Attributes (Start Stop Sequencing [AHU Mixed Air]) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 15.0

Controller Tool Help

Brand
Johnson Controls
Metasys
Product name
Controller Configuration Tool
Document type
User Guide
Document number
LIT-12011147
Version
15.0
Revision date
2022-11-18
Language
English

The following table describes the attributes used by this module.

Table 1. Start Stop Sequencing (AHU Mixed Air) Attributes

Name

Description

Default Value

Cooling Required

Indicates cooling demand. When this input is True, the Start/Stop module initiates a start up sequence.

False

Damper Close Delay

Time required to close the dampers before turning the fan off.

90 Seconds

Duct Static Pressure

Contains the value of the duct static pressure used by this module and passed to the Supply Fan Output controller.

Display Units: Pa, in. W.C.

Duct Static Pressure 1

Supply air duct static pressure. The unit may have two pressure sensors. When the application has one pressure sensor, it must be connected to both Duct Static Pressure 1 and Duct Static Pressure 2.

0 Pa, 0.00 in. W.C.

Duct Static Pressure 2

Supply air duct static pressure. The unit may have two pressure sensors. When the application has one pressure sensor, it must be connected to both Duct Static Pressure 1 and Duct Static Pressure 2.

0 Pa, 0.00 in. W.C.

Duct Static Pressure Setpoint

Contains the supply air static pressure setpoint. This input is used to trigger a state change if the supply fan type is variable speed and static pressure control is used.

250 Pa, 1.00 in. W.C.

Fan Ready

Indicates that the Start/Stop sequencer has reached the On State. The temperature control sequencers (such as the MA SD Sequencer or the MA CD Sequencer) use this information to allow DAT temperature sequencing. This output is delayed one operational cycle after the State output to ensure the Fan Ready output is in sync with the control status inputs (Damper CS, Cooling CS, Preheat CS, and so on) on the lower level sequencers.

 

Fan Sequence

Indicates which fan must start first. The module supports three cases, supply fan first (SF First), return fan first (RF/EF First), and supply fan only (SF Only) for the case where there is no return fan.

SF First

Set Name: AHU Fan Sequence

Fan Start Delay

Time delay between starting the first fan and starting the second fan.

10 Seconds

Fan Stop Delay

Serves a dual purpose. It is the time delay between stopping the first and second fan, and it is the time delay between stopping the second fan and allowing the system to restart.

30 Seconds

Heating Required

Indicates heating demand. When this input is True, the Start/Stop module initiates a start up sequence depending on the status of the Preheat Bonnet Switch, Preheat Percent Cmd, Reheat Bonnet Switch, and Reheat Percent Cmd.

False

Minimum OA Position

Defines the minimum position for the OAD and the EAD. It is used to calculate the Ramp OA delay time used by the FSM.

0%

Occupancy

Contains the occupancy status for the unit.

Occupied

Set Name: Occ Effective

Preheat Bonnet Switch

Contains the bonnet switch input from the preheat device. It indicates whether preheat is hot enough for the fan to start. The bonnet switch is used to provide a supply fan on delay when the AHU has gas heat. The bonnet switch is only supported in systems with a single speed supply fan which starts first.

Hot

Set Name: Cold/Hot

Preheat Percent Cmd

Contains the heating command to the preheat device. This input is used to determine if the unit is heating and if heating or cooling are required.

1.0%

Proof of Airflow

Shows the current airflow status. The output may be either True, False, or Fault. True means the fan was commanded on and airflow has been detected. False means the fan was not commanded on. Fault means the fan is commanded on, but airflow proof has not been detected. This input is used to restart the supply fan after a fan status fault.

False

Set Name: False/True/Fault

Ramp Rate

Defines the rate of change in damper position. It is used to calculate the Ramp OA delay time used by the FSM.

50 Change per Minute

Reheat Bonnet Switch

Bonnet switch input from the reheat device. It indicates reheat is hot enough for the fan to start. The bonnet switch is used to provide a supply fan on delay when the AHU has gas heat. The bonnet switch is only supported in systems with a single speed supply fan which starts first.

Hot

Set Name: Cold/Hot

Reheat Percent Cmd

Contains the heating command to the reheat device. This input is used to determine if the unit is heating and if heating or cooling are required.

1.0%

Stabilize Delay

Defines the amount of time it takes to circulate air within the AHU to stabilize temperatures before opening the dampers.

60 Seconds

STARTSTOP-STATE (State)

Current state of the finite state machine. This output is connected to the state selection matrix.

Set Name: AHU MA StartStop States

See Primary States (Start Stop Sequencing [AHU Mixed Air]).

Supply Fan OnOff

Indicates if the supply fan is responding to this sequencer. This input is the control signal for the supply fan. The enumeration set only has two values, Off and On.

Off

Set Name: Off/On

Supply Fan Percent Cmd

Contains the current value of the supply fan output.

0%

Supply fan Type

Indicates the air handler supply fan type. The module supports two supply fan types, variable capacity and constant capacity.

Variable Capacity

Set Name: AHU Supply Fan Type