42 WGZ030D through WGZ200D OMM 1130
The Stage Down Error Step is added to Stage Down Accumulator once every Stage Down Error Delay
seconds. When the Stage Down Accumulator is greater than the Stage Down Error Set Point another stage
of condenser fans turn off. The last stage on will not shut off until the circuit is in an off state.
When stage down occurs or the saturated temperature rises back within the Stage Down dead band the
Stage Down Error Accumulator is reset to zero.
Forced Fan Stage at Start
Fans may be started simultaneously with the compressor based on outdoor ambient temperature. When
the compressor starts, and after compressor operation is verified by either a 1 psi drop in evaporator or 1
psi rise in condenser pressures, a Fantrol stage is forced based on the following table.
Up to four fans may be forced on when the compressor starts.
After forcing fans on, the saturated condenser temperature may temporarily stay below the target by some
amount. In order to keep the fans from staging off, no stage down error can be accumulated until either
the OAT drops below 75°F or the saturated condenser temperature goes above the target.
Condenser Pump and Tower Control – Water Cooled
Condenser pump and cooling tower control logic requires that the unit be configured as water-cooled in
order to be active.
Condenser Water Pump State Control (Cond State)
If the unit is configured as water-cooled, then the state-transition diagram shown below defines the
condenser pump control logic.
Off
Run Start
Unit State=Auto AND
Any Circuit Available AND
Stage up now = True]
OR
Cond Refrig Freeze Event
AND No Cond Flow Alarm
Cond Flow Alarm OR
[Unit State = Off OR
No Circuit Available OR
Evap Pump State = Start OR
LWT error < Start Delta]
AND
No Cond Refrig Freeze Event
AND
No Compressor Running
[Cond Pump State = Start
AND Flow Switch Closed]
for time > Cond Pmp
Recirc Time seconds
Cond Flow Alarm OR
Unit State = Off OR
Evap Pump State = Start OR
No Circuit Available OR
LWT error < Start Delta]
AND
No Cond Refrig Freeze Event
AND
No Compressor Running
Condenser Pump State Diagram
OAT Fantrol Stage At Start
>75°F Forced Fan 1 SP
>90°F Forced Fan 2 SP
>105°F Forced Fan 3 SP
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