I have 6" metal ducts, so I can't answer your question directly, but grounding flex hose sure helped. On longer lengths of flex hose, I ground the internal wire to the ductwork and /or to the tool. It seemed to solve my static charge issues.

 

It's sucks.I removed it and haven't used it since the first set up. To explain: my first system was completely grounded as Wood magazine explained how important it was to do so (this was in the late 90's). What I found was that every little change (and you will always be making changes to accommodate something) was probably 3X the work because you had to re do the grounding wire. Then as DC systems grew more popular folks started challenging the notion it was needed. That didn't sway my decision, I had reworked my ducting several times and got tired of the ground wire always complicating things, so after the first major overall I tore it out. Surprise, surprise! I didn't miss it, didn't experience severe static shock, saved money (and aggravation), didn't burn the house down, and had no catastrophic explosions/fires. Now there is some data (apparently) that refutes the grounding myth; at least from a safety aspect. Personal comfort may still be a reason to ground the system. But for me: it's good riddance and never again.

 

I have over 80' of PVC pipe going to 5 different machines with a blast gate for each
and I Never get shocked operating any of them.

 

All I'll add here is Stickley Furniture is a local manufacturer. Years ago they had the factory burn down when static electricity ignited dust in their dust collection system. How many hundreds of hours did they get away with it? I don't know, I bet it was thousands but eventually it happened and the effect was devastating. Avoiding a shock may not be worth it but avoiding a fire? Your choice.

 

I'm thinking there is a big difference between a small garage dust collector and a massive factory system.
But like you said, your choice.

 

This is the movie I would show students to make them aware of Static Electricity discharge and its effect in the wood and finishing labs. The idea was to reinforce bonding procedures presented during lectures.

 

I researched this a bit when I installed my 4" PVC ducting. My sense was that there is that static electricity discharge in dust collection systems is real, but, as noted above, is a concern for industrial sized systems that are consistently running. A small system like mine that runs for short periods at a time is not at risk.

I've never experienced a shock.

 

I have 6" metal ducts, so I can t answer your question directly, but grounding flex hose sure helped. On longer lengths of flex hose, I ground the internal wire to the ductwork and /or to the tool. It seemed to solve my static charge issues.

- pintodeluxe

How much of an issue was it before grounding the flex hose?

In my old shop, I'd get zapped about half the time I reached for the flex hose to pull it off a machine. Of course, I had a short piece of PVC sewer pipe on the end of the flex hose that made it easy to couple to the machine's dust port, so the charge probably never got a chance to bleed off to the machine's grounded frame.

 

...and you will always be making changes to accommodate something…

- Fred Hargis

That's a really good point, Fred. I'm even thinking of not gluing the PVC sections to make it easier to re-configure. So this is definitely something to keep in mind.

 

I have over 80 of PVC pipe going to 5 different machines with a blast gate for each
and I Never get shocked operating any of them.

- jbay

Is your ducting permanently connected to each machine? Maybe what I'm learning here is that pipe connected to a machine is grounded well enough through the machine itself to electrical ground that nuisance static never builds up. But flex hose not connected to anything can build up a charge. ?

 

I have over 80 of PVC pipe going to 5 different machines with a blast gate for each
and I Never get shocked operating any of them.

- jbay

Is your ducting permanently connected to each machine? Maybe what I m learning here is that pipe connected to a machine is grounded well enough through the machine itself to electrical ground that nuisance static never builds up. But flex hose not connected to anything can build up a charge. ?

- Crashcup

Not sure about that.
I have the black PVC pipe and Flex hose going to my machines permanently (until I move them)
I used screws to attach them together, no glue on mine.

 

The problem comes in with hoses/pipes not connected to machines that are grounded. Hold a shop vac in your hand and start cleaning your tools with it. Reach out with your other hand and touch the machine. That is the static shock you need to avoid, in the dark you can see the spark. Grounding is simple, just run a bare piece of wire inside your hose or pipe. a small hole lets you pull it outside and around any joints or gates and then back inside and attach the end to your DC housing. For making changes to your system you cut the wire at the joint where you want to change or add a run and just twist the wires back together outside the connections. The DC manufacturers advise grounding the systems for safety and would reject any claims for liability on a system installed without grounding. It costs $5-10 bucks for wire and adds about 30 minutes to installation time for a DC system. I always kept mine grounded and never had a problem, and never will. OK, I'm done, now all the experts can tell me how wrong and stupid I am just like normal.

