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Override the Damper or Flow of a Xenta 102-AX with a SNVT input

Issue

Manual override of the damper actuator position or the desired flow setpoint on a Xenta 102-AX can be accomplished with a network variable (SNVT) input.

Environment

Xenta 102-AX

Cause

There are times when the damper position or flow setpoint needs to be overridden from a supervisory controller.  It may be a special mode for Test & Balance, a smoke control sequence, or a special circumstance where the internal logic of the 102-AX must be ignored in some situation.

Resolution

Manually controlling the Xenta 102-AX damper position, and flow value can be accomplished using the VAV_Controller.nviManOverride SNVT.

This is a three-part structured SNVT. Values for the state portion of the SNVT are:

  1. HVO_OFF disables override
  2. HVO_POSITION sets the damper position output to a desired percentage
  3. HVO_FLOW_VALUE sets the flow setpoint to a desired flow
  4. HVO_FLOW_PERCENT sets the flow setpoint to a desired percent of maximum flow
  5. HVO_OPEN fully opens the damper
  6. HVO_CLOSE fully closes the damper
  7. HVO_MINIMUM sets the flow setpoint to specified cooling minimum
  8. HVO_MAXIMUM sets the flow setpoint to specified cooling maximum

Values for percent and flow are used according to the selected state.

Click here to download a Menta macro for further clarification.

It is important to note that in versions greater than 2.1.2 no other auxiliary control will function when using nviManOverride. Example: if nviManOverride is set to control the damper to a fixed position, the external hot water heat or electric heat will not function.

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Revision #:
1 of 1
Last update:
‎2018-09-07 03:43 AM
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