Troubleshooting - Bosch LM Series Installation, Operation And Maintenance Manual

24 | Troubleshooting

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
Problem Possible Cause
ENTIRE UNIT Power Supply Off
DOES NOT RUN
Blown Fuse
Voltage Supply
Low
Thermostat
BLOWER Thermostat
OPERATES BUT
Wiring
COMPRESSOR
DOES NOT
Safety Controls
Compressor
overload open
Compressor
motor grounded
Compressor
windings Open
8 733 905 315 (2013/9)
LEDs
Unit Troubleshooting
Checks and Correction
Apply power, close disconnect
Replace fuse or reset circuit breaker. Check for correct fuses
If voltage is below minimum voltage specified on unit data plate,
contact local power company.
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.
Check setting, calibration, and wiring
Check for loose or broken wires at compressor, capacitor, or contactor.
Check UPM board red default L.E.D. for Blink Code
If the compressor is cool and the overload will not reset, replace
compressor.
Internal winding grounded to the compressor shell. Replace
compressor. If compressor burnout, install suction filter dryer.
After compressor has cooled, check continuity of the compressor
windings. If the windings are open, replace the compressor
Subject to change without prior notice
LM Series Heat Pump
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.
LM Series Heat Pump