NIST APAR28 – Mode of operation changing state too frequently (Mode Changes)

Applicable Systems

• NISTAPAR: APAR28
• Primary: AHU, RTU, MUA, ERV

Objective/Method/Outcome

• Objective: ndicates that the AHU mode of operation state is changing too rapidly.

• Method: Counts the number of chenges in modes of operation per hour.

• Outcome: An insight is generated when the number of changes in modes of operation is more than 3 times per hour.

Logic

 If (Mode changes per Hour > Max number of changes) { return true; }

Inputs

• AHU_MODE_CTL {ahu, mode} (Real Trend Log)

Parameters

Parameter	Expression Block Series Number	Description	Default Value (Units)
Parameter	Expression Block Series Number	Description	Default Value (Units)
Max number of changes allowed per hour	4	The amount of number of changes allowable for the unit per hour. Anything more than that time is considered a fault.	12 (h)