Is it possibel to have room pressurized with no fresh air intake?

[nevinjohn]

Hi,

This may sound weird, last week one of my clients was arguing with me, with the fresh air dampers closed, and just by recirculating the air (AHU blower), it is possible to pressurise the room. He was confused with the "extrernal static" developed by the AHU fan is suffuciet for pressurising the room.

How can I make him understand that this is not possible? Any justifications is much appreciated.

Thank you
Nevin.

[r.bartlett]

where is he going to magic up this additional pressure - from thin air??:D

[Rob White]

where is he going to magic up this additional pressure - from thin air??:D

Now that is being down right sensible and you should know right
now that customers are vary rarely sensible.....

:D

Rob

.

[TRASH101]

Although not very sensible it can be done LOL

Just make the return air plenum a lot bigger than the room and size your room size not much bigger than the supply duct.

:)

[Brian_UK]

It's very simple really.

The room, sealed, contains a fixed amount of air at a fixed pressure, atmospheric.

Fit an extract duct inlet to the room and then fit that duct onto a fan which has a supply duct outlet also connected to the room. With this layout the room, ducts and fan are now a complete sealed space. Assume that both ducts are of identical size and shape.

Turn on the fan an it will create a negative pressure on the inlet duct to enable it to withdraw air from the room. Now nature abhors a vacuum so in an attempt to replace the air withdrawn by the fan from the room nature accepts the air being blown out by the fan supply duct and the room remains at atmospheric pressure.

Assuming some numbers...

Extract duct resistance is 200Pa, supply duct resistance 200pa.

For the fan to move any air it needs to be able to suck at 200Pa and blow at 200Pa so need to be rated at 400Pa, there is no extra supply pressure within the circuit to pressurise the room.

Tell him to read this..
http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDEQFjAA&url=http%3A%2F%2Fwww.amca.org%2FUserFiles%2Ffile%2Fcermak_AMCA_web.pdf&ei=8Y8uUZyKLsn80QXU44GgDQ&usg=AFQjCNHzWCM9-nL4UwD1ijxkzLRu72tkjw&sig2=_by49t55LGSsQwRVSSlMmQ&bvm=bv.42965579,d.d2k

[nevinjohn]

Thank a lot... Brain... After all customer is the King, even if he is an idiot!

[sterl]

Don't need a fresh air intake. Just a compressed air line.....

[nevinjohn]

Don't need a fresh air intake. Just a compressed air line.....

Storing air in cylinders? How should be the calculations?