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Another dust collection question

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Forum topic by danr posted 08-02-2010 03:50 AM 1675 views 0 times favorited 8 replies Add to Favorites Watch
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danr

154 posts in 2649 days


08-02-2010 03:50 AM

Hi all,

I am in the process of designing my new and improved wood shop. The ceiling will be valted. I am fortunate to allready have a 3hp cylcone with Norfab metal duct work that I aquired at a good price from a comercial shop (half price). I am wanting to place the main dust collection duct trunk and branches in the concrete slab. I don’t want to do trenches with cover plates.

I was planning to use a PVC coated galvanized metal duct. Does anyone here have any direct experience with doing this and/or any on-line resources that I could use? I don’t seem to be able find a lot of information on-line for this application and even had a guy at a company that produces PVC coated metal duct tell me the product would not be good for an in-slab system.

Any feedback would be appreciated.
Thanks,
danr


8 replies so far

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richgreer

4541 posts in 2538 days


#1 posted 08-02-2010 02:35 PM

I have no experience regarding this but I do have experience with vacuum lines clogging up. I would worry a little about that if my lines were under concrete and inaccessible.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

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danr

154 posts in 2649 days


#2 posted 08-02-2010 05:47 PM

Trust me Rich, I have many concerns with putting the duct under/in a slab including the one you point out. At the same time, I have convinced myself that it will be the best thing to do in terms of having a nice obstruction free shop. I know that people have done it so I was hoping to get some feedback from them.

Thanks for your input.

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richgreer

4541 posts in 2538 days


#3 posted 08-02-2010 06:35 PM

I think concern about clogging can be addressed if you have a way to access the plumbing with a long pole or a snake.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

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PurpLev

8523 posts in 3112 days


#4 posted 08-02-2010 06:44 PM

what about a 2×12 floor base on top of the concrete is that feasible? that would allow you to hide the pipes yet still have access to them if needed. would require a re design of the floor though.

for what it’s worth – I’ve installed central vacuum systems for many years. unless the installation was poorly made – there was never a reason to get to the pipes, and if there was – it was 99.99% clearaable with a snake.

As long as you make sure your seems are clean and smooth, there is little need to get to those pipes ever.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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Greedo

470 posts in 2424 days


#5 posted 08-02-2010 07:57 PM

i don’t think you need anythig fancy for the pipes as long as it can resist the pressure of the wet slab, wich cannot be underestimated though.

what else is important is that you need to be 100% sure of the emplacements of your machines, and that they will stay there forever. i rarely have a machine that stays in the same position for more than 3 months, i keep finding better positions and arrangements. im certainly happy that i didn’t “set in concrete” the initial arrangement that seemed best. but if youre certain then go for it no doubt.

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jusfine

2405 posts in 2390 days


#6 posted 08-02-2010 10:49 PM

My ductwork is all below my floor (shop is built in the loft of the barn) and I don’t see any problems to date.

I agree with Purplev, don’t really see why you would need to access your ducting, and a snake should be able to clear up any obstructions you may get… short of sucking in half a package of paper towling, which I have already done. It even passed nicely into the collection barrel on the main floor of our barn without assistance.

It has been common to run metal ducting for heating and cooling in this area in concrete slabs, and they last 50-60 years on the average, and as Greedo says, as long as it can take the initial concrete pour you should be fine.

-- Randy "You are judged as much by the questions you ask as the answers you give..."

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danr

154 posts in 2649 days


#7 posted 08-03-2010 12:11 AM

PurpLev:

“what about a 2×12 floor base on top of the concrete is that feasible?”

I would love to do that but trying to keep cost down. I live in central TX and concrete slabs are the normal foundation around here. If I were up in the mid-west (where I grew up) I would not even hesitate to have a crawl space and eliminate all of the issues with the slab duct placement. I have never had a “clogging” problem with my current set up and I agree that a snake could probably get the issue resolved in most cases.

Greedo:

“what else is important is that you need to be 100% sure of the emplacements of your machines”

I agree and I have spent a lot of time on this. The plan is to have, in the slab, a main trunk and approxumatly 5 branch ducts. 3 of the branch ducts will run to the big machines that are in the center of the floor (i.e. table saw, jointer, planer, surface sander, and bandsaw). Based on the way I am grouping these machines I will need 3 total inlets in the middle of the slab. The other 2 in slab duct branches will go to the 2 long walls and then I will run above floor metal duct to the machines along the wall and the mobile machines that I park against the wall. My shop is going to be sized (30’ x 45’). This is big for me but it seems that in a worse case scenario, I can always tap into a duct on the wall or floor with flex to get to a machine that moved from my original plan without too much trouble (that is basically what I do now in my small shop and I just hang the flex hoses when not in use on a wall hanger and plug / un-plug them from the machines as needed).

Justine:

The metal duct guys I have talked to state that galvanized metal should be painted with rustolium before covering or use the PVC coated metal pipe. The PVC coated metal pipe I have looked at is not crazy expensive but at the same time is not cheap (i.e. 10ft run , 6” diameter = $28). Plain old PVC pipe would probably work just fine also but I’m just not sure and can’t find any body who has done that under concrete. I would also like to ground the inside of the PVC pipe if I use it.

Thanks for the feedback,

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Greedo

470 posts in 2424 days


#8 posted 08-03-2010 08:25 AM

i have put a regular pvc pipe in my slab, but it is to drain away the water from the sink. it’s a smaller diameter, but for dust extraction the pipes would only really be there to form a tube in the slab while it dries. if it was possible you could even remove the pipes after the concrete had set and would still work the same.
the good thing about putting them under the slab is that you can make them take the most direct route to the collector with worrying about it being in the way.

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