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Success Stories  > VAV Boxes

What Are VAV Boxes?

An air handler supplies conditioned air to the rooms in a building. Some buildings supply a fixed volume of air into a room. A variable air volume (VAV) box allows variable air volumes into a space, and provides better control of the room temperature and comfort. 


VAV boxes have a damper that opens and closes to control the amount of air entering the room. Some VAV boxes also have a reheat coil, which is able to heat the air from the air handler before it goes into the room.


The controller communicates with the damper to determine the position and the amount of air that goes to the room. It also communicates with the reheat coil to determine if the air from the air handler needs to be heated to meet the thermostat’s set points.

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Everything Is Connected in an HVAC System

VAV boxes are part of our mechanical systems that determine how much airflow enters the room and at what temperature. If VAV boxes malfunction or fail to communicate with each other, the room temperature can change drastically, having a big effect on comfort. The stories below are instances where your TherMOOstat feedback helped us find and reprogram malfunctioning VAV boxes in order to return the rooms to comfortable temperatures.

King Hall
Olson Hall
Ghausi Hall

In September 2015, we receive 1 chilly and 12 cold votes from Room 1001 in King Hall. The following month we receive another 12 cold votes. The consistent cold votes suggested there may be an issue with the cooling controls to room 1001.


When we went to investigate, we discovered two issues that caused the uncomfortably cold temperature. The first was that one VAV box was trying to cool the room while a second was trying to heat the room. We reset the VAV boxes so they would communicate, instead of competing against one another.

The second issue we found was from an old work order that disabled the thermostat. After we changed the programming to enable the thermostats, we went to the room to manually change the setpoints to 70°F.

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Your Vote Matters!


Have you experienced drastic changes in temperature? This may be a sign that your VAV box is malfunctioning. Ther more details you give us in your TherMOOstat comments, the more likely we are to identify the issue quickly.

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