32 AGZ 025D through 190D OMM 1166-1
Starting a Compressor
A compressor should start if it receives a start command from the unit capacity control logic.
Stopping a Compressor
A compressor should be turned off if any of the following occur:
Unit capacity control logic commands it off
An unload alarm occurs and the sequencing requires this compressor to be next off
Circuit state is pumpdown and sequencing requires this compressor to be next off
Cycle Timers
A minimum time between starts of the compressor and a minimum time between shutdown and start of the
compressor shall be enforced. The time values are determined by the Start-start Timer and Stop-start Timer
setpoints.
These cycle timers should not be enforced through cycling of power to the chiller. This means that if power
is cycled, the cycle timers should not be active.
These timers may be cleared via a setting on the human machine interface (HMI).
Condenser Fan Control
Condenser fan control should stage fans as needed any time compressors are running on the circuit. All
running fans should turn off when the circuit goes to the off state.
Fan Staging
Fan staging shall accommodate anywhere from 2 to 7 fans on a circuit using up to 5 outputs for control. The
total number of fans on shall be adjusted with changes of one fan at a time. The tables below show the
outputs energized for each stage.
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