A reheat VAV box is very simular to a single duct VAV box. The only difference here is electric heat strips or a hot water coil at the discharge of the box that would heat the airflow back up before it enters the space. Calibrating the airflow through the box would be set up the same as a single duct VAV box. The things to check on a reheat electric box would be measuring the heater volts and amps with all stages of heating on. When using heating water the GPM must be set and entering and leaving water temperatures should be taken. It is also a good idea to check the entering and leaving air temperatures. The following is a list of pro's and con's for this type of box:
- Has the ability to give the space cooling or heating without effecting temperatures in other areas.
- Gives the space a larger percentage of fresh air (outside air).
- Airflow is better filtered because all of the airflow is being supplied by the main air handler.
- All airflow entering the space is being dehumidified by the main air handler.
- Airflow that has been cooled to 55 deg. then heated back up is very inefficient and expensive to run.
- Boilers and hot water pumps would have to run all year round when using hot water reheat.
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