Troubleshooting - Bosch LM024 Installation, Operation And Maintenance Manual

18 | Troubleshooting

TROUBLESHOOTING
Problem Possible Cause
ENTIRE UNIT Power Supply Off
DOES NOT RUN
Blown Fuse
Voltage Supply
Low
Thermostat
UNIT OFF ON Discharge
HIGH PRESSURE pressure too high
CONTROL
Refrigerant
charge
High pressure
UNIT OFF ON Suction pressure
LOW PRESSURE too low
CONTROL
Refrigerant
charge
Low pressure
switch
UNIT SHORT Unit oversized
CYCLES
Thermostat
Wiring and
controls
8 733 920 847 (2014/01)
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.
In "COOLING" mode: Lack of or inadequate water flow. Entering water
temperature is too warm. Scaled or plugged condenser. In "HEATING"
mode: Lack of or inadequate air flow. Blower inoperative, clogged filter
or restrictions in duct work
The unit is overcharged with refrigerant. Reclaim refrigerant, evacuate
and recharge with factor recommended charge.
Check for defective or improperly calibrated high pressure switch.
In "COOLING" mode: Lack of or inadequate air flow. Entering air
temperature is too cold. Blower inoperative, clogged filter or
restrictions in duct work. In "HEATING" mode: Lack of or inadequate
water flow. Entering water temperature is too cold. Scaled or plugged
condenser.
The unit is low on refrigerant. Check for refrigerant leak, repair,
evacuate and recharge with factory recommended charge.
Check for defective or improperly calibrated low pressure switch.
Recalculate heating and or cooling loads.
Thermostat installed near a supply air grill; relocate thermostat.
Readjust heat anticipator.
Check for defective or improperly calibrated low pressure switch.
Subject to change without prior notice
LM Series Heat Pump AH
LM Series Heat Pump AH