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You can trend various points (i.e., condenser water supply temperature, tower fan, and pump speeds) to get a
better estimate of the response time.
NOTE For chilled water facilities where the towers are close to the chillers, the response time may be between 4
and 8 minutes. For other facilities, where the towers are more remote, the response time may be higher.
You can get an approximation of the response time by locking the condenser water reset signal Condenser Water
Temperature Optimizer Reset > Optimized Condenser Water Supply Temperature AV (wetb + approach) to a
value 3°F higher or cooler than current setpoint and then verifying response in the tower manager program. This
should result in a temperature change of 3°F. It also includes the total time it takes for everything below to occur:
The time it takes for the condenser water supply temperature to reach the new temperature setpoint
The time it takes for the tower fans to settle to a new speed based on the new condenser water temperature
setpoint
The condenser water pumps (if variable flow) have reached their new speed in response to the new
temperature
All the changes in consumption (kW) are due to the condenser water setpoint change. The effects of the setpoint
change must propagate through the entire condenser water system until all devices in the system become stable.
You may need to tune certain tower or pump program properties, such as PID control loop gains and ramp rates to
get proper response. It is important that the condenser water setpoint be reset predictably and quickly enough for
the optimizer to work reliably. Good response is essential and the actual response time depends on the system.
Adjustments - Minimum & Maximum Increments and Reset Gain
After the program has been running a while, adjust the Minimum Increment and Maximum Increment as shown
below, if necessary.
Minimum Reset Increment
If the condenser water system is not responding to each incremental temperature setpoint change, it could
be the minimum reset increment is too small. If so, increase it by 0.5 (deg) above its current property value.
If the system is still not responding to each incremental change, increase it by another 0.5 (deg).
NOTE Never set the reset increment to more than 1.75 (deg). Values above this may cause overshoot.
Maximum Reset Increment
If the condenser water system is responding too much for each incremental change, the maximum reset
increment is too high. Decrease it by 0.5 (deg) from its current value.
If the system is still responding too much for each temperature increment, decrease it by another 0.5 (deg). It
is preferable to have the Maximum Reset Increment be at least 0.5 (deg) above the Minimum Reset
Increment.
Chilled Water System Optimizer v2
Installation and Start-up Guide
43
Start-up and Commissioning
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