Unit Lockouts - Bosch LM024 Installation, Operation And Maintenance Manual

LM Series Heat Pump
Problem Possible Cause
INSUFFICIENT Unit undersized
COOLING OR
HEATING
Loss of
conditioned air by
leakage
Airflow
Refrigerant
charge
Compressor
Reversing Valve
Operating
pressures
TXV
Moisture,
noncondensables
BLOWER Thermostat
OPERATES
Wiring
BUT
COMPRESSOR
Safety Controls
DOES NOT
Compressor
overload open
Compressor
motor grounded
Compressor
windings open

Unit Lockouts

Periodic lockouts almost always are caused by air
or water flow problems. The lockout (shutdown) of
the unit is a normal protective measure in the
design of the equipment. If continual lockouts
occur call a mechanic immediately and have them
check for: water flow problems, water
temperature problems, air flow problems or air
temperature problems. Use of the pressure and
temperature charts for the unit may be required to
properly determine the cause.
Revised 01-14
Unit Troubleshooting
Checks and Correction
Recalculate heating and or cooling loads. If excessive, possibly adding
insulation and shading will rectify the problem
Check for leaks in duct work or introduction of ambient air through
doors or windows
Lack of adequate air flow or improper distribution of air. Replace dirty
filter
Low on refrigerant charge causing inefficient operation
Check for defective compressor. If discharge is too low and suction
pressure is too high, compressor is not pumping properly. Replace
compressor.
Defective reversing valve creating bypass of refrigerant from discharge
of suction side of compressor. Replace reversing valve
Compare unit operation pressures to the pressure/temperature chart
for the unit.
Check TXV for possible restriction or defect. Replace if necessary.
The refrigerant system may be contaminated with moisture or
noncondensables. Reclaim refrigerant, replace filter dryer, evacuate the
refrigerant system, and recharge with factory recommended charge.
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.
Troubleshooting | 19
8 733 920 847 (2014/01)