DC Steel Duct Install

[Ole Anderson]

I just finished the install of my 2 hp Oneida Super Dust Gorilla. After debating, I finally went with steel ductwork, mainly so I could use 7" and 5" size where needed and so there wouldn't be an issue with static electricity due to the "capacitor " effect of PVC. I seem to be in the minority as it seems most opt for the PVC in 6" and 4" sizes, mostly 6".

I am certainly not a pro when it comes to installing steel duct but here a few things I learned along the way (and I hope some real tin knockers will chime in to tell me how I should have done it):

Make sure you use material no thinner than 26 gauge, some of the BORG stuff is 30 gauge which I realized when I tried to use of an old piece of 6" I had laying around. Big difference.

I used 100 half inch self tapping screws. I wish now that they were 3/8", less intrusion into the duct. I found that they worked much easier when I predrilled the holes on the heavy 26 gauge steel.

It really helped to get my son's discount on pipe and fittings at his HVAC supply store. I got a $40 wye for under $20. Before you order all of your ductwork off the internet, check your local supplier for over the counter cash sales. My wyes were not a stock item and took a week.

Don't tape the joints until you are sure everything is lined up properly. What looks good on the floor may not be quite right up in the air and removing the aluminum foil to rotate a wye is a pain.

Taping the pipes's longitudinal joint is one exception. I found my woodworking vice opened up enough to hold even the 7" pipe for this job. And a J roller really helped flatten the tape in these joints.

The tape lays much flatter if you screw the joints together after, but that contradicts an earlier suggestion.

Cut a circle for each common size out of masonite or plywood to slip over the pipe to help mark where you will cut the pipe. Easier than trying to freehand a mark around the pipe.

A 4.5" angle grinder with a 1/16" cutoff wheel helps, but only use it to cut a starting slot for your jigsaw with a VERY fine metal cutting blade.

Rotating a 4 or 5 piece adjustable elbow to get anything other than a 90 degree bend is fustrating. Oneida sent me a cheat sheet to help with this, still tough, particularly when one section won't rotate. Rubber grip gloves help here too.

Your 1/4" socket in your drill/driver will wear out, just run it up against a grinder to get a fresh bite. My bit had enough meat on it to work for the 3 or 4 times you need to do it on an install.

My 5" aluminum blast gate wouldn't fit into the 5" steel bellmouth for my TS bottom connection. I found that by taking the gate apart and chucking an 80 grit drum in my drill press, I was able to take at least an eight inch off the circumference, giving me a nice tight fit.

My final connection to the DC (in a closet) was a very awkward up and over angle. My local BORG had 7" aluminum flex pipe which I was very leary about, but it was 1/3 the cost of plastic flex in that size so I gave it a try even though it was rated at only 6" of negative pressure. The ID was the same as the DC inlet so I had to get a connector (not at the BORG) to make it work. Still half the price of the plastic, it looks cool and provides a metal ground path without having to jumper the plastic flex with wire. So far so good. With all the blast gates closed, it didn't collapse.

I siliconed a few areas where I could see a gap in an area inacessible to the tape, at the blast gate to hard pipe connection and some of the wye joints. Still on the fence as to needing to silicone all the joints in the bends. And I don't know about the leakage I may be getting with the aluminum flex. But given the suckage I am getting with the new setup, I think I can live with a tiny amount of leakage.

I will post pics in a separate thread of my shop as soon as I get everything cleaned up.

[Jim Finn]

.................................. (and I hope some real tin knockers will chime in to tell me how I should have done it).........................

/......................I used 100 half inch self tapping screws..............

I am a retired tin Knocker..... Pop rivets work great instead of screws. Drilling them out if need be is easy too. When adjusting ells WD-40 helps, as do the rubber gloves. Tapping on the joint with a hammer slightly flattens out the slip joint a little to make it turn easier.
Four hands help in turning the gores of the ells too. After getting everything set in place silicone on the slip joints seals them well and looks better than tape does.

[Neil Brooks]

Great stuff.
Helpful stuff.

And ... I'm envious.

One more small thing: don't put your self-tapping screws OR pop rivets at 6 o'clock (the very bottom OF the duct).

If you do ... it's a good place for sawdust to start to collect.

Three or four around the *rest* of the perimeter ... ought to do nicely.

