Refrigeration Circuit - Bosch FHP RT-20 Installation, Operation And Maintenance Manual

Troubleshooting – Refrigeration Circuit
TROUBLESHOOTING NOTE
Before any components are changed on the
refrigeration system, the cause of the failure must be
identified. Further problems will exist unless the true
cause or problem is identified and corrected.
NOTE: Unit is equipped with a phase loss/phase reversal control. If system does not start, check phase of electrical supply.
Symptom Possible Cause
Open disconnect switch or circuit breaker.
Compressor contactor not closing.
Blown fuse or tripped breaker.
Low line voltage.
Compressor motor protector open.
Compressor
will not run
or
does not
Compressor defective.
try to start
High or low pressure switch open or defective.
Open room thermostat or control
(no cooling required).
Loose wiring.
Low refrigerant charge.
Compressor starts
but cuts out on low
Airflow restricted.
pressure
Low pressure
Restriction in refrigerant line.
switch activates
at 50 psig for R-410A
Defective low pressure switch.
Always have a completed Pre Start-Up Checklist, unit Start-Up Checklist, and Optional Accessories Checklist prior to requesting parts or
service information.
IMPORTANT
Do not release refrigerant to the atmosphere! If
required service procedures include the adding or
removing of refrigerant, the service technician must
comply with all federal, state and local laws. The
procedures discussed in this manual should only be
performed by an EPA Certified Technician.
Corrective Action
Close switch and / or breaker.
Check voltage to contactor coil, transformer,
slave relay, system. Replace parts as necessary.
Check for reason and repair. Replace fuse after
correcting problem.
Check line voltage. If more than 10% from
compressor marking, correcting is necessary.
Motor thermal protector automatically resets.
Allow time (2 hrs.) for compressor to cool down
so protector will reset. Restart and check for
reason overheat occurred.
Check motor for open circuit, short circuit,
grounded windings or burn out.
Compressor may be seized; check refrigerant.
If necessary, replace compressor.
If (high pressure), reset switch. (Switch opens
at 600 psi and will not reset above 420 psi
for R-410A.) If HP switch does not reset and
everything else is OK, replace switch.
If auto reset (low pressure) does not reset and
everything else is OK, replace switch.
Check room temperature. If temperature is
proper, wait for thermostat to close.
Check all wire terminals and tighten as
necessary.
Check refrigerant pressures. If refrigerant
pressure is low check for leaks.
Check for dirty evaporator coil, dirty filters,
dampers closed, iced evaporator coil, improper
belt, check motor amps, check duct design.
Check refrigerant pressure, check and adjust
thermal expansion valve. If not functioning
properly, check for pressure drop across the filter
drier.
Replace.
Model RT Energy Recovery Unit
43