Good evening. I hope I am posting this in the right section. 

 

Today I was milling a ton of Eastern Cedar boards that I am going to use for my grandson toybox Christmas build. When I went to empty my dust collection I got the snot shocked out of me. It was loud enough that someone across the street asked if I was okay. Notice my bucket was charge pretty good with shavings clinging to it. I thought maybe my hose was touching something that was not grounded so I changed it's position. The next time it was time to empty out the bucket with gloves on I got bit hard again. I had everything plugged into the same power strip so i decided to unplug everything in that power strip except the planer. I plugged the dust collection into a separate power strip that was plugged into a different power receptacle. Samething happened two more times.

 

I know this can be a very dangerous situation if indoors and dust is in the air. Are there some woods more susceptible to static than others? What should I look for to keep this from happening again for safety sake. 

 

I have enclosed some pictures of my setup. In one of the pictures you can see the shavings "clinging" to the chop saw and hose.  

 

Thank you!

 

 

 

A couple of things probably happening in concert. 
Judging from the amount of sunshine, I think you are probably experiencing very dry air which can contribute to static buildup. Secondly, it looks like you have plastic hose for the collector runs. Plastic will also contribute to static development by air movement. 
l don’t know if some species are more prone to static. I’m guessing that really dry wood might be more likely than wet wood. 
A grounding wire setup should help drain the charge. 

I am thinking along the lines Lew was. I would say somewhat like computer experts do and even in some offices before touching the computer they touch a grounding pad to discharge the static electricity. For your case use a grounded wire and touch it to the canister before you touch it. That would be easier to do than permanent grounding a mobile setup you appear to have.

One issue is that both the planer and the vac are double insulated and therefore not grounded. As the sawdust travels down the plastic ducting the friction between the duct and the sawdust produces a static charge which builds up in the entire system. The plastic ducting can build up a pretty decent charge which is transferred throughout the system. When you touch it you are essentially grounding the system. This is the reason all ducting needs to be grounded. The easiest way to do this is to run a small piece of copper wire through the ducting and attach the copper wire to grounding system. It is very important you do this before you use this system again. A spark from the static charge mixed with the sawdust in the ducting can result in an explosion. 
Paul

Thank you gentlemen for your insight. Now to figure out what to ground it to. I want to work safely that is for sure. Again thanks.

 

I just read some articles and watch some videos on grounding. Does the ground wire have to touch bare ground or would it work just touching my concrete driveway? 

Edited November 7, 20214 yr by KevTN

2 hours ago, KevTN said:

I just read some articles and watch some videos on grounding. Does the ground wire have to touch bare ground or would it work just touching my concrete driveway? 

The best ground point would be a METAL COLD WATER pipe- assuming your house is plumbed completely with metal piping. The next best point would be the electrical ground point on a receptacle. You can make a grounding wire from an alligator clip and a banana plug- or purchase one.

 

The banana plug goes into the "Third" hole in a receptacle and the alligator clip attaches to the grounding wire of your plastic hose

All of the above options will work. If you’re working out in the driveway a lot you can sink a grounding rod right in the lawn where you are working. The grounding rod can be just about anything metal. A tent stake, small piece of metal pipe or even a screw driver will work. 
Paul

6 minutes ago, Masonsailor said:

All of the above options will work. If you’re working out in the driveway a lot you can sink a grounding rod right in the lawn where you are working. The grounding rod can be just about anything metal. A tent stake, small piece of metal pipe or even a screw driver will work. 
Paul

 

I am completely ignorant about electricity, so the grounding cable is attached to the rod in the ground, where does the other end of the cable attach? Thanks!

1 minute ago, John Morris said:

where does the other end of the cable attach?

That end connects to the copper wire that runs inside (or wrapped around the outside) of the dust collector hoses from each dust generating piece of equipment.

The copper wire will be inside the ducting. One end will be grounded using the above mentioned methods. The other end doesn’t need to be attacked to anything. To keep it in place disconnect the duct from your tool and run the wire out of the duct and use the clamp on the duct to hold it in place. 
Paul

Lew is also correct you can use the clamp on the dust collector. Anywhere will work as long as the wire is inside the duct and connected to ground. 
Paul

Thanks guys, that makes sense, I was imagining each machine had to have a wire run to the stake in the yard, seemed like a big hassle to do everytime he sets up outside, but if you just have to connect to the dust hose, seems more doable.

Got another stupid question, why doesn't the ground in the DC plug do the same thing? The third prong?

The wire does not have to be large gauge. A piece of small stranded copper wire will work. 
Paul

The dust collector motor is connected to the ground but your system is using a plastic plenum ( bucket) to attach the ducting to so there is no direct connection to ground. Also is there a three prong plug on the shop vac ? Most do not have it. 
Paul

This is why in a large shop you will see metal ducting and not plastic. The metal ducting is a grounded system. You can use pvc ducting ( I use it in my shop ) but you have to use a grounding wire. With the pvc pipe you don’t have to run the wire inside the pipe. You can attach an external copper wire to the ducting using short self tapping screws every few feet which protrude just slightly inside the pipe. This will ground the inside and outside of the pvc pipe. 
Paul

Personal experience- 

When first setting up my dust collection system, I was very concerned about static electricity (my background is in electronics and computers). I ran the copper wire inside my dust collector hoses. Over time I found the suction to my saw, lathe, etc. seemed to get les and less. I discovered that the planer ships were catching on the wire and building up inside the main hose (all mine are 4").

 

After doing a little research, I found that wrapping the wire around the outside of the hose would do the same thing just takes more wire per hose.

 

Then, after even more research, I began to find credible articles like these:

https://www.finewoodworking.com/forum/grounding-for-dust-collection

 

https://www.woodcentral.com/articles/shop/articles_221.shtml

 

Now, I'm not saying that the dust/spark cannot be a possible source of explosion but analyzing the size of MOST home shop systems the likely hood is quite low.

 

16 minutes ago, Masonsailor said:

Also is there a three prong plug on the shop vac ?

I thought they were three pronged, mine is anyway. That doesn't mean most are like you stated.

So when I had a central DC system, my ducting was all metal, so I never had to deal with this. I know KV can't do metal because of his portable situation.

Thanks Paul and Lew for the lessons!

Another pearl I have learned over the years is not to use the self tappers that have sharp ends. They make ones that have a dull spade like end. Those do not snag my “pig” that I send through the ducting occasionally to clean it out. 
Paul

2 minutes ago, John Morris said:

I thought they were three pronged, mine is anyway.

Even with a 3 prong plug, static can build up. The cases, hose, connections all are made of plastic. Plastic material will build/store static electricity. There has to be a way to drain that electricity off of the plastic surfaces. The strange thing is that plastic will hold the static electricity but won't allow it to move/flow. The addition of a conductor (copper wire) provides a path for the static electricity to move/dissipate to ground.

 

Without grounding, you become that path and feel the shock. Just like sliding across a plastic car seat, in the winter, and touching the door handle. Or, walking across a carpet and touching a door knob. You build up 1,000s of volts from the friction. Then you discharge that electricity into the metal handle. This phenomenon is more prevalent in climates that are dry/cold.