22
COM-SVN01D-EN
Troubleshooting
Important:
Check the unit Installation, Operation, and
Maintenance manual (see
)foradditionalinformation
regarding diagnosis and causes.
WARNING
Hazardous Service Procedures!
Failure to follow all precautions in this manual and on
the tags, stickers, and labels could result in death or
serious injury.
Technicians, in order to protect themselves from
potential electrical, mechanical, and chemical hazards,
MUST follow precautions in this manual and on the
tags, stickers, and labels, as well as the following
instructions: Unless specified otherwise, disconnect all
electrical power including remote disconnect and
discharge all energy storing devices such as capacitors
before servicing. Follow proper lockout/tagout
procedures to ensure the power can not be
inadvertently energized.When necessary to work with
live electrical components, have a qualified licensed
electrician or other individual who has been trained in
handling live electrical components perform these
tasks.
Compressor will not start
•
Refer to the unit Installation, Operation, and
Maintenance manual (see
) for possible diagnostics codes and corrective
action.
•
Verify:
–
Compressor voltage is correct.
–
CSHN/CSHL compressors
—Motor protection
module is the correct voltage.
–
All safety switches are closed.
–
All the contacts on the contactor are pulled in.
–
CSHD compressors
—The internal motor overloads
may be open. Disconnect power to the unit and
disconnect the wires from the compressor
terminals. With an ohm meter, check to ensure that
there is resistance between T1-T2 and T3.
Compressor will not build up pressure
•
CSHD compressor is wired incorrectly
—It will be noisy
and draw 1/2 the expected amps. Shut the compressor
off immediately. Running in this condition for more
than 5 seconds may damage the compressor.
•
CSHN compressor is wired incorrectly
.
•
Check to ensure that any bypass valves in the system
are not open.
•
Four-way reversing valve may be stuck and not
switched properly bypassing from the high side to the
low side of the system; this situation is indicated by an
extremely warm suction inlet to the compressor.
•
Model CSHN374/CSHL374 compressors contain an
internal pressure relief that may have opened.
It may
take two to three hours to reset. The oil sump will be
very warm and the compressor will be tripped out on
the motor protection module. This is caused by a very
high 625–715 psid difference between the high side
and low side of the system. This could occur with either
a blocked high side or low side.
Abnormal running noise
•
Compressor is running backwards—Immediately shut
off the compressor and check wiring and proper
phasing.
•
Excessive floodback—The superheat should be a
minimum of 16°F at full load and oil sump temperature
should be at least 20°F above the saturated suction
temperature. Measure the sump temperature at the
bottom center of the compressor. Chillers with
electronic expansion valves may operate with lower
superheats; check the unit Installation, Operation, and
Maintenance manual (see
) for proper operating superheats.
•
Compressor is full of liquid on startup—The crankcase
heater either was not energized for a minimum of
eight hours, or it is defective.
•
Mechanical damage to the compressor has occurred—
Check compressor amperage. It may also trip the
compressor motor protection module or other unit
electrical protection devices such as circuit breakers.
High-pressure control opens
•
Check the unit Installation, Operation, and
Maintenance manual (see
) for possible diagnostics codes and corrective
action.
•
Also check for:
–
Defective condenser fan motors or controls.
–
Dirty air-cooled or water-cooled condensers.
–
Restricted air flow.
–
Insufficient water flow.
–
System overcharged with refrigerant. Check
superheat and system subcooling.
–
Non-condensables in the system.
Low-pressure control opens
•
Check the unit Installation, Operation, and
Maintenance manual (see
) for possible diagnostics codes and corrective
action.
•
Also check for:
–
Defective evaporator fan motors, belts, or controls.
–
Defective TXV valve.
