Blower Design - When is an Outside Air Connection Recommended?

[ChemE584]

I often get quotes for positive displacement blower packages for jobs of mine. In every quote is an adder for an outside air connection. This is for the blower inlet. When is this needed? I can't seem to find anything in the vendor literature. When would you not want it?

Thank-you.

 

[Artisi]

Have you considered asking the vendor?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[TenPenny]

I would think it would depend on the size of the blower, and the size of the room or building it's in, and the airtightness or environmental factors in the room or building.

The air that goes through the blower has to come from somewhere. Where do YOU want it to come from? Consider whether or not people will be able to open or close the doors to the room where the blower is located, if it's running. I used to go into a pulp mill where the entrance to one maintenance shop was through the intake plenum for a bunch of ventilation fans. Some days, you could hardly open the door, and if you weren't careful, it would slam shut on you or your appendages if you let go of it.

 

[ChemE584]

Artisi, I discussed this years ago with them, but can't seem to find any of the emails on the subject. I was under the impression that this was a recommendation for whenever the blower is located indoors. It was my collegue who questioned it. Thank-you TenPenny. The dwgs for this particular project show the outside connection and show the air coming from outside the room. Makes sense if it's a mall blower/compressor room.

 

[bimr]

As Tenpeny suggests, it is important to duct the blower intake to the outdoors.

Engineers who work on HVAC systems balance the typical building intake air and exhaust air so that the typical building is not over or under pressurized. However, there are applications such as clean rooms where I believe the buildings are slightly pressurized to avoid entrance of contaminants.

Building air is "conditioned". That means the air is cooled or heated, or dehumidified. You would be wasting the funds that you spent to condition the air if the air went into the blower.

There are also noise considerations as well. There will be less noise in the building with an outside air intake.

 

[ChemE584]

Thank-you bimr!