VAV Box Simulator
Lesson 2.2
Map the points. Wire the controller. Learn the sequence. Run the system.
Point Mapping
Each point maps to an I/O category:
- ZN-T (Zone Temperature): Analog Input
- DA-T (Discharge Air Temp): Analog Input
- AirFlow_CFM (Airflow CFM): Analog Input
- Damper_Cmd (Damper Command 0-100%): Analog Output
- Htg Valve (Reheat Valve 0-100%): Analog Output
- Occupancy: Binary Input
Wire Sheet
Controller Terminals:
- Left side: AI1 (Analog In), AI2 (Analog In), UI1 (Universal In), BI1 (Binary In)
- Right side: AO1 (Analog Out), AO2 (Analog Out)
Sequence of Operations
UNOCCUPIED: When OCC is off: Airflow at unoccupied minimum CFM (or fully closed), reheat valve closed.
COOLING: When ZN-T above cooling setpoint: CFM setpoint ramps toward maximum, damper modulates to match, reheat valve closed.
DEADBAND: When ZN-T between heating and cooling setpoints: Airflow holds at minimum CFM, reheat valve closed.
HEATING: When ZN-T below heating setpoint: Airflow holds at minimum CFM, reheat valve modulates open (0-100%).
Live Simulator
Adjust the zone conditions and watch the VAV box respond in real time. Controls include Zone Temperature (55-85 degrees F), Cooling Setpoint (65-80 degrees F), Heating Setpoint (60-75 degrees F), and Occupancy.
Setpoint conflict warning: Heating setpoint at or above cooling setpoint. There needs to be a deadband between them or the controller will fight itself, trying to heat and cool at the same time.