McQuay MCC 010C/CR, Manual, Page: 68 / 78

67
The most common causes of air conditioner failure to “start" are:
a) Voltage not within
±
10% of rated voltage.
b) Power supply interrupted.
c) Control settings improper.
d) Air conditioner is disconnected from main power source.
e) Fuse blown or circuit breaker off.
ii) Diagnosis Of Refrigerant Circuit / Application
There might be some cases where the unit starts running but does not perform satisfactory, i.e.
insufficient cooling. Judgement could be made by measuring temperature difference of indoor
unit's intake and discharge air as well as running current.
Insufficient Cooling
Unit Starts
Excessive heat
source e.g. electric
kettle
High heat load
Refrigerant circuit
Leakage
Restriction e.g. at
strainer, capillary,
filter dryer, etc.
Compressor
Less or no compression
(Low running current)
Room overcrowded
with people
Windows / doors
wide open
Check air circulation
Indoor/Outdoor coil dirty
(clogged)
Air filters dirty
Fan Malfunction
Obstruction at air inlet/outlet
of indoor/outdoor unit
Satisfactory operation with temperature difference of
air intake & discharge of indoor unit 10°C - 15°C
Insufficient Heating
Unit Starts
High heat load
Refrigerant circuit
Leakage
Restriction e.g. at
strainer, capillary,
filter dryer, etc.
Compressor
Less or no compression
(Low running current)
Windows / doors
wide open
Check air circulation
Indoor/Outdoor coil dirty (clogged)
Air filters dirty
Fan Malfunction
Obstruction at air inlet/outlet
of indoor/outdoor unit
Satisfactory operation with temperature difference of
air intake & discharge of indoor unit 16°C - 25°C