McQuay AGS 225D, Operating Manual

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40 OM AGSD-1
Discharge Superheat
Discharge superheat is calculated for each circuit using the following equation:
Discharge superheat = Discharge Temperature – Condenser Saturated Temperature
Oil Differential Pressure
Oil Differential Pressure is calculated for each circuit with this equation:
Oil Differential Pressure = Discharge Pressure – Oil Pressure
Compressor Control
Next On / Next Off
This section defines which compressor is the next one to start or stop. In general,
compressors with fewer starts will normally start first, and compressors with more run hours
will normally stop first. Compressor start sequence can also be determined by an operator-
defined sequence.
Next On
Only circuits that are available to start immediately are eligible to be next on.
•
The circuit with the lowest sequence number should be next on.
•
If the sequence numbers are all the same, the circuit with the lowest number of
starts should be next on.
•
If the starts are equal and the sequence numbers are all the same, the circuit with the
lowest number of run hours should be next on.
•
If the run hours are equal, the sequence numbers are all the same, and the run hours
are all the same, then the lowest numbered circuit should be next on.
Next Off
•
Only circuits that are currently in the run state are eligible to be next off.
•
The circuit with the lowest sequence number should be next off.
•
If the sequence numbers are all the same, the circuit with the highest run hours
should be next off.
•
If the run hours are equal and the sequence numbers are all the same, the lowest
numbered circuit should be next off.
Required Parameters
1. Sequence number setpoint for all compressors.
2. Number of starts for all compressors.
3. Number of run hours for all compressors.
4. Status of all compressors (Available/Unavailable, Pumping down, Running, etc.).