
a valve-closed
inlerlock.)
DOWNFLOW
FURNACE-a
forcB(j.air, central furnace
with essenlially vertical airflow, whjch discharges air
at

or near
lhebotlom
at the furnace; es distingUished
'rom
an uptJow Furnace.
DRAFT-the
difference between atmospheric pressure
and some lower
pl9SSUre
existing
in
the furnace or
gas
passages
of
steam generating unll; also, the move-
ment
of
air Into
anc:I
thro~
a
corrtluslion
charrber,
breeching,
stack:,
anc:I
chimney. Drall may be natural,
resulting frem the difference
in

denslly
of
the heated air
rising through the stack and the cooler displacing air.
Artificial
drall
may be prOVided
by
mechanical means,
Drall is affected
by chimney height
and
cross section,
wind, makeup
air
c:penlng in the boiler room.
and
wealher conditions (barornelfic reading). Also see
FORCED, INDUCED, MECHANICAL. NATURAL, and
OVER-FIRE DRAFT.
DRAFT
LOSS-the
reduction
of
drall intensity caused
by
resistance to
flow
of flue gases through the boiler,
breaching

and
chimney, plus any resistance to flow of
air through the burner.
DRAFT
REGULATOA-a
device which acts to mainlain a
desired draft
by automatically controlling the chimney
drall in:erLSily at the desired value.
DRYBACK
BOILER-a
Scotch, fire-tube ooiler with a ce-
ramic baffle al the back of the furnace
to
direct the
products
of
cornb Islion from the combustion chamber
to the second pass. ll"Je ballle is separate from the
pressure vsssel and
'IS
constrUCled
of
heal·resistant
malerial (generally refractory brick and insulation).
Also
see FIRE-TUBE and SCOTCH BOILERS.
DRY
CONTACTS-contacts
isolated from any source

01
power.
DUAL·FUEL
BURNER-a
burner using 1 prime fuel,
but.
capable
of
using a
slancbl
fuel under peak load cond!-
lions. Changeover from one fuel
10
the other can be
made aUlomatically usIng an electriC temperature
controlle!
or
by use
of
a manual switch. Also see
COMBINATION BURNER.
DUCT
-a
passage for air or
gas
flow; a protective pipe
through which wires or cables are run.
DUCT
FURNACE-a
central furnace designed lor instal·

lation in a duct
01
an air dislribution system to supply
warm air for healing. For
air
circulation,
II
depends on a
blower
not
furnished as part
of
the furnace.
DYNAMIC AMPU-CHECK-HonB'jYfelitrademerk:; a fea-
ture in some Infrared flame
sil;1l81
amplifiers; circuitry
tests only the flame signal amplifier during burner
338
operation and shuts down the burner if lhe amplifier
fails (including a flame-simulating failure).
DYNAMIC SELF
CHECK-
Honeywell trademark; a fea-
.·ture in the rectification
type llame signal amplifiers
or
some flame safeguard controls: circuitry tests all elec-
tronic components in the flame detection system
(am-

plifier and detector) 60 to
240
times a minute during
burner operatior) and shuts down the burner if the
'.detection system faits (including a flame-simulating
failure).
EA~,LY
SPARK
TERMINATlON-a
feature
of
some pro-
gramming controls which allows ignition cutoff
be10re
the main fuel valve(s) opens, resulting in a periOd dur-
ing which onlv the pilot is on.
ELECTRICAL CIRCUIT
-an
electrical path between 2 or
more points; the interconnection
of
a number of de-
vices in 1 or more closed paths to pertorm a desired
electrical or electronic tunction. Also see OYNAMIC
AMPLI·CHECK and OYNAMIC SELF CHECK; and
ALARM, BRIDGE, CONDUCTIVITY, FIRING RATE
SWITCHING, FUP-FLOP, HIGH-VOLTAGE, ISO-
LATED LIMITED SECONDARY, LINE-VOLTAGE,
LOW-VOLTAGE, OPEN, SHORT,
SOUD

STATE, and
TUNED CIRCUITS.
ELECTRIC
IGNITION-ignition
or a pilot or main burner
bV
an electric spark generated
by
a transformer, which
is eilher automaticallV or manuallv energized. Also see
DIRECT SPARK IGNITION.
ELECTRODE-;-a conductor
by
means
of
which a current
passes into or
001
of
a,gas; often one terminal
of
a lead.
Examples: ignition electrcxles, ftame rods, electron
tube elements.
ELECTROMAGNETIC
SPECTRUM-a
chart
or
graph
showing the relationship between all known eleclro-

magnetic waveforms classified
by
wavelengths.
ELECTROMAGNETIC
WAVE-the
radiant energy pro-
duced
by
oscillation
of
an electric Charge. lncluc\edare
radio waves; infrared. visible,
and
ultraviolet light
waves: and
X-,
gamma, and cosmic rays.
ELECTRONIC-of
or pertaining
to
devices, circuits,
or
systems utilizing the motion
or
emission of cur-
rents
01
free electrons, especiallv in vacuum,
gas, or phototubes, and special conductors or
semiconduclors.

EQUAL PERCENTAGE CHARACTERISTlC-a valve
flow characteristic which causes like movements
of
the
valve stem at any point of the
now
range to change ex-
Isting flow an equal percenlage. regardless
of
the exist-
ing
flow quantity.
EXCESS
AIR-air
which passes through the combLstion
chamber and flues in aQjiUon to the quantity which is
theoreticallv required for complete corrtlustion, to
enSlJre
that all of the tuel is burned.
EXHAUST
FAN-a
fan which provides a
SlJcUon
to
re-
move the air, gases, and producls of combustion from
the turnace
or
oven.
In

some systems, it also brings
in
combustion air. Also called a ventilator.
EXPANDING PILOT
-a
pilot that burns throug,out
the
entire lime the burner assemblV is in service

whether
the main burner is firing or
not
Up:lI'I a call for heat, !he
pilol flame is automaticaliV Increased in size
so
as
to
reliably Ignite the main burner. This pilot may be turned
down automaticaliV at the end of the main burner
1lame-ilstablishing periOd.
EX
PLOSION - combustion occurring within a confined
environment at such a rapid rale as to cause detona-
tlon, called a
Fireside Explosion. Also the rupturing of a
vessel due
tothebuildup
otprassure
of
water or steam,

called a
Waterside Explosion.
EXPLOSIVE
MIXTURE-a
flammable mixture
in
a con-
fined space.
EXTERNAL
HEATER~a
heater in which the burners and
combustion chamber are effectivelv separated lrom
the oven chamber or the medium being heated. Also
see
DIRECT-FIRED EXTERNAL
and
INDIRECT-
FIRED EXTERNAL HEATERS.
EXTERNAL-MIX OIL
BURNER-see
ATOMIZING OIL
BURNER.
FAN
-any
device
or
machine
used
to set up a current
of

air. Also see BLOWER
and
BURNER MOTOR; and
EXHAUST, FORCED-DRAFT,
and
INDUCED-
DRAFT
FANS.
FANMIX
BURNER-a
mechanical-oraft burner which
uses the energy
of
high-pressure gas
(10
to
50
psi)
to
Completely premix the air
and
gas. Gas is permitted to
escape IhrClll'j"l a
row
of
small orifices
on
the
ecV3
of

prq:>eller-Hke
blades mounted
on
a ffee-spinning shaft.
Reaction
of
the escaping gas rotales the blades, which
are mechanically
CQl4)led
10
a fan that draws in the
primary air. The
speed
of
the fan varies with the gas
pressure, theretJy automatically adjusting the air
volume [0 maintain optimum corrt:lUstion. Also
see
MECHANICAL-DRAFT and PRE-MIX BURNERS.
FAN
MIXER-an
air blower in which gas is ad"nitled
to
lhe
inlet to be mixed with air.
FEEDBACK POTENTIOMETER-the potentiometer
In
a
mcdJlaling motor which forms part of a
briOole

circuit
along with
lhe
controller potentiometer and balancing
relaV
in the molor. When
lhe
Wiper
on
the controller po-
tenllcmeler
l'T'lOVeS
dJe
10
a change
In
the controlled
339
71-97558-1
variable, the
motor
runs
and
drives the wiper on the
feecback polen(fomeler in the proper direction to
rebalance the
bridge
circuit. When the circuit Is bal-
anc9d


~ElI
motor stops.
FIELD
WIRING-wiring
thaI
musl
be
done
althe
Installa·
lion
site (in aetjilion to 1actory wiring) in order to
com
plete
an
Installation.
FILTER
a
device to remove solid malerial from a fluid
~i~)d
Of"
gas).
In~electronics,
a saleclive network or
resistors Il"d.Jctors,
or
capacitors which otters COOl-
paratively
1i1lle
q::positlon

10
certain
fr9QUBl1cies
or
(0
direct current,
while
blocking
or
anenuating other
trEQJencies.
FIREBOX-see
COMBUSTION CHAMBER.
,.
FIREBOX
BOILER-a
horizontal, fire-lube boiler with a
small,
internal corrt>usllon chamber
of
cubical
dasi'OJ'l.
TIle
short, first-pass bank
of
lubeS Is
COr"ll"l9cted
be-
tween the rear
of

the combustioo chamber
and
lhe rear
of
lhe
OOiler.
The remaining
banks
of
tubes extend the
full length
of
the ooiler, above the combustion chamber
and the first-pass
bank.
The combustion chamber may
be steel, refractory.
or
waler-cooled refractory.
AlSO
see FIRE·TUBE, MULTIPASS. and WATER-LEG
BOILERS.
FIRE POINT
-the
minimum temperature at which a flame
is suslained
for
at least 5 secondS.
FIRESIDE
EXPLOSION-see

EXPLOSION.
FIRE-ruBE
BOILER-a
boiler
in
which the
prCXi.Jcls
01
combustion
pass
through
slraighttubes
surrounded
by
water and steam. The tubeS may run horizontally
or
vertically.
The HOlizonlal-Return-TuOO
(HRn
type has a horl·
zonlal shel: conlarning the tubes. The prooucls of com-
bustion
pass from
Ihe
external combusllon chamber
underneath the
bottom
of
the
she:1

to the end
of
the
boller, and relurn thrOl.:gh the tubes. If the prOducts
01
cQfTClustion
are
paSSEd
Ihrough
the shell more than
once,.
it
Is called a Mullipass Boller.
l1le
Y w1!£.Il!
type
has
a vertical, cylindrical shell Cln"
talnlng the
lubes.
Thfl
prodJcts
of
combustion pass
from the
irternal
cO/T'tlusUon charroer below the shell,
l.p
IhrOLV'i the lI.bes. In a Submerged VertIcal type. lhe
water level exlends h;gher than the tcp

endS
of
the
lubes.
Also
sea
FIREBOX, MULTIPASS,
and
SCOTCH
BOILERS.
FIRING
RATE-corrbuSlion
rate; the rate
e!
which fuel. or
an air-fuel mixture
is
supplied
10
a
burner
or
furnace,
expressed
in
volume. weight,
or
heat units
~1ied
per

unit lime. Also see HIGH FIRE, LOW FIRE.
and
MODULAllNG
FIRE.
FIRING RATE
CONTROLLER-a
centrallar which
p;::lSi-
lions lhe firIng rate
motor
10
automalically regUlate the
burner firing rate
al
a predetermined air-fuel ralio in ac-
cordance with
load
demand, II
ma'1
p;::lSllion the air
and
fuel
SUWI;8S
for low fire
or
for
high fire,
or
it may be a
proportioning

(mooulaling)lype
which grao."al'lY varies
the eir and tuel supplied wlchln limits to meet
(he
lOad
demand, Also see FIRING RATE MOTOR.
FIRING RATE
MOTOR-a
modulating
or
a two-posilion
(q::.en·closed)
malar
WhiCh
p:::lSitions the tiring rale
valve anOior Ihe damper in response to the firing rale
controller,
FIRING RATE SWITCHING CIRCUIT
-a
circUit
In
a pro-
grammin\jl conlrol which switches external devices at
predetermined
limes
10
conlrol
the
firing
rale

01
lhe
bJrner.
FIRING RATE
VALVE-an
automaUc control valve for
reg.rlating the input
of
fuel
to
a burner in response
10
load demand. Also called a Burner-Input Control yalve,
Combustion Control Valve, Meterino Valve or
Jh!Ql-
\Iino Valve. Also see BUTTERFLY, MODULATING,
and MOTORIZEO VALVES.
FIRST-OUT
INDICATION-a
device (usually a lamp)
for
each bur'ler
in
a mulliburner system. The device Indi-
cates the
first
burner
having flame failure.
FIRST·STAGE OIL
VALVE-in

oil
burners
wiln
more
lhar1
1 firing rate level (stage),
the
automatic safely shutoff
valve which opens
firslto
admit the 1uel required for the
lowest rale
of
corrtJostion. In direct
spark
ignition
sys-
'tams, the first stage may take the place
of
a gas pilot.
FLAME-the
visible
or
other physical evidence
of
Ihe
cnemical procsss
01'
rapidly convening fuel end air into
products

