24 | Troubleshooting LM Series Heat Pump
LM Series Heat Pump8 733 905 315 (2013/9) Subject to change without prior notice
TROUBLESHOOTING
LM Series Water Source Heat Pump is equipped
with two (2) externally mounted LEDs (Figure #21)
that blink for unit errors. See Page 27 for error
code descriptions.
Figure # 21
Troubleshooting Information Solution
column may reflect a possible fault that
may be one of, or a combination of
causes and solutions. Check each cause
and adopt "process of elimination" and
or verification of each before making
any conclusion.
Unit Troubleshooting
Problem Possible Cause Checks and Correction
ENTIRE UNIT
DOES NOT RUN
Power Supply Off Apply power, close disconnect
Blown Fuse
Replace fuse or reset circuit breaker. Check for correct fuses
Voltage Supply
Low
If voltage is below minimum voltage specified on unit data plate,
contact local power company.
Thermostat
Set the fan to “ON”, the fan should run. Set thermostat to “COOL” and
lowest temperature setting, the unit should run in the cooling mode
(reversing valve energized). Set unit to “HEAT” and the highest
temperature setting, the unit should run in the heating mode. If neither
the blower or compressor run in all three cases, the thermostat could
be miswired or faulty. To ensure miswired or faulty thermostat verify 24
volts is available on the condensing section low voltage terminal strip
between “R” and “C”, “Y” and “C”, and “O” and “C”. If the blower does
not operate, verify 24 volts between terminals “G” and “C” in the air
handler. Replace the thermostat if defective.
BLOWER
OPERATES BUT
COMPRESSOR
DOES NOT
Thermostat Check setting, calibration, and wiring
Wiring
Check for loose or broken wires at compressor, capacitor, or contactor.
Safety Controls
Check UPM board red default L.E.D. for Blink Code
Compressor
overload open
If the compressor is cool and the overload will not reset, replace
compressor.
Compressor
motor grounded
Internal winding grounded to the compressor shell. Replace
compressor. If compressor burnout, install suction filter dryer.
Compressor
windings Open
After compressor has cooled, check continuity of the compressor
windings. If the windings are open, replace the compressor
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