[Ole Anderson]

I am starting to think that the sharp ends of the screws, sticking in almost a half inch could snag a lot of planer shavings. I may go back and remove them, replacing them with short 1/8" aluminum pop rivets at your suggestion. Thanks.

Oh, and one more point, you WILL need a crimping tool (about $40 at the hardware store and worth every penny) if you plan on reusing cut off duct pieces or you have a joint that just won't quite fit.

[David Hostetler]

I am starting to think that the sharp ends of the screws, sticking in almost a half inch could snag a lot of planer shavings. I may go back and remove them, replacing them with short 1/8" aluminum pop rivets at your suggestion. Thanks.

Oh, and one more point, you WILL need a crimping tool (about $40 at the hardware store and worth every penny) if you plan on reusing cut off duct pieces or you have a joint that just won't quite fit.

I found that to be true with too long screws in a Thien lid as well a while back...

On the crimper, Harbor Freight sells the Pittsburg 5 blade crimper item #93192 for $14.99. I have one and it works great. (Used it to reduce the size of my 5" duct to the plastic 5x4x4 wye fitting on my system.). I would NOT recommend this tool for the professional, but for the hobby woodworker just putting up dust collection ducting, and occasional around the house duct repairs, it's great.

[Scott T Smith]

Great info Ole - thanks for sharing.

One thing that I discovered while working on my system is that if you choose to weld it (which I did), silicon bronze TIG rod or MIG wire works great on galvanized sheet metal - much better than standard steel wire or rod. Also, Harderwoods.com has a great on-line tool that will determine cut angles that allow you to manufacture your own wye's from straight duct.

[Jim Becker]

Pop rivets work great instead of screws.

Agree. I used pop rivet for anywhere I needed the strength of a mechanical fastener. Otherwise, it was just foil tape.

[Van Huskey]

Lots of good info here, thanks!

[Ole Anderson]

Follow up:

I went back and replaced all of the zip screws with 1/8" x 1/8" pop rivets where ever I could get to them, about 65 in all. And with all of my gates shut, I could hear the adjustable bends sucking air, so I went back and used clear silicone on all of the joints. Really helped.

[Chris Fournier]

Great info Ole - thanks for sharing.

One thing that I discovered while working on my system is that if you choose to weld it (which I did), silicon bronze TIG rod or MIG wire works great on galvanized sheet metal - much better than standard steel wire or rod. Also, Harderwoods.com has a great on-line tool that will determine cut angles that allow you to manufacture your own wye's from straight duct.

Probably won't hurt to mention that the smoke given off from welding galvanized steel is not very good for you so be careful!

I used sprial ducting and 3/16" pop rivets and the resulting install went quite smoothly given that I was on the tools. Many of the suggestions here are excellent.

One thing that I did weld up was the Oneida wall mount bracket which I thought was a tad too flimsy. I added two diagional braces that were L section. Thankfully the TIG welder made doing this pretty easy even though the system was mounted and hanging from the wall. Shade tree engineering perhaps but finding my cyclone on the floor would not be pretty...

[Ole Anderson]

One thing that I did weld up was the Oneida wall mount bracket which I thought was a tad too flimsy. I added two diagional braces that were L section. Thankfully the TIG welder made doing this pretty easy even though the system was mounted and hanging from the wall. Shade tree engineering perhaps but finding my cyclone on the floor would not be pretty...

I noticed that also, but let it go when I realized that each leg was only holding less than my weight and the welding looked solid, don't think Oneida would let it out of the shop if it could fail. Do like your braces though. Belt and suspenders approach. Wish it came like that from the factory. I was more concerned with the mounting bolts, doubled up on the upper bolts, went with six RedHead 3/8" masonry anchors into the poured concrete wall. Didn't see any reason to add the wood 2x4 as suggested in the manual. Get absolutely no vibration transmitted to the house given the mass of concrete to which the bracket is attached.

[Chris Fournier]

I often take this approach when my wife asks me to accompany her to a wedding of someone that I don't know. I toss on the belt and suspenders and my favourite t-shirt tuxedo and ask her if she'd really rather not go alone.

Ole, I agree that we often underestimate the wisdom of product engineers and the strength of steel but on my wall bracket, the two horizontal sections had deflected pretty badly, twisting out of the horizontal plan by 5 or so degrees under the load of the cyclone assembly. I couldn't look at it with confindence.

