# dust control clarification questions



## toddclare (Mar 24, 2010)

I just scored a great condition Jet 1100 1 1/2hp dust collector on Craig's List. I've been researching how to set it up (I want to run ducts, not wheel it around tool to tool). A few questions based on what I have (and haven't) found on my own:

I've read a bunch about "to ground or not to ground" and I'm going to ground. It's worth some effort to do it to keep my house from burning down. I know that's a loaded discussion, but better safe than sorry IMHO. Also, it's VERY dry here in Denver, and just playing with it yesterday with a very short run of flexible tube, I got a pretty good ZOT from my mini lathe when I got too close to the motor while the collector was on.

Duct material: I've read about PVC, metal and others. My shop isn't very large so I'm drawn to the metal option. So:

1. I see people saying to not use standard HVAC ductwork and only to use really heavy duty stuff. I assume this is to prevent the less rigid stuff from collapsing? Anyone have thoughts here or experience using one or the other?

2. If I use metal ducts and make good metal to metal contact, I assume I have no need to run the grounding wire since the ducts themselves are conducting the static? I realize I may have to run small wires to cross plastic gates, etc.

Design

I've been reading all about how less abrupt turns are better (45 is better than 90). Most of my tools are along one side of my shop (see the first two pics here). I was thinking of putting the collector where the shelves are in the back corner, and running a 6" duct under the wood rack with 45 degree 4" flexibles at the lathe, bandsaw, and tablesaw. I was then thinking of running some kind of branch up the wall and overhead to split and send 2 4" to the router table and drill press. I'm going to put in blast gates, and the 6" run would be about 13' and the overhead would be a total of about 12 more… too far?

Anyone in Denver want to come over to my house and design this thing for me?


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## Sawkerf (Dec 31, 2009)

Your DC sounds like mine and I think that you'll be pretty happy with it. Does yours have two 4" inlets at the impeller housing? If so, you might want to pop off the plastic piece with the two 4" inlets, hook up a piece of 6" duct, and run a 6" "backbone" with appropriately sized drops and gates to your tools. This is a modification I'm planning to do if I ever work off my backlog.

PVC, ABS, or metal HVAC duct are all good. The tricks are to use the smoothest wall possible, avoid abrupt changes in direction (two 45's are better than a 90), and minimize the use of flexible (ribbed) duct. Grounding is always a subject for debate so ground if it makes you feel better. My system isn't grounded and I have no concerns about blowing anything up.

Other good mods are a pleated cartridge filter, and a remote start/stop switch.

Another handy trick is to drill small (1/8") holes at the corners of your plastic blast gates. Without them, the gate channels collect dust and keep the gates from completely closing. With them, a small amount of air "bleeds" into the channels and keeps them clean. I haven't had a closing problem with any of my gates in the nine months since I drilled them.


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## JohnGreco (Jan 13, 2010)

Grats on the DC! I have one in my shop where I used aluminum stove pipe duct work (I think that's what it's called anyway). I use straight, non-ribbed sections as much as I can, with ribbed flexi for some of the bends and 45's for other bends.

I chose to ground, also going with 'Better safe than sorry'. Knowing copper is a better conductor of electricity, I decided it would be best to run the copper wire the length of the ducting. I have a floor sweep attachment that is not grounded- it feeds into the DC on it's own inlet and is only maybe 6' of duct work- it Does build up static charges, so I'm definitely glad I have the peace of mind of having grounded the rest of the lines.

Best of luck with setting it up


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## JonathanG (Jan 18, 2010)

Sawkerf, interesting that you would actually want to create a leak, but I guess the reasoning behind it certainly makes sense.

Todd, I can come over and be a second set of eyes if you want. I obviously have not set up a dust collection system yet (although I also just picked-up a DC, more or less on Todd's lead), but I have had a little bit of experience with car exhausts, and did a lot of research on that topic, at least from a hobbyist's standpoint. And really, the two are fairly similar, if you think about it. I'd say it's sort of like fluid dynamics, except saw dust and wood shavings aren't exactly a fluid, or a gas, but I suppose the underlying principles still more, or less apply…(I did say roughly, so please don't go off on a scientific tangent here… I'm trying to keep this as simple as possible).

Ultimately, you want the fewest number of bends possible- and as mild as possible (45 is better than 90, agreed)- as short of runs as possible, and a smooth inner surface. Those are the basics.

The same principles also apply to exhaust runs for bathroom fans, dryer vents, or kitchen fans, etc.

I believe that Todd has his shop more or less set-up right now, as far as space goes. Correct me if I'm wrong, Todd. However, I'm not sure how much space I will devote to my shop, so I'm not ready to set things in place with hard lines yet.

I would say though, if you do pretty much have things arranged how and where you want them, then the hard lines are the way to go, as you've already hinted at above, especially since you're talking about multiple runs over a distance.

It's sort of like the KISS method: Keep It Simple Saw-guy! [Just to reiterate, simple means, the fewest number of sharp bends (break them into more open bends, if possible), on the shortest and smoothest route possible].

Not that your house is going to burn down (since it's made of brick), but do ground it so you're not ZOTing yourself! ;-)


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## toddclare (Mar 24, 2010)

Thanks everyone for the info.

Yep I like where things are now, although I might do one last "Am I sure" sanity check before running the ducts.

Mine has the 6" main port off the motor and the black plastic 2×4"wye that is basically friction fit onto it-my thoughts exactly about running the 6" backbone.

Jonathan - I managed to lose your phone number and haven't seen you poking around outside (for everyone else reading this-our houses are back to back). If you're around and reading this, give me a call and we can take a look-tonight or sometime this week?

I'll take car exhaust science over making it up from scratch any day. I'm thinking I will go the standard metal duct approach with 45s where I need them, but the design would love some fresh eyes.


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## Sawkerf (Dec 31, 2009)

Johnathan -

Yeah, I was a little leery about the holes too, but decided to try it since I had a spare 4" gate in the junk box. I'm sure that I lost a wee bit of flow, but I don't really notice it, and not having to use a bent wire to clean the channels every few weeks sure is nice. - lol


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