8.3.2.7 Low pressure protection (For M4OC1-27HRDN1-Q, M4OC-27HRDN1-Q,M4OC-36HRDN1-Q,
M5OA-36HRDN1-Q)
Low pressure protection
Judge 1: The wiring between the low pressure switch and main control
board is connected well or correctly
Judge 2: Whether the low pressure switch is broken
Connect it well
Method: Short connect the low pressure switch socket, check
whether the system can run normally
Check whether the refrigerant system is ok
Yes
No
Judge 3: Check whether the outdoor ambient temperature is too low
Yes
Stop the unit
No
Judge 4: The refrigerant of the system is leakage
Yes
Method: Connect the pressure gauge to the gauge joint of the system,
check whether the pressure is lower than 0.14MPa
Leak hunting: Charge nitrogen or refrigerant to
the system, if the leakage is serious, there will
be distinct gas leakage “cici” sound; if the
leakage is slight, use the suds (mixture of water
and abluent is also ok if it can make bubble) or
electronic leak detector.
Judge 5: The refrigerant pipe is blocked
Yes
Let the refrigerant out, then use the high pressure
nitrogen or refrigerant to blow pipe, vacuumize and
charge the refrigerant again
No
Replace outdoor main board
No
No
Yes
Replace low pressure switch
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