19
The pressure regulator on LP gas models is adjusted for 10.0"
w.c. manifold pressure and is intended to prevent over-firing
only. Do not attempt adjustment of the built-in pressure regu-
lator unless the supply pressure is at least 7.0" w.c. on natu-
ral gas or 14.0" w.c. on propane gas. Check the location of
the ignition electrode and the flame sensor for correct gap
setting.
Flame
Sensor
Ignitor
NATURAL PROPANE
(LP)
400,000
8
50,000
#30
#48
GAS ORIFICES
MAXIMUM
INPUT
(BTUH)
NUMBER
of
BURNERS
MAXIMUM
BTUH/BURNER
HEAT EXCHANGER AND BURNER ORIFICE SPECIFICATIONS
NOTE:
Gas appliances located more than 2000 feet above
sea level must be derated 4% per 1000 feet of total elevation
and that variance in gas heating value and specific gravity
require change in manifold pressure to obtain rating, it is
mandatory that the input be adjusted at the installation site.
All installations should be made as outlined in the latest edition
of the National Fuel Gas Code ANSI Z223.1, section
“Procedures To Be Followed To Place An Appliance in
Operation”. Refer also to the “User’s Information Manual”
supplied with the unit for additional information on the gas
furnace.
Unit Shutdown
1. Set the thermostat to lowest setting.
2. Turn off the electrical power supply to the unit.
3. Remove the heat exchanger door on the side of the
unit by removing screws.
4. Move the gas control valve switch to the OFF position.
Do not force.
5. Close manual gas shutoff valve external to the unit.
6. Replace the heat exchanger door on the unit.
7. If cooling and/or air circulation will be desired, turn
ON the electrical power.
NORMAL SEQUENCE OF OPERATION
H
EATING
This unit has one (RS) Manual Reset Limit Control Switch.
Check the limit to make sure it has not tripped. The limit may
arrive at the job site tripped as a result of shipping shock.
If the ventor motor comes on, but the unit does not attempt
ignition, check if the ALS (Automatic Reset High Limit Con-
trol Switch) requires resetting.
1. With electricity and gas turned on, the system switch
in the “HEAT” or “AUTO” position and the fan switch
in the “AUTO” position, the thermostat will close the
circuit between unit terminals R and W (R-W) when
the temperature falls below the thermostat setting.
2. D1 on IIC energizes relay IDMR.
3. Relay IDMR energizes the ventor motor IDM.
4. Operation of the vent motor closes the pressure switch
PS located in the burner compartment. the control
then initiates a 15-second pre-purge time delay.
During this period, the ventor motor will clear the
combustion chamber of any residual gas.
5. After the pre-purge period, the ignition control
energizes the Wl-C gas valve and simultaneously
initiates a “three (3)-try” spark ignition sequence.
6. When the burners are ignited, a minimum four (4)
micro-amp DC current will flow through the flame
between the sensor electrode and the grounded
burner.
7. When the controller proves that the flame has been
established, it will keep the gas valve energized and
discontinue the ignition spark. First stage manifold
pressure will be approximately 2.0" w.c. for natural
gas and 7.0" w.c. for propane (LP).
8. If the control is unable to ignite the burners after its
initial attempt, it will initiate another purge and spark
sequence. A third purge and spark sequence will be
initiated if the second attempt is unsuccessful. If the
third attempt is unsuccessful, the controller will close
the gas valve and lock itself out. It may be reset by
momentarily interrupting power. This may be
accomplished by briefly lowering the room thermostat
set-point below room temperature, or by shutting off
the main power to the unit. (See TP-105 for more
details.)
9. Integrated ignition control will close its normally open
contacts after a delay of approximately 30 seconds.
This action energizes contactor BC and starts the
supply fan motor. Operation of the supply fan
circulates air across the heat exchanger and delivers
heated air to the conditioned space.
10. When the space temperature rises, the thermostat
will open R-W. Opening R-W will cause the gas valve
to close, and the furnace to shut down.
11. The furnace has three high temperature limit controls,
which can shut down the burner. They do not shut
down the ventor motor.
