20
If the venter motor comes on, but the unit does not attempt
ignition, 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 be-
tween unit terminals R and W (R-W) when the tempera-
ture 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 exces-
sive 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) mi-
cro-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 es
-
tablished, it will keep the gas valve energized and
discontinue the ignition spark. High stage manifold pres-
sure 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 condi-
tioned 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 exchang-
er, its sensing element projects through the blower section
bulkhead and senses the temperature at the rear of the fur-
nace. 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
protects 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 deter-
mined 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 burn-
er assembly, it senses high temperature that could occur if
the heat exchanger tubes were plugged and the flame was
rolling out instead of entering the tubes. It has a manual
push-button reset that cannot be actuated until the limit con-
trol has cooled.
The reason for elevated temperatures at the control should
be determined and repaired prior to resetting this manual
reset control.
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 grommets have been installed and visually check
all piping for damage and leaks and repair if necessary. The
entire system has been factory 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
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