Set Thermostat Heat Anticipator; Check Safety Controls; Check Primary Limit Control; Check Pressure Switch - Carrier 58MVP080 Installation, Start-Up, And Operating Instructions Manual

e. Check Troubleshooting Guide for Gas-Fired Condensing
Furnaces.

SET THERMOSTAT HEAT ANTICIPATOR

The thermostat heat anticipator must be set to match the amp draw
of the components in the R-W/W1 circuit. Accurate amp draw
measurements can be obtained at the thermostat subbase terminals
R and W.
Fig. 47 illustrates an easy method of obtaining thermostat amp
draw measurements. The amp reading should be taken after the
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 the thermostat manufacturer's instructions for adjusting
the heat anticipator and for varying the heating cycle length.
NOTE: When using an electronic thermostat, set the cycle rate for
3 cycles per hr.
3. Return setup switch SW-2 to OFF position and replace
thermostat on subbase.
THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
R Y W G
10 TURNS
FROM UNIT 24-VOLT
TERMINAL BLOCK
5.0 AMPS ON AMMETER
EXAMPLE:
10 TURNS AROUND JAWS
Fig. 47—Amp Draw Check with Ammeter
HOOK-AROUND
VOLT/AMMETER
= 0.5 AMPS FOR THERMOSTAT SETTING
A80201

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 the furnace overheats.
1. The recommended method of checking this limit control is to
gradually block off the return air after the furnace has been
operating for a period of at least 5 minutes.
2. As soon as the limit control has shut off the burners, a 33 fault
will appear on the 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 Switch
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 the pressure switches
are functioning properly, fault code 42 will flash on the
control center approximately 10 sec after the thermostat
switch is closed. If either fault code 31 or 32 is flashed when
the ICM inducer motor is disconnected, the furnace will shut
itself down immediately. Determine the reason the 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.
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.
37

CHECKLIST