HVAC zone control

Local university upgrading systems to reduce energy consumption costs

Acme University’s building supervisor Greg has been asked to establish a plan to make the institution more energy efficient. Greg first notices that each of the rooms in a specific wing of the campus is being heated at varying temperatures, often higher than needed. Greg contacts his mechanical contractor to determine what adjustments can be made to ensure that controlling the temperature zones in the building is at its highest efficiency level.

Zone control is the process of maintaining a specific temperature in a room of a building on-demand according to the needs of the room. In other words, the goal is to supply treated air to destinations in order to meet, but not exceed, the demand required for that room. 

Some rooms in commercial buildings, such as the university’s laboratory, may require that the temperature be a setpoint that isn’t designed for human comfort, but is a controlled environment for experiments to thrive. Whereas others, like classrooms, would require an entirely different environment.

Greg has some options for addressing this issue. He can:

• Use the On/Off method if his application requires basic course control with an acceptable window of tolerance. This is more than sufficient and is the least expensive option
• Apply Pulse Width Modulation (PWM) where more precise control than the On/Off method is needed. This is a mid-range price option.
• Apply Proportional, Integral, Derivative (PID) control where precision and accuracy are critical. This is the most expensive, but most commonly used option. PID can be accomplished using either a VFD control or damper position control.

What Greg chooses to do is dependent upon what’s happening with the furnace. Let’s dig a bit deeper into these methods.