Determine if zone system is slow to meet setpoint on startup

Applicable Systems

  • Secondary: VAV, HP, FCU, UV, UH, RAD, RHT

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 RT 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.

Logic

Determine if zone system is slow to meet setpoint on startup

Inputs

  • RT {sensor, zone, air, temp} (Real Trend Log)
  • RT SP {sp, zone, air, temp} (Real Trend Log)
  • Occ {occupied} (Binary Trend Log)

Rule Template Type

  • Insight Type: Fault Detection
  • Trigger Type: Active High
  1. Input sensor(s) faulty or miscalibration. 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 control loop. Review and modify controller tuning parameters.
  6. Primary air not available. Verify Air Handling Unit operation.

Message

The total time the RT takes be within 1 degree of set point on system startup is longer than 2 hours per week.

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 RT 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

Name Expression Block Series Number Description
CalculatedTrendLog24 24 The amount of time (hours) the HWST temp to reach set point.