01
combustion.
FLAME
BlOW-OFF-the
phenomenon which occurs
when
a llame moves awa:f
from
a burner, often result·
ing in the flame being exlinguiStlEla. A flame blows
off
when lhe air-fuel mix:ure
leaveslhe
burner
af
a
velOCity
greater than Ihe velocity
wilh
which the flame front pro-
\jIress8S
lhrough the mixture.
FLAME CONDUCTIVITY
-the
abilit'1
01
the ionized
gases
of
a flame

10
conduct an electriC current.
FlAME
CURRENT
-sea
FLAME
SIGNAL
FLAME DETECTION
SYSTEM-Ihe
flame detector,
flame signal ampliflS", and
flame
relay (In a flame safe-
QJard control)
which
logether
delermine whether a
sut-
ficientflame
is
present
10
continue
Ihe
q::.erallon
Of
a
burner.
FlAME
DETECTOR-the

components
of
a fla:ne detec-
tion system
which
delect the presence
or
absence
01
a
fJame.
Also see DETECTOR and FLAME
ROO;
and
INFRARED. OPTICAL, RECTIFICATION TYPE.
RECTlFYING PHOTOCELL.
and
ULTRAViOLET
FLAME DETECTORS.
FLAME DETECTOR
RELAY-a
control consisting
of
a
flame detection electronic network
and
a switching
re-
lay which pulls in when flame is detected. This control
340

is
nor
a primary control because
it
does not sequence
burner operation. nor provide a safe start
Check
or
safety shuloown. Do not confuse
it
with FLAME
RELAY.
FLAME
ENVELOPE-lhe
confines (not necessarily
visible)
of
lhe comboslion process {Converting fuel and
air into products
at
combustion).
FLAME FAILURE
~ESPONSE
TIME-the
time interval
between the loss
of
name and the dr<:q:ling aut
of
Ihe

tJame
relay in a flame safeguard control. whlch then
de-
energizeS '{he automatic fuel valve(sj.
FLAME FRONT
-the
plane along which combustion
starts. or the base of the flame.
FLAME PROPAGATION
RATE-the
rate at which a flame
- fronltravels through a corrbustible mixture
or
fuel and
air.
It
is
a function
of
air-fuel ratio. mixture temperature,
and Ihe ambient pressure. Also called burning velocity,
flame
SPeed.
and flame velocity.
FLAME RECTIFICATION-the phenomenon which
causes a name to conduct more currenl in one direc-
tion than in Ihe other. It,:s due
to
the ionizalio:'1 of air in
and around the flame. and

to
the difference in area
of
the electrodes in the flame enveiope.
(The
ground ar9a
is at least 4 times the area
at
the flame rod.)
FLAME RECTIFIER PILOT
-see
PILOT BURNER
ASSEMBLY_
FLAME
RELAY-the
relay in a flame safeguard control
which pulls in when a flame. or a condition simulalinga
flame,
is
detected. It drops out on loss
ot
flame signal.
causing Ihe flame safeguard control to shut down the
burner. Do not confuse it with FLAME DETECTOR
RELAY.
FLAME-RET~NTION
NOZ+LE-a
burner nozzle sur-
rounded wilh small pOrts which act
as

pilots to relight
the main burner name il
it
blows off. The
velOCity
through the small ports is
Jess,
so the flame almost
never blows off
at
then'!.
Also called a stick-tight nozzle.
FLAME
ROD-a
melal
or
ceramic rod projected into the
flame envelope
to
function as an electrode in a flame
detection circuil. Also see CONDUCTIVITY FLAME
ROD
SYSTEM and RECTIPfING FLAME ROD.
FLAME SAFEGUARD
CONTROL-a
safely control which
provideS a means for starting the burner in the proper
sequence. proving that lhe pilot or burner flame is
established, and supervising the flame during burner
operation. safety snuldown occutS if Ihe pilot or burner

flame is not established. or
ilthe
flame goes oul. Also
see CUTOFF, IGNITION RETURN, and MODULAT·
ING. ON-OFF, PRIMARY. PROGRAMMING,
RE·
CYCLING, and NONRECYCLING CONTROLS.
FLAME SAFEGUARD
SYSTEM-the
set
of
equlpmenl
used to provide safe control of ourner operation. This
usually includes the name safeguard control, the Ilame




- I
I.><~:::::::::~:-·
:
__
GIOS¥~Y
i?:,:·:
.
",o-,};}
detection system. all controllers, all limits and intet-
locks, all fuel valves, the ignition system, the firing rate
conlrol system, and any other auxiliary aquipment.
FLAME SENSING ELEMENT -

see
FLAME
DETECTOR
and SENSOR.
FLAME SIGNAL - the current measured al lhe meIer jack
of
a flame signal amplifier in a name safeguard control.
The currenl
is
produced
by
the flame detector when
II
senses a flame.
FlAME
SlGNALAMPLIFIER~the
part
of
the flame delec-
tion system
'l'¥hich
increases the lIame signal
10
a
mag-
nitLJje SUfficient
to
pull in the flame
reray
In

the flame
saleguard control.
TIle amplifier may be a permanent
part
at
the flame safeguard contrOl,
or
It
may
be
a
replaceable, plug-in unit.
FLAME SIMULATOR
-a
device used
10
substitute
tot
the
presence
01
flame in a flame detection circuit
II
is
used
during trOUbleshooting, to check the performance of
the flame delection system. Flame simulators are avail·
able for use wilh rectification
or
ultraviolet amplifiers.

In
infrared systems, the flame Signal can
be
simulaled
wllh a
'l'¥ire.
FLAME
SPEED-see
FLAME PROPAGATION
RATE.
FLAME VELOCiTY
-see
FLAME PROPAGATION
RATE.
FLAMMABLE
LIMITS-the
maximum and minimum per-
centages of fuel in an air-fuel mixture that
'l'¥iU
burn.
FLAP TYPE
DAMPER-a
damper consisting of 7or more
blades, each pivoled about 1
ec:li;;;le,
and all linked
together for simullaneous operation. Also
see
OPPOSED and PARALLEL BLADE DAMPERS.
FLASHBACK-the phenomenon which occurs when a

flame front moves back through a ourner nozzle
(and
lXlSSibly
back to the air-fuel mixing painl).
FlastOa.ck
occurs because the flame
pr~gation
rate exceeds
Ihe veloCity with which the air·fuel mixlure
flows
through the ourner nozzle.
FLASH POINT
-Ihe
flash
p:::tinl
of
a liquid is an in::lication
of the maximum temperature at
'l'¥hich
it can
be
stored
and handled 'l'¥ithout serious fire hazard.
FLIP-FLOP CiRCUIT
-a
circuU which provides automatic
aitemation between 2 possible circuit paths.
FLOW CHARACTERISTICS -
see
VALVE

FLOW
CHARACTERISTIC.
FLOW
COEFFICIENT
-see
CAPACITY iNDEX.
FLOW
RATE-the
amount
at
flUid passing a given paint
per
Uf1i!
lime. Also. the luei input to a
OUrner
measured
in suitable unils; e.g
.•
cubic centimeters per minute,
gallons
per
hOur,
poundS per hour; referred to as
the
firing rate.
FLUE-a
duct or passageway for conveying
the
products
or combustion (flue

gases) to the outer air.
'"
71·97556-1
FLUE
COLlAR-the
portion of an
awliance
desl\}"leCl10r
attachmenl
of
the chimney to the 1lue pipe. Also see
FLUE PIPE.
FLUE
GAS-gaseous
products of combustion in the flue
10
the stack.
FLUE GAS
LOSS-the
sensible heat carried away
by
the
dry flue
~,
and
lhe
.~nslble
and latent heat carried
away by'the water vapor in
the11ue

gas. Also referred
10
as
stack
loss·
FLUE
PIP'e:-lhe duct connecting an appllance with the
vertical flue
or
a chimney; also called breaching or
~
cQlJneclor. (A flue collar is the part
01
the
awliance
10r
attaching the flue pipe.)
FlUID-'f3l"ly Slbstance that can
flow:
I.e., move and
char'lQe
shape without separating when
uroer
pres-
sure;
1iQ.lld
or gas.
FLUID POWER - Honeywell trademarl< tor the actuators
used wllh V5055 InckJstrial Gas Valves to provide a
1amlly

01
aulomatic safery
shuloff
valves; driven
by
a
1luid (usually oil)
PJmpec:I
by
an electtlc motor.
FORCED·AIR
FURNACE-a
central furnace equipped
with a
'Ian
or blower to provide the primary means for
circulation
01
air.
FORCED DRAFT -mechanically-produCed airflow into
and through the combustion chamt:er, blown in
by
a
fan or blower locatoo at the inlet air
passage
to the
furnace. This air movement minimizes problems resull-
ing from insufficient stack. wind. weather,
and other
conditions.

FORCED·DRAFT BURNER
-a
gas burner in which com·
bustion air is blown in
by
a molar driven Ian. Commonly
called a Power Burner. Examples are Aspirating. Gun
Type, Mect)anical·Premix,. and Zero-Governor
Burners. Also see MECHANICAL·DRAFT BURNER.
FORCED·DRAFT
FAN-a
1an
or blower that
sUI=PlieS
air
under pressure to the fuel burning equipment.
FORCED VENTILATION - mechanically prodJcad air·
flow
throug,
a
room
or M area.
FREQUENCY - the number
of
recurrences
of
a periodic
phenomenon in a unit of lime, usuallv expressed
In
hertz

(Hz).
FUEL-any
material which is burned
10
SUl=Ply
heat or
power.
FUEL-AIR
RATIO-see
AIR-FUEL RATIO.
FUEL
OIL-any
hydrocarbon oil as defined
by
Commer-
cial Standard CS12 or ASTM 0396-1969.
FUEL
RICH-the
ratio of
air
to fuel
SUl=Plied
to a furnace
which
prOVides
more tuel than the optimum air·1uel
ratio.
FUll
LOAD-the
greatest load a piece

of
equipment is
designed to carry under specified conditions.
FURNACE
-an
enClosed chant:ler or structure, including
a burner end cOlTtlustion chamber, which
Is
provided
tor the colTt:lustlon
01
fuel. The heat
prodJced
Is
used
tor healing
a building or for processing materials. Also
see BATCH TYPE, CENTRAL. CONTINUOUS,
DOWN FLOW, DUCT, FORCED-AIR, HORIZONTAL.
INDUSTRIAL and UPFLOW FURNACES.
FURNACE
PRESSURE-the
gauge pressure in a furnace
combustion chamber. The furnace pressure is said to
t:e
~
tt
greater than atmospheric pressure,
[l~:
J jyj,

tf less than atmospheric pressure, and
~
i1
ElQJ81
to atmospheric pressure.
GAS-the
fluid form of a SlhSlance
In
which
It
cen expand
indefinitely
a~
COrTPle1ely
fill Its container; 10rm that is
neither liquid nor solid;
a
vaj.X)l";
any mixture
01
inflam-
mable
gases used for lighting or heating. Also see
BLAST FURNACE, FLUE, UOUEFIED-PETROLEUM,
MANUFACTURED, MIXED, NATURAL, and ZERO
GAS.
GAS
BURNER-a
burner
10r

use with gaseous fuel. Also
see ATMOSPHERIC, MECHANICAL-DRAFT, RAW
GAS, PARTIAL-PREMIX, PREMIX. INSHOT, and
UPSHOT BURNERS.
GAS
MIXER
-a
device
10r
mixil"l;;l gas and air. such as a
1an,
aspirator, or inspirator.
In
an injection type burner,
it is the combination
01
mixer head, mixer throat, and
mixer tube.
GAS-OIL
BURNER-a
burner capable of burning either
gas or
oil-some
types can burn both simultaneously.
Also
see COMBINATION BURNER.
GAS-PRESSURE
REGULATOR-a
device for controlling
and maintaining a uniform gas pressure.