 

Has anyone ever heard of an explosion or fire caused by un-grounded PVC?
I haven't

http://www.rockler.com/how-to/exploding-pvc-dust-collection-ductwork/

 

Has anyone ever heard of an explosion or fire caused by un-grounded PVC?
I haven t
http://www.rockler.com/how-to/exploding-pvc-dust-collection-ductwork/

- nkawtg

I've read in several places that there's never been a documented instance of an explosion in a small-shop environment from a dust collector.

I'm mostly trying to avoid the jolt, but maybe there's something to be said for covering all your bases. If there was a fire in the shop, and an insurance adjuster questioned your un-grounded PVC duct collection piping, then you'd have to find the documentation to show how you don't believe it was due to a spark generated from the DC system. The insurance guy (or gal) might be dead wrong, but it could be a PIA proving it.

Maybe similar thinking to electrical permits. I don't even do small electrical jobs without it. Even if I'm comfortable that I've got everything correct, I don't want to give the insurance company a reason to deny a claim.

 

I've read enough knowledgeable discussion on this subject that I believe grounding small systems is a waste of effort but if it makes you feel warm and fuzzy, do whatever you want.

 

http://www.rockler.com/how-to/dust-collection-system-design-equipment/ and http://www.woodmagazine.com/woodworking-plans/dust-collection/installing-a-dust-collection-system And even Harbor freight…. http://manuals.harborfreight.com/manuals/97000-97999/97869.pdf Read any of the owners manuals and they all say the same thing. There must be some reason, maybe they just like wasting their time and money when writing the manuals. I know the end users are smarter than the manufacturers engineers! 8-0

 

^I've been using PVC for over 25 years. I can only speak from my own experience, nothing I've read.

The earths polarity must be different where I work.

 

Crashcup,

How did you ground the system?

I elected to undertake a serious effort to dissipate the build-up of static charge both inside and outside the PVC piping. I was persuaded by OSHA that this could be a good idea.

https://www.osha.gov/dte/grant_materials/fy08/sh-17797-08/cd_instructor_manual.pdf

This effort took a fair amount more time and money to complete. I ended up overlaying about 40% of the interior and exterior of the PVC with metal HVAC foil tape, hoping that this would be enough surface area to dissipate static charge before the static discharge could reach built to the level where a discharge could ignite an explosion. The weakness in my method is that I did not provide a path to ground for static charges that may build up in the generally short section of flex hose. However, I plan to address the static charge build up in the flex hose in the near future. Otherwise I am reasonably confident that high energy static discharges will be avoided. But if the garage workshop blows-up one day I may change my mind.

I documented my SDR 35 PVC dust collection piping installation at…

http://www.clearvuecyclones.com/forum/forum/clearvue-cyclones/piping-and-dust-pickups/1361-duct-work-installation-using-sdr-35-6%C2%94-pvc

Where did you connect the ground to? (I imagine to the building's electrical system ground, but where did you tap in?)

I bonded the duct work grounding tape to an electric switch enclosure that houses switching to operate the dust collection. The enclosure is grounded to my homes grounding systems which ultimately goes to ground at a pair of grounding rods to which the main and sub-panels are grounded. As I installed the duct work, I checked for electrical continuity so that every leg of the duct work would have a path to ground.

And how effective has it been in preventing buildup of static charge?

I am not sure how to answer this question. I have yet to have an explosion or a static electric shock. Also, dust does not seem to settle on the duct work anymore than it settles on other surfaces in the work shop. I would think that if static charge was building up on the PVC duct work, dust would be preferentially attracted to the duct work.

Is your ducting permanently connected to each machine?

My duct work is permanently connected to the machinery with short lengths of smooth walled PVC flex hose. The flex hose is easier to make the connection of the machines to the PVC duct work and allows machinery to be moved around the workshop for servicing of machines and for unusual operations that may require more room for an unusual task. I work in a two car garage. I regret that I did not pay the extra for the static dissipative smooth walled flex hose.

But flex hose not connected to anything can build up a charge. ?

