Primary States (Occupied Sequencing [AHU 100% OADD]) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 13.1

Controller Tool Help
Product
Controls > Control Tools > Controller Configuration Tool
Document type
User Guide
Document number
LIT-12011147
Version
13.1
Revision date
2019-12-04

In the following descriptions, HX stands for Heat Recovery.

  • Satisfied: The sequencer is in this state if no heating or cooling is required.

    The sequencer transitions to Satisfied from HX Cool+Mech if the cooling device is not responding to the sequencer or the Process Variable is less than the Setpoint and the cooling device PID saturated low.

    When heat recovery is modulated, the sequencer transitions to Satisfied from HX Heat if the Process Variable is greater than the Heating Setpoint, and either the heat recovery device control status is low or the heat recovery device is not responding to the sequencer.

    When heat recovery is two position (Heat Recovery Modulated is False), the sequencer transitions to Satisfied from HX Heat if the Process Variable is greater than the Heating Setpoint.

    The sequencer transitions to Satisfied from Heating Idle if the Process Variable becomes greater than the Setpoint and Preheat Percent Cmd is zero.

  • HX Cool+Mech: The sequencer enters this state from Satisfied if cooling is required and the cooling device is responding to the sequencer. In this state, the heat recovery device is on and cooling device controls the process variable.

  • HX Heat: The sequencer enters this state from Heating Idle (and Satisfied) if the startup sequence has completed and therefore the fan is ready and the Process Variable is less than the setpoint (heating is required) and the Preheat Percent Cmd is greater than zero and heat recovery is modulated.

    The sequencer enters this state from HX Heat+Preheat if the Process Variable is greater than the Setpoint and either the Preheat Control Status is Low or the preheat device is not responding.

  • HX Heat+Preheat: The sequencer enters this state from Heating Idle if the startup sequence has completed and therefore the fan is ready and either Preheat Percent Cmd is greater than zero or heat recovery is not modulated.

    The sequencer enters this state if after being in HX Heat the process variable is still less than the setpoint and any of the following three conditions is true:

    • The heat recovery output controller is not responding to the sequencer.

    • The heat recovery PID has saturated high.

    • The heat recovery device is not modulated. In this state, Preheat is set to its maximum position, and the reheat output controller controls the process variable.

  • Heating Idle: The sequencer enters this state through Satisfied if the Process Variable is less than the Setpoint or Preheat Percent Cmd is greater than zero. The sequencer enters Heating idle from any heating state if the Start Stop sequencer informs that the fan is not ready.

  • Temperature Unreliable: The sequencer enters this state if the process variable sensor is unreliable.