Ventilation? "I see," said the blind man.

BrownGirl · #1 2011-06-12, 10:08pm

So, the hubs and I have toiled and toiled over this. This weekend we bit the bullet and switched around my DINKY TINY studio. Exact measurements are 7.5' by 10ft with an extra little cubby that is 45" by 33". We built a base cabinet in this little cubby that is on the northern wall of the room. The table is 44" by 28". About 10' away are the windows (2) that will bring in my make up air. Immediately to the west is a wall with three windows. The furthest window is where I will be ducting my fan out of. My question is this: If I were to build a hood like this:

http://www.homedepot.com/webapp/wcs/...cStoreNum=3011

a few feet above my work table (which is counter height so I can stand at it), with a 1250 CFM exhaust, will that type of hood work? I am ABSOLUTELY not going to buy that hood from HD because, well, I can't possibly afford it. But, if I got/made one very similar, and used flex 8" ducting (the all metal stiffer kind, not the dryer type), would it work? Will it offer enough "coverage" to suck out all the evil fumes? I am in the process of buying a used 1250 fan from a gentleman on here and want this kind of hood. If I were to use stiff metal ducting, I would end up needing to use so many elbows, I would be lucky to end up with 400 CFM's *laughs*. I also need to use that same window to feed the propane hose out of. Space is a serious issue.

So far, how does this sound?

--Monica

Lorraine Chandler · #2 2011-06-12, 10:55pm

Monica, I tried several different hoods ( box styles).

Until I made a barley box type hood with full sides, a front baffle and a back, with hole for the ducting to fit snugly into for exhausting there was just too much turbulence no matter which speed I set my unit on. It has three speeds.

My torch flame was bouncing everywhere. Now I have a complete hood all around with front baffle and use 1100 CFM and around 1800 on high for gold, enamels, silver, 96 coe frits and silver glass. It works great.

So I really think you will just have to try it and then if you need to add sides, a back and a front baffle, if your flame is dancing all over and smoke bomb tests fail.. you can easily add to your hood. Smoke bombs are real cheap at magic stores.

I found out it just wasn't about pulling out the bad fumes.....

The CFM was right but the hood design wasn't.

BrownGirl · #3 2011-06-12, 11:09pm

Lorraine, did you ever try a fume funnel? I am not completely opposed to doing a barley box but... I just feel like it might get a little claustrophobic. How big is your barley box/fume hood? I keep having visions of bumping my elbows, hitting my head on the baffle...

cheng076 · #4 2011-06-13, 10:28am

My original "studio" was exactly that size, 7.5' x 10' with the bench across one narrow end. I used it for several years until I had the opportunity to build a much larger studio. You didn't say what type fan you were buying. My hood in that studio was home made. I had a sheetmetal place bend a piece of 20 ga. steel plate 3' x 4' into an 'L' angle that had 2' legs and was 3' long. I had them cut a 2' square across the diagonal so I had triangle end pieces. I welded these to the 'L' shaped piece but I could have used corner brackets and pop rivets and metal duct tape to put it together. I cut a hole in one of the sides of the 'L' near the fold and attached duct work to the fan and out the wall. Total cost was less than $75 and a few hours work.

BrownGirl · #5 2011-06-13, 10:59am

Cheng> It's a 1250 CFM Squirrel cage fan. He hasn't gotten back to me yet (he works 3rd shift, let the fella sleep!) but he said thinks it is a variable speed.

I really like what you described in your above post. I am going to call around and price out sheet metal. I was hoping I could find some kind of old metal cabinet that is light and the right size. I have a little time to look around. I still have to grout the tile on my bench.

Does then fan need to be mounted on top of my fume hood/range hood or can I have it at the end of the ducting? I was hoping to rig up something so that I could have it at the tail end of the ducting and heading out the window.

Thanks for all your advice, Cheng. It's so easy to read and easy to follow.

--Monica

Lorraine Chandler · #6 2011-06-13, 12:26pm

Monica, Yes we started out with a funnel ( still using it) although it is square and comes down over the middle of the bench. Too much turbulence without the box system.

I know you will get it all figured out

but I just wanted to let you know that sometimes it's not the fan or the funnel but the surroundings. Ours was apparently too open and once we enclosed the area Barley box style it was perfect.

cheng076 · #7 2011-06-15, 9:33am

Thank you, Monica, always happy to help.

Something I've seen/heard other people using is a wash/water tub; the sort you find in a feed store. They are about a foot deep and oval shaped and come in various sizes. Mount the fan inside the tub and no enclosure is needed. Then run the duct to a window or where ever. I'll make a drawing and post it later.
PJH

cheng076 · #8 2011-06-15, 10:08am

Here is a drawing illustrationg my comment. I have also heard of people using the sheet metal cabinet from an appliance such as a dryer as an enclosure.

BrownGirl · #9 2011-06-15, 5:04pm

Those all look really good. I just have to make sure the weight can be supported. I can't wait for it to be done. I have to go out to a feed store this weekend. I'll check if they have something like that.