NIST APAR11 – Supply air temp should be less than mixed air temp (Mode 3 – Mech. Cooling w/100% OA)

Applicable Systems

  • NISTAPAR: APAR11
  • Primary: AHU, RTU, MUA, ERV

Objective/Method/Outcome

  • Objective: Indicates an inconsistency between supply and mixed air temperatures while the unit is in Mode 3 (Mechanical Cooling w/100% OA)
  • Method: Check if the SAT is more than the MAT for over 8 occupied hours per week while the unit is in Mode 3.
  • 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 3.

Logic

If( SAT > MAT + Temperature Threshold + Temperature Rise Over Fan) { return true; }
NIST APAR11 – Supply air temp should be less than mixed air temp (Mode 3 – Mech. Cooling w/100% OA)

Inputs

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

Parameters

ParameterExpression Block Series NumberDescriptionDefault Value (Units)
Const- Temperature Rise Over Fan31The estimated air temperature rise over the fan1.1 (C)
Temperature Threshold30This is the minimum temperature difference between MAT and SAT needed to enable the rule2 (C)
Acceptable Hours per Week33The amount of time that this error is allowable for the unit per week. Anything more than that time is considered a fault.8 (h)
image_printPrint