NIST APAR3 – Heating coil valve command is fully open and SAT error exists (Mode 1 – Heating)

Applicable Systems

• NIST: APAR3
• Primary: AHU, RTU, MUA, ERV

Objective/Method/Outcome

• Objective: Indicates that the heating coil valve is fully open and the SAT is less than the setpoint while the AHU is in Mode 1 (Heating).

• Method: Check if the SAT is more than 2 degrees below set point for over 8 occupied hours per week while the unit is in Mode 1 (Heating).

• Outcome: An insight is generated when the SAT is more than 2 degrees below set point for over 8 occupied hours per week while the unit is in Mode 1 (Heating).

Logic

If (SAT SP - SAT) > (Temperature Threshold && HCV > 2% Open) { return true; }

Inputs

• SAT {sensor, discharge, air, temp} (Real Trend Log)
• HCV {cmd, heat, water, valve } (Real Trend Log)
• SAT_SP {sp, discharge, air, temp} (Real Trend Log)
• AHU_MODE_CTL {ahu, mode} (Real Trend Log)

Parameters	Expression Block Series Number	Description	Default Value (Units)
Temperature Threshold	75	The acceptable temperature deviation from set point that is considered normal	2 (C)
HCV Error Threshold	74	The movement tolerance of the HCV. This is used to define when the valve is open -everything above the formula (100 – HCV Error Threshold) is considered saturated.	2 (%)
Acceptable Hours per Week	60	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)