NIST APAR20 – Cooling coil valve is frequently fully open (Mode 4 – Mech. Cooling w/min OA)

Applicable Systems

  • NISTAPAR: APAR20
  • Primary: AHU, RTU, MUA, ERV

Objective/Method/Outcome

  • Objective: Indicates that the cooling coil valve is frequently fully open while the unit is in Mode 4 (Mech. Cooling w/min OA). This rule is a warning and indicates that the system may be out of control. If APAR19 is active, this rule is suppressed.
  • Method: Check if the CCV is fully open for over 8 occupied hours per week while the unit is in Mode 4.
  • Outcome: An insight is generated when the CCV is fully open for over 8 occupied hours per week while the unit is in Mode 4.

Logic

If (APAR19_CTL TRUE && CCV > 2% Open) { return true; }
NIST APAR20 – Cooling coil valve is frequently fully open (Mode 4 – Mech. Cooling w/min OA)

Inputs

  • CCV {cmd, cool, water, valve } (Real Trend Log)
  • AHU_MODE_CTL {ahu, mode} (Real Trend Log)
  • APAR19_TRUE_CTL {apar19} (Real Trend Log)

Parameters

Parameter Expression Block Series Number Description Default Value (Units)
CCV Error Threshold 74 The movement tolerance of the CCV. This is used to define when the valve is open -everything above the formula (100 – CCV 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)