GAS VENT
-the
piping end
Mings
used to convey flue
gases to the outside atmosphere.
GAUGE
PRESSURE-the
difference between atmos-
pheric pressure and [he absolute pressure
t:einlOl
measured; abbreviated: psig.
GLOBAR-a
conductive ceramic 1rom which high tem·
perature flame rods are made.
It
has a maximum tem·
perature rating of 2600 F [1425 Cl.
GRACE
PERIOD-the
lime required to build
up
an
explO-
sive charge in a burner; the maXimum lime the
unigniled cOn"Oustible reactants can salely
be
pul
into
aOO

retained
in
a combLstion chamber.
GRADES OF FUEL
OIL-voluntary
commercial stan-
dards recommended
by
the U.S. Bureau of Standards
for dlnerenl classi1icalion
of
fuel oils, based on charac-
teristics such as
speCifiC
graviry
and
viscosity.
GRAVITY FEED-sul=P1ying oil to a burner from a graVity
tank. using the force
of
graviry.
342
GROUND-a
metallic connection with the earth
10
estab-
lish 't!round potential.
G!.Jlp!; see
VALVE GUIDE.
GUN TYPE

BURNER-a
power
burner in
w!""lch
a fan, or
blower,
blows
air al high velocity past lurtlulators. The
gas, at regulaled pressure, is released into the turbu-
lent airstream
-typically
Irom a ring at Ihe mouth of the
purMer (in which case
it
is also called a Ring Burner).
The
'tJ3S
es~s
through orific85 around the periphery
at,lhe ring. Gas
03:nd
air
are adjusted simultanElOllSly to
maintain Ihe proper air-fuel ratio as the firing rate
changes.
In
Hiah-Pressure Gun Burners, the gas is
ejected al pressures
l4)
to 15 psi from

spuds
located
in
the
center
of Ihe turbulent airstream instead of
at
the
putside. Also see FORCED-DRAFT
ancI
RAW GAS
BURNERS.
HEAD-see
BURNER HEAD.
HEADER - a manifold or supply pipe to which a nurrber
of
branch pipes are connecled.
HEAT
BLOCK-insulation
material installed between Ihe
cell mount
of
an infrared flame deteclor and
the
sight·
in't! pipe to reduce heat conduction to the cell.
HEATER-an
apparalus for giving heal or warmth; a fur·
nace, oven, stove, radialor, or similar device. Also
see

AIR, BOOSTER, CENTRAL. DIRECT·FIRED, EXTER·
NAL, INDIRECT-FIRED, INTERNAL, MAKEUP AlR.
RADIANT·TUBE TYPE. SPACE,
ancI
UNIT HEATERS.
HEAT
EXCHANGER-any
device tor trans1erring heat
trom
ono
rn9dium to another. A direct heat exchanger
is a self-contained device which transfers heat gener-
ated in the combustion
charmer
directly Ihrough lhe
walls
of
Ihe heat exchanger to lhe heatin;t medium.
An
Indirect heat exchanger contains a heatin't! medium
and Iransfers heat
10
anolher mediurn separately con-
rained in close cbntacf with
or
directed through the heat
exchanger.
HEATING
MEDiUM-air,
sleam. waler, or

~heal
transfer
f,uids - used
10
trans1er heat.
HEATING
SURFACES-all
surfaces which Iransmit heat
direCtly from the flame or flue
gases to
lhe
medium
ba-
ing
heated.
HEATING
VALUE-
the heat released
by
the combustiOl'l
01
a unit quantify
of
a fuel, measured in calories or Btu.
HEAVY FUEL
OIL-gradeS
5
and
6,
used in commercial

and industrial burners; generally rsquire preheating.
Heating values range trom
146,600 {o 155.900 Blu per
gallon.
HERTZ (Hz) - a unit
01
frequency equal to 1 cycle per
second.
HIGH
FIRE-the
maximum
liring
rale
of
a burner
Of
furnace.
HIGH FIRE
INTERLOCK-an
Interlock which proves-the
damper
Is
open for prepurge.
HIGH FIRE
SWITCH-see
HIGH FIRE INTERLOCK.
HIGH
UMrr
- a controller which shuts down the
SYSlem

il
a condition exceeds its maximum value tor safe
~a
tion. See UMIT.
HIGH-LOW
FIRE-provision
in a burner tor either of 2 tlr-
in't!
rales, high
or
low (no rale in between), selected
ac-
cording to load demand
by
lhe
firing rate controller. A
system is normally wired for guaranteed low fire start.
HIGH PRESSURE BOILER
(hoi
waler
or
sleam)-a
boiler
fumishing
hal
water
al
pressures in excess of 160
pounds per
SQUare

inch (psig)
or
atternperatures
in
ex·
cess
of
250 F [121 C]; a boi!er fumishing steam at pres-
SlJres
in
excess
of
15 psig.
HIGH-PRESSURE GUN
BURNER-see
GUN
TYPE
BURNER.
HIGH PRESSURE SWITCH
-see
PRESSURE SWITCH.
HIGH TEMPERATURE BOILER
(hoI
waler)-a
boiler fur-
nishinQ hot water at temperatures exceeding
250
F
1121
C]

or at pressures exCeeding 160 pounds per
square inch
(psig.
HIGH-VOLTAGE CiRCUIT
-a
circuit inVOlving a polantial
of
more than
600
volts: not defined
by
Underwrilers
Laboratories Inc.
HORIZONTAL
BOILER-see
WATER-TUBE BOILER.
HORIZONTAL
FURNACE-a
forced-air, central furnace
desi~
with essentially norizontal airflow.
HORIZONTAL·RETUAN·TUBE (HRT)
BOILER-see
FIRE-TUBE BOILER.
HORIZONTAL ROTARY OIL
BURNER-see
ROTARY
OIL BURNER.
HORSEPOWER
(hpj-a

unit
of
power
eqJalto
550
bJt
pounds per
secord,
33,000 foot jXlUnds pel miAJte,
Ot'
746
watts.
HOT
UNE
- incoming, live (not Qrounded) wirers) used
10
power a device, usually designated L
1.
HOT
REFRACTORY HOLD-IN TEST
-a
tesl,
tor
a
name
safaQJard control using a rectifying pholocelf, a
cad-
miUlTl
sulfide cell,
or

an Infrared flame detector, to
make certain thai hot refractory
will not
cause
the
name
relay
10
stay pulled
in
atler
the
burner
flame !;PBS oot.
HOT REFRACTORY OVERRIDE TEST
-see
HOT
REFRACTORY SATURATION TEST.
HOT REFRACTORY SATURA110N TEST
-a
test, tor a
nama
safeguard control using
an
infrared flame delec-
lOt',
to
make
cenain that radiation
trOll

hal refractory
ooes
nol
mask Ine fliCkering radlalion
c1lhe
nama it-
self. Also called HOT REFRACTORY OVERRIDE
TEST.
71-97558-1
IGNITER-any
electrical
or
macranical
device and
re-
Imed equipmanl used
10
I~n\te
a fuel-aIr
midure.
Also,
a
burner
(like a pilot)
USing
gas
or
01110
ignite very large
gas,

Oil,
or
pulverized coal burners In very large waler'
tlbe
boilers [normally field-erected).
IGNmON lhe
acl
of
starting c(J('l'i)usllon. Also see
AUTOMATIC, CONTINUOUS, DIRECT SPARK,
ElECTRIC,
INHERENT, INTERMITTENT, INTER-
RUPTED,
MANUAL
PROVED, PROVED SPARK,
TO~€?H,
and
UNPROVED IGNITION.
IGNmON'ELECTRODE-a
metal
conciJctor
USOO
[ogan-
erale a spark across a
narrow
gap to grl:JJnd in order to
IlJl1ite
a fuel·air m'lxlu'8.
IGNlT10N
INTERFERENCE-

electrital noise, caused
by
ignition currant feeding
Ihroug,
the flame
10
the llama
rod,
which
is
superirrposed
on the
f1ame
si~1
~Iame
rod detectors only).
lhe
interference may be ad:::lilive
or
subtractive.
(II
may increase or decrease the flame Sig-
nal.) S!.btractive interference may cause the flame (e-
lay to drop
out; severe addilive interference may
damage
Ihe
flame relay unless
an
arc gap protector is

In
lhe
circuij.
IGNFTlON1NTEAFERENCE
TEST-a
test to make
certain
lhal
ilJl1ition current
is
not
interfering with the
prcper q::.eralion
of
a flame rod.
See
IGNITION
INTERFERENCE.
IGNITION
RETURN-immediate
restoralion
of
ignilion.
without pr",ignilion
purging
or interlock checks,
af1er
loss
of the rn.a,in'burnef flame.,lf
Ihe

main burner flame
is
not
re-established, safety shutdown occurs. Also
called~.
lGNmON
SPARK RESPONSE TEST
-a
lest for a
flame'
seleQ.Jard conlrol
using
an
ultraviolet flame detector, to
make,certaln lhat the
ignition
spark
Is not actuating the
trame
relay.
IGNmON
TEMPERATURE-lhe
minimum lemperature
al
which
combuStion becomes self-sustaining.
IGNITION TIMING
-a
period
of

lima
during which ig"liliOn
flleans are on.
This
provideS a means or eslablishing
a"'ld
stabililing
Ihe
flame to ensure prq::.er burning
of
lhe
fuel when the main burner is firing.
IGNmON
TRANSFOAMER-a
deviCe which prOVides a
hig,-voflage
spark which will cause Ignition.
IGNmON TRIALS
-a
period
of
lime
wring
which the pilot
and main
tlJrner
musl
be
Igliled
(main bUrner only If

t.sIng direct spark Igr'lmon).
Also
see PILOT FLAME-
ESTABUSHING PERIOD
and
MAIN BURNER
FLAME·EST
ABUSHING
PERIOD.
'.
IGNITION
VelOCITY-sea
FLAME
PAOPAGAllON
RATE.
IMPELLER
-a
series
of
rOlatlng blades
or
vanes similar to
(he old-fashioned paddle
wheel. In an cpen Impeller,
the impeller blades rolale betW88'l the stationary walls
of
the blower rousing. The walls
lend
to channel the air
so

that most of
il
fiows out through
the
lips
of
the
blades,
bul
some aIr stips out
slOOways
from
be/ween
the bladeS end short-circuits
baCk
10 the impeller inlet.
A closed lf1l)eller
has
tover
plate discs
allachsd
/0
lhe
sides
of
the
blades, and thus short·circuiting is
minimized.
INCANDESCENCE-the
state

of
a malerial
with
SUCh
a
hiOh
t~ra/(J(e
tnat it gives
off
fight.
INCH
OF
MERCURY
-a
,il
of
p-essure aqual 10 the
pressure exened
by
a column
of
mercury'
InCh
high at
568 level
and
at
a
t~rature
of

0 C
132
FJ,
INCH OF
WATER-a
unit
of
pressure equal to the pres-
sUfeexerted
by
a column
ot
liquldwaler
1 inch high at
sea level
anc:l
at
a t9l"fl)8rature of 4 C (3S.2
F]
.
INCOMPLETE
COMBUSllON-cort'tlustion
in which the
fuel is only partially t:lJfnecl
and is capable
of
being
bUrned further
under
P'~

cordilions.
It
results from
an
inadequate amount
of
air
for
the c,.Jantity
of
fuel pro-
vided. II cen
also
occur, even in excess air conditions,
if
mixing is poor
andlor
the flame
is
chilled below Ihe igni-
lion
tef1l)erature before
lhe
full combustion reaction
can take place.
An
example
Is
lhe
burning

of
carbon,
prodJcing carbon monoxioo
(CO);
with
mora air, car-
bon
dioxide (CO.)
WOUld
result.
INDEPENDENT
UGHTOFF-separate
ignition of each
burner in a multlburner
syslem. Each burner can
be
started up
or
shut
down
by
itself.
INDIRECT·FiRED
HEATER-a
heater in which the prod-
ucts
of
combuStion
(flue
gases) are not lTlixed with the

medium
being
healed.
AlSO
see
INDIRECT-FIRED
EXTERNAL, INDIRECT-FIRED INTERNAL.
lind
R;z.,::llAN'T-
TUBE
TYPE
HEATEAS.
INDIRECT-FIRED EXTERNAL HEATER
-any
oven
heal-
ing system
in
which
the oven
all1lOSpl18re
is kept sepa-
rate
from
the combustion gases,
and
in which the
burners and cornbus!ion chamber are outside
at
the

oven chamber. There are
3 types;
1.
Recirculaling-oven
atmosphere is returned to
tM
heater to be reheated.
2.
Nonrecirculaling-ovan
atmosphere is not
re-
turned
10
the heater.
3 Internal
radialOl-prCducts
of
corrbuslion
from
the heater are circulated through radiator tubes
located wiThin the oven chamber.
INDIRECT-FIRED INTERNAL HEATER any oven heal-
Ing system
in
which the oven
allT'QSphare
is kepl sepa-
rale
from
the combustion gases,

anc:l
in
which the
burn&rs are conlainea In
gas-ti~t
radiators within the
oven chamber. Thera are 2
~;
1.
Explosion resisting-constructed to withstand
explosion pressure from ignition
01
a gas'air mix-
ture in the radiators.
2.
Nonexploslon
resisting-with
gas·tighl radialors
which are
not designed to withstand
an
internal
explosion.
INDUCED
AIR-air
which flows
inlO
a furnace because
the furnace pres:;ure is less than atmospheric pres-
Sure.

