NIST APAR16 – Supply air temp should be less than mixed air temp (Mode 4 – Mech. Cooling w/min OA)

Applicable Systems

  • NISTAPAR: APAR16
  • Primary: AHU, RTU, MUA, ERV

Objective/Method/Outcome

  • Objective: Indicates an inconsistency between supply and mixed air temperatures while the unit is in Mode 4 (Mechanical Cooling w/min OA)
  • Method: Check if the SAT is more than the MAT for over 8 occupied hours per week while the unit is in Mode 4.
  • Outcome: An insight is generated when the SAT is more than the MAT for over 8 occupied hours per week while the unit is in Mode 4.

Logic

If (SAT > MAT + Temperature Threshold + Temperature Rise Over Fan) { return true; }
NIST APAR16 – Supply air temp should be less than mixed air temp (Mode 4 – Mech. Cooling w/min OA)

Inputs

  • SAT {sensor, discharge, air, temp} (Real Trend Log)
  • MAT {sensor, mixed, air, temp} (Real Trend Log)
  • AHU_MODE_CTL {ahu, mode} (Real Trend Log)

Parameters

Parameter Expression Block Series Number Description Default Value (Units)
Const- Temperature Rise Over Fan 31 The estimated air temperature rise over the fan. 1.1 (C)
Temperature error Threshold 30 This is the minimum temperature difference between SAT and MAT needed to enable the rule. 2 (C)
Acceptable Hours per Week 33 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)