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

ParameterExpression Block Series NumberDescriptionDefault Value (Units)
CCV Error Threshold74The 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 Week60The 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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