method of obtaining the actual amp draw. The amp reading
should be taken after the blower motor has started. 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.
E.
Check Safety Controls
The flame sensor, gas valve, and pressure switch were all checked
in the Start-up Procedures section as part of normal operation.
1. Check primary limit control.
This control shuts off the combustion control system and
energizes the circulating-air blower motor if the furnace
overheats.
The preferred method of checking the limit control is to
gradually block off the return air after the furnace has been
operating for a period of at least 5 minutes. As soon as the
limit has shut off the burners, the return-air opening should
be unblocked. By using this method to check the limit
control, it can be established that the limit is functioning
properly and operates if there is a motor failure.
2. Check draft safeguard switch.
The purpose of this control is to permit the safe shutdown
of the furnace during certain blocked vent conditions.
a. Disconnect power to furnace and remove vent connector
from furnace outlet collar. Be sure to allow time for vent
pipe to cool down before removing.
b. Restore power to furnace and set room thermostat above
room temperature.
c. After normal start-up, allow furnace to operate for 2
minutes, then block flue outlet 100 percent. Furnace
should cycle off within 2 minutes.
d. Remove blockage and reconnect vent pipe to furnace
outlet collar.
e. Wait 5 minutes and then reset draft safeguard switch.
3. Check pressure switch.
This control proves operation of draft inducer blower.
a. Turn off 115-v power to furnace.
b. Remove control door and disconnect inducer motor lead
wires from wire harness.
c. Turn on 115-v power to furnace.
d. Set thermostat to "call for heat" and wait 1 minute. When
pressure switch is functioning properly, hot surface
ignitor should NOT glow and control center diagnostic
light flashes a 31 fault. If hot surface ignitor glows when
inducer motor is disconnected, shut down furnace im-
mediately. Determine reason pressure switch did not
function properly and correct condition.
e. Turn off 115-v power to furnace.
f. Reconnect inducer motor wires, replace control door, and
turn on 115-v power.
F.
Checklist
1. Put away tools, instruments, and clean up debris.
2. Verify manual reset switches have continuity.
3. Ensure blower and control access doors are properly in-
stalled.
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. 13—Amp Draw Check With Ammeter
A80201
R
Y W G
10 TURNS
THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
HOOK-AROUND
VOLT/AMMETER
EXAMPLE:
5.0 AMPS ON AMMETER
10 TURNS AROUND JAWS
= 0.5 AMPS FOR THERMOSTAT SETTING
FROM UNIT 24-VOLT
TERMINAL BLOCK
—14—
