03: Unusually Low Pressure (Decrease Of Suction Pressure); 04: Low Oil Pressure (Low Lubricating Oil Supply Pressure) - mycom 3225**C Series Instruction Manual

02: Compressor stops immediately after startup (continued)
Direct cause
Low pressure protection
circuit activates.
Motor overload

03: Unusually low pressure (decrease of suction pressure)

Direct cause
Refer to direct cause,
"Low pressure protection
circuit activates", in Item
02 above.

04: Low oil pressure (low lubricating oil supply pressure)

Direct cause
Oil filter element is
clogged.
* Pressure difference
between the outlet port
and inlet port is large.
Insufficient oil in oil
separator.
Compound 2-stage Screw Compressor 3225**C
Root cause
Insufficient refrigerant flow
 Insufficient liquid supply
Heat exchange failure in heat
exchanger
Failure of low pressure
protection device, pressure
sensor, relay, etc.
Motor overload that occurs just after startup is mostly caused not by the
refrigeration cycle but by the motor. Refer to the instruction manual of
the motor.
Root cause
Same as left
Root cause
Contamination of lubricating oil
Internal defects of compressor
Oil heater is not functioning,
refrigerant dissolves
excessively when the machine
is stopped, and oil loss occurs
at startup.
Insufficient oil return due to
insufficient refrigerant
circulation
Troubles such as clogging in oil
return passage
6-2
2202MYJE-MY-C8-N_2018.02.
Chapter 6 Troubleshooting
Action
To correct insufficient liquid supply,
inspect expansion valve and liquid
supply strainer. Take necessary
actions.
In addition, inspect devices and
parameters (set values) of the
expansion valve aperture adjusting
mechanism, and take necessary
actions.
If there are any problem (insufficiency)
in heat exchange, such as
malfunction of defrosting, investigate
the cause and take necessary
actions.
In case of malfunction of pressure
control valve, replace the valve or
remove the cause.
Identify defective devices, investigate
causes of failure and take necessary
actions.
Then, replace failed device(s).
Action
Same as left
Action
Remove clogging, and check oil for
contamination/replace oil.
Check for oil contamination and
conduct vibration/noise diagnosis.
Overhaul compressor if necessary.
Inspect oil heater alone, inspect
relays, etc. on related circuits, and
replace parts as necessary.
Correct insufficient refrigerant
circulation, and return oil from
load-side heat exchanger.
* Supply lubricating oil temporarily.
Remove causes of the trouble, and
restore the system.