NIST APAR15 – Outdoor air temp too low for Mechanical Cooling w/min OA (Mode 4)

Applicable Systems

  • NISTAPAR: APAR15
  • Primary: AHU, RTU, MUA, ERV

Objective/Method/Outcome

  • Objective: Indicates that the OAT is too low for the AHU to be running in Mode 4 (Mech. Cooling w/min OA)
  • Method: Check if the OAT is less than the changeover air temperature for switching from Mode 4 to Mode 3, for over 8 occupied hours per week while the unit is in Mode 4.
  • Outcome: An insight is generated when the OAT is less than the changeover air temperature for switching from Mode 4 to Mode 3, for over 8 occupied hours per week while the unit is in Mode 4.

Logic

If (Changeover Temp - Temperature Threshold > OAT) { return true; }
NIST APAR15 – Outdoor air temp too low for Mechanical Cooling w/min OA (Mode 4)

Inputs

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

Parameters

Parameter Expression Block Series Number Description Default Value (Units)
Const- Changeover Temp for Switching Between Modes 3&4 73 To change changeover temperature for switching between Mode 3 and Mode 4, edit block 73 17 (C)
Temperature Threshold 74 This is the minimum temperature difference between OAT and Changeover Temperature needed to enable the rule. 2 (C)
Acceptable Hours per Week 77 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)