When I built my shop I installed 6″ pipe under the slab for my dust collection system. Wires were run with all the buried pipe to support grounding the system once up and running. It appears something happened to the wire between my planer and the dust collector as a lot of static electricity builds up when I run this machine. My question…. Can I drill a small hole into the 6″ plastic pipe and run the wire INSIDE the pipe over to the dust collector, then have the wire exit the buried pipe thru another small hole? I can then attach at each end to ground it. Just not sure if the wire running inside the pipe will affect the dust collection. I’m not concerned about the fire or explosion risk everyone raises. The grounding is more to avoid the nice shock I get when I touch the pipe. Thanks in advance.
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I'm in no way an expert on this, but I've come across many discussions on various forums, so, caveat out of the way, there's a lot of disagreement on the necessity of grounding pvc duct. What seems, to me anyway, to be true is that pvc is not a good conductor of electricity, static or otherwise. I think the majority of people agree that there's no risk of explosion or fire in the average wood shop, so the only issue might be, as you've said in your case, the annoyance factor. If you agree that pvc is a poor conductor of the static charge, that means in your case you can just ground the pvc at the ends where it comes out of the slab, no need to run a wire inside the duct.
I don't have any grounding for my ducting and have never experienced static in my system but for a ground wire to work it needs to be grounded. Maybe to a metal receptacle box .
Grounding story: I purchased an old cast iron jointer and had been using it for a couple of weeks. I put it on casters because everything in my shop has to be able to move. My concrete floor is covered with rubber matting. Everything seemed fine with the jointer but one day I rolled it over next to my tablesaw and it came in touch with the cast iron top of the saw. When I turned on the jointer it immediately began to try and weld itself to the saw. Bench testing the motor I discovered that ever bit of it was hot ,the case, the shaft, the pulley. Why it didn't short out I have no idea.. The motor went in the bin! Apparently the tsaw provided a better ground than the wire to the recepticle though that must have been working because the jointer didn't knock me across the room.
Your ground wire is outside the plastic ducting? The pvc is a poor conductor, the static builds up inside. I don't see how that would work very well. I'd fish a wire through. Isn't there a big opening on each end of your system?
Yes. When the 6" pipes were trenched in wire was run alongside the outside of the pipe. So once everything was backfilled and the concrete slab poured, everywhere the plastic pipe comes up thru the concrete, so does a wire. All works well with the exception of my planer (DW 735). As I tried to describe, wondering if I can run the wire inside the pipe since there is no way to now run one under the slab. As EDDO234 notes above, wondering if I can just ground the planer and dust collector on each end. Again, it's only to avoid the shock.
Pantalones868, as I mentioned, I'm in no way an expert on this, but I have a question. If, as you say (and I agree) that PVC is a poor conductor, and the static builds up inside, how are some people getting shocked from touching the PVC duct.... on the outside? I don't think anyone's sticking their arms down the duct to get shocked. I've read of people screwing into their PVC duct and attaching a ground wire to that for protection.
Yep. I have 4" white PVC pipe connected to the back of my planer (DW 735). This runs to a gate and then an adapter from 4" to 6" as it nears the floor. If I have the planer and dust collector on, the plastic pipe that exits the back, center of the planer will give me a very nice shock if I were to touch it. It's enough that when planning a board, when I retrieve a board exiting the planer, the hairs on my are will all stand on end due to being close to that pipe.
PVC is indeed a poor conductor, which is the reason static builds up - if it were a good conductor, the static would be instantly dissipated.
PVC is a very good static generator, witness what happens with the particles when you saw through a piece - they cling so tightly that it can be hard to get rid of them. Static can build on the inside and not be apparent on the outside.
In my previous shop, I ran 4" PVC into the wall, up and over the ceiling and down the opposite wall to the collector. There were 2 branches.
I ran bare wire inside the PVC, out through 1/16" holes at each joint and connected all sections together. I grounded it on both ends - after the ground wire came loose when it was grounded on one end and I got zapped. The wire was pulled very tight to keep it out of the air flow zone in the center of the pipes. I used ordinary electric fence wire, as it was cheap.
