Trouble Shooting - Bosch FHP ES Series Installation And Maintenance Manual

16

TROUBLE SHOOTING

PROBLEM POSSIBLE CAUSE
Power supply off
ENTIRE UNIT DOES
NOT RUN
Blown fuse
Voltage supply low
Thermostat
Thermostat
BLOWER OPERATES
BUT COMPRESSOR
Wiring
DOES NOT
Safety controls
Compressor overload open
Compressor motor grounded
Compressor windings open
UNIT OFF ON
Discharge pressure too high
HIGH PRESSURE
CONTROL
Refrigerant charge
High pressure
Suction pressure too low
UNIT OFF ON
LOW PRESSURE
CONTROL
Refrigerant charge
Low pressure switch
UNIT SHORT
Unit oversized
CYCLES
Thermostat
Wiring and controls
Unit undersized
INSUFFICIENT
COOLING OR
Loss of conditioned air
HEATING
by leaks
Airflow
Refrigerant charge
Compressor
Reversing valve
Operating pressures
TXV
Moisture, noncondensables
6720220330 Revised 05-12
CHECKS AND CORRECTIONS
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.
In "COOLING" mode: Lack of or inadequate water flow. Entering water temperature too warm.
Scaled or plugged condenser.
In "HEATING" mode: Lack of or inadequate air flow. Blower inoperative, clogged filter or
restrictions in ductwork.
The unit is overcharged with refrigerant. Reclaim refrigerant, evacuate and recharge with factory
recommended charge.
Check for defective or improperly calibrated high pressure switch.
In "COOLING" mode: Lack of or inadequate air flow. Entering air temperature too cold. Blower
inoperative, clogged filter, or restrictions in ductwork.
In "HEATING" mode: Lack of or inadequate water flow. Entering water temperature 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.
Loose connections in the wiring or a defective compressor contactor.
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 to suction side of
compressor. Replace reversing valve.
Compare unit operating 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, evacuate and recharge with factory recommended charge. Note: a liquid line dryer
may be required.
ES SERIES