MCQUAY Service Guide Book    Controller Configuration 
 
29 
   
6. Defrost Option 
 
Select whether compressor will turn off or remain 
on when 4WV changes at beginning of defrost 
cycle. 
 
  Dip switch 8 
a. Compressor off  Off 
b. Compressor on  On (C2.4 spec) 
 
7. Summary of Models available 
 
SQCn     Cooling Only model 
SQHnh   Heatpump  model 
 
n = number of compressors: 2, 3, 4 
h = number of heaters: 0, 1, 2 
 
Factory preset (default setting) 
 
Model S1 S2 S3 S4 S5 S6 S7 S8 
SQCn  Off Off Off Off Off Off Off Off 
SQHnh On On Off Off On On Off On 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
8. Sequential Control 
 
Cool Mode: The starting sequence for indoor fan, 
outdoor fan and compressors is shown as below: 
 
Start      Indoor 
 
       Outdoor fan 1         Compressor 1* 
 
       Outdoor fan 2         Compressor 2* 
 
       Outdoor fan 3         Compressor 3* 
 
       Outdoor fan 4         Compressor 4* 
 
 
Heat Mode: The starting sequence for indoor fan, 
outdoor fan and compressors is shown as below: 
 
Start       Indoor  All 4-way valves 
 
       Outdoor fan 1         Compressor 1* 
 
       Outdoor fan 2         Compressor 2* 
 
       Outdoor fan 3         Compressor 3* 
 
       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. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2s 
2s 
2s 
2s 
2s 
15s 
15s 
15s 
15s 
2s 
2s 
2s 
2s 
15s 
15s 
15s 
15s 
2s 
2s