Can I have your input on my ventilation system?

[Flonche]

I've been reading a lot about this topic these days and the more I read, the more I realize each system is custom-designed and what works for my buddies may not work for me.
However, I would be grateful if those with experience and knowledge would let me know if they see something wrong with my design and/or planned equipment.
Here's the deal:
I just moved from the kitchen to the basement. The only "ventilation" I have used so far was to crack open one or two windows and open the garage door that I sat right next to and where a box fan was running backwards at full speed. This is also our A/C in the summer as we live right on a marsh and the fan is good at sucking in the cool air though the entire house. It probably worked really good because I smoked in the house and it has never smelled like cigarette inside, nor have I felt nauseous or headachey after several hours at the torch.
BUT I stopped smoking, obviously for other reasons than just stop freezing the house in the winter, and we are soon replacing all our ticky-tacky windows and will make the house much tighter. All in all, we are becoming a little more reasonable.
So we moved my torch table to the basement, where for the moment all I have is the same kind of "reverse" window fan and no make up air.
Here's the pic of new situation:
[IMG][/IMG]

I don't want to be enclosed in a hood; I want a funnel system that goes in the alignment of the flame, maybe 12" up. I think I can do this efficiently because of the short distance between where the torch is and where we can put a whole in the wall.
So I'm thinking of buying this fan

http://www2.panasonic.com/webapp/wcs...1&displayTab=F

basically because its noise rating is only 2 sones, compared to the 10 sones of the Vortex inline fans. My husband ran his Delta dust collector engine, 1 HP, to give me an idea of the sound of those squirrel cage fans and I decided I couldn't live with that kind of noise. This fan has the following characteristics (extract from detailed description):
# Air Volume (CFM) 472 at 0.0" static pressure, 440 at 0.2" static pressure, and 408 at 0.4" static pressure
# Noise (sones) 2.1
# Power Consumption (Watts) 132
# Energy Efficiency (CFM's/Watt) 3.3
# Speed (RPM) 1150
# Current (Amps) 1.10
# Thermal Fuse Protection
# Duct Diameter (inches) 8"
# Totally Enclosed Condenser Motor, for long life - Rated for continuous run

This fan hooks on 8" ducting, and I would have a 10-to-8 reducer at the end for a funnel (used backward of course).

For make up air, we are going to put another hole in the wall (not too close from the "soiled air" one) and have some ducting come under the table through a grill/vent of some sort. My honey is not too excited about those 2 holes but it looks like the only way of doing it properly. We can't have the make up air coming from the wall and the soiled air going out straight through the roof, for instance, because, well, right upstairs is not the roof, it's our bedroom.

I'm probably forgetting many things, but for now, am I on the rightish track?

[NMLinda]

As attractive as they are, the unfortunate thing about the funnel system is that no one I've seen posting here or elsewhere, or with whom I've had a chance to PM, knows how to properly design these and spec the fans. The hood style, conversely, has a great deal of solid industrial basis supporting how to make them safe and effective.

The other problem with the funnel style is how to align the funnel to the flame so that it actually captures all of the fumes that are created. Remember that the extremely hot air of the flame causes fumes to rise to your face extremely rapidly, which is why good vent designs stress that you need to have your hood pretty much completely over the flame for full capture and extraction. Most of the funnel systems that I've seen have the funnel somewhere at the back of the flame so that the entire flame is exposed. It's likely that some fumes are extracted - eventually - but how long would you have been breathing them until they are? Ideally, you want a smoke source held next to your running flame to be pulled into the hood exhaust in less than 2 seconds - less than one is even better. Hard to see how a funnel style ventilation system would be able to do that.

I don't mean to rain on your parade - I wish there was more vetted safety info out there, or even a published design approach with some scientific support behind it. I'd love to have one of these myself for the same reasons as you.

Regardless of which way you decide to go on your hood, you don't need to skimp on your fan (and risk your health....) because of the sone level. There was a nice post on either ISGB or WC that recommended mounting the fan outside with a sound muffler. Some folks tried it and posted that it worked great. Others have posted that, if the fan can't go outside, enclosing it in a baffle and wrapping the vent ducting with insulation (like the batting used in walls) can help significantly.

Good Luck
Linda

[Flonche]

Thank you Linda, I'm like you on the lack of scientific knowledge about this funnel system, however, and with all the ignorance I can boast, it seems logical to me that if it's properly designed it can work. I have seen some funnel systems that I can't figure out how they can possibly be efficient, where the funnel sits under the flame or way too high above, for instance, and I've seen hood system that I wouldn't trust either or that require insane fan power in order to be efficient.

