SET THERMOSTAT HEAT ANTICIPATOR
The thermostat heat anticipator must be set to match the amp draw
of components in the R-W/W1 circuit. Accurate amp draw
measurements can be obtained at the thermostat subbase terminals
R and W.
Fig. 52 illustrates an easy method of obtaining thermostat amp
draw measurements. The amp reading should be taken after blower
motor has started and furnace is operating in low heat.
1. To operate furnace in low heat, turn setup switch SW-2 to ON
position (See Fig. 25) and connect ammeter leads across
thermostat subbase R-W.
2. See thermostat manufacturer’s instructions for adjusting the
heat anticipator and for varying heating cycle length.
NOTE:
When using an electronic thermostat, set cycle rate for 3
cycles per hr.
3. Return setup switch SW-2 to OFF position and replace
thermostat on subbase.
CHECK SAFETY CONTROLS
Step 1—Check Primary Limit Control
This control shuts off the combustion control system and energizes
the air-circulating blower motor if furnace overheats.
1. The recommended method of checking this limit control is to
gradually block off return air after furnace has been operating
for a period of at least 5 minutes.
2. As soon as limit control has shut off burners, a 33 fault code
will appear on control center.
3. The return-air opening should be unblocked to permit normal
air circulation.
By using this method to check the limit control, it can be
established that the limit is functioning properly and the furnace
will operate safely if there is a restricted return-air supply or motor
failure. If the limit control does not function during this test, the
cause must be determined and corrected.
Step 2—Check Pressure Switches
This control proves operation of the draft inducer. Check switch
operation as follows:
1. Turn off 115-v power to furnace.
2. Remove control access door and disconnect inducer motor
12-pin wire harness at inducer motor.
3. Turn on 115-v power to furnace.
4. Set thermostat to call for heat. When pressure switches are
functioning properly, fault code 42 will flash on control center
approximately 10 sec after thermostat switch is closed. If
either a fault code 31 or 32 is flashed when ICM inducer motor
is disconnected, the furnace will shut itself down immediately.
Determine the reason pressure switches did not function
properly and correct the condition.
5. Turn off 115-v power to furnace.
6. Reconnect inducer motor wire harness. Reinstall furnace
access door.
7. Turn on 115-v power to furnace.
8. Reset thermostat to desired temperature.
CHECKLIST
1. Put away tools and instruments. Clean up debris.
2. Verify manual reset switch has continuity.
3. Verify that blower and control access doors are properly
installed.
4. Cycle test furnace with room thermostat.
5. Check operation of accessories per manufacturer’s instruc-
tions.
6. Review User’s Manual with owner.
7. Leave literature packet near furnace.
Fig. 52—Amp Draw Check with Ammeter
A96316
R
Y W G
10 TURNS
THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
(ANITICIPATOR, CLOCK, ETC.,
MUST BE OUT OF CIRCUIT.)
HOOK-AROUND
AMMETER
EXAMPLE:
5.0 AMPS ON AMMETER
10 TURNS AROUND JAWS
=
0.5 AMPS FOR THERMOSTAT
ANTICIPATOR SETTING
FROM UNIT 24-V
CONTROL TERMINALS
45
