Objective/ Method/Outcome
Objective: Determines if pre-heating coil is leaking.
Method: Determines if there is a temperature increase across the inactive pre-heating coil by comparing the preheat coil leaving temperature to the outdoor air temperature and the defined temperature deadband. If the preheat coil leaving temperature is greater, the hours of faulty operation are calculated. Avoidable Cost and Potential Savings are calculated using the defined Natural Gas Rate.
Outcome: This rule generates an insight if the Weekly Hours of Faulty Operation exceeds the acceptable weekly threshold.
Description
Reference: ASHRAE36-5.16.14.3/4
This rule is applicable for integrate cooling mode, meaning mechanical cooling is dealing with addition cooling load which are not able to be fully covered by outdoor air solely. Generally, Integrate cooling mode happens when OAT is higher than supply air temperature setpoint and lower than return air temperature. In this mode, RAD shall fully closed and OAD shall fully open. Beyond that, mechanical cooling valve modulates to meet cooling load.
This rule is part of the CopperTree Standard rule-set. (Aliased Celsius)
Default Priority
Medium
Diagnosis
1. Input sensor(s) faulty or miscalibration. Verify input sensor(s) operation.
2. Review control sequence. Ensure AHU is not in correct mode. Mechanical cooling with min OA is not being used when mechanical cooling with 100% OA should be used (when OAT is lower than changeover set point).
Message
Outdoor air damper is not fully open in integrate cooling mode.
Rule Template
Insight Type: Fault Detection
Trigger Type: Active High
Notes
1. Expected values for “SF Status” inputs are “0” or “1”.
2. Expected values for “Supply Fan Speed” inputs are “100” if they are constant speed fans or not available.
Default Values:
Const. – Changeover OAT High Limit [°C]: 13
Const. – Changeover OAT High Limit [°C]: 22
Const. – Outdoor Air Damper Threshold [%]: <95%
Const. – Threshold – Weekly Hours of Faulty Operation [Hours]: 8
Const. – AHU Rated CFM: 10000
Const. – Electricity Rate($/kWh): 0.1
Const. – Weeks of Operation: 8
CTLs:
OAD is not fully open in Integrate Cooling Mode – Weekly Hours of Faulty Operation (KPI)
OAD is not fully open in Integrate Cooling Mode – Hours of Faulty Operation (CUSUM)
OAD is not fully open in Integrate Cooling Mode – Avoidable Cost [$]
OAD is not fully open in Integrate Cooling Mode – Potential Savings [$/Year]
