vav solutions

[antony09]

I HAVE THE FOLLOWING QUESTION, A NEW VAV SYSTEMS HAVE 5 FIVE BRANCH, BUT ONLY TWO HAVE VAV BOX, I DONT SEE PROBLEM WITH IT, BECUASE WHEN A VAV BOX CLOSE, THE STATIC PRESSURE IN THE DUCT INCREASE AND THE SENSOR INSTALLED 2/3 LENGHT OF THE DUCT SEND A SIGNAL TO THE PID CONTROLLER AND DECRESASE THE FRECUENCY AND THE SYSTEM WORK CORRECTLY.

 

[ChasBean1]

Dynamics/duct shape might have an affect, but I think what you say is generally a pretty safe assumption.

 

[DouginMB]

To evaluate what you are trying to accomplpish, you need to answer a few questions. Does the air handler fan run continuously? What controls heating or cooling mode? What happens if a non-VAV space is satisfied and a VAV space is not? What about the reverse? Is there re-heat?

 

[antony09]

THE AHU RUN CONTINOUSLY, AND WORK IN COOLING MODE, NEVER HEAT. WE INITIALLY BALANCE THE SYSTEM WITH ALL BOX OPEN TO GARANTICE THAT THE AIR GO TO THE NON-VAV SPACE. WE HAVE INSTALLED A PRESSURE SENSOR IN 2/3 OF DUCT. IF ANY BOX CLOSE THE PRESSURE INCREASE AND SEND THE SIGNAL TO THE VFD, CONTOLLLING THE AIR INSIDE THE DUCT.

 

[antony09]

THIS SYSTEMS DONT HAVE RE-HEAT.

 

[DouginMB]

I assume it okay for the three non-VAV spaces to be continuously cooled. If that's true then I don't see a problem. There's nothing magical about the 2/3 duct location for the pressure sensor. It simply a rule of thumb for a full VAV system. In your case, you need to make sure it's located in the duct trunk between the fan and the first VAV box.