Operational space humidity - Johnson Controls - LIT-12011950 - Building automation software - Smart Equipment Controller - 5.0

Smart Equipment Controls Sequence of Operation Technical Bulletin

Brand
Johnson Controls
Product name
Smart Equipment Controller
Document type
Technical Bulletin
Document number
LIT-12011950
Version
5.0
Revision date
2024-06-06
Product status
Active
Language
English

Setpoints and related data

The setpoints and related data include the following items:

  • Operational space humidity (OprSH)
  • Space humidity source (SHSrc)

Inputs

The inputs include the following items:

  • Network override space humidity (NetSH) communicated value on FC bus
  • Net sensor space humidity value to the SA bus
  • Return air humidity (RAH) to RAH terminals

Dirty Filter Switch can be used for Dehum call (new in version 4.0)

DFS ships as the default setting, but when HGR-En is on, a new point appears “UseDFSforDehum” with enum set Yes/No, default No. If No, DFS will still alarm Dirty Filter Switch. If Yes, the HGR Sequencer will read DFS input for a binary call for dehumidification, the same as if RAH% were above the setpoint. Normal, alternate and hybrid modes still work as described. Dehumidification only shuts off when the DFS input goes low. If DFS is used for Dehumidification, the use of a Dirty Filter Switch is excluded.

A point has been added under the Details → Hot Gas Reheat → Setup menu called “Use DFS For Dehum”. When this is enabled, a high logic signal on the DFS input represents a call to dehumidify. DFS alarms are masked when using this input for dehumidification behavior.

Operation

The operational space humidity (OprSH) is effective only if an input has been entered following the last RELEARN SYSTEM (Relearn) operation. The operational space humidity (OprSH) parameter is then shown in the UCB display.

The highest priority valid input is used for the operational space humidity (OprSH). The operational space humidity (OprSH) has assigned priority for inputs in the following order from highest to lowest:

  • Network override zone humidity (NetSH)
  • Net sensor space humidity value
  • Space humidity RAH input (RAH)

If the input in use becomes invalid, the operational space humidity reverts to the next highest priority input.

The space humidity source describes the input in use for the operational space temperature, and the indications include the following items:

BAS Override
Indicates network override zone humidity (NetSH)
Network Sensor
Indicates a net sensor
Local Input
Indicates space humidity RAH input
Unreliable
Indicates no valid input is available and control functions that use operational space temperature (OprSH) are not permitted

The network override zone humidity is used if a value is set or communicated within the past 15 minutes. If 15 minutes pass without a communicated value, the UI displays Value Timed Out and the next highest priority input is used.

The net sensor space humidity value is used after approximately 30 seconds from the time a net sensor with space humidity capability is connected to the SA BUS.

The space humidity RAH input is used if the humidity sensor is connected to the RAH terminals on the UCB.

If no valid related input is available for the operational space humidity, control functions that use operational space humidity (OprSH) are not permitted.