McQuay MDB075B, Manual

Page: 102 / 163

101
8. Sequential Control For Cool Mode
The starting sequence for indoor fan, outdoor fan and compressors is shown as below:
2 seconds
Start Indoor fan
15 seconds 2 seconds
outdoor fan 1 compressor 1*
15 seconds 2 seconds
outdoor fan 2 compressor 2*
15 seconds 2 seconds
outdoor fan 3 compressor 3*
15 seconds 2 seconds
outdoor fan 4 compressor 4*
* if available and applicable
The compressors will be turned on one by one depending on the on/off conditions shown in the above
9. Sequential control for heat mode
The starting sequence for indoor fan, outdoor fan and compressors is as shown below :
2 seconds 2 seconds
Start Indoor fan all 4 way valves
15 seconds 2 seconds
outdoor fan 1 compressor 1*
15 seconds 2 seconds
outdoor fan 2 compressor 2*
15 seconds 2 seconds
outdoor fan 3 compressor 3*
15 seconds 2 seconds 15 seconds 15 seconds
outdoor fan 4 compressor 4* Heater 1* Heater 2*
* if available and applicable
The compressors will be turned on one by one depending on the on/off conditions shown in the above.
Troubleshooting
When any air conditioner malfunction is noted, immediately switch off the power supply to the unit and
contact the local dealer, if necessary. Some simple trouble shooting tips are given below :
Trouble Probable Cause Suggested Action
1. Fan does not work 1. No power supply
2. Fan capacitor faulty
3. Fan motor faulty
4. Switch faulty 1. Check power supply
2. Contact local dealer
3. Contact local dealer
4. Change switch
2. Fan works, but
compressor does
not work
1. Thermostat setting too high
2. Dual pressure control trip
3. Compressor faulty
4. Compressor contactor faulty 1. Reset thermostat
2. Reset Pressure Control
3. Contact local dealer
4. Contact local dealer
3. Both fan and
compressor does
not work
1. Power failure
2. Starter trip
3. Fuse blown in power switch or operating
unit
1. Operate when power supply resume
2. Reset starter
3. Check and replace fuse
4. Air-conditioner
works but cooling
not satisfactory
1. Thermostat setting too high
2. Doors and/or windows not closed
3. Condenser coil dirty
4. Some objects blocking the inlet and/or
outlet of the unit
5. Insufficient refrigerant charge.
1. Reset thermostat
2. Close doors and/or windows
3. Contact local dealer
4. Remove the object
5. Contact local dealer