Please Help my with my vent design - it's not working.
 

Please help me figure out why this isn't working - I don't know what to try next.

This is my vent hood - an upside-down washtub. It has 8 inch vent pipes and the fan is on the other side of the wall. It's 24 inches above my table, 18 inches above my torch. Incense test failed - the smoke just wafts about going here and there and eventually most of it goes up.



The fan is this one from grainger:
Blower,495 CFM,115 V
Shaded Pole Blower, Air Flow @ 0.000 Inch Static Pressure 495 CFM, Speed 1570 , Voltage Rating 115 Volts, Power Rating 225 Watts, Current Rating 3.25 Amps, Frequency 60/50 Hertz, Thermal Protection Auto, Wheel Diameter 6 1/4 Inches, Wheel Width 4 1/4 Inches, Air Flow @ 0.100 Inch Static Pressure 476 CFM
Grainger Item # 4C445

The fan box looks like this, except it has 3 extra 2.5 inch holes drilled in the bottom of it to provide air to the motor:





The make up air - door open or shut, same deal. I also have the vents in the wall above the table, behind the hood, I've tried them open and shut, doesn't seem to make a dif. We've gone over the whole system, it's all screwed and taped tight.

I tried adding some back and side baffles, no help. The fan seems to be exhausting strongly. I tried blocking part of the vent hole in the hood and it grabbed right on to the hard plastic sheet I had and held it up by itself.

I called grainger and the tech guy there suggested I change to 6 inch pipes. Dale says that info is incorrect.

I don't know what to look for next. Please, any ideas?

Thank you.

and there are more photos of my set up from beginning to end here, if it helps:
http://www.bluebetween.com/studio.htm

Thanks again.

And the last thing. I just lit my torch to see if the flame would bend uptoward the hood like it did in my old studio with my old kitchen hood (dual fan 400 CFM when both were on) and it does NOT bend upward.

It should, right?

Incense smoke just wafts around, sometimes blowing right back toward my where I would be sitting. not good.

Ok I know I'm just talking to myself here. But my hvac friend agrees with Dale and says don't go to 6 inch vent pipes. He says if anything 10 inch would be better. But 8 should be fine.

<sigh>

OK... so... tried the baffles again. Door shut, the smoke wafts slowly up better than with door open.



Perhaps I should can the hood idea and do something like this?

http://www.lampworketc.com/forums/up...p?viewid=62580

http://www.lampworketc.com/forums/sh...84&postcount=6

Maybe try putting baffels on either side of the hood to direct the bad air up towards the fan - This can , I believe be done with clear acyrylic panals so it wouldnt obstruct your visual space. My set up is just the 8" pipe coming down to about 12" up from my table top (no hood) My torch is pointed towards it , my cfm is 800 but I think it could be less, since there is so much pull,
Kinda like this: (right pic)

Ps I'm NO expert but this seems to be working for me.

thank you sally, at least I'm no longer talking to myself.

IS clear acrylic ok? I'd like it better than metal. But I'm afraid my torch would melt it, the back of the hood is not that far back from the flame. Perhaps it's a good thing too because then my make up air has absolutely not chance of interfering with the fume direction?

The plastic up there is just some old stiff plastic/acrylic I pulled from picture frames that I used to make my show booth displays with. We used the plastic for painting to protect the table... that's what the gunk is.

BUT HERE IS THE THING. Shouldn't the smoke whoosh up instead of waft up?

My hood is like neither of those diagrams - mine hangs over the center of my workspace and has air behind it. I wonder if that is part of the problem. Though it seems more like the suction just isn't very strong.

Sorry about that my dial up is driving me nuts so slow then I click too many times, and I have no idea why the frowny face is there!
I don't mean acrylic like that I mean the very stiff kind of panel ~ That type is way to flimsy and could blow into your flame~and you shouldnt need it in front of you~just to either side of the torch ( and not behind it) Where is your air intake coming from ? Could it be interfering with your vent?

yes, I would think it would have to be the thicker acrylic, though since my tub is rounded it would need to bend. Perhaps metal would be best.... but still the problem of the smoke wafting up, not whooshing up.

my air intake is in the two vents in the wall in front of the torch - rather than have them in the table, we put them there.

Other air comes from the door with is open to my right if I'm sitting at the torch.

Your hood is so cute and I think it can work fine, Maybe if you put a section behind like in the link you posted ( acrlylic not good there) it would draw from the torch better and the vent behind not interfere (?)
I paneledthe back of my torch area with that type of metal form home depot $10 for q 2 X 8 foot piece. But her rain gutter thing might be just the right size too.
I'm sure someone that knows more than me will be on later and can help you.

ok, I can do this... and it can still be "cute" because form is just as important to me as function (obviously). But I'm worried about the incense test - is the smoke supposed to get sucked up better than it is, or am I just being paranoid?

And thank you so much for trying to help, I really appreciate it!

One thought here - are you doing the incense test with the torch on? I seem to remember someone saying it should be done this way. The fumes you are trying to vent are hot and the hot air may help to carry the fumes (and smoke) up enouch to be captured by the hood. I use a box-type fume hood with a baffel across the front. The smoke does waft up, but it is captured and exhausted. Without the front baffel, some smoke does escape. I haven't tried testing without the torch on - actually I just turn the oxy down until I can see a little smoke to test the exhaust.

thank you Judi - then maybe I'm doing the incense test wrong for three days. I tried lighting my torch and thought the flame would bend a little up like it use to with my old vent hood - but it doesn't.

It would concern me a bit too if the old hood pulled the flame up and the new one doesn't. With a box-type enclosure I've got a little more leeway than you have with the overhead hood - no place for the fumes to go in the box but up or out the front.

ok, I did this, and the smoke now goes pretty much straight up, though it still is slow about going up. I expected more suction and I really don't know how to tell if this is working right or really SAFE. I guess I'll just try and see.

