Chiller is overcooling

Objective/Method/Outcome

Objective: Determines if the chiller is overcooling for more than the acceptable amount of time.

Method: Compares the chilled water supply temperature to the chilled water supply temperature setpoint. When the temperature is below the setpoint, the chiller is overcooling and if it is overcooling for more than the acceptable amount of time (4 hours by default), insight is triggered.

Outcome: Triggers an insight if the chiller is overcooling for more than the acceptable amount of time.

Applicable System

CWS

Description

Monitors chilled water supply temperature while chiller is active to determine if chiller is overcooling the water, resulting in excess energy consumption.

This rule is part of the CopperTree Standard rule-set.

Default Priority

Medium

Diagnosis

Review chilled water system programming.

Message

Chiller may be overcooling, as CHW supply temperature is below threshold.

Rule Template

Insight Type: Fault Detection

Trigger Type: Active High

Logic

Logic for determining if the chiller is overcooling

Inputs

Input Unit Tags Description
Chiller Status Chiller Status, Chiller Command The recorded chiller status
Threshold – Weekly Hours of Faulty Operation The weekly acceptable hours of fault above which an insight is triggered
Chilled Water Supply Setpoint °F/°C Chilled Water Supply Temperature Setpoint The recorded setpoint
Chilled Water Supply Temperature °F/°C Chilled Water Supply Temperature The recorded CWS temperature
CHW Supply Temperature Deadband  °F/°C The allowable deviation from setpoint

Notes

Default Values:

  • CHW Supply Setpoint Deadband: 2°F or 1°C
  • Threshold – Hours of Faulty Operation: 4