This includes air brought inlo (I. furnace by
emr(l.inmenl'
in'
a high velocity stream.
INDlk::ED DRAFT
-air
movemenl into and through the
combustlon chamber
(l.nd
breaChing, procluced by (I.
pa;ni(l.1
vacuum within the cot1"tluslion chamber crealed
t/IJ
a
fan
althe
outlet
of
the chamber.
INDUCED-DRAFT
BURNER-a
gas burner which
uses
an
induced
dr(l.ft
to bring in combustion air. Also see
INDUCED DRAFT and MECHANICAL·DRAFT
BURNER.
INDUCED-DRAFT

FAN
-a
fan
or
blower that
proc:k rces
a
nega.tive
pressure
In
the combuslion chamber, causing
(I. suction which draws in air.
INDUCTIVE
LOAD-a
lagging load: (I. 103d'that is pre-
dominantly inductive, so that the alternating current
lags behind the allerrlating vollage,
i.e.,
the current
does not change direction until after the
vOltage
does.
An
example is an ignition transformer.
INDUCnVE
PICKUP-the
generation of a voltage in one
conductor
t/IJ
induction- from another nearby

conductor.
INDUSTRIAL
FURNACE-a
process type heater which
changes the charaC1erlslics
of the material being proc-
essed.
II
Is
usually
C1J6rated
at
temperatures above
1200
F.
INDUSTRIAL
OVEN-a
process type healer normally
used for drying.
It
is generally operated at
terf1)Elra-
tures from 400 F to 800
F.
INERnNG-introclucing
an
Inen medium inlo a furnace,
pulverizer,
or
other enclosure to reduce the

~
content of the resuJllng mixture below the limits
01
nammabilily.
INERTS-noncombustible substances in a fuel.
INFRARED FLAME
DETECTOR-a
detector lhat
re-
sponds to Ihe infrared radiation (wavelength between
0.75 and 1000 microns) emitted by a flame. Also see
LEAD SULFIDE
CELL
INFRARED
(IR)
RADIAnON-invisible,
electromagnetic
waves
ot
tow frequency (long wavelength between
0.75
and 1000 microns). They are generated by thermal al;li·
tation and radiated
t/IJ
everything with a
terTf.lElralure
above absolute zero [minus 273 C); the holler the
c:tr
ject, the greater Ine Infrared radiation. Infrared radia-
tion corrprises about

90
percent of the light spectrum,
ranging from the low end
up to Ihe while visible light
range. Also see HOT REFRACTORY HOLD-IN
TEST
and HOT REFRACTORY SATURATION TEST.
INHERENT
IGNITION-feed)ack
of
pan of the heat
gen-
erated by the flame
10
1't1"lte
more
of
the combustible
mixture; il must
!<eep
lhe fire going after l't1"ition
Is
terminated.
INJECTION
BURNER-see
INS
PIRATING BURNER.
INPUT COMBUSTION
CONTROL-see
FIRtNG

RATE
CONTROLLER.
INRUSH-in
a solenoid or coil, the steadV-state current
drawn from the line when the armature is
In
its maxi-
mum cpen position. Allowable Inrush can be
up to 10
times the pilOI
ci.Jly
rating (running currenl).
INSHOT
BURNER-a
gas
burner
In
which the
gas
is
delivered from lhe side(s)
of
the cot1"tluslion chamber,
resulting in a horizontal flame.
INSPIRAnNG
BURNER-a
gas
burner which uses
ven-
turi action to bring in combustion air. Also called

an
Injection Burner or Venturi Mixina Burner. Also see
ATMOSPHERIC BURNER and VENTURI.
INSPIRATOR
MIXER-a
mixing device in which a jel
01
gas is used to entrain primary air at a rate proportional
to the
gas
flow rate. Also see INSPIRATING BURNER.
INTEGRAL
TANK-any
fuel tank furnished by the
manu-
facturer
as
a
comfX)OEl(ll
part
oflhe
complete
assem-
bly; eilher allached [0 the
awliance,
cr
intended for
separate mounting adjacent to the
awliance.
INTERLOCK-an

automatic conlroUer
or
switch
whiCh
monitors the physical state of a
rElQJired
condition and .
furnishes proof to the tlame safeguard control fhalthe
condition is proper for burner operation
to
start
or
to
continue. Also
see
HIGH FIRE, LOCKOUT,
LOW
FIRE, PREIGNlnON, RECYCLE, RUNNING, START,
and
VALVE-CLOSED INTERLOCKS.
[NTERMITIENT
IGNITION-ignilion
t/IJ
an
ener~
source
Which
is automallcally energized each time there is a
call for heat,
and

which Is maintained ciJring the entire
run periocl. This ensures that a means
of
igniting the
In-
coming fuel will always be present.
INTERMITIENT PILOT
-a
pilot automatically ignited
each lime there is a call for heat and maintained
CiJrlng
the entire run periocl.
It
is shut
off
with the main burner
at
the end
Of
heat demand.
INTERNAL
HEATER-a
heater in which Ihe burner(s)
and
combustion cl"\arl1)er are within the oven charrber
and
in contact with the medium being heated. Also see
01·
RECT-FIRED INTERNAL and INDIRECT-FIRED
INTERNAL HEATERS.

INTERNAL-MIX OIL BURNER
-see
ATOMIZING OIL
BURNER.
INTERRUPTED
IGNmON-iglilion
t/IJ
an energy source
Which
is automatically energized each lime there
i5
a
345 7'-97558-1
eel! for heat,
and
cut off automalically after ftame Is
proved or at the
end
of a predelermlned lime.
INTERRUPTED PILOT - a
pilei
automalleally Ignited
Mcn
lime
there Is a call
for
heal
end
cul
off automati-

cally at
lhEl
end
of the maIn burner ftame-establishlng
period.
IONIZATION - a
proc~
by
which electrons are detached
frO'lTl
atoms
or
molecules,
tnus
originating ions and free
elEiclrons.
Thi~
is
achieved
by
collisions or
by
high-
Eine~~
radiation.
IRIS
SUDE-a
thin plate with a small aperturEi. Example:
the Yti13A Stack Smoke Deleclor provides a selection
of

iris slides
wilh
dltl"rent
sized apertures to permit
1i~1
source-to-sansor distances of 1-1{210
10
feet.
,',.
ISOLA-lED
UMllED
SECONDARY CIRCUIT
-a
circulI
of
limited energy derived
from
an i$Olaled secondary
winding of a transformer having a maximum capacity
Of
100 voll-arrperes
011<:)
and
an open circull secondary
\IOrtagE!
raUng
not
exceecMg 1000 Volts.
JEWF
All.OY

"K~
- a chromium-aluminum
aUoy
iron
wire which is
resislanlto
OXidation
up
to 2200 F [1200
CJ;
used for flame
(<Xis
in
flame detectors.
JUMPER-8
short length of wire used to complete a
cir_
cuit temporarily or
10
bypaSS par!
of
a circuil. Also, the
aclion of using a jumper.
KANTHAL
A-l-a
staInless Sleel alloy used in the manu-
facture of flame
rOds.
II has a mal(imum continuous
cperating temperature

raling
of
2462 F [1350
C].
KNOCKOUT - a removab'le portion in the side
of
a bol( or
cabinet During Installation,
it
can
be
readily taken out
with a hammer, screwdriver, or pliers
so
wires, cables,
or fillings can
be
allached.
LA-RGE
PORT
BURNER-see
SPREADER BURNER.
LEAD SULFIDE
CEll an
infrared sensor using lead sui·
fide
(PbS)
as the sensing matarlal. The resistance
of
lead sulfide decreases when exposed

10
infrared radia-
tion, resulting in Increased current now.
lEAKAGE
PATH-a
palh, norma:ly
01
high resistanCe,
through whict] an undesirable slray current (leakage
current)
flowS
to ground; caused
by
buildup
of
mois-
ture,
5001, or accumUlated dirt.
LEAN
MIXTURE-an
air-fuel
mixlure
In which an el(cess
of
air
Is
SLflPlied in
pr~rtlon
10
the

amounl
01
fuel.
Also
see
AIR
RICH.
UFT
-valve
slam travel.
UFTING FLAMES - flames which lift from
or
blow
off
llle
pilot or main burner ports.
Caused
by
an overrating of
lhe burner, too hard a primary air adjustmenl, or
bolh.
UGHT
FUEL OIL - grades 1 and
2.
which are distiHate fuel
oils
used
predominantly in
etmeslic
heating equip-

ment. Heating values range
from 132,900
to
141,800
Btu per gauon.
UGHTOFF-
the proceciJre of igniting a burner or sysfem
of
burners. Also see INDEPENDENT, SEQUENTIAL,
and UNISON UGHTOFF.
UMlT
-a
control/er which continuously monitors a condi-
tion (such as temperature, pressure, or liquid levet) in a
conlrolled medium
arv::l
rBSjX)rw:iS
Immediately to shut
down
the system
~
a dangerous, predelermined condi·
tion occurs.
II
is
normally set
beyOnd
the operatinQ
rang& of the coni rolled equipmenl.
LIMIT

ACTION-the
contacls of a limit controller
~
to
shut down a burner
(ard
in
some instances make
an
alarm circuit) because of an abnormal
or
unsafe
condition.
UNE-acolloquial-lerm
for
poW91
line; the cQr'ductors
carrying
powEir
from
llle
generating equipment.
LINEAR
CHARACTERISTIC-a
valve flow Characteristic,
apprQl(imaling a
sltaigtlf
line
relationsh~,
which

ra-
SllUS
In
equal volume Changes for equal movements of
the valve stem, regardless
of
the perCentage or valve
cpening.
LINER-see
RADIATION SHIELD.
llNE-
VOLTAGE CiRCUIT
-a
circuit involving a poten-
tial of more than
30
valls and
tess
than
600
volts (gener-
ally
120
or 240 volts ac). Underwriters la!:oratorias
Inc.
a/so catls
thiS·
at1igh-vouage
circuit
LINING

-Ihose
interior surfaces
of
a cotT1l:lJslion cham-
ber which are exposed
10
combustion during use
of
the
device.
LINKAGE-a
mechanical arrangement for lrans1errirQ
rootion in a desired manner, conSisting
of
SOlid
pieces
with movable joints.
The connections Ihrough which
ij"I
actuator opens. closes,
or
positions a valve
or
damper:
usually consists of a push roo, 2
crank
arms, and 2 ball
pints.
LJQUEFiED-PETRQlEUM
(LP)

GAS
-fuel
gases. inch.n-
ing commercial propane /predominantly propane or
propylene)
or
commercial bulane (predominantly
bJlane, isobulane,
ar4Ior
butylene), which
ar<a
sold
in
metal bollies under pressure as a liquid and called
bOt-
tled cas. These gases are higher hydrocarbon gases
346
normally obtained
asa
by-product of oil refineries or by
stripping natural gas.
LIQUID-the
fluid form of a subslance in which
it
can

assume the form of Its container while retainIng ils
independent volume; form lhat is neither
gas
nor solid.

LOAD
-the
actual instantaneous outpul rale
of
a boiler;
also, the power. consumed
by
a machine or circuit In
performing Its function. A device that
absorbs power
,
andconvetls
it into lhe desired form. The impedance to
which energy
Is
being S\.Wlied. Also
see
CAP
ACInVE,
FULL, lNDUCTIVE, and NET LOAD.
LOAD RELAY
-a
relay in a name safeguard control circuit
that starts the burner operating sequence.
LQ.CKED
ROTOR-In
a molar, the steady-state current
laken from the line while the rotor
Is
locked and the

rated voltage (and frequency in alternating current
m0-
tors) is applied to the motor. Allowable locked rolor cur·
rent can
be
up
to
6 times the full load rating.
LOCKa
lIT
-see
SAFETY SHUTDOWN.
LOCKOUT
INTERLOCK-a
running interlock
usee!
with a
primary or programming control which will cause safety
shutoown (will not recycle) il an improper condition
occurs. The interlock may
be
a combuStion air con-
troller {airtlow switch) or a fuel pressure switch.
See
RUNNING INTERLOCK.
LOCKOUT SWITCH
-a
lime delay device in a Ilame sate-
guard control which trips and locks out the control
(safety shutoown) if improper conditions occur.

