# 30ga Metal Ductwork Installations



## Bill7255 (Feb 23, 2012)

I am getting ready to set up my DC system. I have a Jet 3hp that will be used with a eBay cyclone. Specs for the Jet at 8" are air flow 1900cfm, velocity 5,629fpm, 12.5" static pressure. The impeller is 14". I have the Wynn filters for the exhaust. I bought 30ga 6" snap lock (5' sections) metal for all the runs about a total of 100 feet with 25 feet being the longest straight run. I have wyes for the take offs. I will run this over my 12 drop ceiling. I know 26ga is the preferred and 30ga could collapse. Searching the Internet many have used 30ga without problems. Some have installed plywood rings around for added support. Some have a vacuum relief. I will make sure I always have a gate open, but I could plug the system. $$ is the reason I am using 30ga as well as the eBay cyclone vs Clear Vue. I had the Jet DC. 
My questions are )1 should I try and reinforce the pipe with plywood rings? Do you think hose clamps would be adequate around the pipe, say two per section. 2) Off the Jet impeller/motor housing I have a 5X7" rectangle outlet. What is the best way to convert to a 7" round pipe? 3) I would also like to set up a diverter in a wye so I could change from filter to outside exhaust. Has anyone made a diverter? 
Any other comments welcome, thanks.


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## Finn (May 26, 2010)

You can make a taper eight inch to seven inch from flat sheet metal or you can use a short section of eight inch pipe and overlap one end to form the taper. Kinda crude but would work. To make a "diverter" you could make a wye with two blast gates. Opening one or the other as needed to divert the air flow. I used six inch, twenty-six Gage, pipe on my system and I have only a two horse power dust collector. Eight inch snap lock , thirty gage, is pretty light. I suggest you install pop rivets or screws through the snap lock seam in the center of each section to help it resist all that static pressure. The snap lock seam in that light duct is a weak point.


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## MrRon (Jul 9, 2009)

I don't think plywood rings would prevent the duct from collapsing. A diverter should not be a problem. Just take a wye section; add 2 blast gates to the divergent ends and duct one to the filter and the other to the outside. You could also fabricate a wye from plywood with built-in blast gates.


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## Bill7255 (Feb 23, 2012)

Jim, I will add screws to the snap seam. I am also going to tape them and joints with aluminum tape. Note I am using 6" for the runs. 
MrRon, I think the idea behind the rings, when the duct collapses it changes shape becoming longer in one direction. The ring is to prevent that. I don't know if it works or not. But I think it is more of a pain to do. 
Right now the simplest solution is to build a weighted damper that will start to open before a duct gets blocked. 
I was trying to think of a way to switch the airflow with some type of diverter internal to the wye, but I guess blast gates are the only real solution.


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## MrRon (Jul 9, 2009)

It's the space between rings that would collapse easily. Don't underestimate the force of suction. I once had a heavy fiberboard barrel I was using for chip collection and I blocked the inlet to the barrel It collapsed in seconds like an empty beer can. I don't know, but 26 Ga ducts could also collapse if the suction is high enough, so maybe 30 Ga is OK as long as you can ensure constant flow.


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