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Dehumidification using Xenta 121-FC

Issue

Dehumidification using Xenta 121-FC

Environment

  • Xenta 121-FC
  • Xenta 121-HP

Cause

Some aspects of how the dehumidification mode in the Xenta-121 operate are undocumented.

Resolution

The dehumidification feature of the Xenta 121 can operate either by turning on external dehumidification equipment using one of the digital outputs or, if no external equipment is provided, it will use the cooling for dehumidification. In the latter scenario, the heat continues to be operational when the cooling is forced for dehumidification. Additionally, if there is an outside air damper, it will be controlled to its minimum position before forcing the cooling on.

When is external dehumidification enabled?

  • For On/off cooling, cooling is enabled for dehumidification when the nvoDehumidActive value is greater than 10% and is disabled when the nvoDehumidActive value drops below 5%.
  • For all other types of cooling, nvoCoolPrimary is set to match the nvoDehumidActive whenever it is a greater than cooling PID output + 5% or whenever the cooling PID output is less than 5%.

The dehumidification feature can be configured using the ZBuilder configuration tool. However, the individual features can also be accessed via the points listed below using either Vista Workstation or another Lon management tool such as LonMaker:

Applic

UCPTappOptions

Bit Usage If FALSE If TRUE Additional notes
5 Dehumidification control enable Not active Active  
6 Dehumidification type Internal External Only applicable if bit 5 = true. External control can be hardwired or via SNVT. Internal will force cooling as a dehumidification method.
7 External dehumidification active on Open contact Closed contact Only applicable if bits 5 and 6 are both true.

UCPTappOptions2

Bit Usage If FALSE If TRUE Additional notes
7 External dehumidification type Digital Analog If true then the RH reading is mirrored to the analog output (0-100% = 0-10V). Only applicable if UCPTappOptions bits 5 and 6 are both true.
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Revision #:
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Last update:
‎2018-09-06 01:27 PM
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