Troubleshooting - Bosch TW Series Installation And Maintenance Manual

20 TW Series / Water to Water

TroubleSHooTInG

Problem Possible Cause
Compressor Power Supply Off
does not
Blown Fuse
operate
Broken or loose
wires
Voltage supply low
Controller
Safety controls
Compressor
overload open
Compressor motor
grounded
Compressor
windings open
Unit off on
Discharge pressure
high pressure
too high
switch
Refrigerant charge
High pressure
switch
Unit off on low
Suction pressure
pressure
too low
switch
Refrigerant charge
Low pressure
switch
6 720 220 047
Checks and Corrections
Apply power, close disconnect
Replace fuse or reset circuit breaker. Check for correct fuses
Replace or tighten the wires. Check for loose or broken wires at com-
pressor, capacitor, or contactor.
If voltage is below minimum voltage specified on unit data plate, contact
local power company.
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.
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)
If the compressor is cool and the overload will not reset, replace com-
pressor.
Internal winding grounded to the compressor shell. Replace compres-
sor. If compressor burnout, install suction filter dryer.
After compressor has cooled, check continuity of the compressor
windings. If the windingsare open, replace the compressor.
In "COOLING" mode: SOURCE COIL - Lack of or inadequate water flow.
Entering water temperature too warm. Scaled or plugged condenser.
In "HEATING" mode: LOAD COIL - Lack of or inadequate water flow.
Entering water temperature too warm. Scaled or plugged load coil.
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: LOAD COIL - Lack of or inadequate fluid flow.
Entering water temperature too cold. Scaled or plugged load coil.
In "HEATING" mode: SOURCE COIL - Lack of or inadequate fluid flow.
Entering water temperature too cold. Scaled or plugged source coil.
The unit is low on refrigerant. Check for refrigerant leak, repair, evacu-
ate and recharge with factory recommended charge.
Check for defective or improperly calibrated low-pressure switch.
Subject to change without prior notice
Troubleshooting
Revised 03-11