Primary States (Start Stop Sequencing [AHU Mixed Air]) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 13.1

Controller Tool Help

Brand
Johnson Controls
Metasys
Product name
Controller Configuration Tool
Document type
User Guide
Document number
LIT-12011147
Version
13.1
Revision date
2019-12-04
Language
English
  • Off: This is the Off state. Here, the fans are off, and the dampers are closed. The unit waits for the signal to begin the start up sequence. The start sequence begins if heating or cooling is required.

  • SF Starts First: This state is used if the supply fan must start first. The supply fan is turned on.

  • RF Starts First: This state is used if the return fan must start first. The return fan is turned on.

  • Ramp SF: A variable capacity supply fan is set to ramp so it slowly speeds up and slowly increases the duct static pressure. The FSM switches to the Stabilize state when the duct static pressure is above the duct static pressure setpoint.

  • Stabilize System: This state is used to circulate the air in the AHU and allow temperatures to stabilize before opening the dampers.

  • Ramp Min OA: This state is used to ramp the dampers from closed to minimum position.

  • On: The fans and dampers were sequenced properly for a startup condition. Control of the dampers is released to a lower level state machine. The AHU is allowed to run.

  • Fan Fault: The FSM enters this state after proof of airflow fault. The FSM remains in this state until airflow is proven. Once airflow is proven, the FSM transitions to the RAMP SF state to restart the supply fan.

  • Close Dampers: This is the first step in the stop sequence. The dampers are closed during this state.

  • RF Stops First: The fans are stopped in the opposite order they were started (first on last off). This state is used when the supply fan started first. The return fan is off in this state.

  • SF Stops First: The fans are stopped in the opposite order they were started (first on last off). This state is used when the return fan started first. The supply fan is off in this state.

  • Fans Off: This state is used to turn off the fan that started first or turn off the supply fan when there is no return fan.