This control proves operation of the draft inducer. Check switch
operation as follows.
a. Turn off 115-v power to furnace.
b. Remove control box cover and disconnect inducer motor
lead wires from control board.
c. Turn on 115-v power to furnace.
d. Set thermostat to "call for heat." When the pressure switch
is functioning properly, the ignitor should not spark. If the
ignitor sparks when the inducer motor is disconnected, shut
down the furnace immediately. Determine the reason the
pressure switch did not function properly and correct the
condition.
e. Turn off 115-v power to furnace.
f. Reconnect inducer motor lead, reinstall control box cover,
and turn on 115-v power supply.
3. Check pressure switch P2 (blocked drain safety switch).
This control ensures the condensate drain is open to allow
condensate flow and that combustion air is flowing through the
unit prior to starting the ignition cycle. The blocked drain safety
switch has only 1 tube connected to it. Check switch operation as
follows.
a. Place unit into operation with burners on.
b. Pinch off tube leading to pressure switch P2. The burners
should shut off.
c. Release the restriction on tube and furnace should begin an
ignition trial.
d. If burners do not shut off, determine reason pressure switch
did not function properly and correct condition.
CHECKLIST
1. Put away tools and instruments. Clean up debris. Verify that
blower and control access panels are properly installed.
2. Cycle test furnace with room thermostat.
3. Check operation of accessories per manufacturer’s instruc-
tions.
4. Review User’s Manual with owner.
5. Leave literature packet near furnace.
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