It
must
be
manually reset
to
restart the system.
LOCKOUT SWITCH
TIMING-the
length
of
lime (usually
15
or
30 seconds nominal) that the heater in a lockout
switch must be energized before if causes the switch to
trip
1PoP.
out).
LOCKOlIT
TIME-the
time a flame safeguard control
takes
10
be
electrically inoperative.
see
LOCKOlIT
SWITCH TIMING.
LONG FLAME
8URNER-a

burner which purposely
has
fXlOr
mixingo(fuel
and
air"(using secondary air only)
so
thai the fuel lakes more time to
bum,
thus prcrl.Jcing a
long,
ll.lmir'lOl L9
flame. Also called a Diffusion Flame
.ewmtL
Luminous Flame Burrer, or Yellow Flame
6l.m.eI. Also see DELAYED MIXING.
LONGITUDINAL-DRUM
BOILER-see
WATER-TUBE
BQILER.
LOUVER TYPE
DAMPER-a
damper consisting
of
several blades, each piVO!ed about its center, and all
linked together
for
slml.lllaneous operation. Also
see
OPPOSED and PARALLEL BLADE DAMPERS.

LOW
FIRE-the
mlnlrTl.lm firing rate
of
a burner
or
f\Jrnace.
LOW FIRE
INTERLOCK-an
Interlock which proves
the
damper is closed prior
10
I""ition
trials.
LOW FIRE START
-Ihe
firing
of
a burner with the
ft.JEl1
controls in a low fire position
to
provide a minimum
of
incoming fuel Irom the main fuel valve(sj to give a
smooth start
and
to provide a safe operating condition
ci.Jrlng 1ig,loff.

In
a system with guaranteed low fire
start, interlocks are used
to
prevent
start~
if the
burner is not in the low fire
slart
position,
LOW FIRE START/HIGH FIRE
RUN-operation
se-
QUence
in which the burner starts in the low fire posi-
tion. After the flame is proven, !he bUmer goes
to
the
hiQh
fire rate for the duratlon
of
the run period.
LOW FIRE
SWITCH-see
LOW FIRE INTERLOCK.
LOW-HEAD
BOILER-see
WATER·TUBE BOILER.
LOW-HIGH-LOW
PREPURGE-a

prepurge period
ci.Jrlng
which the air damper is driven
open
for the purge pe-
riod
ard
then back to low fire position fur the burner
Iig,toff. This is called LOW-HIGH-LOW PRQVEN
PREP URGE if suitable interlocks indicate that
me
damper actually reached the open position
dUring
prepurge,
and
then closed again before ignilion trials.
LOW UMIT
-a
controller which shuts
oown
the system ifa
condition
dl"~
below its minimum value for safe
operation.
See LIMIT.
LOW OIL TEMPERATURE
SWITCH-a
temperature
actuated device arranged to effect the safety shutcbwn

of
a heavy oil burner or to prevent it from starting
when
the
ft.JEl1
all temperature falls below the limits required to
maintain the Viscosity range recommended
by the
burner manufacturer.
LOW
PRESSURE BOILER
(hOt
water or
steam)-a
boiler
furnishIng
hoi water at pressures not exceeding
160
pounds per square Inch (pSig) and at temperatures not
more [han 250 F
{121
CJ
; a boiler f\Jrnishing steam al
pressl.lres not more
than 15 psig.
LOW PRESSURE
SWITCH-see
PRESSURE SWITCH.
LOW-VOLTAGE CIRCUIT
-a

circuit involving a potential
of
not more than 30 volts ac (42.4 volts peak) or
30
valls
de
in which
lhe
cl.lrrent is Sl.WlIed
by
a primary battery
or
by
a standard Class 2 transformer
or
other suitable
transforming device,
or
by
a suitable
CQI1'tllnation
of
Irans10rmer and fixed Impedance having the output
charaeterisllc.s
of
a Class 2 transformer. A circuit
derived from a line-voltage
or
a high-voltage circuil,
by

connecting series resistance
to
limit the voltage and
currenl, is
!:!Qt
considered to be a low-voltage circl.lil.
LOW WATER
ClITOFF-a
device
to
shu!:
down
the
burner when the water level in a boiler falls
to
a pre-
determined, dangerously low level.
LP
GAS-see
UQUEFIED-PETROLEUM GAS.
LUBRICATED PLUG
VALVE-a
manual
shuto1'l'
valve
with a tapered plug, which uses a
ILbricantto
t'ryQ'aull-
cally
Uft

the
plug
from Its seat and to seal the valve
against leakage
10
lhe
closed position.
LUMINOUS FLAME
BURNER-see
LONG
FLAME
BURNER.
347
11-91558-1
MAGNETIC
VALVE-see
SOLENOID VALVE.
MAIN
AIR-see
COMBUsnON
AIR.
MAIN Ei.URNER-lhe burner
(as
Olslingulshed from the
pilot ,burner)
which
delivers fuel to the combustion
chatTlt:le:r
(and
mixes

iI
wilh
air) where it
is
burned to
provide heat to the deSired space.
MA!N BURNER FLAME·ESTABLISHING
PERIOO-the
period
01
time In ig"lltloo trials curing which the flame
safeguard control permits the
main fuel valve(s) to be
qB1befOfe
the flame detector
is
requirGd (0
detectlhe
maIn
burner
flame.
MA!N
CIRCULAnNG
LOOP-Ihe
section of
an
all han-
ding
syslem which delivers the oil from storage
to

the
branch circuits and relurns the Uflusaa
all
to
the slor·
age tank.
MAlN
Ft.AME
TRIAL-see
MAlloJ
BURNER FLAME·
ESTABUSHING PERIQQ.
MAlN FUEL
VALVE(S)-an
automatic,
or
marual reset,
safety
shutoff valve/s} l'Itlich control.; the tuel input to
lhe main burnar
ana
is energized
by
the flame
saf~
~rd
contlOI. Also
see
MANUAL RESET, MOTOR·
JlE.l?,SQL~NOI9,

,and
SAFETY
SHUTOFF VALVES.
MAKEUP AIR
HEATER-a
heater which raises the tem-
peralure
of
ouldoor
ait
thai
is
brO<JghI
into
a building
10
compensate
for
air
removed
by
exhausl
taIlS
or
by
other methods.
MAKEUP
WATER-water
which
is ad::led to a boiler, tank,

Of
some
ol~r
container to (eplace water whiCh has
beEw11os1,
thus mainlaining the prcper waler level.
MANIFOLD-a
pipe
with 1 inlet ano several outlets
or
with
1 oulle!
and sev&ral
;Me!S,
for
connecting with
olher
.
pipes. In a mulllb Jrner system, the duct which distrib-
utes
fuel to the indillidJal burnels. Also
see
HEADER.
MANIPULATED
VARIABLE-that
CJ.Wltity
or
condition
which is regJlaled
by

lhe
automatic control system in
&uch a
mant'lEl!r
thai
if
causes fhe desired change in the
controlled
~ariable.
The
manipulated variable
ts
a char·
acteristic
C1f
the control agent.
MANOMETER-an
instrument, usually a U-shaped tube,
lor mGasuring the pressure
of
gases
or
vapors. A col-
umn
of
inGOITpfesslble
liQUid,
SUCh
as
mercury. is dis-

placed an amounl proponional to the magnitude
of
lhe
gas pressure.
Thus
the heiQht
01
the column indicates
(he pressure.
MANUAlIGNITION-ignilion
by
an
enerw
source which
is
manually energized,
ano
wnere the fuel
10
the main
burner is turned
on
only
by
hano
and
ig;iled
under
supervision
at

the
~rator.
MANUAll.
Y IGNITEO BURNER
-a
burner
in
which fuel
to themain
burner is
fUlnadononly~
hand
and
ig"lited
under supervision.
MANUAl RESET
-Ihe
manual opera/ion req.dred after
safety shutdown before the system can
be
restarted.
MANUAL RESET
VAlVE-a
safety
shuloff
vallo'&
which is
opened
manually and held
in

the
~n
position electri·
cally or pneulT'lalically.
It
is
closed automatically
by
the
control
S)ISIem
and
cannot
be
q::aenad
me.nuany
until
power is restored
by
the control system.
MANUAl
SHUTOFF
VALVE-a
manually q:lBrafed valve
in
afuelline
(main
or
pilot) for
Ihe

purpose
of
cOlTpletely
turning
on
or
shutling
at! the fuel supply. Also see
LUBRICATED PLUG VALVE.
MANUAL START
-the
burnar is staned
by
~rator
ac-
lion,
&uch
as
pushing the
stan
bullon
on
a controller;
sometimes r9QJired
by
local
codes
10
ensure that
an

cperalor is actually presem at
stan~.
MANUAL
SYSTEM-a
system which
rElQJiras
811
manual
cperalions; a system in whiCh the
burner
is
purged.
started. iQlliled,
secpenced,
modUlated,
and
slopped
manually.
MANUFACTURED
GAS-a
gas made aniflciaUy
for
U6EI
as1uel; made
by
the distillation or cracking of oil or coal,
by
the steam-carbon rGaclion,
or
Dt

combinatlons
at
these processas. Examples are coke
oven
gas
and car-
buleled waler
gas.
MASTER FUEL
TRIP-a
device
for
rapid automalic shu!-
off
01
all fuel, including ig"liters; may have manual
or
automatic initiation.
MASTER SWITCH
-the
manual switch through which
power is applied to a flame
safBlJUarO
contrOl; the prln·
cipal disconnect means. Also called a
DjScoQ,1ect
Switch.
MECHANICAL
ATOMIZER-a
device

which
brooks fuel
l.4=l_
inlo tiny drq:::.lets without usinc
an
atomizing
me-
dium.
Also
see
ATOMIZER.
MECHANICAL-ATOMIZING OIL
BURNER-see
ATOM-
IZING OIL BURNER.
MECHANICAL DRAFT
-the
pressure difference, created
b)I maChinery such as a fan
or
blower, sufficient to
sLPPly
all, or
pan
of. lhe reqJired combustion
aJr
into
the
COr'1"tJustion
chamber. Also see FORCED and

INDUCED ORAFTS.
MECHANICAL·DRAFT
BURNER-a
gas burner retying
Otl machinery
10
bring
in
combustion air. several meth-
ods are
used
to
get air
inlo
the combuslion chamber.
Forced-Draft Burner (commonly called
a
~
~-combusljon
air is blown In
by
a motor
driven fan. ExalTples are Aspirating, Gun
Type, Mechanical-Premix, and Zero-Governor
Burners.
,,.,,
Induced-Draft
Burner-a
fan al the outlet of the
combustion chamber creates a slight partial

vacuum within the charrber; the higtler atmos·
pheric pressure outside will force air Into the
combustion chamber.
Fanmlx
Bumer
air
is
drawn
in
by
a fan, which is
driven
by
hig pressure fuel gas escaping from
small
Cilrifices
in
driver arms attached to the fan
blades.
MECHAf',IICAL-PREMIX
BURNER~a
power burner in
"'
which the air-and gas are mixed, under pressure,
in
a
motor-driven blower. Simultaneous modulation
01
air
and

gas allows adjustment
of
the air-fuel ratio over a
wide range, so an extremely short hot
flame can be
produced. Also
see FORCED-ORAFT
ard
PREMIX
BURNERS.
MEMORY
-a
capability
of
sloring information.
FOl'
exam-
ple, in the W860A Trouble Tracker, once a trouble-light
indicator is energized, it will stay on even though the
cause
of
!rouble may correct itself.
METERING
VALVE-see
FIRING RATE VALVE.
MICROAMP-1
millionth
of
an ampere.
MICRON t/J.)-1 millionth

of
a meter.
MILLIMETER
OF
MERCURY
-a
unit
of
pressure
squalto
the pressure exerted
by
a column
of
mercury 1millime-
ter high at
sea level and at temperature
01
0 C
[32
Fl.
MINIMUM FIRING
RAlE-the
lowest input rale tor a
burner or a process.
MINIPEEPER-Honeywelt
trademark; a COrrp3ct. ultra·
violet flame delector (C7027A, C7035A, or C7044A),
which
consists mainly

of
a high power sensing
tlbe
called a
UV
power tube.
MIXED
GAS-a
mixture
of
natural and manufactured
gases. Mixed gases result from the increased dislribu-
tion
of
natural gas. through transcontinental pipe
lines.
into areas having existing manufactured gas facilities.
MIXER-a
device which combines things so lhat the
re-
sulting substance is uniform
In
composition, whether or
not the separate elements can be distinguished.
See
GAS MIXER. Also see FAN, ASPIRATOR.
ard
INSPIRATOR MIXERS.
MIXER
FACE-the

air inlet end
of
the mixer head.
MIXER
HEAD-that
portion
at
an inlection type burner,
usually enlarged, into which primary air flows to mix
with the
gas stream.
MIXER THROAT
-that
portion of the mixer which has the
smallest cross-sectional area
and
which lies between
the mixer head
and
the mixer
lube.
MIXER
TUBE-that
portion
01
the mixer which lies
be-
tween the mixer fhroat and the burner head.
MIXING
VALVE-a

three-way valve with 2 inlets
and
1out-
let, designed specifically for mixing applications.
The
proportions
of
the fluid leaving the outret can be varied
by
moving the valve Slem.
It
cannot be
used
lor divert-
ing applications because
II
has
only 1 disc an:! 2
seats.
MODULATE -
10
adjust
by
Increments
and
decrements;
to
modify
by
varying a

second
condition; the firing rate
positlon during which the firing rate motor
Is
LIldar
the
control
01
an external series 90 conlroller.
MODULAnNG
CONTROL-a
flame
safea card
conlrol
that provides an infinite number
at
firing rate positloos
to fire the burner
In
response to
demard.
Example-R4140G
or
R4140L
MODULAnNG
CONTROLlER
-a
proportioning control-
ler which automatically
positions the device it controls

anywhere between its extreme positions
In
response to
Changes In the controlled medium. Also
see RRING
RAlE
and PROPORTIONING CONTROLLERS.
MODULAnNG
FIRE-varying
the firing rate as
the
load
varies. This results in longer burner operation because
the firing rate
is
lowered as temperature or pressure
builds
up
toward the cutoff point. It deCreases on-off
operation and increases the efficiency
of
the system.
MODULATING MOTOR
-an
electric motor,
used!o
drive
a valve or damper,
which
can position the valve

