McQuay MicroTech III RAH Operation And Maintenance Manual page 97

McQuay OM 920-1
Six Equal Sized Compressors, Six Circuits, No WRV
Only one sequence is provided so the user makes no selections.
• Total cooling stages = 6.
• Maximum cooling stages is always set to 6.
• 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's on.
Table 65: Standard Staging
Staging Stage 1
Sequence Comps
Std-1 1
Std-2 2
Std-3 3
Std-4 4
Std-5 5
Std-6 6
StgdClgCap 17%
Six Equal Sized Compressors, Six Circuits, Water Regulating Valve
Only one sequence is provided so the user makes no selections.
• Total cooling stages = 6.
• Maximum cooling stages is always set to 6.
• If both circuit # 1 and circuit # 2 are enabled, the staging sequence is Std-1 if compressor # 1
has fewer hours than compressor # 2, and the staging sequence is Std-2 if compressor # 1
does not have fewer hours than compressor # 2.
• If Circuit # 1 is disabled, the staging sequence is Std-2.
• If Circuit # 2 is disabled, the staging sequence is Std-1.
• If both circuit # 1 and circuit # 2 are disabled, the staging sequence is Std-1. Only
compressors 3, 4, 5, and 6 are used.
• The Compressor Sequence changes based on Run Time 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.
• The compressor sequence changes immediately if a circuit is disabled to keep either
compressor # 1 or # 2 on. This will result is compressors being turned off and others being
turned on in this emergency condition.
• 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.
Standard Staging
Stage 2 Stage 3 Stage 4
Comps Comps Comps
1,2 1,2,3 1,2,3,4
2,3 2,3,4 2,3,4,5
3,4 3,4,5 3,4,5,6
4,5 4,5,6 1,4,5,6
5,6 1,5,6 1,2,5,6
1,6 1,2,6 1,2,3,6
33% 50%
Operator's Guide
Stage 5 Stage 6
Comps Comps
1,2,3,4,5 1,2,3,4,5,6
2,3,4,5,6 1,2,3,4,5,6
1,3,4,5,6 1,2,3,4,5,6
1,2,4,5,6 1,2,3,4,5,6
1,2,3,5,6 1,2,3,4,5,6
1,2,3,4,6 1,2,3,4,5,6
67% 83% 100%
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