Determine if heating control is ineffective/unresponsive

Applicable Systems

  • NIST: APAR1
  • Primary: AHU, RTU

Objective/Method/Outcome

  • Objective: Determine if the heating system is having issues due to possible improper sequencing or equipment failure. Based on NIST APAR 1.
  • Method: Check if the SAT is less than the MAT when the HCV is open during occupied hours.
  • Outcome: An insight is generated if the SAT is less than the MAT while the HCV has been open for more than 8 hours.

Logic

If(MAT + Temperature Rise Over Fan - Temperature Threshold > SAT && HCV > 20% Open) {return true;}
Determine if heating control is ineffective/unresponsive

Notes

This rule compensates for the temperature rise across a supply fan between the MAT and SAT sensors. This value varies per system, and the parameter should be changed within the logic flow accordingly. The temperature rise over a fan is currently to 1.1 degrees in accordance with NIST recommendations. The HCV must be over 20% in order for this rule to take effect, as its cooling effects will be insignificant otherwise.

Inputs

  • SAT {sensor, discharge, air, temp} (Real Trend Log)
  • MAT {sensor, mixed, air, temp} (Real Trend Log)
  • HCV {cmd, heat, water, valve } (Real Trend Log)
  • Occ {occupied} (Binary Trend Log)

Parameters

Parameter Expression Block Series Number Description Default Value (Units)
Temperature Threshold 37 The acceptable temperature deviation from set point that is considered normal 2 (C)
Temperature Rise Over Fan 64 The temperature increase caused by air passing over a fan. This should be changed based on the site and system. 1.1 (C)
Valve Open 66 The valve position for which the cooling provided by the CC is considered significant. 20 (%)
Acceptable Hours per Week 72 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)