Bosch EP Series Installation And Maintenance Manual page 27

EP Series
Problem Possible Cause
UNIT OFF ON Discharge
HIGH PRESSURE pressure too high
CONTROL
Refrigerant
charge
High pressure
UNIT OFF ON LOW Suction pressure
PRESSURE too low
CONTROL
Refrigerant
charge
Low pressure
switch
UNIT SHORT Unit oversized
CYCLES
Thermostat
Wiring and
controls
INSUFFICIENT Unit undersized
COOLING OR
HEATING
Loss of
conditioned air by
leakage
Airflow
Refrigerant
charge
Compressor
Reversing Valve
Operating
pressures
TXV
Moisture, non
condensable
EP Series
Unit Troubleshooting
Checks and Correction
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.
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 non
condensable. Reclaim refrigerant, replace filter dryer, evacuate the
refrigerant system, and recharge with factory recommended charge.
Troubleshooting | 27
8733953041 (2019/01)