Objective/ Method/Outcome
Objective: Determines if energy recovery equipment’s sensible heat effectiveness is too low.
Method: Determines the Sensible Heat Transfer Effectiveness from the defined ASHRAE Effectiveness equation, based on the dry bulb temperature for supply air, return air, and outdoor air. If the Sensible Heat Transfer Effectiveness is lower than the Effectiveness Threshold, the hours of faulty operation are calculated. Avoidable Cost and Potential Savings are calculated based on the Electricity Rate and Natural Gas Rate.
Outcome: This rule generates an insight if the Weekly Hours of Faulty Operation exceed the acceptable weekly threshold.
Description
Reference: ASHRAE Handbook—HVAC Systems and Equipment Chapter26
This rule determines if energy recovery equipment’s sensible heat effectiveness is too low. The Effectiveness equation is from ASHRAE Handbook—HVAC Systems and Equipment Chapter26. Dry bulb Temperature is used for this calculation.
η = [Vs • (x1 – x2)] / [Vmin • (x1 – x3)]
Where:
η = Total effectiveness
x1 = OA temperature(°C)
x2 = SA temperature(°C)
x3 = RA temperature(°C)
Vs = Supply air volume (cfm)
Vmin = The lower of the exhaust or supply air volume (cfm)
This rule is part of the CopperTree Standard rule-set. (Aliased Celsius)
Default Priority
Medium
Diagnosis
1. Outdoor air damper stuck
2. Exhaust air damper stuck
3. Energy recovery equipment is operating at economizer mode
4. Energy recovery equipment requires maintenance
Message
Sensible Heat Transfer Effectiveness is low.
Rule Template
Insight Type: Energy
Trigger Type: Active High
Notes
1. Expected values for SF/EF rated CFM are “0” If an airflow station is present.
2. Expected values for SF/EF rated CFM are from building documents if airflow station is not present.
3. Only one “Airflow”, [LPS] or [CFM] is needed.
4. The input(s) that is(are) not used should be set to “0”.
5. Expected values for “SF Speed” inputs are “100” if they are constant speed fans or not available.
6. Expected values for “SF Status” and “EF Status” inputs are “0” or “1”.
Default Values:
Const. – Weekly Faulty Hours Threshold [hrs]: 4
Const. – Effectiveness Threshold[%]: 50
Const. – Electricity Rate[$/kWh]: 0.1
Const. – Natural Gas Rate [$/mmBTU]: 3
Const. – Weeks of Operation: 52
CTLs:
Sensible heat transfer effectiveness low – Hours of Faulty Operation (CUSUM)
Sensible heat transfer effectiveness low – Weekly Hours of Faulty Operation (KPI)
Sensible heat transfer effectiveness low – Avoidable Cost [$]
Sensible heat transfer effectiveness low – Potential Savings [$/Year]
