68 WGZ030D through WGZ200D OMM 1130
Set Cooling Tower Control
The MicroTech II controller is capable of controlling cooling tower water temperature on chillers using
water-cooled condensers. Output wiring connection points are shown on the field wiring diagrams.
[Water Cooled = Y] - Condenser Pump on with first Compressor on. Tower fan control is active when the
Tower Control setpoint is set to Temperature and the condenser pump is in the RUN state. Staging is
based on Entering Condenser Water Temperature (ECWT). Operation depends on the following.
Condenser pump state
ECWT OR Lift pressure
Stage up and stage down timer values
Tower setpoints (Tower Control, Tower Stages, Stage Up Time, Stage Down Time, Stage Differential,
Stage #1 ON, Stage #2 ON, Stage Down @, Stage Up @)
When the condenser pump starts, the stage up timer shall start. The first stage shall turn ON when the
following conditions are met:
The stage up timer completes
The ECWT is > Stage #1 ON setpoint
Bypass valve position is > the Stage Up @ setpoint (only if Valve/VFD Control setpoint = Valve
Stage)
Additional stages can turn on (up to the number specified by the Tower Stages setpoint) when above
conditions are met for the next stage plus the following condition:
VFD Speed is > the Stage Up @ setpoint (only if Valve/VFD Control setpoint = VFD Stage OR Valve
SP/VFD Stage)
Down staging shall occur when the following conditions are met:
The stage down timer completes
The ECWT is < Stage #X ON (Temp) setpoint – Stage Differential (Temp) setpoint point
Bypass valve position is < the Stage Down @ setpoint (only if Valve/VFD Control setpoint = Valve
Stage)
VFD Speed is < the Stage Down @ setpoint (only if Valve/VFD Control setpoint = VFD Stage OR
Valve SP/VFD Stage)
Each stage up or stage down event shall restart both the stage up and stage down timers. Only one fan
output shall be switched at a time (except that all outputs switch OFF when the condenser pump state
equals OFF).
Water-cooled On
SET TOWER SPs (1)
Tower Control= None
Tower Stages = X
StageUP/DN=XXX/XXX%
When Tower Control is None the control of condenser water temperature is not by the MicroTech II
controller and assumed to be furnished elsewhere.
Tower Stages is the number of tower fans to be staged by the controller, choices are 0, 1, or 2. "0"
indicates control will be by a bypass valve or variable speed pump controlled by the MicroTech II
controller.
StageUP/DN imposes a time delay between fan stages when turning on or turning off.
Water-cooled On
SET TOWER SPs (2)
Stage ON (Temp)F
#1 #2
XXX XXX
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