DC Grounding

[steve-norrell]

A question about grounding dust collection systems . . . .

I am installing 4" ducts (Schedule 20 and flexible hose) for a new DC (Jet DC650) and I have a question about how to ground the anti-static wires. There is one "Y" in the system. One branch goes to the the Shark Guard on BT3100 and he other branch goes to a plug-in that serves the rear DC port on the BT3100 and a router table. The longest distance between a tool DC port and the dust collector is about twenty feet.

I ran the wires through the all duct work and was planning to ground the wires at the dust collector. Assuming the dust collector is properly grounded itself (with the three-prong plug), I expect that would be adequate.

Since the Shark Guard is plastic, it would be difficult to ground the wire in that branch of the system.

Any comments would be welcome.

Regards, Steve

[thestinker]

None of mine is grounded, but I think the danger from static discharge is pretty slim. I seem to recall reading that the explosion risk was pretty small.

Riley

[dbhost]

My comment is fuggidaboutit...

I have yet to see even the slightest shred of evidence that a typical home workshop DC system can generate enough static to come even close to igniting the wood dust in the plumbing / dust bin. The more humid the environment, the less of an issue it is.

I didn't catch your location, but unless you live in the Desert Southwest and your RH rarely, if ever goes over 30%, I would not even think of worrying about grounding the system...

Do a google search for home woodshop dust explosion, and dust collector explosion, and you will find the links all point to somebody trying to sell you something or another. Usuaully metal duct work. The remaining links seem to be reports of issues involving HUGE industrial systems servicing hundreds of machines at once...

I am not saying officially do not ground it, but I am saying that not grounding is a choice I am making based on the evidence of risk I have available to me at this time.

[rjwaldren]

http://www.bt3central.com/showthread.php?t=43903

Above is a previous thread on the subject there's an interesting read linked. Bottom line is that the only way to fully ground PVC is to use metal instead, and there's no real reason to ground it anyway.

[master53yoda]

If you are working in is an area where the relative humidity stays above 30% grounding is probably not required. If the area you are working in is below 30% the dust will generate a static discharge when it passes through a metal portion of the system. the wire run down the duct and grounded at the dust collector as you described does eliminate any potential problem. The relative humidity is the controlling factor whether you will generate a static charge or not.

As most have suggested here a home system probably has minimal issues due to the small amount of dust being transported in the system and the periods of time between transports providing time for the static charge to dissipate..

hope this helped answer your question.

[steve-norrell]

Thanks for the feedback and the reference to the previous post. After reading that post, it seems that I really didn't need to worry too much. Anyway, I have already put the ducts together with a wire inside. I will ground that to a convenient spot on the dust collector and rest easy.

I guess all I am out is the cost of the grounding kit.

Thanks again for all the info. Regards, Steve

[cabinetman]

In my locale the RH is hardly ever under 50% and the static charge can be minimized by simply running a copper ground wire. I don't find a problem at any collection point, but along the run of tubing the charge can build up. Running copper wire, connected to actual ground is effective. I connect to the conduit to the outlets, or that run to the foundation, and actually into the ground. There is still the presence of static felt on the tubing.
.

[LCHIEN]

ground your equipment (should already be done with the three prong plug).
Static can build up on the PVC but not a lot since it by itself is non conductive. A lot of static could build up if you have conductive (e.g. metal) piping that is insulated (not grounded) but this is not the case. The static buildup on PVC won't be enough to ignite dust density found in a home workshop.

[steve-norrell]

Thanks Cman and Loring!

Our RH gets pretty low in the winter, maybe down to the high 20s inside, and static electricity events (sparks flying) become much more common.

If I had received these comments before installing the PVC duct work, I probably would not have bothered with the grounding wire. Nevertheless, it is already inside the ducts, was almost no extra work to install, and will be grounded to the DC (which itself is grounded with a three-prong plug).

To sum it up, considering how easy it is to install the grounding wire, it is probably wise to do so even though the chance of a static electricity ignition of the dust is only a very remote possibility. I wouldn't lose any sleep if it wasn't installed.

Thanks again to all. Regards, Steve