In my specific case, I thought I had some cards in my hands allowing this design to work for me, i.e.
- make up air coming from straight under the table and not some remote open window or fan behind me, hence a faster air flow
- less than 3' of a perfectly straight line between the funnel entrance and the fan outlet, in a 8" wide expressway.

I'm not trying to "skimp" on the fan. I don't care how much it costs as long as it does the job, and if it's much more expensive but is quieter, I'll take the one that does the job quietly. If someone proves me that in my configuration I need much more than 400 cfm, then I'll buy an even more expensive, more poweful, quiet fan, and I'll probably install it outside with a muffler, too.
Even though I would really like to avoid it, I'm still open to the hood idea, if everybody gives me proof that my ideas don't make sense!

[NMLinda]

The make-up air under the bench won't help make the air flow faster, per se, but it does, of course, give you critical fresh air to breath. It's good that you're using an 8" duct - especially if you use smooth-wall ducting (the flex stuff is terrible - horribly lossy). The length and diameter of the flex ducting means you can get away with a smaller fan than you would if you were using longer runs, lots of bends, or smaller diameter ducting. To first order, however, it doesn't solve the problem of catching all the fumes before they rise to your face, unless perhaps you have a really, really big fan, relatively speaking - which is what no one seems to know how to analyze. Not sure anyone could comfortably tell you whether the 472 cfm fan you have in mind is too small, good enough, or even too much.

There's a post here on LE somewhere that you might find interesting - wish I had the link handy for you. I think it was posted 2-3 years ago. It was a rather clever mini barley box hood that looked like it had all of the advantages folks seem to like about the funnel style (small, compact, not confining or in the way), but seemed to do a reasonable job at solving the problem of covering the flame for better fume capture. If you can find it (either in safety or studio), you'll see that it looks like a relatively small open-fronted metal box taped to the workbench. The vent duct comes out the back, ala funnel style, but the torch is tucked into it such that the flame is almost fully covered by the top of the box. It's hard to describe it well, and I'm sure I'm not doing it justice, but it looked like there was enough room to work comfortably at the flame. It was also designed such the analysis methodology used for the more tradition hood-style vent systems might reasonably apply.

Linda

[Dale M.]

Don't Ask........

How about a adaptation of something like this...



I know its a fireplace but it has all the proper features...Use imagination and adapt a bit....


Dale

[Lorraine Chandler]

Okay. I won't ask...but I luv it!

[NMLinda]

Dale and others have mentioned a great article that was published, I think, in The Flow magazine (maybe Annealer?). There was some discussion here on LE about it a while back. Sounded like a great article - the author took pictures of what the exhaust plume around the flame looks like both with nothing inserted in the flame and with a glass rod in the flame. Both the pictures and the article might answer your question about whether the funnel idea you have in mind will be effective or not.

[houptdavid]

You are on an outside wall, using a small torch.
Can I suggest that you mount hardie backer to the wall
Use a table that is 24" deep and move your kiln to one side and mount this
on the wall venting directly out.


http://www.kitchensource.com/range-hoods/br89000.htm

[Flonche]

Thanks David, that looked good but I already ordered the fan I had planned.

[macsynchro]

The article was in the Annealer... my husband read it recently when I started getting headaches. I gave him everything I had on ventilation...

[Flonche]

So I hear that my choice of fan is not good enough, that's why I go dig this one year old thread.
This is what I ended up with



Not much static pressure here.
We did smoke tests with torch lit with a burning 2x2 stick of wet white oak held at face level and it does work. Later on in the summer I briefly took up smoking again and that was another satisfying test for the fan. Heck, if I don't tie my hair it flies off in front of me.

Now the thing that doesn't work is that my husband (he installed it while I was away, the smart man) decided he didn't want 2 holes in the wall. After 2 winters he now understands his mistake as the entire house upstairs gets MUCH colder when the fan is on in the basement. Even with those tight new windows and all doors closed, we both feel a draft, him in one corner of the house upstairs and me in the same corner downstairs. The vaccum thing is very real. So I don't get much air at all for breathing as my marginal fan sucks it all out, and that's the one thing that was done wrong with my system.
Now, should I go around recommending this fan to everybody, probably not, but in my situation, it does the job.

[houptdavid]

And for a cricket the way you have it set up it more than likely works. Put it in a hood, add 6' of pipe and a bend or more and it would be marginal.

[Flonche]

Yesssss