I used four half inch RedHead fasteners into concrete block, trying to hit the block webs and stay away from the edges. I glued .100" hard rubber to the back of the bracket to soak up surface variations and perhaps dampen any rattling. I must admit that the cyclone doesn't vibrate much, there's no doubt that Oneida spent the time and $$$ to dynamically balance the impeller you could see the machining and the addition of a rivet to one of the veins.

[Harvey Pascoe]

Ole, I agree that we often underestimate the wisdom of product engineers . . .



Oh, really? I never underestimate the stupidity of product engineers. My philosophy re: products is that if it looks like it will fail, it surely will and much sooner than expected. Chris, I know you're just being diplomatic, however, I question whether product engineers deserve it. BTW, your shop looks great.

[Chris Fournier]

I guess I don't have much of a poker face Harvey, you caught me.

[Ole Anderson]

Oh, I have found plenty of poorly designed products and take nothing for granted. A lot of what you see as engineering in a product is just someone's idea that is interpreted by a designer or draftsman and handed to a fabricator and may be a long ways from being properly engineered. A good experienced fabricator, working with a designer, however can turn out a product that is more than adequate. In this case, I felt the design and workmanship was likely of a higher caliber than average when looking at how the cyclone itself was designed and built, structurally. I just checked the deflection of the arms (not the twist though) and they were at 0.6 degrees from a true 90, but not having a before measurement, I have no idea how much of that was due to fabrication and how much was due to the weight of the unit. If the support arms had been just welded to a 2" vertical angle leg, I would have been very suspect, but the support leg that the arm is welded to gives 3.5" of support to the arm. Still, I would have liked to have seen a knee brace installed at the factory, as Chris added, just for redundancy.

[Steve Ryan]

Probably won't hurt to mention that the smoke given off from welding galvanized steel is not very good for you so be careful!

...
+1 Breathing the fumes can make you really really sick. They call it metal fume fever.

[Chris Fournier]

I think that you're right Ole; in some circles the engineers spend a lot of time designing redundancy! I just got out muh welder - and suspenders.

[Harvey Pascoe]

ULtimately its all a matter of price, and most products are designed to sell the maximum # of units at the lowest, or nearly so, possible price. A good example of this is the Porter-Cable router I recently bought for around $160, a tool that previously cost about $300 and I was suspicious of the price - and rightly so. It had a plastic part in it that broke even before I ever turned it on (I pushed a lever the wrong way, trying to understand how it worked). They sent me a new one and that one burned up within week of light use. I should have known better, the price was too good.

So, who's to blame? OTOH sometimes we get more than we pay for like the Delta DC I just bought for less than $400. Such experiences lead us down the primrose path of expecting much while paying little.

[Ole Anderson]

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[Mike Desch]

Howdy:

Hey there, Ole.

Any chance that you could "share" with us the cheat sheet from Oneida?

I, for one, have been going nuts trying to get a good looking 45 degree bend in the adjustable els. Mine never seem to be able to stay in the same plane--wandering all over the place. Yea, I'm a real novice at sheet metal work but I'm hopefully not alone in not being able to get a smooth arc for a 45 bend!

[Ole Anderson]

Mike,

I have a 4 meg .PDF from Oneida titled "Ductwork Resource Kit" which is a plethora of good duct work design and installation tips including the 45 degree tip. Can anyone tell me how to post it? PM me with your email and I will send you a copy. The basic tip is to mark each joint when the ell in a good 90 degree bend position using a marker, then rotate each section 90 degrees alternating directions with each section. But first, and this isn't mentioned in the manual, you want to mark where that 90 degree position is by marking 1/4 of the circumference. Guessing the 90 doesn't work.

[james glenn]

Ole

Would you mind sending me a copy as well if you could.
I PM'd my email to you.

Thanks

[Peter Hanson]

I'd like a copy, too. PM sent. Perhaps you can find a hosting site for others?

[Neil Brooks]

I have a 4 meg .PDF from Oneida titled "Ductwork Resource Kit"

Is it this (http://www.oneida-air.com/design/ductguide.pdf) ?

If so ... it IS a great resource.

Might save you a couple of e-mails, if it's the same one ;)

[Ole Anderson]

Neil,

The file I have is more comprehensive at 38 pages instead of 10 pages, but page 7 in the Oneida web PDF you posted is the instructions for rotating an ell to get a 45, the same page 28 in the larger file. Creekers are limited to posting a 1 meg PDF. I don't know where to get the larger file hosted. Meanwhile I will email copies out.