One of our buildings has a 30 ton Carrier (48AKE030) with gas heat that was originally setup with a VVT system with 17 zones. The building has ceiling return. This unit replaced the old unit 5 years ago. The old system used a constant volume blower and relief dampers that dumped supply air directly into the unit return. The new unit came with a VFD to control motor speed.
We have up graded the controls because the Carrier parts are becoming obsolete.
The question I have is on a VVT system do I want to use the VFD to control static duct pressure, or relief dampers.
I have called our Carrier distributor and received two different answers. It depends on who I talk to.
Also if the relief dampers are used, shouldn't the supply air be discharged away from the unit return and mix with the building return before it enters the unit?
If more information is needed let me know. This in not the best system setup, but I have to live with it for a while.