Demand ventilation - Johnson Controls - LIT-12011950 - Building automation software - Smart Equipment Controller - 5.0

Smart Equipment Controls Sequence of Operation Technical Bulletin
Product
Building Automation Systems > Building Automation Systems > Smart Equipment Controller
Document type
Technical Bulletin
Document number
LIT-12011950
Version
5.0
Revision date
2024-06-06
Product status
Active

This section details the setpoints and related data, inputs, outputs, general functionality, and operation regarding the economizer’s demand ventilation feature.

Setpoints and related data

The setpoints and related data include the following items:

  • Demand ventilation mode of operation (DVent-Mode)
  • Demand ventilation maximum economizer position (DVentMaxEconPos)
  • Demand ventilation differential setpoint (DVentDiff-Sp)
  • Demand ventilation indoor air quality setpoint (DVentIAQ-Sp)
  • Indoor air quality sensor range (IAQRange)
  • Outdoor air quality sensor range (OAQRange)
  • Supply air temperature (SAT)
  • Operational indoor air quality (OprIAQ)
  • Operational outdoor air quality (OprOAQ)

Outputs

The output for demand ventilation is 2 to 10 VDC from the ECON terminal to the economizer actuator.

Operation

The control must be in occupied status with the indoor fan operating. If the low ambient minimum position is in effect, it overrides the demand ventilation operation.

If the demand ventilation mode of operation is set to enabled and the operational indoor CO2 level is greater than the demand ventilation setpoint +100 ppm, the current operating minimum position increases as follows.

  • With a CO2 level between the demand ventilation setpoint +101 ppm and +200 ppm, the operating minimum position increases 1% per minute.
  • With a CO2 level greater than the demand ventilation setpoint +200 ppm, the operating minimum position increases 2% per minute.

When the CO2 levels drop to equivalent values below the demand ventilation setpoint, the current operating minimum position decreases at the same rates.

While in a demand ventilation mode, if the supply air temperature drops below 49°F, the economizer outside air dampers close until the supply air temperature rises above 49°F but does not go below the current economizer operating minimum position. The economizer then modulates to control the supply air temperature at 50°F.

Note: The exception to this rule occurs when hydronic heat enable and SAT tempering with hydronic heat enable (40°F default) are both on. Hydronic heat is used to control the supply air temperature in this situation and the hydronic heat tempering setpoint is above 45°F.

If differential AQ enable is on and the OAQ is greater than or equal to the IAQ by more than the demand ventilation differential setpoint, the outside air dampers close completely and override all other minimum position functions.