VAV Diffusers

[susanp]

Has anyone utilized the VAV diffusers? I am wondering with the thermal element inside the diffuser determining how much air to space to contro temp- what tells the unit to be in heating or cooling? outdoor air temp only? What allows the unit to maintain constant volume?

 

[tombmech]

Typically, an additional sensor is used upstream to determine the heating/cooling switchover, and then two elements are used for control - one heating, one cooling.

Personally, I would stay away from them. The ones I'm familiar with work about six months, then never work again.

 

[walkes]

If you're talking about the thermafuser then the unit is at the mercy of the main zone in the system. The diffuser is independant of the air handler control. I believe the thermafusers are used to get some means of control on a small space in one zone. The thermafuser reacts to the induced air temperature in the space, as it restricts airflow one of the "constant" volume zones will get additional airflow.