There was never a issue with dust catching on the wire and causing a problem. I don't think the density of the dust cloud is high enough to cause a dust explosion, but........
I also ran 6” PVC under the slab of my shop for dust collector. It as been installed for 11 years now and never any issues.
I have 6” galvanized pipe from my cyclone (Oneida) along the outside wall. I transitioned to PVC under the slab, than back to galvanized to a 4” transition and blast gate, then finally flexible hose to to the planer (DW735). No grounding thru the PVC. Every once in a while I have noticed static (notice by touch) build up at the point where the flexible hose attaches to the plastic fitting on the planer. I have never had any static at the blast gate. I suspect wrapping a bare wire around the hose at the machine fitting and grounding it would solve the problem. I have just never done it.
My point is to confirm where your static problem is. You may have as easier option to ground at the machine rather than running a wire thru the whole pipe.
Thanks. You make a good point. I've never gone and checked my dust collector to see if there is a static build up on that end. Only noticed it at the planer. I may do as you suggest and run a wire from the pipe that exits the planer and then ground it. Now for the stupid question, where would one ground this? The conduit that runs power to my machines under the slab is plastic. Would I need to drill a hole thru the slab and put a metal post thru the concrete and into the ground below to achieve this? Sorry, feel like I should know this.
I suspect you ran an extension cord in the conduit and plug the planer into the cord above ground. And assume that cord is 3 wire ( has ground). Put a metal power strip in line and run your ground line to the power strip.
Assuming your outlets are properly grounded you can simply attach a green ground wire to the screw the cover plate to the outlet. Properly installed that screw would be grounded to whatever earth ground is connected to your panel and would constitute a legal ground for that purpose.
Electricity and especially static electricity is not often well understood by woodworkers. Those who say it's unnecessary to ground PVC dust collection pipes because theirs isn't aren't taking into account the number of variables involved in how much static charge builds up in any given shop. Things like the humidity in the air, dry air will cause more charge to build, the type of floors, concrete floors make a better ground than wood, the type and size of the dust collector will have an impact, the faster the air moves the more static charge is released, etc. All these factors come into play when deciding if you need to ground your PVC ductwork.
You are on the right track by not being concerned about wood dust exploding due to static charge the conditions for that to happen are just too remote in any shop let alone a small to mid-sized one. On the other hand getting zapped by static charge from your ductwork can be a very real and annoying problem and potentially dangerous if you keep flammable chemicals in your shop and fumes build up just when an arc of static charge leaps from your ductwork.
To overcome the problem it helps to understand it. Electricity is nothing more but the flow of charged ions either on a conductor or though the air. These ions have one purpose in life to get back to mother earth, the ground, and they will look for the path of least resistance to get there. When given a conductor like a copper wire these ions can be tamed and controlled and put to good use. When left to their own devices they can become problematic and we get things like lightning and static charges which can wreck all kinds of havoc. It also helps to understand that electricity does not flow through anything it flows on the surface. Copper wires are not water pipes this is one of the reason you need larger wires to handles larger amperages because if too much of the current is forced to flow in the wire rather than on the wire it causes friction which creates heat and bad things happen. The difference between a conductor like copper and an insulator like PVC is the electrons can move freely over the surface of copper like skating at the local ice rink whereas it is like skating at the beach for them to move over PVC. This causes them to slow down and get stuck but if the source of charged electrons keeps creating more they start building up in the form of potential energy until they have enough energy to overcome the resistance presented by the PVC and leap to the closest path to ground, usually through your body and you get zapped.
The simple solution for your problem, after my long winded attempt at being Bill Nye the Science Guy, is to wrap your exposed PVC pipe tightly with a stranded, not solid, solid wire will not provide good contact with the pipe, bare copper ground wire. This wire will provide a path of less resistance to ground for the electrons and will prevent them from building up to the point they can arc through your body to get to ground. A wire run through the pipe will be of little value because it needs to be in tight contact with the pipe surface to work. Make sure you connect this wire to a solid ground source, preferably a connection to a ground rod, but a case of a properly ground outlet box or even a tool will work, with the advent of plastic plumbing inside and out, water pipes aren't as reliable as they once were but you know your shops construction. Use short screws drill into the PVC to help anchor the wire and act as anodes to gather charge from the air moving through the pipe. How closely wrapped your pipes will need to be will depend on how much pipe is exposed and how much charge is be created that needs to be disapated. I would start with wraps about 6" apart and go from there.
