How do you ground a dust system to a shop vacuum?
How do you ground a dust system to a shop vacuum?
Last edited by Darren Wright; 02-03-2014 at 09:19 PM.
David. Can you tell us more about your system. Is it a fixed system with metal pipe, PVC, flexible pipe? I always thought we grounded those things to prevent some kind of dust explosion from the static build up. A shop vac might be too small a volume to worry about, although I sure have had some real wake up static zaps from my shop vac hose. I'm sure others who are more knowledgeable will chime in.
Short answer? I don't.
Long answer? If you use PVC duct work, you can't ground it. It's an insulator and by definition cannot be grounded. Secondly, you don't need to anyway. There are no known reports of a home shop explosion due to static electricity discharge from their dust collection. Physics simply won't let it happen. You're not dealing with the scale that a flour mill silo might see and it's the all-too-often analog to show that it's possible. Yes. Dust can explode with static electricity. It's VERY hard to MAKE happen when you want to, and the scale of the discharge has to be so great to hold enough spark to ignite the right size dust particles in the right concentration at a high enough volume moving at just the right airspeed in order to trigger the chain reaction that causes an explosion. ALL of those stars must align.
Now - if you're just trying to prevent nuisance shocks -- i suggest waiting a few months of using it and getting that fine cake layer built up on the ducts - from what I'm given to understand, the shock hazard drops incredibly once you've reached that point. I don't use PVC ducts myself but if i did, I wouldn't worry at all about grounding. Take a look at this article:
Following both the earlier posts, your title mentions collector, and the text mentions vac. Not sure which you mean, but in either case my answer would be what Jason said: I don't. There are no safety issues, though personal comfort does come into play. I simply try to avoid (on the DC and ductwork) coming into contact with anything while the system is running. With my vac I haven't experienced anything but minor annoyances, and I've learned to live with it.
Thanks gentlemen for the responses. It is annoying to get bit when I turn off the vacuum after a dust collecting bout from what ever equipment. That was my original thought, how do you ground a plastic pipe. Just let my hair get curly from the shock and don't worry about starting a fire.
david i have a fair sized shop and ran PVC pipe for majority of it underground and some metal fittings above the floor but mostly PVC and i have had one shock so far and it wasnt anymore than what you might get off the carpet in a living room.. and it was off the drum sander that i was using at the time
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I remember, but never tried, that some folks claimed putting a metal chain on the vac, and letting it drag on the floor (which was always concrete) reduces that static shock. I never tried it because I was skeptical....but it can't hurt to try; won't cost much either.
I've not experienced more than a nuisance shock from the hose on my shop vac. In my shop, the real static generator is a buffing wheel on the lathe. I have learned to keep a leg touching the metal lathe bed at all times when buffing a turned piece like a bowl or hollow form. The static it strong enough that it can easily discharge through a pair of jeans. If I don't ground myself to the lathe, I'm setting myself up for a nasty "bolt of lightning" shock. I learned this the hard way one night when I took a direct hit to the crotch. By my unscientific calculations, it was approximately 1.4 zillion volts. I suspect I'm now unable to have children. To this day, it still makes my eyes water a little just thinking about it.
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Eliminating static shock is all about giving the charge an easier path to ground than yourself. This is how wire wrapped PVC pipe in DC installations work since you can't really ground plastics and rubbers. The wire gives the charge somewhere to go before it builds to a point where you become an attractive grounding point.
Shop vacs are a bit tougher. Static dissipating hose is available but a bit pricey. My shop vac hose is too flexible along its length to allow a wire to be wrapped around it. Hanging a bit of chain on the hose in the hopes of touching the cement is of little help as the charge is creted by the friction of te moving material and air along the length of the hose. If the vac has a grounding location on the housing (a screw into metal shared by the earth ground of the power cord) you could attach a piece of 14 gauge stranded copper wire, poke a small hole at the vac end and drag the wire through the hose to within a few inches of the end. This would create a path to ground that would not get unwound or catch on things. If your vac is "double insulated" and runs a two prong plug, the point is moot.
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