Very simple positive pressure system 1

[baltikabear]

Hi all, I need to have 4 rooms which are within an overall structure and need to have varying levels of positive pressure , decreasing with levels of importance for the rooms application. I am looking to put simple filter in and blow air into the room with fan and then controll the exhaust with a fixed damper . It is for a mould growing environment that we have in our cheese business so we dont want any mould from one room entering another room . We have one room which gorws the white mould for our brie type cheese which is quite critical and needs to be higher pressure. the others not so critical but would still need air change and temperature control. If anyone has any ideas how i could calculate the volume of air i would need to push in and exhaust that would be great. The largest room we have is 120cubic meters and they are all very well sealed with only one entry point and has sealed doors. We have contacted a few engineers but they all seem quite busy and look for the larger jobs !!

 

[tys90]

If the rooms are well sealed that's half the battle. The key to positive or negative pressure rooms is to give yourself flexibility with the mechanical equipment. Too many times we've encountered a room that's supposed to be well sealed and turned out to be leaky and it was difficult to get the required pressure differentials with the equipment we had.

As far as how to do that exactly, there are many different ways. Supply air volume is going to depend on a lot of factors and it's difficult to tell you how to determine that. On the exhaust side, if the room is well sealed 100-200 less CFM than supply per door should get the positive pressure you need. That's rough rule of thumb and is usually a good starting point. Once it's installed we use the flexibility that's designed to adjust the pressure as needed.

 

[willard3]

I suggest you consult an Engineer who is familiar with air systems.

 

[cry22]

Balti

You need an HVAC engineer, period.

I suspect that your fans will have filters and coils. When dealing with pressurization, you need pressure monitoring stations that act on supply and exhaust variable air volume boxes/air valves which will open/close to maintain pressure set points between two rooms.
Widely used in TB patient room pressure control in hospitals.
As you filters load up, you deliver less air, and lose pressure on the supply side, the VAV boxes and pressure monitoring stations will vary the flow accordingly, in other words, you cannot perform an air balance and be done with it.
You would need VFD's on Supply and exhaust fans, air valves on exhaust and VAV boxes on supply in addition Pressure stations (check out TSI instruments)
You need equipment, controls and know-how - if you want to do it right i.e