Flex hose without any provision to dissipate static charge will build up and hold the charge. I notice this phenomenon mostly when planning. I can feel the static charge on the PVC flex hose connecting the planer to the PVC piping when working at the planer. I am not sure how I will address the static charge build-up; with HVAC foil tape or a bare copper wire. Flex hose that dissipates static charge is available, but it comes at a price premium.

 

Thanks for the detailed response, JBrow. And everyone else who replied, thanks.

I guess everyone has to do his own risk analysis on any danger of a spark igniting wood dust. I'm not concerned about it… I could be wrong. It's kind of like the choice of protective gear on a motorcycle. Anyone here ATGATT? I choose to ride often enough without riding pants and sometimes without jacket if it's hot enough. Always helmet, boots and gloves though. That's the risk I'm comfortable with. I don't give the ATGATT guys crap, and I don't expect to get crap from others for riding with jeans on.

But I do want to avoid the jolts like I got in my old shop, and I think I've gleaned some good advice for that. My shop won't be big enough to leave everything in place and always connected to the DC. Tablesaw, router table, miter saw, oscillating sander probably yes. But the jointer and planer are usually going to have to be pulled out in the middle to use, so that means a length of flex hose to connect. That will be my first priority, to be sure those are wrapped and can dissipate the charge.

I'm going to read some more of the articles on the links provided and try to decide on the rest of it, whether it seems worthwhile. The walls are open now, electrical rough-in approved, so now is the time to connect some extra ground wires to the boxes if I'm going to. Before I insulate.

Keith

 

Seems to me that the danger of sucking up a nail or screw and causing a spark against the steel fan blade is many many times greater than a static spark and yet they still use steel fans. Or at least some companies do. Nothing in the design prevents metal from hitting the fan and there is no provision for additional grounding built into the design of the dust collector. So they put a legal disclaimer in the manual but that's it. Another thing, the only place dust can create a "cloud" of the right particle size is inside the collection bag/bin so if static does build up on the pipes, it would have to travel across the fan and metal housing (both of which should be grounded?). I guess if you attach a separator then you preempt the metal housing. So if there is any possibility, the only way I can see it happening is in a separator with a lot of wood flour in suspension and I think you would want to ground the connection between pipes and separator. I still don't believe it's a credible threat but the thought exercise is fun.

 

http://www.rockler.com/how-to/dust-collection-system-design-equipment/ and http://www.woodmagazine.com/woodworking-plans/dust-collection/installing-a-dust-collection-system And even Harbor freight…. http://manuals.harborfreight.com/manuals/97000-97999/97869.pdf Read any of the owners manuals and they all say the same thing. There must be some reason, maybe they just like wasting their time and money when writing the manuals. I know the end users are smarter than the manufacturers engineers! 8-0

- papadan

Or maybe, like most things, it's been over-lawyered.

 

This has been discussed so many times. Of course dust collector mfg will tell you to ground your system as it protects them. In reality, the risk is extremely small and close to zero. I found the best explanation done by an MIT professor.

The Best article

I do not ground my PVC based system and do not get shocks. But, if it makes you feel safer, then you should do it. However, it is very difficult to ground a non-conductor because you have to ground all of it. If you are truly concerned about static discharge, you should use metal ducting.

 

When I first did my system I did get a little jolt from touching a metal blast gate so I grounded all the gates.

I think with PVC you can get some static initially, but once you've used the system a while you won't have the problem, probably because the inside of the pipe get a coating of fine dust on it.

Bottom line: I wouldn't worry about it too much.

 

I have 6" metal ducts, so I can t answer your question directly, but grounding flex hose sure helped. On longer lengths of flex hose, I ground the internal wire to the ductwork and /or to the tool. It seemed to solve my static charge issues.

- pintodeluxe

How much of an issue was it before grounding the flex hose?

In my old shop, I d get zapped about half the time I reached for the flex hose to pull it off a machine. Of course, I had a short piece of PVC sewer pipe on the end of the flex hose that made it easy to couple to the machine s dust port, so the charge probably never got a chance to bleed off to the machine s grounded frame.

- Crashcup

If I had more than about 5' of flex hose attached to a tool, I would get this annoying machine-gun paced static shock from the hose and tool. When I upgraded to a wall mounted cyclone it got worse (more air moving through the pipes). Grounding the flex hose wire fixed it completely (with metal ductwork).

 

I've never been shocked from my flexible hose, any part of my dust collector, or anything at all in my shop.