Exhaust fan

[whitemtnelf]

Hi folks,

Long time stalker, first time poster. I'm building a 26x30 shop. I'm going to be doing welding, painting, etc. What have folks done for an exhaust fan for this type of setup (i.e. blade size, cfm, etc)?

Thanks

 

[Rich H.]

Mine has around a 14 or 16 inch blade, but I don't know the cfm because I got it used....it was a discarded cell tower/server piece from a buddy.

http://garagejournal.com/forum/attachment.php?attachmentid=136790&d=1316738912

If I could make suggestions:

-try to get one with a louver that opens and closes along with the fan, try to find one with a louver that really seals up nicely (though I'm not sure if anyone makes one quite that good, see below)

-whichever wall the exhaust fan is mounted in, put at least one good sized window at the opposite side of the shop so the fan can draw air through it, which will then give you flow through venitilation, and you'll be replacing the bad air with good air. (You can disregard that if you don't intend to seal the building up very well, but at that point will be relying on whatever leaks the ceiling and wall assemblies for the fresh air, kind of hard to control and a bad deal, but I've seen it done that way before).

Two things about mine that I'm going to change:
-The louver "closes" but does not really seal particularly well when closed. The wind can blow through it around the edges. I will probably make an insulated plug that pops into it at some point, for when I don't want it to be ventilated.
-although the insects haven't discovered the louver yet, I should really put a screen on the outside of it to discourage wasp nests and so on.

 

[Provincial]

I used this one on my 40x60 shop. Mounted it as high as possible in the end gable. I crack open an overhead door at the far end for draft.

This one has louvers that don't seal that well. I put a piece of aluminum window screen between the fan and the louver, with four self-drilling screws in addition to the fan mounting hardware. I am holding off doing more to seal it while I monitor the heating this winter.

I have an all-metal building, so I made a mounting box out of steel stud runner (light gauge u-channel) to attach it to the girts and steel siding.

I put a smaller (12") version of this fan in my house to pull the hot air out in the summer. On that one I used a backdraft damper as a seal. I am pulling the air from 12 feet away from the that fan, so I put a round damper in the duct. The local sheet metal shop made an adaptor for me. You can buy square dampers if you want to attach it directly. The damper I got is gravity-operated and has a seal at the flapper, and can be pushed open if the air pressure inside the building gets greater than the outside pressure. This would happen if the wind blowing over the building caused a vacuum at the outside of the gable or if you had the door open into a wind. You can buy a motorized damper if you want a more positive seal. I have not found it to be a problem.

http://www.northerntool.com/shop/tools/category_fans+exhaust-fans

I bought my through a local supplier, and got a better deal than this.

 

[whitemtnelf]

Thanks for the replies. I live in NH and will be heating the shop so I am concerned about heat loss when the fan isn't on - which will be most of the time.

I'm also considering skylights that can open to just let the smoke vent out the top. But on really cold days I've seen the cold air blow the smoke down my chimney until it gets hot enough.

I like the idea of some kind of plug / door but the fan will be around 18' high.

 

[Robleticia]

Grainger carries wall fans with motorized damper, or you can buy just the damper if you already have the fan. Wire the damper with the fan and it will cloze when the fan is off and the blades have rubber gasket on them and are fairly air tight.