A question for electricians about grounding PVC and copper wire gauge

[Aaron Rosenthal]

I'm fixing up my dust collection ducting, using 6" (150 mm) PVC Sewer pipe and fittings. Into almost every joint I have screwed a high copper alloy screw, and I have wrapped these screws with some stranded 14 Ga extension cord wire (bared at the copper screw terminal).
My objective is to lower the static electricity charge inside the pipe and outside the pipe.
Is the copper wire OK at that light gauge, or do I need solid 12-3 for more robustness.

Thanks

[mike stenson]

You really can't ground it, because it's an insulator. 14ga is more than sufficient for dispursing surface static. It's high voltage, low amp, in nature.

FWIW I haven't bothered with my 6" S&D pvc runs.

[Steven O Smith]

It sounds like you are insulating the 14 g wire intended to draw charge (except at the alloy screws). If so, this is self defeating. You want the wire bare (but I have no idea if this internal wire approach actually does much).

[Michael Burnside]

Electrical Engineer here, not an electrician, but Mike is correct. Your pipe is an insulator. The screws every so often are certainly going to have some help letting the charge inside come through those screws and find a lower potential, but not likely to do much. After some use they're likely to be caked with debris, egro becoming an insulator and cease to function as intended. I personally wouldn't bother. If you're concerned with fire, which IMHO is categorically so improbable as to be a non issue, then you better have a wire inside along the full length.

That said, generally the intention is to ground the outside so you don't get shocked. In that case, just winding the copper wire around the pipe is adequate. The current is very low, so 14 ga NON INSULATED bare copper wire is more than sufficient. And of course, ground the wire

[Frank Pratt]

Electrician here. We did work in a tire retreading facility. They had a large PVC duct connected to the machine that grinds the tread off old tires. They were getting shocked from several feet away from the static. Wrapping the duct with a grounded bare copper wire solved the issue. But you could still get zapped if you touched the part of duct the wasn't near that wire.

[Bill Howatt]

I have a metal ducting system but with lengths of plastic hose with wire embedded for strength connecting from the fixed metal duct to the tools. I could get shocks from the plastic surface but it was solved as mentioned above by wrapping some bare wire loosely along the length and grounded.
My understanding is that in a non-commercial (as in small) dust collection system the conditions will not support a dust explosion or fire from arcing. Biggest risk is probably sucking up a "glowing ember" of wood or metal.

[Michael Burnside]

Electrician here. We did work in a tire retreading facility. They had a large PVC duct connected to the machine that grinds the tread off old tires. They were getting shocked from several feet away from the static. Wrapping the duct with a grounded bare copper wire solved the issue. But you could still get zapped if you touched the part of duct the wasn't near that wire.

Fun fact related to this. I had a buddy with a CNC that was skipping once in a while. He couldn't explain what was going on. He has about 20' of PVC and a final 5' of flex hose. The flex hose is grounded to the CNC, through the metal coils and connected to the other end to a copper wire wound around the PVC. I brought my o-scope over and connected a high impedance probe between one coil and half-way to the next, which was about 18-ish inches. We surfaced his spoil board a couple of times testing and I could actually see a potential between them. So, with a few tests we just increased the number of windings and it completely solved his problems. We ended up moving the windings closer to about about 6-8" apart. We also taped the wire every so often to make sure it's actually making contact to the PVC. He was trilled it wasn't the CNC and hasn't had a problem since.

[Bill Dufour]

Do your screws go clear through the pipe wall and expose metal inside? Is this wire attached to the screws connected to anything else or is it just a lighting rod exposed to the air? That wire really needs to be connected to a ground at one end. Now is the time of the year to buy metal tinsel garlands and wrap them around the pipe and connect one end to a ground wire.
Bill D