static pressure hi & low

[ccut]

I'm looking for hi and low static pressure limits for a air handler with vortex vanes supplying air to vav's and fpb's. I am reading about .45"wc but was expecting a min. of 1"wc am I off? thanks

[lwarren]

Most boxes require 1'' of static to achieve full flow. Normally the system would control static 2/3 of the way down the main trunk line to ensure enough static at the farthest point. Where is the static being controlled or sensed?

In the winter time static pressure can be reduced in most cases and still provide adequate cfm to the zones.

What is the static setpoint on the system? Does the system have the capabilty to reset the static pressure?

If you have the TAB reports for the system they should state the operating static of the system at the time of balance.

[maxster]

1.5" is typical in cooling season at 55F anything more your losing air in the connectionsif your probe is field installed on the job ductwork that is critical to your setpoint maintaining that...Trane last i heard wanted them 2/3rds down the duct and not near any takeoffs...keep in mind the A/B flow rings if you have them on each box they are looking for the straightest of air into the box also.if you have a snake of supply going to a VAV and it seems not to be reacting just straightening out the inlet air flex .the result will give the box something to see..instead of that bouncing 1.5" volume of air

[ccut]

Thanks for replying guys, I appreciate being able to bounce this off someone. The sensor is located only a short distance from the unit, whereas the ductwork is a realitivily straight run and about 150 ft. I guess the sensor is so close for convienence purposes. I tried to free up the vortex vanes, but everthing is so corroded I didn't make much progress. I'm leaning towards sugggesting a freak drive.

[Tech Rob]

When you speak in terms the customer can understand ($$$$ saved), a vfd sells itself.

Like the other guys stated, traditionally, the static pressure pick-up is located 2/3 of the way down the duct run, away from any changes in direction, take-offs, or possible turbulence. On most VAV systems, you'll see them controlled to between 1" and 2", usually 1.5"

Are these pressure independent terminals?

[ccut]

thanks for your help. It's a kind of weird situation,we supply 55-60 degree air to these tenant spaces, but don't service the vav's.

[Tech Rob]

Shopping malls do it all the time. As long as you're providing 55-60* air at whatever the design static is, it's someone else's problem, right?

[ccut]

Shopping malls do it all the time. As long as you're providing 55-60* air at whatever the design static is, it's someone else's problem, right?

I never thought about that but I imagine the stores have to hire their own contractors.thanks