Control Scheme (VAV-DD) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 13.1

Controller Tool Help

Johnson Controls
Product name
Controller Configuration Tool
Document type
User Guide
Document number
Revision date

The Control Scheme for Dual Duct applications determines how the Setpoints and Output Control Logic are configured. Constant Box Flow configurations are set up so the Hot and Cold Deck Dampers are controlled to maintain constant flow delivery into the space. The Variable Box Flow configurations are set up so the Cold Deck Damper and Hot Deck Damper maintain separate flow setpoints depending on whether the zone requires heating or cooling to maintain heating and cooling zone temperature setpoints.

The Selection options for Control Scheme are:

  • Constant Box Flow

  • Variable Box Flow

    • Optimized Minimum Flow: The total minimum box flow is proportioned from the hot and cold deck during the deadband when the box is satisfied. When in heating or cooling, the total minimum box flow is taken from the hot or cold deck, respectively.

      When the Occ Cold Deck Min Flow and Occ Heat Deck Min Flow (values set in the Balancer Override DD module) are set to 0 CFM, the box has 0 CFM setpoints when the room temperature is between the Effective Cooling Setpoint (EFFCLG-SP) and Effective Heating Setpoint (EFFHTG-SP).

      The total minimum flow through the box is proportionally calculated as the zone temperature drifts through the setpoint dead band between the EFFCLG-SP and EFFHTG-SP. If the desired behavior is to have a total box minimum flow at all times, set the Min Flow setpoints for both Decks at the desired total box minimum flow. If only one deck has a minimum flow setpoint = 0 CFM and the other deck flow setpoint = 100 CFM, the total box flow will drift from 100 to 0 CFM between the Effective Setpoints.