18
If the venter motor comes on, but the unit does not attempt igni-
tion, check if the ALS (Auxiliary High Limit Control 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 venter motor IDM.
4. Operation of the venter motor closes the pressure switch
PS located in the burner compartment. Unless excessive
temperatures or shipping shock have opened high limit
control ALS, power is fed to the integrated ignition control,
which then initiates a 15-second pre-purge time delay.
During this period, the venter 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 one (1) 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. High stage manifold
pressure will be approximately 3.5" w.c. for natural gas
and 10.0" w.c. for propane (LP). Low fire natural gas is 2.0”
w.c.; low fire propane 6.0” w.c.
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 venter motor.
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 shut off 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.
A
UTOMATIC
R
ESET
H
IGH
L
IMIT
C
ONTROL
(LS)
Located in the burner compartment on the heat exchanger, its sens-
ing element projects through the blower section bulkhead and
senses the temperature at the rear of the furnace. It will cycle the
furnace off if the temperature exceeds 100°F plus maximum rise.
A
UXILIARY
H
IGH
L
IMIT
C
ONTROL
(ALS)
Located in the blower compartment on the blower housing, it
senses air temperature within the blower compartment and pro-
tects the filters from excessive temperature. It will shut down the
furnace if it senses excessive temperatures.
Elevated temperatures at the control are normally caused by
blower failure. The reason for the opening should be determined
and repaired prior to resetting.
M
ANUAL
R
ESET
F
LAME
R
OLLOUT
C
ONTROL
(RS)
Located in the burner compartment at the top of the burner as-
sembly, it senses high temperature that could occur if the heat
exchanger tubes were plugged and the flame was rolling out in-
stead of entering the tubes. It has a manual push-button reset that
cannot be actuated until the limit control has cooled.
The reason for elevated temperatures at the control should be
determined and repaired prior to resetting this manual reset con-
trol.
WARNING
T
O AVOID PROPERTY DAMAGE, PERSONAL INJURY OR DEATH DUE TO FIRE
OR EXPLOSION, A QUALIFIED SERVICER MUST INVESTIGATE THE REASON FOR
THE ROLLOUT PROTECTION DEVICE TO OPEN BEFORE MANUALLY RESETTING
THE ROLLOUT PROTECTION DEVICE.
R
EFRIGERATION
S
YSTEM
C
HECKS
This unit is equipped with a piston type metering device or non-
adjustable TXV.
Ensure the hold-down bolts on the compressor are secure and have
not vibrated loose during shipment. Check that the vibration grom-
mets have been installed and visually check all piping for damage
and leaks and repair if necessary. The entire system has been fac-
tory charged and tested, making it unnecessary to field charge.
Factory refrigerant charge is shown on the unit’s nameplate.
To confirm charge levels or, if a leak occurs and charge needs to be
added to the system, it is recommended to evacuate the system
and recharge refrigerant to the unit’s nameplate specifications.
This unit has been rated in the cooling mode at the AHRI rated
conditions of: indoor (80°F db/67°F wb) and outdoor (95°F db).
While operating at this condition, the superheat should range from
9°F to 11°F for each refrigeration circuit measured at the suction
service port located near the compressor.