01'
da~r
anywhere between fully open or fully closed in
proportion to changes in !he controlied mediLm.
Example-M941.
Also see FIRING RATE MOTOR.
MODULATING
VALVE-an
automatic control valve de-
signed so that the valve opening is varied within narrow
limits throughout the 8f1tire range from high tire to
row
fire position
by
means
of
a proportional actuator. Also
see FIRING RATE VALVE.
MODUTROL MOTOR - Honeywell trademark;
see
MODULATING MOTOR.
MONITOR - a device which senses a
cordition
req

Jirlng
attention
ard
gives an alarm without initiating correc-
live action.

MOTORIZED
VALVE-an
automatic control valve which
is completely opened
by
the rotation
of
an electric
m0-
tor, and is generally automatically closed
by
a spring
or
other mechanical means when the electrical circuit is
broken. Also
see FIRING RATE MOTOR, RRING
RATE VALVE, and SAFETY SHUTOFF VALVE.
MOUSE TRAP
~another
name for the balanCing
reray
in
a
Modutrol motor.
See
BALANCING RELAY.
MULTIBURNER
SYSTEM-a
healing system with more
than 1 main burner.

MULTIFUEL
BURNER-see
COMBINAnON
BURNER.
MULnpASS
BOILER-a
horizonlal,
fire-lL
.
.oe
boiler in
which the flue gases are
passed
back and forth throo;;tl
the boiler shell 2 or more times
by
means
of a
IL be
arrangemenl
or
baffles. Each
Change
in direction
is
called a pass. In order to maintain the flue gas velocity,
each succeeding
pass is reduced in tolal cross section
to corrpensate for the reduced flue
gas volume

as
the
349
71-97558-1
gases
cool. Also see FIREBOX,
FIRE-TUBE,
and
SCOTCH BOILERS.
MULTIPORT
BUANEA-a
burner having a nlJl'l'tler
of
nozil9S from which fuel
and/Or
aIr are discharged into
the corrtx.Jstion
chaJ'J1)9r;
as diStinguished from a
Sinole-Port Burner.
NATURAL DRAFT
-Ihe
pressure difference r8Sulting
from the tendency of hoi
gases
to rise
"'"
a vertical flue
or
Chimney,

thus creallng a parttal vacuum In the fur-
na~.
Natural draft Is primarily a function
of
the vertical
flue' height and the lerrperature difference belween Iha
inlel and outlet points of lhe flue.
NATURAL-DRAFT
BURNER-a
gas burner which
depends
on
a natural draft
10
brJng
In
combuStion air.
Also see ATMOSPHERIC BURNER
and NATURAL
DRAFT.
NATURAL
GAS-a
mixture of several combustible
gases
and, usually, a small percentage of inert
gases,
cbtained from geologiC formations
In
nature. These
gases

consist mostly of a mixture of organic
com-
pounds (normany methane, butane, prq:ane, and
ethane).
The healing value
of
nalural
gases
varies be-
Iween 900 to
'400
Btu per
cu
n;
the usual range for
use
is
1000
to 1050 Btu per
cu
fl.
NEC
CLASS I
WIRING-wiring
melhtXis and materials
re-
quired
by
the National Electrical Code for voltages not
eXceeding 600 (line voltage) e){cepl where speCifically

permitted. This
does
not Involve remote-control, low·
voltage relay switching,
10w-enerfJ)'
power and signal
systems, or
&cinmunicati~
SySlems
as
defined
by
lhe
Code.
.
NEGATIVE PRESSURE-less than atmospheric pres-
sure. Atso see FURNACE PRESSURE.
NET
LOAD-heat
req.llremenlS exclusive of piplrl{llosses
and'pIck"",.'
.
NET
RATlNG-lhe
rating ot a bOiler which indicates the
net load that may be conneclljoj satiSfactorily to
II,
pro-
vided the piping losses and pick"", load
do

nOI
exceed
lhe slandard allowances.
NEUTRAL
PRESSURE-squalto
atmospheric pressure.
Also see FURNACE PRESSURE.
NOMINAL BODY
RATING-see
VALVE BODY RATING.
NON
RECYCLING
CONTROL-a
flame safeguard control
which
does no! recycle after g,utdoWn.
See
CUTOFF.
NORMAL CARE
-the
periodic tasks usually performed to
operate and maintain
an
appliance, such
as
air,
fuel,
pressure, and lemperature regulation; and cleaning,
lubricatlon, and
raselU~

of controls.
NORMAL FUEL SUPPLY PRESSURE-
the pressure at
the fuel service
COl'V18cUon
for which the fuel bJrnlng
system
is designed.
NOZZLE-MIXING
BURNER-a
burner
In
which the fuel
and air are not miked until just
as
they leave Ihe burner
port, after which miking is usually very rapid.
The flame
cannol
flash
back in this type of burner.
OFF
PEAIOD-Ihe
period of time, olher than safety
shwt-
down,
ciJrlng
Which
lhe burnet Is not firing.
OFFSET

-a
sustained deviation between the actual
control point and
the
set point under stable operating
ccndilions.
OIL
BUANER-a
burner for firing oil. Also see ATOMIZ·
ING
OIL,
ROTARY
OIL,
and
PRESSURE-ATOMIZING
GUN
TYPE BURNERS.
ON-OFF
CONTROL-a
flame
safSOJard
control which
turns the bJrner on or orr but ooes not vary the firing
rate.
Example:
R4140M.
ON·OFF
VALVE-see
lW() POSITlON VALVE.
OPACITY-the

state or quality of baing
cpaQue;
smoke
density measured in Flingelmanns. Smoke c:pacity
which exceeds a preset level
will
GaL/Se
a stack smoke
detector to
pUll
in
an
alarm
relay.
OPEN
CIRCUIT
-a
Circuit which ooes nol provide'a com·
plele path for lhe current
10
follow.
OPEN
DAMPER PURGE-ciJring prepurge, the damper
opens
10
high fire p::lSilion
and
the burner motor drives
air
IhrOUQh

the combustion chanber to remove any
~
tenlially explosive fuel or fumes. The damper closes to
low fire p:lSition
for ignition Irials, and opens again to
high tire p:lSilion for the run period. Flame saleguard
controls
prOViding
this feature have only 1 lermlnal for
liring rate switching; they
do
nol provide modulation
during the run period.
OPERATING
CONTROL-a
conlrol (other than a safety
control or interlock) which stans, stops, and regulates
burner firing according to load demand.
It may also ac·
tuate auxiliary
equipment_
OPERATING
CYCLE-the
complete sequence of opera-
tions req.Jired in the normal functioning
of
an
ilem of
equipment. For a flame safeguard contrOl, the opera·
tions periormed between a call for heat and satisfaction

of
the call
for
heat (when the cperating set
p::Iint
is
reachedl. Atso see
TIMER
CYCLE.
OPERATING
RANGE-the
fegion between lhe maximum
fuel input and minimum fuel
IflXilln
which the burner
flame can be maintained, continuous and slable.
OPPOSED
BLADE
DAMPER-a
flap or louver type
darrper in which alternate blades rolate in opposite
350
directions. This type provides an equal percentage flow
characteristic - successive aqual increments or rOla'
tion produce equal percentage increases in flow. This
is particularly useful for throttling
awlications
where
accurate conlrol at low flow
ralas is req.Jlred.

OpnCAL
FLAME
DETECTOR-a
detector that responds
to
the
Ii\;jht
(visible or otherwise) emitted by a ftame.
Also
see RECTIFY:ING PHOTOCEll INFRARED, and
ljLTRAVIOLET FLAME DETECTORS.
OPTIMUM
AI~
SUPPLY-the
quantity
of
air which will
give greatest thermal effic;ency under actual condi-
tions. With perfecl mixing
of
fuel and air, the optimum
air supply is equal
10
(he
chemically correct amount
of
air. Also
see
AIR-FUEL RATIO.
ORIFICE - an q)Elning or window, such

as in an aperture
disc or iris stide.lnaburner, the opening
ina
cap,
spud,
or olher device whereby the flow
01
fuel
is
limited and
through which the fuel is discharged
10
the burner.
ORIFICE CAP
{HOOD)-a
movable filting having an ori-
fice which permits adjustmenl
of
the flow of fuel by the
changing
of
its position with respect to a fixed'needl60r
other
deviCe.
ORIFICE SPUD
-a
removable plug or cap containing an
orifice which permits adjustment
of
the fueillow, either

by substitution
of
a spUd WIth a different sized orifice or
by the motion
of
a needle with respect to il.
ORIFICING
-a
procedure used
to
reduce the field
of
view
of
a detector by means at an cpaque plate or card wilh a
selected sized opening. This
is
frequently required to
reduce refractory interference
to
acceptable levels.
OVEN
-a
compartment or receptacle
tor
heating, baking,
or drying
by means
of
heat.

AlSO
see INDUSTRIAL
OVEN.
OVER-FiRE DRAFT
-the
drat!.
measured over the flame
within the combLIStion charrf)er.
OVERRATE
FIRING-firing
a ooil9( at an inpul rate
in
excess at its rated capacity. The rated capaCity
of
a
oo.iler is based upon its heat transfer surface area.
OXIDIZING
FlAME-a
lean flame
or
fire resulting from
combustion
at a mix
lure
containing
100
much air
(or
too
little fuel). This kind

at flame prlXiJces an oxidizing at-
mosphere, which tends
to
oxidize materials placed in it.
PACKAGED
BOILER-a
steam or hot
WOller
boiler in
which the pressure vessel, furnace, and comrols are
designed, assembled, wired,
and
shi~
as
an
Inle-
gral unit. PaCkaged ooilers are fIOtmally compacl
and
efficient, delivering about 1 boiler horsepower
/BoHPJ
for every
5leet
of
heating surface.
They
are available in
oolh fire-tube
ard
WOller-lube
types. Flr9'tube pack-

aged ooi/ers range in size Irom about
500,000
to
30
mil-
lion Btuh
(10 to
600
BoHP); water-tube packaged
ooilers range
in
size from about 12.5 million to 75 mil-
lion Btuh
(250
10
1500 BoHP). Also called a
~
Generator.
PARALLEL BLADE
DAMPER-a
flap
or
touver
type
damper
In
which all blades rotate
In
lhe
same

direction.
This
type
provides a fairly linear flow
characterisllc-
the flow is nearty pfOJXlrtionai
10
the damper
Shaf1
rota-
tion. This is particularty useful in mixing awlications
where
2 dlfferenl flow rates musl be corrbined'.
PAR71AL-PREMIX
BURNER-a
gas burner in which
paM
of the combustion air is miXed with the gas before they
are introduced into the corrbusUon chamber, usually
by venturi action.
lhe
required secondary air reaches
the
COITt>ustlon
charrber
/hrou;tl
spaces between the
burner heads. Exal1lJles are lnspirating, Spreader,
ard
Tunnel Burners.

