Chapter 6 Troubleshooting
UD-series Screw Compressors
6-4
Trouble
Direct causes
Factors
Actions
05
Abnormally
high
pressure
(abnormal
discharge
pressure)
Excessive
refrigerant charge
Repetitive
refrigerant charge
by mistaking
insufficient cooking
as a lack of
refrigerant in the
system.
Adjust refrigerant to proper amount.
Insufficient capacity
of heat exchanger
If the trouble is caused by change in
operating conditions, re-examine
the conditions to improve.
If it is difficult to improve, add more
heat exchangers or increase the
size.
Defect in discharge
pressure detection
feature
Malfunction in
abnormal high
pressure protection
device(switch),
pressure sensor,
relays, etc.
Identify malfunctioning devices,
examine their causes, and take
measures.
Then, replace malfunctioning
devices.
Liquid stoppage,
etc, by clogging in
the tubing for high
pressure protection
switch.
Remove clogging. Check oil
contamination level and replace oil
as necessary.
Closed outlet stop
valve for oil
separator
Neglected to
restore after
closing.
Human error
Open valve or stop immediately.
Make sure to perform tagout during
valve operation.
Make sure to perform a valve check
before starting compressor.
06 Abnormally
high
discharge
temperature
Overheating during
operation
Insufficient refriger-
ant circulation
Refer to Factors of item 02.
Heat load on
system load side is
higher than design
value.
Inspect the situation on load side
(loading volume, opening and
closing of doors, etc.), and take
necessary measures.
Malfunction in low
pressure protection
device, pressure
sensor, relays, etc.
Identify malfunctioning devices,
examine their causes, and take
measures.
Then, replace malfunctioning
devices.
Non-condensable
gases in the system
Intake air to low
pressure side
Inspect for leak, and take necessary
measures.
Then, air purge the heat exchanger.
