pvc duct static discharge?

[Ken Fitzgerald]

In my opinion, both arguments are correct...........you can't ground an insulator.....but....you can provide a physically closer path for discharge ...

While we don't want to induce humidity into our woodworking shops, I can tell you that on two different occasions, I got sent to help others troubleshoot intermittent electronics problems with CT scanners. Both of the hospitals were located in desert areas...one in Texas and one in central Washington. The frequency of the occurrences prevented the two hospitals from scanning patients. In both cases, I could sit at the console and tap my foot and draw an arc that was probably 1/2" to 3/4" and it hurt intensely.

When I measured the relative himudity via a sling psychrometer the two computer rooms measured less than 15%. After a humidifier was installed and the humidity rose above 20-25%, the machines ran without any problems.

Relative humidity has an effect on static electricity.

[Mark Burnette]

I can only speak for myself. I was going to be cheap and skip the "ground" wire until I after got the first few hits, then I installed one. All I know is that installing a bare wire instantly stopped the hits, presumably due to constantly discharging the static build-up. Do I know if the sawdust build up would have stopped it? No, I don't and I wasn't in the mood to wait to find out. The shocks hurt too much. Do I know if an insulated wire would have helped? No, as mine is bare.

So to a certain extent I agree with you. But I do refrain from commenting of the sawdust built option and the insulated wire option as I do not have any personal experience with either and my education didn't cover the effects of sawdust on the dissipation of a static charge.

This is exactly my experience. For 16 years in my current shop and over 5 years in my previous basement shop I have used thinwall "sewer & drain" pvc throughout a system with a high-volume 1.5HP 2-stage DC. No metal at all--even the blastgates are home-made pvc & hardboard. Originally when I assembled the system I had so much static buildup that the pipes were furry & bristling with dust. I got static shocks often on the basement system because I was physically close to the pipe and could feel my hair stand up as I walked under a pipe. Following "brilliant" ideas in the magazines I ran a bare copper wire through the inside of the pipe but no matter how I tried to position it it would only trap planer shavings & clog the system. Then I tried overwrapping with bare copper-plated steel antenna guy wire (wire type likely doesn't matter--I used it because it's cheap and you can't break the stuff)

With the wire installed I no longer get any shocks at all AND there is only a light trace of dust on the plastic between wraps and none immediately around the wire. This to me is clear visible evidence that the static attraction is a fraction what it used to be. Period.

My cramped old basement shop:



My current setup:

[John P. Smith]

People who are quick to deny established and proven theories are often the ones with the most tenuous understanding of them.

Dan, I am not denying any theory, and certainly not denying any established and proven facts. And a lot of what you and other members have full understanding of, I admit my understanding may be tenuous, at best. In some cases, nonexistent. I am just saying, what works, works. I appreciate you and others here who tell us what should and shouldn't work, based on facts that you know and understand. I also appreciate others who tell us what does and doesn't work, based on real world experience.

[Greg Peterson]

I have not seen a professional shop with PVC ductwork. Indeed, they use steel ductwork.

But most of the shops being discussed here are home shops. Many home shops don't even bother with dust collection.

Glad to read that you have a pro grade work shop.