mycom UD Series Instruction Manual page 131

Trouble
06 Abnormally High oil supply
high temperature
discharge
temperature
Defect in discharge
temperature
detection and
protection devices
Insufficient supply
oil
07 Leak from Initial leak after
mechanical replacement until
seal mating surface(seal
and shaft) fit each
other.
Damaged sliding
surfaces due to
excessive heat of
sliding surfaces
UD-series Screw Compressors
Direct causes
Heat exchange
failure in oil cooler
Failure in oil
temperature
increase protection
feature
Malfunction in
temperature protec-
tion device,
temperature
sensor, relays, etc.
Refer to item 04,
"Low hydraulic
pressure (low
oil-supply pres-
sure)".
Initial wear stage of
mating surface.
Most cases are due
to excessive
repetition of
compressor
start/stop.
*Under normal
operating
condition, more
than 4 times /h is
considered as
excessive.
A lot of refrigerant
mixed into the
lubricant, resulting
in decreased
viscosity.
Overheat operation
High supply oil
temperature
Factors
For water-cooled oil cooling, refer to
"Heat exchange failure at
condenser (heat exchanger)" in
item 05.
For liquid-injection oil cooling,
inspect liquid supply expansion
valve, temperature sensor, related
relays, wiring, terminals, etc., and
take necessary measures.
Inspect temperature protection
device (switch), temperature
sensor, related relays, wiring,
terminals, etc., and take measures.
Identify malfunctioning devices,
examine their causes, and take
measures.
Then, replace malfunctioning
devices.
Same as on the left
For initial leak, amount of leak might
increase temporarily. However, it
will gradually decrease, so check
that the amount of leak does not
increase continuously.
Period of initial leak might differ
according to design and operating
conditions. 200 hours can be a
rough guide.
If heat load is below the design
operating conditions, re-examine
the conditions and set the control
settings to fewer start/stop times.
For capacity control malfunctions,
see item 10, "Capacity control
malfunction".
For liquid backflow operation,
remove the causes.
For malfunction of oil heater and
other devices on control circuit,
replace them.
Refer to Factor "Insufficient
refrigerant circulation volume" in
item 02.
Refer to the Direct cause "High
supply oil temperature" in item 06.
6-5
Chapter 6 Troubleshooting
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