OMM TGZ-1 TGZ 040A through TGZ 190A 67
TGZ unit for heat mode operation
LowSourceTmp=XX.X °F
LowSourceDif=XX.X ºF
Set Cooling Tower Control (TGZ in cooling mode)
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 parameters.
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).
SET TOWER SPs (1)
Tower Control= None
When Tower Control is None the control of condenser water temperature is not by the
MicroTech II controller and assumed to be furnished elsewhere.
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