CHWST is Higher in the Secondary Loop than that in the Primary Loop

Objective/ Method/Outcome

Objective: Determines if the chilled water supply temperature is higher in the secondary loop than in the primary loop.

Method: Compares the primary and secondary loop supply temperature to determine if the chilled water supply temperature is high.

Outcome: This rule generates insights.

Description

This rule is applied to primary/secondary system. It determines if the chilled water supply temperature in the secondary loop is noticeably higher than that in the primary loop.  

Normally,  It is essential to have the flow rate in the primary loop equal to or greater than the flow rate in the secondary loop. When the secondary flow exceeds the primary, return water from the system flows back through the common pipe and mixes with the supply water from the chillers. This increases the temperature of the supply water to the secondary system. A system with secondary loop supply temperature setpoint is excluded from this rule.

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

Default Priority

Medium

Diagnosis

1. Verify proper operation of the chilled water system’s temperature sensors.
2. Check for bypass flow in the chilled water loop.
3. Lower the secondary pump speed.

Message

Secondary loop chilled water supply temperature is higher than the primary loop chilled water supply temperature.

Rule Template

Insight Type: Energy

Trigger Type: Active High

Notes

1. Expected values for “Chiller Status” inputs are “0” or “1”.

2. Expected values for “Pump Speed” inputs are “100” if they are constant speed pumps or not available.

3. The input(s) that is(are) not used should be set to “0”.

Default Values:

Const. – Temperature Error Threshold [*C]: 2

Const. – Threshold for Weekly Hours of Faulty Operation [Hours]: 2

Const. – Energy Rate [$/kWh]: 0.1

Const. – Desired Secondary Loop Delta-T [*C]: 6

Const. – Weeks of Operation: 26

Const. – Pump Rating [HP]: 10