NIST APAR24 – Cooling/mixed air damper control is overlapping (Mode 5 – Unknown Occupied Mode)

Applicable Systems

• NISTAPAR: APAR24
• Primary: AHU, RTU, MUA, ERV

Objective/Method/Outcome

• Objective: Indicates that the CCV is open while the MAD is modulating during occupied hours.

• Method: Check if the CCV is open while the MAD is modulating for over 8 occupied hours per week while the unit is in Mode 5.

• Outcome: An insight is generated when the CCV is open while the MAD is modulating for over 8 occupied hours per week while the unit is in Mode 5.

Logic

If( MAD > 20% Modulating; Temperature Threshold && CCV > 2% Open ) { return true; }

Inputs

• CCV {cmd, cool, water, valve} (Real Trend Log)
• AHU_MODE_CTL {ahu, mode} (Real Trend Log)
• MAD {cmd, mixed, air, damper} (Real Trend Log)

Parameters

Parameter	Expression Block Series Number	Description	Default Value (Units)
Const – MAD min	81	The minimum damper position to be considered open	20 (%)
CCV Error Threshold	70	The movement tolerance of the CCV. This is used to define when the valve is open -everything above the formula (100 – CCV Error Threshold) is considered saturated.	0 (%)
Const – Damper signal threshold	82	The movement tolerance of the MAD.	2 (%)
Acceptable Hours per Week	73	The amount of time that this error is allowable for the unit per week. Anything more than that time is considered a fault.	8 (h)