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31-5000734 Rev. 0
Motor Start-Up
When B3 begins start-up, the motor gently vibrates back
and forth for a moment. This is normal. During this time
the electronic controller is determining the exact position
of the rotor. Once the motor begins turning, the controller
slowly eases the motor up to speed (this is called “soft-
start”). The motor may take as long as 10-15 seconds
to reach full speed. If the motor does not reach 200 rpm
within 13 seconds, the motor shuts down. Then the motor
will immediately attempt a restart. The shutdown feature
provides protection in case of a frozen bearing or blocked
blower wheel. The motor may attempt to start eight times.
If the motor does not start after the eighth try, the controller
locks out. Reset controller by momentarily turning off
power to unit.
The DC filter capacitors inside the controller are connected
electrically to the motor supply wires. The capacitors take
approximately 5 minutes to discharge when the disconnect
is opened. For this reason it is necessary to wait at least 5
minutes after turning off power to the unit before attempting
to service motor.
Disconnect power from unit and wait at
least five minutes to allow capacitors to
discharge before attempting to service
motor. Failure to wait may cause personal
injury or death.
DANGER
Power Choke (L13)
A choke coil is used on NF80XV 4 and 5 ton units equipped
with 1 hp motors. The choke is located on the blower
housing and is used to suppress transient current spikes.
Troubleshooting Motor Operation
To verify motor operation see steps below and Figure 8
and Figure 9.
1. Remove J48 (5 pin power plug) from P48 on the motor.
2. With the power on at the furnace and door switch
depressed, use a test meter to verify 120V between
pins 4 and 5 on J48.
3. Reconnect J48 to P48 on the motor.
4. Remove J49 (4 pin low voltage connector) from P49
on the motor.
5. Using test jumpers, apply 24V to pins 3 and 4 on P49
on the motor.
NOTE:
Do not apply 24V to pins 2 and 4 on P49. Doing
so will cause permanent damage to the motor.
6. Motor should run at 75%.
7. Test is complete. Remove jumpers and reconnect
plugs.
Another option is to use the TECMate PRO motor tester
with the 16 to 4 pin adaptor. The use of the TECMate PRO
isolates the motor from the integrated control. Follow the
instructions provided with the kit. If the motor runs do not
replace.