PECKING
RELAY~see
CHECKING RELAY.
PERFECT COMBUSTION
-burning
with exactty the cor-
recl proportion
of
air
to
fuel so that all
01
the
fuel
ard
oxygen are burned. Also referred to as stoichiomelrlc
b1.!I!Jlog
and thaqretical combusllon.
PETCOCK-a
small, manually q)Elraled faucet or valve
used for draining unwanted or excess liQuidor
gas from
the
main syslem. or for
tawing
a small amount for
testing.
PETROLEUM-see CRUDE
OIL
PHOTOCELL-see

REcnFYING
PHOTOCELL FLAME
DETECTOR.
PILOT
-a
small burner {or a flame, smaller than the main
burner flamel which is used to
ligt1t
off the main burner
or burners. Also see CONTINUOUS (CONSTANT,
STANOING), EXPANDING, INTERMIITENT, INTER-
RUPTED, and PROVED PILOT.
PILOT AND MAIN FLAME
SUPERVISION-the
pilot and
main burner flame are
~rvised
simultaneousty by 1
detector. '
PtLOT BURNER ASSEMBLY
-a
combination gas pilot
burner
ard
flame rod flame deteclot; may also include
an ignition electrode for
spark ignition
of
the pilot, Of a
thermocol4'le adapter.

AlSO
called a Rectification
PilQt
or Flame Rectifier Pilot. Example: Q179A,B,C, or
D.
PILOT DUTY - a rating
awlled
10
Incilctive loads (usually
a solenoid or
coil)
with a ma»mum power factor of 35
percent. AJlowable Inrush can
f:)EI
l4'
10
10
times the
pilol
dUty
rating
(ruming
ClJrrent).
PILOT FlAME-ESTABUSHING
PERIOD-the
period
of
time in i'tTIiliOn trials clrring which the llame safeguard
control permits the pllOI valve
to

be q)Eln before
the
llame detector is required
to
detecl the pilot
flame.
PILOT
UNK-a
jlJl'T'4:l9r
screw
or
iurrper
wire which by-
passes a
fIOrmatty
q)An
load relay contact in the flame
detection circuit
at some fiams
saJ8Q.J8rd
controls.
If
351
71-97558-1
{emoved, It allOws the control
10
be
used
with a con-
linuous pilot (safe stan check Is not applicable).

PILOT
ONLY-see
EARLY SPARK TERMINATION.
PILOT sTABiLIZATION
PERIOD-a
limed interval slart-
Ing wilh the
proo1
of
the pilot and encting with the cpon-
lng
of
the main fuel valve(s). This period permits
lhe
pilot to establish Itself before permitting lhe inrush
of
main fuel .
PILOT
SUPERVISION-detecting
the presence or ab-
sence
Q1,
a pilot name.
PILOT
TRIAL-see
PILOT FLAME·ESTABUSHING
PERIOD.
PILOT TURNDOWN TEST
-
a test

to
determine If the
smaUliI6t
pilol capable of holding in the flame relay Is
large
enough
10
safely light
off
the main burner.
PILOT
VALVE-an
aulomalic safety shutoff
valw
which
conlrols the fuel if1)Ut
to
the pilot.
PIPE-a
seamless tube conforming
10
the particular
dimensions
commercially known
as
Standard Pipe
Sizes; usually
ccpper or brass.
PLENUM-an
air companrnent which Is part

of
a distribul·
ing system,
10 Which 1
or
more ciJcts are connected.
It
rnay
be aUached to, or be an integral part
of,
lhe supply
ouIlet or the return air Inlet
of
a fumece.
PLUG
COCK-see
COCK.
PNEUMAnC-
operated
by
or filled with compressed aIr.
PORT
-an
orifice or opening
In
a burner head through
wt1ich
fuel or an air-fuel mixture
Is
diSCharged for

1"",ltion. .
POSISTOR-a
thermally sensitive resistor Which
has
a
positive lemperature coefficienl
of
resistance. Also &ee
THERMISTOR,
POSInVE
PRESSURE-greater
than atmospheric pres-
sure. Also see FURNACE PRESSURE.
POSTPURGE-a
period.
of
time
aC~r
the run period dur-
Ing which the burner motor (blower or
1anj continues to
run, driving aJlthe prOducts
of
COf'I"bJslion
and any un-
burned
fuel
trom the corrb.JsUon chamber and
~Iy
ing air

10
bum
fuel be1rv purged from the fuel
'Ine
cbWnstream from Ihe safety shutoff valve.
POT
-shart
for potentiometer.
POTENTIOMETER-an electromachanlcal device con-
sislinQ of a resistive element with a lermlnal at each
end,
and
a third terminal connecled to fhe wiper
contact.
As
the wiper moves along the element, it
changes the resistance
In
each leg
(poMion
of
the ele-
ment between each end terminal and the wipe!). Thus
lhe electrical
Irput
or
OUlput can
be
changed
me-

Chanically. Also see
AUXIUARY
and FEEDBACK
POTENTIOMETERS.
POUR POINT
-the
minimum terrpwature at which liquid
fuels
can
be
punl=J9Cl
or flow readily.
POWER
BURNER-a
gas burner in which Combustion air
is blown in
bv
a motor driven fan. Also
caUed
a
~
Draft
BUrnElL
Exsrrples are Aspiraling, Gun Type,
Mechanical·Premix,
anct
Zero-Governor Burners. Also
see MECHANICAL·DRAFT BURNER.
POWER
TUBE-see

ULTRAVIOLET POWER TUBE.
PREHEATED
AIR-air
heated prior to its use for
comblJs
tion; frequently the
heatil1l',;;l
is done by hot
l1ue
gases.
PREIGNInON
ItlTERLOCK-an
Interlock which proves a
conctltlon is proper for burner Stanl.f.l and operation
through prepurge, prior to Ignition trials.
It
usually
proves the main fuel valve(s) is closed.
II
may also be a
damper position Indicator (low or high fire prov'lnQ
switChl, fuel pressure switch, or oil preheate! control-
lsr.
Also
see
VALVE·CLOSED INTERLOCK.
PREMIX
BURNER-a
gas burner in which the
QaS

and air
are
mixed before they are inncduCed into the com-
bustion chamber. Usually, the
gas and air are both ted
into
a tan or blower, and the mixture
Is
Ihen blown into
the Combustion charrber. A premix burner burns wilh a
shan, hoI flarne with high heat reletase. Ex8f1l'1es
are
Mechanical·Premix, Fanmix, and Zero-Governor
Burners.
PREMIXER
-a
deVice 10
mb:
gas and air before delivery
to a burner, such as an aspirator, an inspirator, or a tan
mixer.
PREPURGE-a
perioc:l
oflirne
afler burner stanl.f.l (call for
heal) during which the burner molar \blower
Dr
fan}
runs to change the air
0'

the combustion chamber and
breaching prior to ignition trials. This removes any un-
burned fuel so only the incoming fuel
win
be presenl for
ignition.
PRESSURE-force
per unit area; usually measured in
pounds per square inch
(PSil,
or by the height
of
a col-
umn of water
or
mercury Which the force witl
Sl.PPQn
(in
feat, inches, or millimeters). Also see ABSOLUTE,
ATMOSPHERIC, FURNACE, GAUGE, NORMAL
FUEL SUPPLY, and
STAnC
PRESSURE.
PRESSURE·ATOMIZING GUN TYPE
BURNER-the
SIJ11)lest,
and probably the most common, Mechani·
cal-AlomlzJng
OilSUrner.
Ug,t

all under pressures
of
l.f.l to 150 pounds per square inch is discharged
thro:Jgh a nozzle
or
orifice, prockJClng a cone-shaped
spray. Action
of
the
nonie,
plus the irrpact
of
a rotating
airstream from a tan, mixes the oil and air. Also see
ATOMIZING OIL BURNER.
PRESSURE-ATOMIZING OIL
BURNER-synonymous
wllh Mechanlcal·Alomlzioo
011
Burner.
See
ATOMIZ-
ING OIL BURNER and PRESSURE-ATOMIZING GUN
TYPE BURNER.
PRESSURE
CONTROUER
- a controller Which monitors
the pressure
of
steam, air, gases, or liquids, and oper-

ates to keep the pressure within predetermined limits.
352
1/
It
may
operate as a pressure switch (ON·OFF).
or
il
may
be
a prcporUoning controller. Also see PRESSURE
SWITCH and PROPORTIONING CONTROLLER.
PRESSURE DROP
-pressure
drop
(h)
is the difference in
pressure between
two
lXlints, for example belween the
upstream pressure and the cbwnstream pressure
of
a
fluid passing through a valve.
The
critical pressure
sHgg
(equal
10
1/2

the absolule upstream pressure) is
. the
maximum
pressure
drop
allowable to ensure noise-
free operation and minimum valve wear.
PRESSURE
REGULATOR-a
device used to maintain a
constant pressure in a fuel supply line regardless
of
the
flow. It cannol maintain a pressure greater
lhan
its inlel
pressure.
PRESSURE
SWITCH-a
switch that monitors the pres-
sure
of
sleam, air, gases,
or
liquids, and breaks a cir-
cuil when the pressure either rises or fails to a preset
value.
II
is
used as a limit

or
interlock with a flame safe-
guard
control
10
shul Cbwn
Ihe
burner
if
Ihe pressure
exceeds (High pr&$$ure Switch!
or
falls be/ow
~
Pressure Switch) a preset value. It may reset automati-
cally when the pressure returns to normal,
or
it may
require manual reselling.
PRESSURETROL-HoneyweU
Irademark; see PRE$-
SURE CONTROLLER.
PRESSURE
VESSEL-a
closed vessel
or
container
designed to conIine a Iluid
211
a pressure above

atmospheric.
PRIMARY
AIR~lhe
air
introduced
into
a burner which
mixes with the fuel before it reaches the combuslion
chamber.
PRIMARY
~0NTROL-a
ftame safeguard control which
starts the burner In
lhe
proper sequence, proves that
the
burner flame is established,
ard
SLPSrvises lhe
flame
wring
burner operallon.
II
causes safety shut-
Cbwn
on
failure
10
ignite the pilot
or

main
bumElr
or
on
loss
of
flame.
PROGRAMMER-see
PROGRAMMING
CONTROL
PROGRAMMING
CONTROL-a
flam.,}
safeguard control
that adds a
liming
funclion to the primary control to
sequence addilional burner lunctlons
such
as
prepurge, IXlstpurge, limed trials for pilot and main
burner
f:.lme, and firing rate switching.
PROPANE-an
easily liquefiable hydrocart:x:ln gas. Pro-
pane
is
Of"e
of
the components

of
raw nalural gas, and
II
is
also derived from petroleum relining processes.
PROPORTIONAL
ACTUATOR-an
actuator which can
position
a
damper
or
valve anywhere between fully
open
or
tully closed in
prcportion
to changes In the con-
trolled medium.
When
lhis
action Is
done
automati·
cally, it
is
called modulaUon. Also see ACTUATOR.
PRopORnONING
CONTROLLER-a
controller which

includes a IXllentiomeler to
permilthe
device it controls
to
be
set anywhere between
lis
extreme positions.
When this action is
done
automalically in response
10
changes in the conI rolled medium,
It
is called
mo::1.Jla-
tion. Also see MODULATING CONTROLLER.
PROTECTORELAY-Honeywell
trademark; see PRI·
MARY
CONTROL
PROVE
-to
eslablish by measurement
or
tesl the exis-
tence
of
a specified condition,
such

as
name,
level,
flow, pressure,
or
posillon.
PROVED IGNITION
-Ignition
by
an
energy source
wtJich
Is
supervisecl
by
a flame saf8QJard conlrol that musl
delect the presence
of
energy for Ignition prior to
per-
milling
the main fuel valve(s) to open.
PROVED PILOT
-a
pilot flame which
is
supervised
by
a
flame safeg.Jard control that must detect the presence

of
the flame
prior
to permitting
the
main
tuel valve{s} to
open.
PROVED SPARK
IGNITION-direct
spark ignition which
musl
be
proved belore Ihe main tuel vaive(sl can
opEn;
usually used
wilh
small oil burners. Also
see
DIRECT
SPARK
ard
PROVED IGNITIONS.
PROVEN COMBUSTION
AlA-see
AIRFLOW SWITCH.
PROVEN
PREPURGE-system
in
which

the progral1l'
ming
control includes a
provision
for
prevenling burner
operalion unlil satisfactory airflow Is estabrishedduring
prepurge.
PULSING
RELAY-see
CHECKING RELAY.
PURGE-e1iminaling a substance
Irom
a pipe
or
furnace
by
flushing it out with
anolher
substance, as In purging
a furnace
of
unburned gas
by
blOWing air through it.
Also
see
POSTPURGE
ard
PREPURGE.

