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Safety -- Make sure you are safe!

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  #1  
Old 2006-01-29, 10:32pm
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Default Added more ventilation - now OK?

Several years ago when I started lampworking we had the plumbing/heating guys come install a squirrel cage for ventilation. My studio is in the basement and there is a window well 5 feet from my torch area so I thought this was an easy job. The guy refused to send it out the window well. He was afraid the fumes would settle back in the window well and leak back into the basement. Instead he sent it out the side of the house - cut through our brick - ran a pipe up the outside of the house - cut through the roof to finally exit 20-25 ft away. Instead of using an 8" pipe like the cage, he put a converter right after the cage and the rest of the pipe is 4". He didn't start the pipe where I torch, so he left me a plastic (like celophane) extension that lead to the proper area. I was furious. Who in thier right mind would hang loose plastic over a torch! Anyway, although the on/off switch was snazzy, the damn thing never worked well - had to travel too far before it exited. Have always wondered if the 4" pipe is also a problem. My DH would always complain that the house smelled when I torched so I didn't do it very often.

When we had the house reroofed, the guys cut the pipe off so it now goes about 5 ft out the side of house and then straight up 3-4 ft. It seemed to work better but still had smell. For Christmas my DH gave me a kitchen fan to boost the squirrel cage. We installed it right over the torch. Both the hood and cage are wired to the same switch. This system moves a ton of air, infact I have to run the hood on low because hi gives a form of backdraft. Problem - still have the smell upstairs on days I torch.

Are we expecting too much? My DH feels that if you can smell the torch bad things are remaining in the house. Oddly the basement where I torch doesn't usually have that much smell - it's on the first floor right over my studio area. If the scent is harmless, we'll just ingnore it - it does go away in a couple hours - if it isn't harmless, we need to correct the problem.

Thanks for any help.
Kathy
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  #2  
Old 2006-01-30, 2:54am
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Kathy, if you can smell it, it's not harmless. It seems I remember you posting when you were going to install your system, was it at WC or the ISGB board a few years ago, or do I have a different person?

When the guy ran your exhaust pipe out your brick, why did he then go up through your roof? I know you can't go from a 8" duct to a 4" because you loose alot of output. Is there anyway you can post some pics of your vent system, I'm having a hard time picturing what they did.

I'm sure some others will chime in with better advice, but a pic would probably help.
Edie
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  #3  
Old 2006-01-30, 7:05am
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By going from 8" to 4", you are losing about 75% of your air movement.

What the installers did was entirely WRONG. They should have put 8" all the way through.

Using two fans is not a good idea - they will tend to fight each other and in so doing, aren't moving enough air, as you found out by having to keep the one fan set on low. One fan, the right size, is all you need in any given system.

How about a fresh air source? Where is that, and how big is it?
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  #4  
Old 2006-01-30, 11:32am
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Squirrel cage blower may be enough (depending on actual CFM). All ducting should be at least 8 inches in diameter for complete run. Venting it partially up the wall outside is probably ok. In real life it need to get outside and be at least 10 feet away from fresh air intake source (for proper dilution). You also need rigid metal duct from blower to hood over torch. Plastic or flex duct is not good. At bench (torch) a well designed metal hood or a "barley box" style fume cabinet is all you should need.

I don't see that if your exhaust is away from any air intakes, why you have odor in house, unless you are back drafting from other gas appliances on upper floor. IN that case you do not have enough direct make up air into basement from outside and studio fan is trying to draw air from house appliance flue pipes. Not good! You probably need to do study of air flow into studio.

A second hood with its own fan will probably not be any help...

http://www.artglassanswers.com/forum...opic.php?t=150

Dale
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Last edited by Dale M.; 2006-01-30 at 11:40am.
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  #5  
Old 2006-01-30, 2:54pm
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Have never posted a photo before so I hope this works. Actually my 12 yr old son just showed me how - love how kids embrace tech.

The pictures should show our current setup. The basement is approx 35x65 ft. My studio area is not sectioned off with a wall of any sort. There are two other windows that can be used for fresh air. There is also a fireplace and built in BBQ that could be used for fresh air with the flues open. In the winter when it is so cold instead of opening the window I have left the basement door open. Our 1st floor is approx 3000 sq ft. The house was built in the early 60s so it is not air tight like newer constructions. The current system moves so much air that when running it feels like a heat vent outside. Could it be that I need to box in my torch area to better direct the fumes?

Apparently the heating guy used 6" metal from the torch area to 8"squirrel cage then swithed to 4" PVC. Is it possible that because he went down in pipe size that it somehow escapes the squirrel cage and rises through the floor boards which allows the smell to be in the 1st floor?

Don't know if it makes a difference but I run a Lynx.

Thanks,
Kathy


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  #6  
Old 2006-01-30, 5:00pm
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As stated before whole duct system should have been probably 8 inch...

Also fan as I see it is not real squirrel cage, it appears to a axial flow inline fan and may not be best style for installation.

8 inch duct has a area of about 50.3 square inches.

6 inch duct has a area of about 23.3 square inches.

4 inch duct has a area of about 12.6 square inches.

See the relationship on which size duct will carry the most volume of exhaust air out of basement.

Each 90 deg turn used is further restriction to air flow. Each 90 deg elbow causes the static pressure in duct to increase and that is more restriction the fan has to over come to force exhaust air out of basement. The vent cover if its if a flapper valve or louvers in un-natural position is also a restriction to air flow.

As a pure guess (example) if you fan is capable of 500 CFM air flow, and with all the different sizes in ducting, the turns included, and the outlet louver you may be moving 250 CFM of air IF you are lucky.

