Determine if primary system is slow to meet setpoint on startup

Applicable Systems

  • Primary: AHU, RTU, MUA, ERV

Description / Method

Determine if the zone temperature control is taking too long to reach its desired setpoint, on system startup. Check the amount of time the SAT takes to reach within 1 degree of its set point. This check only occurs after the system is enabled and before the temperature setpoint is reached.

Rule Template Type

  • Insight Type: Fault Detection
  • Trigger Type: Active High

Inputs

  • SAT {sensor, discharge, air, temp} (Trend Log)
  • SAT SP {sp, discharge, air, temp} (Trend Log)
  • Equip status {cmd|status|occupied} (Binary Trend Log)

Rule Template Explanation

Logic

Determine if primary system is slow to meet setpoint on startup
  1. Input sensor(s) faulty or miscalibrated. Verify input sensor(s) operation.
  2. Chilled water not available. Verify chiller plant operation.
  3. Heating water not available. Verify boiler plant operation.
  4. Automatic control has been overridden. Revert equipment back to automatic control.
  5. Issue with the control loop. Review and modify controller tuning parameters.

Message

The SAT takes longer than 1.75 hours per day to reach the desired set point on system startup.

Notes

This logic flow only activates the initialization of the unit. If the temperature falls below the set point a second time, this will purposefully not trigger. However, this rule will activate every time a unit engages. If the unit changes status multiple times per day, a building occupancy trend log may be more suitable to define unit status.

Parameters

Parameter Expression Block Series Number Description Default Value (Units)
Temperature Threshold 7 The acceptable temperature range the SAT has to enter to be considered normal 1 (C)
Acceptable hours per day to reach Set Point 26 The amount of time that this error is allowable for the unit per day. Anything more than that time is considered a fault. 1.75 (h)

Calculated Trend Logs

Control Loop Name Description
Calculated Trend Log 24 CalculatedTrendLog24 Tracks the number of minutes per hour the unit takes to get to the setpoint at startup