The 100 OA Start Stop Sequencer module sequences the fans and dampers for a controlled start and controlled stop in a 100% outdoor air system. The module accepts Heating Required and Cooling Required inputs that are used to initiate a start or stop sequence. The module accepts several user adjustable times such as Fan Start Delay and Fan Stop Delay. The module accepts inputs for static pressure such as Duct Static Pressure 1, Duct Static Pressure 2, and Duct Static Pressure Setpoint. The module accepts a configuration input Supply Fan Type. The module also has supply fan status inputs such as Supply Fan OnOff and Supply Fan Percent Cmd. The module has a state output and a duct static pressure output.
The unit initiates a start sequence if any of the following is true:
Cooling Required = True
Heating Required = True
The unit goes through the shutdown sequence if either of the following conditions is met:
Cooling Required = False AND Heating Required = False
The duct static pressure sensors fail.
The unit goes directly to Off, without passing through the normal shutdown sequence if the Supply Fan Control Status stops responding. This happens when a higher level sequencer, such as the No Air Flow Sequencer or the Emergency Mode Sequencer, takes control of the supply fan.
You can view and modify the modules in this group’s logic. The Finite State Machine cannot be modified. For information on how the FSM determines the state, see FSM (AHU 100 OA Start Stop Sequencer).