Bosch TW Series - INITIAL CONFIGURATION

Subject to change without prior notice Revised 03-11
6 720 220 047
20
TW Series / Water to Water
Troubleshooting
TROUBLESHOOTING
Problem Possible Cause Checks and Corrections
Compressor
does not
operate
Power Supply Off Apply power, close disconnect
Blown Fuse Replace fuse or reset circuit breaker. Check for correct fuses
Broken or loose
wires
Replace or tighten the wires. Check for loose or broken wires at com-
pressor, capacitor, or contactor.
Voltage supply low If voltage is below minimum voltage specied on unit data plate, contact
local power company.
Controller Set controller 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 the compressor does not run in all cases, the controller could
be miswired or faulty.To ensure miswired or faulty thermostat verify 24
volts is available on the unit section low voltage terminal strip between
“R” and “C”, “Y” and “C”, and “O” and “C”. Replace the controller if
defective.
Safety controls Reset the controller to “OFF”. After a few minutes turn to “COOL” or
“HEAT”. If the compressor runs, unit was off on one of the safety con-
trols. (See problem for possible causes)
Compressor
overload open
If the compressor is cool and the overload will not reset, replace com-
pressor.
Compressor motor
grounded
Internal winding grounded to the compressor shell. Replace compres-
sor. If compressor burnout, install suction lter dryer.
Compressor
windings open
After compressor has cooled, check continuity of the compressor
windings. If the windingsare open, replace the compressor.
Unit off on
high pressure
switch
Discharge pressure
too high
In “COOLING” mode: SOURCE COIL - Lack of or inadequate water ow.
Entering water temperature too warm. Scaled or plugged condenser.
In “HEATING” mode: LOAD COIL - Lack of or inadequate water ow.
Entering water temperature too warm. Scaled or plugged load coil.
Refrigerant charge The unit is overcharged with refrigerant. Reclaim refrigerant, evacuate
and recharge with factory recommended charge.
High pressure
switch
Check for defective or improperly calibrated high pressure switch.
Unit off on low
pressure
switch
Suction pressure
too low
In “COOLING” mode: LOAD COIL - Lack of or inadequate uid ow.
Entering water temperature too cold. Scaled or plugged load coil.
In “HEATING” mode: SOURCE COIL - Lack of or inadequate uid ow.
Entering water temperature too cold. Scaled or plugged source coil.
Refrigerant charge The unit is low on refrigerant. Check for refrigerant leak, repair, evacu-
ate and recharge with factory recommended charge.
Low pressure
switch
Check for defective or improperly calibrated low-pressure switch.