Dust Collection Grounding

[John Lail]

He guys my first post or question. I just installed dust collection in my shop and hear about grounding the pvc. I chose to use metal stove pipe, mainly because of cost. My building is metal with metal post into the ground. Am I correct in thinking the metal post are grounding my building and as long as I am connected to it I am grounded. Thanks in advance for any help.
Thanks John

[Roger Chandler]

If your electrical panel is grounded [which should be code]. Then your duct work grounded to the metal of your building should also be grounded, as the metal panel box is attached via ground wire to the ground rod from the panel.

[Brice Rogers]

From a static-electricity point of view, an earth ground will work well. Hopefully, as Roger mentioned, the earth ground and electrical panel ground are bonded together somewhere. But honestly, either one will keep from developing enough potential to give you a static electricity zap.

[david privett]

I thought that the static zap to your person was not really the reason for grounding dust systems it was to prevent a dust explosion as like a dusty grain silo getting hit by lighting. BOOM. I used pvc pipe on mine and I wrapped the whole thing in wire and grounded it on both ends to my metal bldg. also drove in a extra ground rod on the opposite end of the bldg. of the power panel rod. I had a tractor shed that is close to my main barn it was hit by lighting and cooked the metal roofing and wiring that was on shed and jumped over to the main barn but did no damage beyond power panel, maybe cause of the extra grounding don't know for sure.

[paul cottingham]

You can't ground PVC. And for what it's worth, the mythbusters tried really hard to cause a wood dust explosion, and weren't able to do it, using static. Given their predilection for being able to blow stuff up, I'm pretty comfortable with up that being pretty strong evidence. Further research yields that (as far as anyone can tell) no one has ever had a saw dust explosion from a spark in PVC in a wood shop.

[Brice Rogers]

With my small shop vac, I sometimes get static electricity shocks from the hose. The hose is flexible plastic but it has a coil of wire in the ribs to provide form. So it is creating some sort of Van De Graff generator with the particles flying through the hose.

What I am wondering about is whether a static charge could build up and discharge into the electronics of my lathe motor controller. If it is plugged in, it is grounded (I think that I'm going to double check that). But if it isn't plugged in, I'm not sure.

[Roger Chandler]

I used thin wall pvc for my dust collector system. I drilled small holes and ran a bare copper wire through the system and grounded it. The issue of dust explosion, or static has been eliminated from my system. I got the information from a book written specifically for dust colection systems and setting them up properly. Never had a single blockage inside the pvc ducting, in 15 or so years of use.

[John Beaver]

With my small shop vac, I sometimes get static electricity shocks from the hose. The hose is flexible plastic but it has a coil of wire in the ribs to provide form. So it is creating some sort of Van De Graff generator with the particles flying through the hose.

Since you already have the wire in the hose, just expose a bit of the wire near the connection and ground it to the unit. Easy fix.

[glenn bradley]

The phrase "grounding" when we talk about dust collection commonly refers to providing a path for static discharge. Its very simple. All you want to do is provide a better path to ground than your body provides.

I run ASTM-2729 plastic pipe. I wrap an insulated wire along the ducting and terminate it at a ground point at both ends (one end will do). The wire insulation is no problem for a charge stout enough to already jump through the duct wall.

There is never a static shock to the operator since the charge never really builds up much. It is draining to the easy ground frequently as it reaches whatever level it takes to make that jump.

duct examples (1).jpg

One of my grounds is simply a 6" x 12" 'patch' of foil tape on the concrete with a flap sticking up for the wire to attach to. At the end of a duct where a hose may attach I add an alligator clip to clip to the metal helix of the hose.

duct examples (2).jpg

[Bruce Page]

You can't ground PVC. And for what it's worth, the mythbusters tried really hard to cause a wood dust explosion, and weren't able to do it, using static. Given their predilection for being able to blow stuff up, I'm pretty comfortable with up that being pretty strong evidence. Further research yields that (as far as anyone can tell) no one has ever had a saw dust explosion from a spark in PVC in a wood shop.

I agree with Paul. I run a grounded line through the ducting to my cnc router but only to protect the machines electronics.

[John King]

Everything you could ever want to know about dust collection at http://billpentz.com/woodworking/cyclone/index.cfm. - John

[paul cottingham]

I agree with Paul. I run a grounded line through the ducting to my cnc router but only to protect the machines electronics.

I would run it on the outside (my system is in a pile right now) just because I hate getting zapped, and I don't think it's good for my shunt. In fact (anecdotally) I suspect static discharge has reprogrammed it more than once.

[John K Jordan]

This is a controversial subject. I studied it for months and the more I studied the more controversy I found. Many ideas and speculation get repeated so often they become "fact." I decided to listen those who actually did careful scientific tests that showed how grounding wires/metal tape inside or outside PVC pipe do nothing useful.

But don't take my word for it, do your own research! I only recommend paying attention to things said by people who did experiments and tests - instead of the people repeating what they read or what they always heard or what that expert said or what they read in a book or on the internet or even what just seems to make good sense. (or what anyone says who is trying to sell you something)

I also ignore all anecdotal evidence and rumors ("Mine have been grounded for 20 years and..." or "I heard about an explosion in...")

BTW, understand that you can in fact get a whopping painful shock that can't possibly ignite an air/dust mixture (according to researchers who have tried). A friend of mine and I once built a 100,000 volt electrostatic generator that would make 11" sparks from the end of his tongue or powerful smacks to your forearm. Couldn't get it to ignite anything since the current was tiny. If I had concern about a charge buildup I would engineer an array of discharge points since high voltage charge "sprays" harmlessly into the air from a point.

For those who really want grounded ducts make sure to install metal.

JKJ

[Jim Silva]

I ground all of my DC's as, if nothing else it prevents painful shocks which I've received from ungrounded lines. I've personally had a dust explosion in a DC but it was from a spark from the motor not the static. However, can't hurt either way. Not being poked when touching metal after sanding with the dc is enough to make it worth it for me.
Jim

[Roger Fournier]

My dust collection system is constructed of 4" PVC pipe, but unlike most systems I have seen, it runs along the outside of the shop 2 car garage) on the floor with drops from the tools going down to it. Whether it is because of the PVC being in contact with the concrete floor, or just luck, I have never gotten ANY shock from it.