McQuay OM 920-1 101
Operator’s Guide
The number of compressor stages increases when:
• The time since the last stage change exceeds the cooling stage timer AND
• Discharge air temperature is greater than the Discharge Cooling Setpoint by more than half
the deadband AND
• The current cooling stage is less than the number of available stages AND
• The last stage change was a stage up AND
• Dehumidification is not active
OR
• The time since the last stage change exceeds the cooling stage timer AND
• Discharge air temperature is greater than the Discharge Cooling Setpoint by more than half
the deadband AND
• The current cooling stage is less than the number of available stages AND
• The last stage change was a stage down AND
• The Degree Time Above Value is greater than or equal to the Degree Time Below value
AND
• Dehumidification is not active
OR
• The time since the last stage change exceeds the cooling stage timer AND
• Dehumidification is active AND
• Leaving Coil Temp is greater than the Maximum leaving coil Setpoint AND
• Current Stage is less than the available number of stages
The number of compressor stages decreases when:
• The time since the last stage change exceeds the Cooling stage timer AND
• Discharge air temperature is less than the Discharge Cooling Setpoint by more than half the
deadband AND
• The current cooling stage is greater than zero AND
• The last stage change was a stage down AND
• Dehumidification is not active
OR
• The time since the last stage change exceeds the Cooling stage timer AND
• Discharge air temperature is less than the Discharge Cooling Setpoint by more than half the
deadband AND
• The current cooling stage is greater than zero AND
• The last stage change was a stage up AND
• The Degree Time Below Value is greater than or equal to the Degree Time Above value
AND
• Dehumidification is not active
OR
• The time since the last stage change exceeds the Cooling stage timer AND
• Dehumidification is active AND
• Leaving Coil Temperature is less than the Minimum leaving coil Setpoint AND
• Current Stage is greater than 0
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