I second this. It is exactly what I did. Wrapped the pvc every 6-4 inches,
Put in a short screw and wrapped the wire around that every 4 feet or so. Tied the wire on to the chassis of the fixed tools, jointer, bandsaw, dust collector. Table saw and planer did not get the additional ground but it is sufficient to eliminate that zap! I would get from the Dewalt planer.
Awesome info esch5995!! Thanks so much. Will give this a shot to see if I can eliminate my getting zapped when planning. Thanks again.
Did esch5995’s suggestion resolve the issue?
According to the original post the pvc duct is buried in or under the concrete floor. Wire was run before being buried but is not having the desired effect so maybe it was damaged or compromised somehow and of course not repairable. The question he poses- can he fish a new wire through his duct on the inside and eliminate the static charge. I think he understands about grounding etc. He seems more concerned about the internal wire possibly causing clogs than anything else. This is understandable to me because a built up dust clog somewhere in your buried pipe could be a real problem to remedy. A wire running loose inside the pipe could interfer with your clearing a dust clog as well. I don't see you being able to use a rotorooter for example.
So, have you tried using an ohm meter to determine if in fact the wire is broken? Is the wire attached in anyway to the duct that was buried? If you have continuity and if you believe your wire makes contact with the pvc pipe then it could be that you have insufficient contact or grounding on the ends.
If you are getting shocks, you should first check that your planer is earthed.
Do you have an earth pin on your socket? I'm not sure how things work in the US, but elsewhere, a separate earth return is required. This will usually be connected to the casing of the machine so that any live parts that make contact with the casing will cause a short circuit and blow the fuse.
If this is the case, you could simply run a wire from your machine casing using a self-tapping screw and wrap that round the offending pipe.
As others have said, this static build-up poses no risk at all other than the annoyance it causes. How much wrapping you have to do will rather depend on how sensitive you are. Static will build up on any parts not near to the conductor and will discharge to earth where it can. You may need a goodly bit of wire to fix the problem.
I have a central 7" line. The metal pipe was super expensive and I was rather strapped at the time so I used 2 sections of concrete forms for my central line. I'll pause for the shocked and horrified people.
It works so well i never changed it. My system goes to 7 machines. Each uses a metal blast gate and I have a grounding wire on each gate, metal trash can (used as a seperator) is grounded, then of course the machine itself.
I'm also no expert but I have yet to get shocked. The system gets a ground at every metal point. Seems to be more than enough.
Where I live the humidity only gets low enough during the winter months, but if I lived in AZ or CO that would be different. I only get zapped if my arm gets too close the duct. I grounded all my aluminum blast gates.
When we go to CO every year in the summer, I have to touch the door jamb of the car when getting out to avoid getting zapped. My wife no problems.
Which brings up another point -do different people have different body resistances? I am one of those who get zapped when others don't, such as the example above.
More than likely caused by different fabrics and shoe materials affecting either how much charge an individual builds up and how insulated from the ground you are.
I refer to my grandfather as the first electrician. He retired at 65 in 1952 as an electrical foreman at US Steel. He started working for Andy Carnegie when he was 11 years old -- the first electrician-
One of my grandfather's favorite jokes was he would be holding the positive end of a wire in his hand -120 v "Is this wire hot? I can't tell" and maybe he couldn't, then he would poke you with his finger on the other hand. It hurt like hell ! He said how in the old days they would test the voltage on industrial electrical wiring by licking their fingers and smacking them across the wire! They could tell by the spark they got what the voltage was! So yes, I believe some people are more sensitive than others.
Wow. They sure don't breed 'em like they used to.
Folks these days probably don't even check the RPM of their table saw blades using their thumbnails. Wimps....
Well they would but they can't, they all bought Sawstops! We're reduced to proving we're real men by buying very large pickup trucks!
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