Cooling Tower staging and fan speed control is poor

Objective/ Method/Outcome

Objective: Determines if the cooling tower and fan speed controller for Chilled Water System is effective.

Method: Compares the different fan speeds and determines if the fan sequence is staged.

Outcome: This rule generates an insight.

Description

Reference: ASHRAE Guideline 36-5.20.12.1/ASHRAE90.1-6.5.5.2

This rule determines if maximum number of fans are operating at same speed as opposed to staged (on/off) operation. Maximizing the quantity of operating towers minimizes fan power because fans have variable speed drives. For instance, one tower at full speed uses approximately four times as much power as two towers at half speed.

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

Default Priority

Medium

Diagnosis

1. Please check is chilled water supply temperature or condenser water supply temperature is in normal range.
2. Check if chiller is out of maintenance.
3. Review and update chiller sequencing, if required

Message

Chiller Efficiency is low.

Rule Template

Insight Type: Energy

Trigger Type: Active High

Notes

1. Only one “Flowrate”, [LPS] or [GPM] is needed.

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

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

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

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

Default Values:

Const. – Daily Threshold of Faulty Chiller COP Operation [hrs]:2

Const. – Acceptable COP Threshold: 5

Const. – Weeks of Operation: 26

Const. – Energy Rate [$/kWh]: 0.1