AIR VALVE V.A.V.

[supertek65]

While thumbing through the TRANE air conditioning manual I read on page 346 that the heart of the VAV is the AIR VALVE and it also discusses the flow ring.
On page 324 it shows a dual duct VAV and points towards the round duct and the arrow says AIR VALVES.
If the AIR VALVE is not the flow ring then what is an air valve?
Is it the damper?

[hvacowboy]

yes, but it moves in and out, not a butterfly damper, more linear

[supertek65]

Then is a VAV with just a motorized damper with no volume controller or flow ring still officially a VAV?

[hvacowboy]

yes, just less precise, its still varying air flow

[maxster]

if a metal box is controlling a constant tempered air(55f) either by damper or plate that screws down a rotating shaft it is a VAV....flow rings or not.the rooftop or air handler is the other end that they try to slow the air down with VFDs,IGV,by-pass dampers in the duct,fan curves..etc

[duke of earl]

If a VAV box does not have a flow ring, it is pressure dependent meaning that the air flow is dependent on the supply air pressure being consistent and high enough to deliver the rated volume of air to satisfy the required cfm's. If the box contains a flow ring, it can actually read airflow fairly accurately which gives feedback to the UCM. By operating on this principle if the supply duct pressure were reduced somewhat then the air valve will open more to compensate and deliver the needed airflow to the zone.This allows for better control of the air valve position and reduces valve hunting. This makes for a more energy efficient delivery of conditioned air to a zone or zones.Also a note on the "D" style air valve is that the drive motor is not continuous duty so if anyone other than Trane is controlling the valve, make sure the controls are setup for intermitten pulse action is selected. This will extend the life of the motor.

[r404a]

That reply is another reason we need you back, Duke. I hope all is well with you, been hating life over at the shipyard on start ups lately. Take it easy.

r404a

[supertek65]

great reply, thanks, Frank!

404a I noticed on your profile Trane 3 stage.
I am not a centrifugal mechanic, but is that the sidewinder?

[hvacowboy]

Frank, 3 stage is a 3 impellar machine,with inlet guide vanes, and economizer, and 3rd stage vanes, vanes modulate for unit capacity. allthough I could be wrong.

Brad

[agrv8d]

Thank you Duke. I like to read the residential section too, just to catch the bullsh***ers. Someone will ask a question and a ton of BS soon follows on some of the more tech questions. I am glad to see an accurate concise and more importantly correct answer to someone's question.