PURGE
EXTENDER-an
auxiliary
timer
used wilh a pro-
grammIng control to lengthen the prepurge perioo at
hig.
fire in order to meet Factory Insurance Association
IF.I.A.)
requirements.
Some
programming
controls
have optional plug.in pUrge extenders with field selec-
table liming.
PURGE
TIMER-an
aUXiliary
timer
used
wilh a primary
conlrol to add prepurge Capability.
II
may
be
an
q:>-
tional plug.in device with preset liming, such as an
$171A Prepurge Timer for use with
an

R4795 Primary
Control;
or
it may require mounting, such as
an
S4278
or
C
P.urge
limer
for general
awlications.
PURPLE
PEEPER-Honeywell
trademark for the C7012
series
of
ultravioleC flame detectors. These detectors
use a low
power
sensing tube called
an
Aquadag
1L.be,
and require a rectificalion type flame Slg'l2ll
~Ufler.
The C7012E
ard
F prOVide
the

Dynamic
self
Check
feature.
353
71-97558"
RADlANT-HEAD BURNER
-8
raw
gas
burner
wil"
a head
(or
headsl
constructed
of
refractory malerial. The raw
gas
is ejected from spuds
into
an
openil"lQ
in
the
head(si. Corrt:!ustion h9ats the head(sl to lncandes·
cence,providing 8'large amounl
of
radiant heat which
lends

lo.lnCrease
the
speed
at
flame Pfc:pagalion
and
keep the flame Shorter. Also see RAW
GAS
BURNER.
RADIANT-TUBE TYPE
HEATER-an
indirecHired heat·
.Irg
$)'Slam in which
healing
is
accorrplished by radia-
tiOn
or
convecllon from
llbul5l'
elements. The ILbes are
•
gas-Ii~.
neal-resistant,
cpen
at
one
or
both

ends.
and
Capable
of
withstandil"lQ explosion pressure from igni-
lion
of fuel·air mixtures. Each tube
has
an inlet and/or
bomBr arrangernenl where corri:lustion
is initialed, a
ISIJilable
IlWlglh where combustion occurs, and
an
oul-
let
for lhe
combustbn
prodllcts
formed.
R,4DfAnON-the
process In which energy in
thB
form
01
rays
is
emitted from atoms.
and
molecules as

lhey
U'Ki:l1VJ
Internal change.
Also
68E INFRARED
<IR)
and ULTRAVIOlET
(UV)'
RADIATION; and VISIBLE
UGHT.
RADIATION
SHIELD-a
separate panel
or
panels inter-
plSEId
between heating surlaees and adjacenl
ob}Elcts
to
rBCiJce
heat transmission
by
radiation. Also called a
!ir!I!.
RANGEABIUTY - the
ralio
of
the maximum controllable
flOW
to Ihe minimum controllable flow

throu~
a
valVE!.
For
SlCample,
a valve witi, a rangeabHity
of
50 to 1 ha\l-
loga
lolal flow capaclly
of
100 gallons
per
minUle (gpm)
tuff open can
a~culate! "
control a flow as low
as
2
gpm,
RAW
GAS
BURNER-a
gas
bulner
in which raw
gas
is
ejected into
the

combusUoo chamber from multiple
pons.
Orly secondary eir it;
used
for
cOfTbuSlion;
no
mlJ.lng occurs before
the
gas
i$
ejected.
TI1e
ports are
.rlW'lg9d
10
resulf
InC
maximum
milling
of
gas
and
air.
Ex~Ie!i
are Radiant-Head, Ring,
anct
HIgh-Pressure
Gun Burners.
READILY

ACCESSIBLE-
capable
of
beino reached eas·
ily and quickly for operation, adjustment, and
Inspeclion.
RECTIFICATION-the conversion
of
allernaling current
to unidirectionar
or
direct
current.
AlSO
see
FLAME
RECTIFICATION.
RECTIFICATION PILOT see PILOT BURNER
ASSEMBLY.
IiECTlFICATION
SYSTEM-a
name proving system
Which
operates on a
dc
flame signal providec:l
by
a recti·
fication type flame detector.
RECTIFICATlON TYPE FLAME

DETECTOR-one
lhal
uses.lhe r&Ctification principle to indicate the presence
of
a flame,
RECTIFYING FLAME
ROD-a
melal
01 ceramic rocl used
as
a
flamEl
detector in a detection system using the
flame rectification principle. AI50
see
FLAME
RECTIFICATION.
RECTIFYING PHOTOCELL FLAME
DETECTOR-a
detector lhal responds
to
\he visible light (wavetengtn
between 0.4
and
0.8 micronl emitted
by
a flame.
II
con·
sists mainly

of
a high vacuum photocell thaI rectifies
allernating currenl
to direcl curren! when
eJ[~
10
visible light.
TI1e
cathode
01
the p/"Qlocefi is coated with
caesium
ol(icfB
or
anolher
malerial thaI emits electrons
when lighl strikes it.
RECYCLE-the
process
of
QOII"lQ
through another operat-
ing cycle. For a Ilame saf9j).JiUd control, automatically
QOing
Ihrough another timar cyCle after a shutdown
in
an
alterrplto
res\an the burner.
RECYCLE

INTERLOCK_a
runnino interlock used with a
Pfimary
Of
Pfogramming control which
will
shu!
down
the burner
if
an improper condition occurs. The control
wi!! recy:)a:
it
wi!!
reslan
lhe
burner
11
111&
condition
corrects itself. The interlock
is
usually a combustion
air controller (airllow swIICh).
See
RUNNING
INTERLOCK.
RECYCUNG
CONTROL-a
flame safeguard control

which recycles fOllowing a shutdown:
It will restart the
burner
V conditions causing the Shutdown have
been
correcled.
REDUCiNG
FLAME-a
rich flame or fire resulting from
cC\ll"DJslion
of
a mixture containing
100
much fuel and
too lillie air. This kind ot flame produces a reducing
atmosphere.
REFRACTORY
-heal-resistant
material
used
10
line fur-
naces.,
kilns, ovens,
and
corrtlustion Chambers.
REFRACTORY
BLOCK-a
piece
0:

refractory malerial
molded with a conical
or
cylindrical
hole
through
lis
cenler and mounled
SO
lha!
the
flwne fires Ihrough this
hole.
The block helps
to
maintain continuous combus-
tion,
aPd reduces
Ihe
prctlabllity
of
flashback and blow-
off. Also called a
burner
block,
bJner
life, combuslion
liIe, combustion block, refractory lila,
or
burner

refractory.
RE~RACTORY
HOLD·IN TEST
-see
HOT REFRAC-
TORY HOLD-IN TEST.
REFRACTORY OVERRIDE TEST
-see
HOT REFRAC-
TORY SATURATION TEST.
REFRACTORY SATURATlON TEST
-see
HOT
RE-
FRACTORY SATURATION TEST.
REGISTER-the
paning,
grill
worlo;
or
dalTpElr arrange-
ment through which
air
is
Introduced
into
the corrbus-
lion
chamber around the lxJrner p::lns
or

nozzles.
It
may
354
also conlrol the direction and velocity
ollhe
airstream
for
efficienl mixing with the incoming fuel. Also
see
AIR
REGISTER.
REGULATOR
-a
device that functions to keep a quanllty
or
quantities al a certain value
or
between certain
limits.
AlSO
see ATMOSPHERIC (ZERO GOVERNOR).
DRAFT, GA&PRESSURE. and PRESSURE
-REGULATORS. :
RELAY-an
ei8ctromechanical device with coolacts thai
~n
and/or closa when its coil is energized orde-ener-
gized in response
10

a change in the conditions
of
the
electricat circuit. The
~ration
of
the contacts affect
the operalioo
01
other devices in the same circuit
or
in
other circuits. Also
see
BALANCING, CHECKING,
-FLAME
DETECTOR, FLAME, and LOAD RELAYS.
RELAY
CHATTER-noise
ciJe to the rapid opening and
closing
of
relay contacts.
RELIABLE-the
degree
or
safety that indicates a reason-
able 1reedom
1rom
hazards will be maintained during

continuous or extended operation.
RELIEF
VALVE~a
valve which opens at a oesignated
pressure and bleeds a system in order
to
prevent a
buildup
of
excessive pressure which mignt damage
reQulalors and other instruments. Also
see
VENT
VALVE.
RELIGHT
-immediate
restoration
of
ignition, wilhout
preignition
purgingor
interlock cnecks. after loss
ot
the
main burner
fJame.
If
the main burner flame
is
not

re-eslabtished. safety shutdown occurs. Also called
Ignition Return.
REPEATABILITY
-Ihe
ability
of
a controller or interlock
to
maintain.a constant set ,point characteristic.
REPLACEMENT
PACKAGE-parts
included in a single
paCkage
intended
tor
replacement
ot
a device.
RESIDUAL
OILS-oils
which are too heavy
to
be e'iapo-
rated in
any, normal evaporation
ard
distillation
process and so are left olfSr tram that process.
RESONATE-IO
maximize or minimize Ihe amplitude

or
Olher characteristic
ot
the response
of
a gilfSn system
or
dE

ice.
RESPONSE
TIME-see
FLAME FAlLURE RESPONSE
TIME.
RICH
MIX-an
alr·fuel mixture in which an excess
of
fuet
is supplied in prcportion
to
Ihe amounl
01
air a'iaifatlle.
Also see FUEL RICH.
RlNG BURNER
-a
gun type, raw
gas
burner in whicn jets

of
QaS are directed Into whirling airstreams from
orifices around the periphel)'
of
a ring al the mouth
01
the burner. Also see GUN TYPE and
RAW
GAS
BURNERS.
RINGELMANN-unil measure
of
smoke
<::pacity;
1
Ringelmann equals
20 percent smoke density,
and
5
Ringelmanns equal 100 percent smoke density.
ROTARY OIL
BURNER-a
burner
tn
which atomlzatlal
Is
accomplished
by
feeding oil to a rapidly rotating
~or

10 spinning plates. centrifugal force throws off lhe oil in
droplets at Ihe peripnery
of
Ihe cup
or
plates. Also
called a centrifugal Atomizira
Oil Burner. There
are
2
basic types.
Horizontal Rolary Qil
Burner-oil
is pufTl)6d
tnrough a horizontal, hollow, drive shaft
10
a spin-
ning cup. The axis
of
the \:up is also horizonlal.
VertIcal Rotary Qil
Burner-Ihe
oil tank is mounled
hig,er
than lhe burner,
and
oil flows downward
by
gra'ilty to the spinning plales.
RUN

PERIOD
-the
period
01
time after ignilion trials
and
be10fe
the
~rafing
set point is reached during which
the main burner is firing.
(In
a flame
sat~rd
pro-
gramming control, the timer stops.)
RUNNING CURRENT
-the
steady-state current drawn
from Ine line wnen a molor is running at
its
rated speecI.
or the armature of a solenoid
or
coit
is
in its ciosed
JX)Siflon.
RUNNING
INTERLOCK-an

interlock which prcwss a
condition is proper lor burner
~ration
to contirvJe
through prepurge. ignition trials, and the
f\Jfl
pericx:l.
II
is
used
with a primary or programming control which
will shul down the burner it an ifl¥)rcper
condition
occurs. The interlock may be a combustion air
can-
troller (airflow switch), a
~r
posUion indicator
(low
or
hig,
fire prQ'{ing switch),
or
a fuel pressure switch.
tl
can be a recycling type, or il may require manual reset.
Also
see
LOCKOUT and RECYCLE INTERLOCKS.
SAFE START CHECK - a feature or flame

satElQJard
c0n-
trols to pre'iant a burner start if a flame is detected,
or
if
a condition simulating
a name exists in the
ttame
dalec·
tion circuit.
SAFETY CONTROUCONTROLLER
-an
aulomalic con-
trol or interlock Oncluding relays, switches.,
and
other
aUlliliaty equipment used
to form a safety control sys-
tern)
which
is
intended to prevent unsafe
C\?9rahon
01
the controlled equipment.
SAFETY CONTROL CIRCUIT
-a
Circuit in'iol'iing 1 or
more safety conlrolS/conlrollers.
SAFETY UMIT

CONTROLLER-see
UMtT.
SAFETY SHUTDOWN
(LOCKOUl)-the
action of shu(·
ling
off
all fuel and ignition energy to lhe burner by
means
01
a safety control
or
controls such that restart
cannot be accomplished wilhoul manual
reset Also
see LOCKOUT SWITCH.
355
71-97558-1