96 McQuay OM 920-1
Operator’s Guide
Six Equal Sized Compressors, Two Circuits
The user selects the following:
1 Staging Type = Standard or Alternate Staging
2 Lead Circuit = Auto, # 1 or # 2.
• Total cooling stages = 6.
• If Lead Circuit is set to Auto and neither circuit is disabled, the Staging sequence is the
Standard or Alternate sequence that contains the Stage 1 Compressor with the fewest run
hours. Maximum cooling stages is set to 6.
• If Lead Circuit is set to # 1 and Circuit # 2 is enabled, the Staging sequence is Std-1, Std-3,
or Std-5 that contains the Stage 1 Compressor with the fewest run hours.
• If Lead Circuit is set to # 1 and Circuit # 2 is disabled, the Staging sequence is Alt-1, Alt-3,
or Alt-5 that contains the Stage 1 Compressor with the fewest run hours.
• If Lead Circuit is set to # 2 and Circuit # 1 is enabled, the Staging sequence is Std-2, Std-4,
or Std-6 that contains the Stage 1 Compressor with the fewest run hours.
• If Lead Circuit is set to # 2 and Circuit # 1 is disabled, the Staging sequence is Alt-2, Alt-4,
or Alt-6 that contains the Stage 1 Compressor with the fewest run hours.
• The Compressor Sequence changes only when the compressor stage equals 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.
• If a circuit is disabled, Maximum cooling stages is set to three. Any compressor on the
disabled circuit stays off if it is already off and is turned off if it is on.
• If dehumidification is active, Alternate Staging is used regardless of the Staging Type=
setting.
Table 63: Standard Staging
Standard Staging
Staging
Sequence
Stage 1
Comps
Stage 2
Comps
Stage 3
Comps
Stage 4
Comps
Stage 5
Comps
Stage 6
Comps
Std-1 1 1,2 1,2,3 1,2,3,4 1,2,3,4,5 1,2,3,4,5,6
Std-2 2 2,3 2,3,4 2,3,4,5 2,3,4,5,6 1,2,3,4,5,6
Std-3 3 3,4 3,4,5 3,4,5,6 1,3,4,5,6 1,2,3,4,5,6
Std-4 4 4,5 4,5,6 1,4,5,6 1,2,4,5,6 1,2,3,4,5,6
Std-5 5 5,6 1,5,6 1,2,5,6 1,2,3,5,6 1,2,3,4,5,6
Std-6 6 1,6 1,2,6 1,2,3,6 1,2,3,4,6 1,2,3,4,5,6
StgdClgCap 17% 33% 50% 67% 83% 100%
Table 64: Alternate Staging
Alternate Staging
Staging
Sequence
Stage 1
Comps
Stage 2
Comps
Stage 3
Comps
Stage 4
Comps
Stage 5
Comps
Stage 6
Comps
Alt-1 1 1,3 1,3,5 1,2,3,5 1,2,3,4,5 1,2,3,4,5,6
Alt-2 2 2,4 2,4,6 1,2,4,6 1,2,3,4,6 1,2,3,4,5,6
Alt-3 3 3,5 1,3,5 1,3,4,5 1,3,4,5,6 1,2,3,4,5,6
Alt-4 4 4,6 2,4,6 2,3,4,6 2,3,4,5,6 1,2,3,4,5,6
Alt-5 5 1,5 1,3,5 1,3,5,6 1,2,3,5,6 1,2,3,4,5,6
Alt-6 6 2,6 2,4,6 2,4,5,6 1,2,4,5,6 1,2,3,4,5,6
StgdClgCap 17% 33% 50% 67% 83% 100%
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