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Troubleshooting - Bosch EP015 Installation And Maintenance Manual

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36 EP Series

TROUBLESHOOTING

Problem
Possible Cause
Entire unit does
Power Supply Off
not run
Blown Fuse
Voltage Supply Low If voltage is below minimum voltage specified on unit data plate,
Thermostat
Blower
Thermostat
operates but
Wiring
compressor
Safety Controls
does not
Compressor
overload open
Compressor motor
grounded
Compressor
windings Open
Unit off on
Discharge pressure
too high
high pressure
control
Refrigerant charge
High pressure
Unit off on
Suction pressure
too low
low pressure
control
Refrigerant charge
Low pressure
switch
Unit short
Unit oversized
cycles
Thermostat
Wiring and controls Check for defective or improperly calibrated low pressure switch.
8733922168
Checks and Corrections
Apply power, close disconnect
Replace fuse or reset circuit breaker. Check for correct fuses
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 (reversing
valve deenergized).
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 that 24 volts is available at the 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".
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.
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 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.
Subject to change without prior notice
Revised 12-13

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