My not-so-cute vent system now:

One thing I noticed... you really want your make-up air to be coming from BEHIND you, not from in front of you!

This may or may not be relevant, but what happens when you hold the incense out of the hood, like about half way between the torch and bottom of the hood, but out of the hood a few inches. This would be your breathing area. Can you see the incense being pulled into the hood and up??? The only other thing I can think of is to ask your HVAC guy if he can measure your air flow coming out of the blower. That sized fan should be doing a better job of pulling the smoke. Maybe your fan isn't working properly.

Yes, I'm pretty sure when I asked about that when we were installing it Dale said it would be fine. my hvac friend thought it would be fine too, but lampwork hoods are not his specialty.

I'll ask him if he has a tool for measuring airflow -that would be good. And I'll try moving the incense around and see what happens - I'm kinda sick of incense though, sheesh, me and my studio stink now.

sorry, I'm just so bummed with how this is all turning out now :(

Your design looks great. There has to be a reason it's not working properly.

Okay... I have to jump in here. Congratulations on your studio, btw! It is awesome and I LOVE your idea for the hood. The Dayton 4C445 495cfm blower is the exact one that I have and have had nothing but issues. Based on calculations of my hood, it should be sufficient. It is enclosed all over with the baffle also in the front. I am wondering now, after reading this thread and your other one, if this is why the model has been discontinued. Going to Grainger tomorrow to upgrade, but not sure what I will end up with. Just thought I would let you know, it may not be your setup at all. Hopefully it will save you some time and from feeling ill, like I felt week before last. Was no fun at all. I'm so ready to not have to worry about ventilation. Will more than likely go overkill on cfm's tomorrow. Hope you are up and running soon too!

Hi,
I have the same problem with my ventilation system. I'm the "Mike, Dale, Ferris Buhler..." post that's been floating around in this Safety section of the site. I was wondering about putting a baffle of aluminum around the back and sides. I think my problem is that I hang my head way too far over the torch and I suck up the gunk. My fan works like a mo'fo! We even lit a papertowel and the fan sucked so hard it wouldn't catch on fire, just sucked the flame right out. It does the same thing with my matches when I light the torch.
Did you see on one of the posts on the thread I started where Dale said we shouldn't have space between the back of the table & the wall? He suggested that perhaps the excess exhaust fumes - essentially - fall down onto the floor and are sucked back up over my head. And that makes sense, because CO2 is heavier than air so it would tend to hang out on the ground.
I'm going to put up an aluminum baffle and also a piece of plexiglass on the front. That way when I hang my big head too far into the hood I'll bonk it! PLEASE keep us posted on how the baffling thing is going for you!!! I feel your pain, sister! :)

Lenora, thank you for the great advice about where to hold the incense - it worked - it pulled it all in and up, so now I have more confidence. I'm going to try it tomorrow, melting glass for real, and see how it goes, if there is any odor after melting some glass, if I feel ok or get a headache... and take it from there. My nose and throat are still full of stinky incense... yuck.

Leah, I'm sorry to hear you have this fan and it's giving you problems, but thank you for letting me know, if things don't work out, I'm going to follow your lead and get a bigger fan. I didn't want to get one too big because I didn't want to feel all drafty while I was working... but I'd rather be safe than sorry. Good luck with your new fan tomorrow, I hope it's perfect. Let me know, ok?

You are so welcome and thank you for the good luck wish! I am interested to hear how your torch time goes tomorrow. I hope so much that I just got a bad fan. Now that you have located the spot for it to suck up to, my fingers are crossed that you have a awesome first torch day in your sweet place!

It is going to be a good Friday, right??!! [-o<

Alexis, yes try the baffle idea - maybe it will help you, though it sounds like your fan is doing a much better job pulling the air than mine is. I'm afraid this washtub idea is not ideal - If I'd wanted a box type of vent system, this is not how I would have designed it... and I'm afraid I'll only be able to look at it for so long before I need to do something differently, but who knows, maybe I'll grow to love it (hope, because I'm ready to move on to the melting glass/creating art part). I hope the extra sheet of metal will work for you. The sheet of metal I got today was only $11 at home depot and is flexible so it curved with the tub. I just had to cut part of it a little shorter and then taped it in. If that helps.

Leah, yes it's going to be a good friday all around :) Thanks for the well wishes, I'm going to have fun out there no matter what, even if it's just organizing glass and setting up my bead table!

Just a quick update - I spent about an hour and a half out there making beads (yay!) and no odors or headaches to speak of. Even when I drained my propane hose, I did not smell the propane, so perhaps all is well (though that baffle really takes up a lot of my work space - I really don't like it.)

Good to hear! Keep us posted on how you're doing, I'm really interested.
Have fun! I'm jelous...... :(

here's the box i had fabricated for my set up. there is plexiglass that comes halfway down in the front too.

My first thought, as I read from your Problems was, that your duct-running is too short. One advice that I heard from for a ventilation was, that the duct-runnig has to be at least 5 feet for a good effect. Perhaps it may be the problem?
The second thing for me is, that the hood is a little bit too high above your workbench. It could be a little bit lower for my sensation.

In spite of everything: I love your wahtube-hood since I see it the first time!

Thank you,
Barbara

(Please forgive my syntax, english is not my native language)

Hey Pam,
How's it going with the wash tub setup going. Did you stick with it or change it up? Did you find that the fan was sufficient ? I am considering duplicating what you have there. I have 6' wide by 3' deep work space and plan on fuming so I upgraded to a 1165 cfm inline.



I am also considering this below.

Yeah, still works great after all these years. It's cute, but takes up a lot of room, if I were to do it over again, I might do something like this: http://www.andreaguarino.com/read-me/