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.
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Originally Posted by Ole Anderson
