Troubleshooting - McQuay MWM 007G Manual

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By means of pressure readings :
PRESSURE
Data
Circuit
High Side
Low Side
High Side
Low Side
High Side
Low Side
High Side
Low Side
High Side
Low Side
By Means Of Diagnosis Flow Chart
Generally, there are two kinds of troubles, i.e. starting failure and insufficient cooling/heating. "Starting Failure" is
caused by electrical defect while "Insufficient Cooling/Heating" is caused by improper application or defects in
refrigerant circuit.
i) Diagnosis Of Electric Circuit
Check power supply
- voltage
- phase
- frequency
Check circuit breake & fuse
Fan fails to start
Fan Motor Capacitor defective
Loose Connections,
Contactors
Irregular motor resistance (Ω )
& insulation (M Ω )
Replace Fan Motor
Compressor locked (to replace compressor)
1. Overcharged with refrigerant.
2. Non-condensable gases in refrigerant circuit (e.g. oil).
3. Obstructed air-intake/discharge.
4. Short circuiting of hot air at condensing unit.
1. Poor compression/no compression (compressor defective.)
2. Check valve stick in open position.
3. Reversing valve leaking.
1. Undercharged with refrigerant.
2. Refrigerant leakage.
3. Air filter clogged/dirty (indoor unit).
4. Indoor fan locked (cooling).
5. Defective defrost control, outdoor coil freezed up (heating).
6. Outdoor fan locked (heating).
1. Outdoor fan blocked (cooling).
2. Outdoor coil dirty (cooling).
3. Indoor fan locked (heating).
4. Indoor filter clogged/dirty (heating).
5. Non-condensable gases in refrigerant circuit (e.g. air).
1. Air intake temperature of indoor unit too high.
No Cooling / Heating
Unit fail to start
Thermostat setting too high
Protection Device Actuated
Reset
Regular but fails
to start
PROBABLE CAUSE
Check settings of remote control box
Check power source cord
Voltage supply not within range
Loose Connections,
Improper wiring
Compressor
Capacitor Defective
Check motor resistance ( Ω ) and insulation (M Ω )
Irregular
Compressor Motor damaged ( to replace compressor)
94
Compressor fails to start