THERMOSTAT IN VAV/CAV SYSTEM

[dux77]

Hi,

I just want your thought about an issue we are facing now in our design drawing. we are now in the execution stage that's why this issue is raised.

Issue is: 1. we have VAV boxes without thermostat in the drawings. I insisted to contractor that each VAV box should have its own thermostat to control it.am i right?
2. we have multiple VAV boxes( 3 units) in 1 Room, our design drawing states only 1 thermostat. However, I insisted to have thermostat in each one of the VAV boxes.is it
right?
3. we have also CAV boxes in the return ducts which do not have thermostat. I assume that there should also be thermostat even in return ducts.is it right?

I would appreciate your replies.thanks.

 

[willard3]

Thermostats are not required for every VAV unit is they all serve the same thermal zone. You should talk to the original Engineer who designed this system rather than guessing.

 

[DRWeig]

Do what Willard3 said. Then, while you're talking to the original Engineer, ask him to explain the purpose of the CAV boxes in the return ducts.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[BronYrAur]

dux77,

I am just now seeing your post. Did you get it resolved? I agree with Willard3 that you only need 1 thermostat per thermal zone, especially if it's an enclosed room. If you had multiple thermostats, they would be set at the same temperature anyway in an enclosed room.

What happened with the CAV boxes on the return? I have never seen such a thing other than on a laboratory or some other critical space where the supply and return must be closely and constantly maintained. It doesn't make sense in my mind to have variable supply and constant return.

please let us know what happened.

 

[trashcanman]

How do you have constant return air volume if the supply air volume varies???