Instruction manual

98 McQuay OM 920
Operator’s Guide
Eight Equal Sized Compressors, Eight Circuits, No WRV
Only one sequence is provided so the user makes no selections.
• Total cooling stages = 8.
• Maximum cooling stages is always set to 8.
• The Staging sequence is the Standard sequence that contains the enabled Stage 1
Compressor with the fewest run hours. Compressors in disabled circuits are ignored when
only enabled compressor run hours are compared.
• The Compressor Sequence changes only when the compressor stage is Maximum cooling
stages or zero. This means that disabling and re-enabling the compressors or turning the unit
off and on may be necessary to cause sequence changes.
• The same staging sequence is used whether a circuit is disabled or not. This means that units
will remain at a stage for an extra stage time when staging up if a disabled circuit is added at
that stage. It also means that units will remain at a stage for an extra stage times when
staging down if a disabled circuit is turned off at that stage.
• Any compressor on the disabled circuit stays off if it is already off and is turned off if it is
on.
Table 67: Standard Staging
Standard Staging
Staging
Sequence
Stage 1
Comps
Stage 2
Comps
Stage 3
Comps
Stage 4
Comps
Stage 5
Comps
Stage 6
Comps
Stage 7
Comps
Stage 8 Comps
Std-1 1 1,2 1,2,3 1,2,3,4 1,2,3,4,5 1,2,3,4,5,6 1,2,3,4,5,6,7 1,2,3,4,5,6,7,8
Std-2 2 1,2 1,2,8 1,2,7,8 1,2,3,7,8 1,2,3,4,7,8 1,2,3,4,5,7,8 1,2,3,4,5,6,7,8
Std-3 3 3,4 2,3,4 1,2,3,4 1,2,3,4,8 1,2,3,4,7,8 1,2,3,4,6,7,8 1,2,3,4,5,6,7,8
Std-4 4 3,4 3,4,5 3,4,5,6 2,3,4,5,6 1,2,3,4,5,6 1,2,3,4,5,6,8 1,2,3,4,5,6,7,8
Std-5 5 5,6 4,5,6 3,4,5,6 3,4,5,6,7 3,4,5,6,7,8 1,3,4,5,6,7,8 1,2,3,4,5,6,7,8
Std-6 6 5,6 5,6,7 5,6,7,8 1,5,6,7,8 1,2,5,6,7,8 1,2,3,5,6,7,8 1,2,3,4,5,6,7,8
Std-7 7 7,8 1,7,8 1,2,7,8 1,2,6,7,8 1,2,5,6,7,8 1,2,4,5,6,7,8 1,2,3,4,5,6,7,8
Std-8 8 7,8 6,7,8 5,6,7,8 4,5,6,7,8 3,4,5,6,7,8 2,3,4,5,6,7,8 1,2,3,4,5,6,7,8
ClgCap 13% 25% 38% 50% 63% 75% 88% 100%
Table 68: Alternate Staging
Standard Staging
Staging
Sequence
Stage 1
Comps
Stage 2
Comps
Stage 3
Comps
Stage 4
Comps
Stage 5
Comps
Stage 6
Comps
Stage 7
Comps
Stage 8 Comps
Std-1 1 1,3 1,3,5 1,3,5,7 1,2,3,5,7 1,2,3,5,6,7 1,2,3,4,5,6,7 1,2,3,4,5,6,7,8
Std-2 2 2,4 2,4,6 2,4,6,8 1,2,4,6,8 1,2,3,4,6,8 1,2,3,4,5,6,8 1,2,3,4,5,6,7,8
Std-3 3 1,3 1,3,7 1,3,5,7 1,3,4,5,7 1,3,4,5,7,8 1,2,3,4,5,7,8 1,2,3,4,5,6,7,8
Std-4 4 2,4 2,4,8 2,4,6,8 2,3,4,6,8 1,2,3,4,6,8 1,2,3,4,6,7,8 1,2,3,4,5,6,7,8
Std-5 5 5,7 1,5,7 1,3,5,7 1,3,5,6,7 1,2,3,5,6,7 1,2,3,5,6,7,8 1,2,3,4,5,6,7,8
Std-6 6 6,8 2,6,8 2,4,6,8 2,4,5,6,8 2,4,5,6,7,8 1,2,4,5,6,7,8 1,2,3,4,5,6,7,8
Std-7 7 5,7 3,5,7 1,3,5,7 1,3,5,7,8 1,3,4,5,7,8 1,3,4,5,6,7,8 1,2,3,4,5,6,7,8
Std-8 8 7,8 4,6,8 2,4,6,8 2,4,6,7,8 2,4,5,6,7,8 2,3,4,5,6,7,8 1,2,3,4,5,6,7,8
ClgCap 13% 25% 38% 50% 63% 75% 88% 100%
Table 69: Standard Staging
Standard Staging
Staging
Sequence
Stage 1
Comps
Stage 2
Comps
Stage 3
Comps
Stage 4
Comps
Stage 5
Comps
Stage 6
Comps
Stage 7
Comps
Stage 8 Comps
Std-1 1 1,2 1,2,3 1,2,3,4 1,2,3,4,5 1,2,3,4,5,6 1,2,3,4,5,6,7 1,2,3,4,5,6,7,8
Std-2 2 1,2 1,2,8 1,2,7,8 1,2,3,7,8 1,2,3,4,7,8 1,2,3,4,5,7,8 1,2,3,4,5,6,7,8
Std-3 3 3,4 2,3,4 1,2,3,4 1,2,3,4,8 1,2,3,4,7,8 1,2,3,4,6,7,8 1,2,3,4,5,6,7,8
Std-4 4 3,4 3,4,5 3,4,5,6 2,3,4,5,6 1,2,3,4,5,6 1,2,3,4,5,6,8 1,2,3,4,5,6,7,8
Std-5 5 5,6 4,5,6 3,4,5,6 3,4,5,6,7 3,4,5,6,7,8 1,3,4,5,6,7,8 1,2,3,4,5,6,7,8
Std-6 6 5,6 5,6,7 5,6,7,8 1,5,6,7,8 1,2,5,6,7,8 1,2,3,5,6,7,8 1,2,3,4,5,6,7,8
Std-7 7 7,8 1,7,8 1,2,7,8 1,2,6,7,8 1,2,5,6,7,8 1,2,4,5,6,7,8 1,2,3,4,5,6,7,8
Std-8 8 7,8 6,7,8 5,6,7,8 4,5,6,7,8 3,4,5,6,7,8 2,3,4,5,6,7,8 1,2,3,4,5,6,7,8
ClgCap 13% 25% 38% 50% 63% 75% 88% 100%