NIST APAR5 – Outdoor air temp too high for Cooling w/OA (Mode 2)

Applicable Systems

  • NISTAPAR: APAR5
  • Primary: AHU, RTU, MUA, ERV

Objective/Method/Outcome

  • Objective: Indicates that the OAT is too high for the AHU to be running in Mode 2 (Cooling w/ OA).
  • Method: Check if the OAT is greater than the SAT SP for over 8 occupied hours per week while the unit is in Mode 2.
  • Outcome: An insight is generated when the OAT is greater than the SAT SP for over 8 occupied hours per week while the unit is in Mode 2.

Logic

If OAT > (SAT SP - Temperature Threshold + Temperature Rise Over Fan) { return true; }
NIST APAR5 – Outdoor air temp too high for Cooling w/OA (Mode 2)

Inputs

  • SAT_SP {discharge, air, temp, setpoint} (Real Trend Log)
  • OAT {sensor, outdoor, air, temp} (Real Trend Log)
  • AHU_MODE_CTL {ahu, mode} (Real Trend Log)

Parameters

ParameterExpression Block Series NumberDescriptionDefault Value (Units)
Const – Temperature Rise Over Fan73The estimated air temperature rise over the fan1.1 (C)
Temperature Threshold74This is the minimum temperature difference between OAT and SAT SP needed to enable the rule.2 (C)
Acceptable Hours per Week77The amount of time that this error is allowable for the unit per week. Anything more than that time is considered a fault.8 (h)
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