I need some suggestions for controlling building pressure for the system below:
1. Four packaged VAV Roof Top units (one for each floor).
2. One dedicated VAV Outdoor Air unit with energy recovery wheel that serves all four floors.
3. Combination of parallel and series fan powered boxes, and some vav boxes.
The RTU systems are straightforward with economizer and have they capability to perform building static pressure control.
The dedicated OA unit serves selected areas throughout the building based on CO2 in some cases or occupancy in others. This unit also handles the bathroom exhaust for the building via exhaust boxes, (vav), at each bathroom. There is an exhaust box on each floor connect to this unit for ‘volume’ control.
The OA unit exhausts more air on each floor than it supplies, so there is an overlap between the systems, (the RTU serving the floor and the OA unit).
Air flow stations are called for on the supplies and returns of all units. Engineer’s intent was to total the supply cfm, subtract the return cfm (with an offset), and modulate the exhaust ‘volume’ box to maintain that value, thus controlling building pressure.
The shafts are the only location for air flow stations, and they’re not the best. In addition the owner isn’t happy with the added cost of them.
Any thoughts or comments would be greatly appreciated.
Thanks – IDJIT