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Furnace Terminology - Atwood 79 Series Service Manual

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AC Motor
A Motor operating on 120 volts A.C.
Adjustable Register A heat outlet capable of being opened
and closed.
Air Speed Indicators (Velometer) A tool used to measure
the velocity of air movement from a
duct outlet.
Ambient Air Temp.
Current room air temperature.
Amp Draw
The amount of current required to run
a given component.
Burn Off
The time it takes for the furnace
Combustion Chamber to burn off all
the oils and lubes used in production.
The component in the furnace where
combustion occurs creating the main
source of heat within the Combustion
Burner Flame Lift Off When the flame lifts off the Burner.
A small flame at the Main Burner
Orifice when the Valve is in a closed
Circuit Breaker
A normally closed switch that
automatically interrupts an electrical
circuit under abnormal AMP loads.
Circulating Air
Air drawn into the furnace by the Main
Air Wheel then heated and forced out
the heat outlets.
Combustion Air
Air supplied to the Burner specifically
for combustion.
Combustion Chamber The component where combustion
occurs and transfers heat to
circulating air.
Component that is used to change
120 VAC to 12 VDC. Available in linear,
pharo-resonant and switching styles.
The normal on and off operation of the
furnace controlled by the thermostat.
DC Motor
Motor operating on 12 VDC.
Circuit Board
A Circuit Board in the furnace
controlling the ignition sequence and
proves a flame has been established.
Both a conductor establishing an
electrical spark at the Burner to ignite
the air to gas mixture, and a sensor to
signal the circuit board the flame is


Fan Switch
A normally open switch that closes at
a set temperature allowing power flow
to the motor, and allows the motor to
run after the burner shuts down to
cool down the combustion chamber.
The Wiring Harness that connects the
Electrical Hook Up
furnace to the coach wiring.
Flair Fitting
Brass fitting used to connect the
furnace to the gas supply.
Flash Back
A condition when the flame burns on
the inside of the burner.
Flex Ducting
A round, collapsible, wire reinforced
product used to deliver the heated air
from the furnace to the living area.
Forced Combustion
A type of combustion when a second
air wheel is used to force air into the
burner to increase the air to gas
Gas Pressure
The amount of gas being supplied to
the furnace, measured in column
Gas Valve
A mechanical device by which the flow
of gas is started or stopped by an
electrical signal.
Gravity Combustion
A type of combustion using no other
source but gravity to supply
combustion air for the proper air to
gas mixture at the burner.
Hard Ducting
(See Floor Ducting)
Heat Anticipator
Component of a Thermostat that can
be adjusted to increase or decrease
the length of the heating cycle.
Heating Element
(See Combustion Chamber)
High Tension
The wire carrying the high tension
Lead Wire
spark from Circuit Board to Electrode.
Incline Manometer
Tool used to measure Static Pressure
of the furnace plenum.
Junction Box
A box inside or outside of the furnace
where electrical connections are made.
Limit Switch
A normally closed switch that opens at
a set temperature which does not
allow the furnace to over heat.
A condition caused by over-heating
the Limit Switch The burner turns on
and off during a heating cycle.

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