Fireplace /BBQ flues and open door to other portions of house no matter how big it is not a answer for DIRECT makeup air through a duct or window or door directly from outside into basement.

I think with the nature of PVC pipe joints and they are probably good and it appears most metal to metal joints are made well.... I suspect if you are getting odors into rest of house its not coming from vent duct. Its either being drawn in from outside (end of vent pipe) or being sucked from other sources inside house. Again suspect maybe a unsealed sink drain or flue duct for kitchen stove, or water heater on first floor. Ideally if you can effective seal basement and supply direct makeup air to basement (through window) you should not be getting any odor or gases being pulled into other parts of house.

Dale
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Last edited by Dale M.; 2006-01-30 at 5:24pm.
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  #7  
Old 2006-01-30, 9:19pm
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Removing the basement ceiling tiles to take photos has served another purpose. We put our hands around the squirrel cage (?) as it was running and discovered that every joint is leaking air like crazy. The original installer did not tape any joint and I assume the problem is aggrevated by the reduction in pipe size. There are at least 4 connections in less than an 18" run and every single one is leaking. Apparently the ceiling tiles created an effective barrier in the basement but allow the fumes to seep through the floorboards to the family room above.

Well at this point we will need to replace the pipe with a larger diameter. Think we will do it ourselves - the heating guy already did enough damage. Hope we can save my kitchen hood - I really like the light. The fan was sold to me as a squirrel cage - it was supposed to be powerful enough to vent a large bathroom - so hope it will still be OK to use. As long as metal is used from torch to fan, can we use PVC to outdoors? We will try to reduce the number of turns he built in the pipe.

I really appreciate everyone's advise. I feel ridiculous that we didn't check out this part of the system before. Somehow we always thought the fumes must not be getting to the fan or that they were leaking back in the house from the outside. We thought that since the part in the ceiling was done by a professional it must be OK.

Edie, I'm not sure if I am the person you are referring to or not. Maybe 5 years ago I used to visit ISGB but had not seen Wet Canvas until recently. I have made very few beads the last few years because of the venting problem. After my DH spent so much on the installation I didn't know what to do - became a rather sticky point. Concentrated on kiln and stained glass instead. Think we'll finally get it licked this time.

Thanks everyone!
Kathy
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  #8  
Old 2006-01-31, 1:50am
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Kathy, I hope I am seeing your pics correctly, sorry if I'm not In your second picture, to the right, that is the window to the outside, but it is a well window? And you have other windows in your basement on a different wall that could be opened for make up air while you run your exhaust system? Then why did your installer not simply go to the well window with rigid 10" ducting, straight from your hood, when outside he could have installed an elbow, and then a vent cap on top of the elbow. It seems to me the the CFM's lost in one simple elbow would be FAR less in that short amount of distance to the well window as opposed to going throught the ceiling and downgrading the size to a 4" exhaust.
If you are adament about making this system work, then you should add baffles to the sides and back of your exhaust hood.
Edie
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  #9  
Old 2006-01-31, 5:35am
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No - get rid of the PVC pipe and replace it with 8" galvanized metal.

When I get into work, I'll run some sample calculations for you so you can see how much air you are losing (and not removing) with the current set up.

There is no way this system will work with 4" PVC pipe. The pipe diameter alone is probably causing so much back pressure that your fan isn't capable of running at full efficiency. I'll bet that if the fan runs for an hour, it is very hot.

This installation was poorly done and needs to be totally ripped out and done over.
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  #10  
Old 2006-01-31, 7:34am
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As I suspected...assuming the fan is running about 500 CFM, the total system static pressure from the fan to the end of the duct outside is 6.80 inches.

The fan you have is not a classic squirrel cage fan, it is, as Dale pointed out, an axial fan, and these fans typically are not capable of running efficently against high system static pressures.

In the original system, before the roofers cut off and shortened the duct, the system static pressure was 39.17 inches, and you essentially had *NO* exhaust ventilation.

With this high of a static pressure, you are losing all your ventilation efficiency, and as you noted above, most of the exhaust is being lost through the leaks in the system ducting because of a lack of duct sealant on the joints.

If you change the PVC ducting back to 8" galvanized metal, your system static pressure will drop to 0.05, and the existing fan (again, assuming it is 500 CFM) will be sufficient to ventilate your space.

I would, again as noted above, add baffles to your hood to lower the suction area so that you are indeed ventilating the torch area and not the whole room. You should have a baffle running down behind the torch all the way from the hood to the bench top, and the sides at least half the distance.
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  #11  
Old 2006-01-31, 7:33pm
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Thanks everyone! My husband looked everything over today and he doesn't think it will be hard at all to replace the pipe with 8". Glad to know it needs to be metal instead of PVC. The original hole through the brick was made larger than needed so we will just need to knock the cement out. It is only a 3 - 4ft run. The baffles will be easy to construct. He always felt there should be a fireproof wall infront of the torch anyway.

Hopefully next week we can get the job accomplished.

Edie - when we hired the guy we told him we wanted it vented out that window. We would have done it ourselves but it needed to be wired in so we hired a professional. Really thought it would be a 2 hr job - tops. He refused to do it the way we wanted because he felt the fumes would settle in the window well - instead he spent the entire day making a system that left the fumes in the house. We live in a very rural area. There aren't a lot of plumbing heating guys. That company is not coming back here. (They are also the ones that installed the gas line - I had to call them a half hr after they left because I smelled gas. Yep - he never checked his connections before he left. Frustration.)

We will get this straightened out thanks to all your help!
Kathy
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