Bryant 987MB Installation, Start-Up, Operating And Service And Maintenance Instructions page 58

987MB: Installation, Start-up, Operating and Service and Maintenance Instructions
thermostat anticipator should NOT be in the circuit while
measuring current.
a. Set SW1-2 switch on furnace control board to ON.
b. Remove thermostat from subbase or from wall.
c. Connect an amp. meter as shown in
subbase terminals or R and W wires at wall.
d. Record amp. draw across terminals when furnace is in minimum
heat and after blower starts.
e. Set heat anticipator on thermostat per thermostat instructions and
install on subbase or wall.
f. Turn SW1-2 switch OFF.
g. Install blower door.
h. Electronic thermostat: Set cycle rate for 3 cycles per hr.
Check Safety Controls
The flame sensor, gas valve, and pressure switch were all checked in the
Start-up procedure section as part of normal operation.
1. Check Main Limit Switch
This control shuts off combustion system and energizes
air-circulating blower motor, if furnace overheats. By using this
method to check limit control, it can be established that limit is
functioning properly and will operate if there is a restricted
return-air supply or motor failure. If limit control does not function
during this test, cause must be determined and corrected.
a. Run furnace for at least 5 minutes.
a. Gradually block off return air with a piece of cardboard or sheet
metal until the limit trips.
b. Unblock return air to permit normal circulation.
c. Burners will re-light when furnace cools down.
2. Check Pressure Switch(es)
This control proves operation of the draft inducer blower.
a. Turn off 115-v power to furnace.
b. 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 igniter
should NOT glow and control diagnostic light flashes a status
code 32. If hot surface igniter glows when inducer motor is
disconnected, shut down furnace immediately.
e. Determine reason pressure switch did not function properly and
correct condition.
f. Turn off 115-v power to furnace.
g. Reconnect inducer motor wires, replace blower door, and turn on
115-v power.
h. Blower will run for 90 seconds before beginning the call for heat
again.
i. Furnace should ignite normally.
Checklist
1. Put away tools and instruments. Clean up debris.
2. Verify that switches SW1-1 and SW1-6 are OFF and other setup
switches are set as desired. Verify that switches SW1-7 and SW1-8
for the blower OFF DELAY are set as desired per
3. Verify that blower and control doors are properly installed.
4. Verify that there are no unsealed openings in the blower shelf or
casing.
5. Cycle test furnace with room thermostat.
6. Check operation of accessories per manufacturer's instructions.
7. Review Owner's Manual with owner.
8. Attach literature packet to furnace.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
Fig. 66 across the R and W
Table 12.
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