# VAV's and control wiring...



## Zaped (Jul 6, 2008)

Where to find any posts on electriciantalk.com on the topic of VAV's and control wiring for VAV's ?


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## Chris Kennedy (Nov 19, 2007)

What do you want to know about them?


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## Boomer (Oct 19, 2011)

What controls are on the VAV? Valve(s) as well?


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## wildleg (Apr 12, 2009)

you need to proviide a little more info if you want help wiring them - manuf, model#, etc


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## Greg (Aug 1, 2007)

There are quite a few of us that do control wiring but with out the specs on the VAV it is hard to tell you what it (VAV) can and cannot do and what needs to be wired.


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## StephB (10 mo ago)

Zaped said:


> Where to find any posts on electriciantalk.com on the topic of VAV's and control wiring for VAV's ?


I have a question about a VAV situation. I'm supplying 120v to the VAVs and when I opened one up I saw there were no guts in it. No transformer, no actuator. Just a switch with leads which will ultimately supply power. They have only blue and yellow, which I see is common and..... What's yellow? And how does that translate to my 120 coming in. I just rolled the MC up until I know for sure that A ) that switch is intended as a disconnect means and B.) Which wire is which as far as my hot and neutral are concerned? From what I've gathered, the switch has pre-stripped leads for me, the other side has terminals for the step down... Then the other side of the transformer goes to the terminal blocks on the actuator or whatever else is going in ... Any info would be appreciated. Thanks.


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## Southeast Power (Jan 18, 2009)

We recently connected several VAVs.
They were all heat only with no actuators.
We installed 277volts with a toggle switch in a 1900 box with an industrial cover as a local/ safety disconnect.
The controls contractor supplied a relay connected to the Building Management System


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## SWDweller (Dec 9, 2020)

First I have always HATED VAV boxes and controls. I think it is the WORST way to control a buildings air.

You have to have a source of air. Usually a fan on a VFD pressurizing a duct. As the VAV boxes open for distribution the air pressure lowers in source duct. Causing the Supply Air to either *to *ramp up or start another fan. The VAV's usually respond to local controls t stats through a energy management system of some sort. 
The exact method is by the prints and specs of the system. Most I have done were low voltage.

Fought with one building for 9 months. 4 250 hp fans on drives. Took 2 fans at 100% to pressurize the duct. Then the third fan had to start to supply the air leaving the VAV's.
Chased ghosts for 9 months and I got another assignment. No one was comfortable in the building either to hot (most of the calls) or not enough air to the labs that had to be pressurized when the fume hoods were on.


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## joe-nwt (Mar 28, 2019)

SWDweller said:


> First I have always HATED VAV boxes and controls. I think it is the WORST way to control a buildings air.
> 
> You have to have a source of air. Usually a fan on a VFD pressurizing a duct. As the VAV boxes open for distribution the air pressure lowers in source duct. Causing the Supply Air to either *to *ramp up or start another fan. The VAV's usually respond to local controls t stats through a energy management system of some sort.
> The exact method is by the prints and specs of the system. Most I have done were low voltage.
> ...


There are people that are trained and have equipment for balancing air in a building. You should have hired one.


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