Xenta 102-AX Effective Setpoint (nvoEffectSetPt) Calculation

Issue

  1. The nvoEffectSetPt is different than the nviSetPoint
  2. The nvoEffectSetPt is different than the cooling or heating setpoint (SCPTsetPnts)

Product Line

TAC Vista, SmartStruxure Solution

Environment

Xenta 102-AX

Cause

The nvoEffectSetPt is calculated according to nviSetPoint, cooling or heating setpoints (SCPTsetPnts), nviStPointOffset, and thermostat offset.

Resolution

The nvoEffectSetPt is a SNVT network output in Xenta 102-AX and represents the current effective setpoint that the controller is utilizing in its control loop.

nvoEffectSetPt can be configured to display in two different manners: Actual and Normalized. (As defined bynciVAVselctcCntl.oP.ESS (UCPTvavSelection))

  • Actual nvoEffectSetPt displays the setpoint that corresponds to the currently active application mode of the controller (occupied cooling, unoccupied cooling, standby cooling, occupied heating, unoccupied heating, and standby heating).
  • Normalized nvoEffectSetPt displays the average of the cooling and heating setpoints for the currently active occupancy mode (occupied, unoccupied, standby).

NOTE: Whether nvoEffectSetPt is set to Actual or Normalized only affects how the effective setpoint is displayed and does not affect how the application operates. The 102-AX application utilizes the setpoint that corresponds to the currently active mode (occupied cooling setpoint, etc.). In addition, the thermostat adjustment of the setpoint will not appear in any SNVT in Xenta 102-AX controller. This offset is captured in the Xenta 102-AX's memory, and although it is not displayed, it is utilized into the nvoEffectSetPt calculation.

Also note that the below scenarios only apply to the occupied and standby modes since the unoccupied setpoints are unaffected by nviStPointOffset, nviSetPoint or by the thermostat offset.

  1. Scenario 1: nviSetpoint is unused

    1.1 Actual nvoEffectSetPt calculation:



    In this scenario, the nvoEffectSetPt is the sum of one(1) of the four setpoints (occupied cooling, standby cooling, occupied heating and standby heating) plus the offsets (nviStPointOffset and thermostat offset).

    1.2 Normalized nvoEffectSetPt calculation:



    In this scenario, the nvoEffectSetPt is the average of heating and cooling setpoints ( 1/2(Occupied Cooling Setpoint + Occupied Heating Setpoint) or 1/2(Standby Cooling Setpoint + Standby Heating Setpoint) ) plus the offsets (nviStPointOffset and thermostat offset).
     
  2. Scenario 2: nviSetpoint is used

    2.1 Actual nvoEffectSetPt calculation:




    In cooling mode, the nvoEffectSetPt is the nviSetPoint plus half of the difference between cooling and heating setpoints ( 1/2(Occupied Cooling Setpoint -Occupied Heating Setpoint) or 1/2(Standby Cooling Setpoint - Standby Heating Setpoint) ),  plus the offsets (nviStPointOffset and thermostat offset).

    In heating mode, the nvoEffectSetPt is the nviSetPoint minus half of the difference between cooling and heating setpoints ( 1/2(Occupied Cooling Setpoint - Occupied Heating Setpoint) or 1/2(Standby Cooling Setpoint - Standby Heating Setpoint) ), then plus the offsets (nviStPointOffset and thermostat offset).

    2.2 Normalized nvoEffectSetPt calculation



    In this scenario, whether the application is in the cooling mode or the heating mode, the nvoEffectiveSetPt is the sum of the nviSetPoint and the offsets (nviStPointOffset and thermostat Offset).

    Therefore, when nviSetPoint is used and nvoEffectSetPt is to Normalized, the actual heating and cooling SCPT setpoints do not matter; only the difference between them is significant. For example, setting occupied cooling and heating setpoints to be 75°F (24°C) and 65 °F (18°C) will give the same resulting nvoEffectiveSetPt as setting occupied cooling and heating to be 45°F (7°C) and 35°F (1°C).
     
  3. Example

    Occupied Cooling = 72°F (22°C), Occupied Heating = 68°F (20°C), nviSetPoint = 75°F (24°C), assuming the nviStPointOffset and thermostat offset are zero.

nvoEffectSetPt in Occupied Cooling or Heating Mode

 

Scenario 1.1

Scenario 1.2

Scenario 2.1

Scenario 2.2

Cooling Mode

72°F (22°C)

70°F (21°C)

77°F (25°C)

75°F (24°C)

Heating Mode

68°F (20°C)

70°F (21°C)

73°F (23°C)

75°F (24°C)