sizing a fart fan

[Tommy1010]

I have an industrial rooftop fart fan in a mens room. People complain that it doesnt work well and doesnt remove humidity.
...Storys been told that when the old supervisor was here years ago, he realized it was undersized but didnt want the hastle of returning it.

So how would i properly size one of these things?

[Southern Mech]

1st you have to get an idea how many fart's per hour, the cfm per fart, devided by the cubic foot of room area, - make up air. you are going to have to take some field measurments 1 day.


sorry couldn't resist.

[energy star]

Call Greenheck. They will tell you in about 2 minutes. They love that stuff. Measure the room, get the distance from room to roof, call.

http://www.greenheck.com/

[dandyme]

you might want to take the exhaust pipe loose and see what it looks like inside

[Miller257]

code around here is a minimum of 75cfm per fixture.

[y7turbo]

1st you have to get an idea how many fart's per hour, the cfm per fart, devided by the cubic foot of room area, - make up air. you are going to have to take some field measurments 1 day.


sorry couldn't resist.

CFM per fart? Strap a flow hood to someones ass and have them fart?? LOL

[Cooked]

It depends on where you live. They tend to be larger down here due to the high consumption of enchiladas and refried beans.

Truth is I never had to size one. Where's genduct when you need him? That guy is an airflow expert.

[Tommy1010]

I ripped it apart to access the blades and what do you know....1/2'' of dirt surrounded each side of each blade.(no exageration) Theres also damper directly under the fan. Which I dont know why since the fan runs 24-7. The damper didnt have enough flow to open. When i measured the cfm's at first..I was getting an average of 205 in the main bathrooms return. After cleaning and restarting, I got an average of 315. BTW, theres 2 toilets and 2 urinals in there. Its a 1725 rpm motor. 3/4 hp, 120v

[dandyme]

you got to hand it to this crowd, any subject can be taken to the crapper in a short # of post.

[hotrodrob]

the damper is a backdraft damper from the sounds of it. is this a belt driven fan, check amp draw and see if you can sheave it up a bit for more air flow.

[HvAckid82]

Code book states minimum of 75 cfm per fixture (toilet, urinal). If this area is in heavy use, go bigger. Make sure you have makeup air for the bathroom.

[Miller257]

By code you need 300, I like to size them a little more than design then slow them down, if I ever need to speed it up I can. Is it direct drive or belt? Any room to speed it up?

[vangoghsear]

Code book states minimum of 75 cfm per fixture (toilet, urinal). If this area is in heavy use, go bigger. Make sure you have makeup air for the bathroom.

That's changed. 2009 IMC says It's 70 cfm per if the room is used frequently, 50 per if usage is lower. The old requirement was 75 per WC or Ur.

I would go with the higher 70 cfm or more if there have been complaints.

Also, is there any supply or makeup to the system (louvered door, undercut, supply diffuser/register) you can't take air out if you don't let some in.