Dust Collection grounding

[lcm1947]

I have been reading lately about needing to ground the DC. Anybody know anything about this or can refer me to some info on the subject? I have a HF DC but the instructions don't mention that grounding is needed or at least I don't remember them mentioning it. I roll the DC from machine to machine and use the black hose. I wonder if just the DC's that are hooked up to PVC and is permanent setups need this? Anybody.

[dlminehart]

The modern consensus seems to be that grounding is more an issue of personal comfort (no shocks to you) than safety (avoid explosions). Exploding dust collection systems are so rare as to be non-existent. The far bigger danger is starting a fire (often a delayed one) by getting a spark on some sawdust and then sucking it into the dust collector.

[LCHIEN]

quote:Originally posted by lcm1947

I have been reading lately about needing to ground the DC. Anybody know anything about this or can refer me to some info on the subject? I have a HF DC but the instructions don't mention that grounding is needed or at least I don't remember them mentioning it. I roll the DC from machine to machine and use the black hose. I wonder if just the DC's that are hooked up to PVC and is permanent setups need this? Anybody.

Pretty much your DC is grounded by the third wire in the power cord..

The problem with grounding is that the hoses are pretty much insulators and the air rushing through them at failry high velocity can build up static electricity on the hoses. Like rubbing the rubber stick on the rabbit fur in elemetary school.

Its not really dangerous. Just shocking. Not really enough energy to ignite anything.

[drumpriest]

This also then has to relate to the length of your runs. If you are using a portable or 1hp collector with nothing more than 10-20 foot runs, you are less likely to even get shocked, yes?

[JimD]

I have never been shocked by my DC. Fine Woodworking did a somewhat authoritative article a year or more ago that concluded that home DCs are very unlikely to ever have the right conditions to have an explosion. You would need bigger pipe than the typical 4 or 5 inch pipe of home systems. You have to have exactly the right concentration of dust and air and then you have to have a spark. A far more plausable issue would be a fire. Say you cut through a nail and the piece got sucked into the DC. It might be hot enough to ignite the collected dust. Even that is a pretty remote possibility. I put magnets at my floor sweep, however, to try and avoid sucking in metal that would impact the impeller of the DC (which is steel) and possible damage it or create a spark. I did not attempt to ground all my plastic pipe. It is not a bad idea to use metal pipe and ground it or run a ground wire through the inside of plastic pipe but I think it's overkill for a typical home system based upon everything I've read.

Jim

[LCHIEN]

quote:Originally posted by drumpriest

This also then has to relate to the length of your runs. If you are using a portable or 1hp collector with nothing more than 10-20 foot runs, you are less likely to even get shocked, yes?

I have not had a static probelm with my HF 2 HP DC connected to my BT3000 with 10 ft of 4" flex hose choked down to 2.5" at the saw.

I think the metal spiral in the saw, though not grounded directly, will dissipate static to some degree since static will jump a 1/4" gap with smallish amounts of static. thus relieveing itself before it gets too big.

I think the worst case may be those who use PVC pipe, that might build up a lot of static on a cool, dry day, but I don't think its dangerous, again.

[lcm1947]

Thank you gentlemen that puts my mind at ease. Just thought I'd better check on it though just in case. Again, thanks for the replies and help.

[gerti]

I use the DC hose to suck up the shavings from wood turning. If the weather is just right, and if I used dry (kiln dried) wood, and if the debris has just the right size, I might get a fairly mild shock from the hose.

Most articles seem to agree that a shop-size DC just isn't even remotely likely to produce the environment needed for a dust explosion.

So I'd agree with what has been said above, not really necessary.

Gerd

[lcm1947]

I wasn't so worried about getting shocked as I was about fire or blowing up so I'll just lay this worry to rest. Heck, a little shock is nothing.

[Roger109]

I have had worse shocks getting in and out of my car than I have had from my DC ducting.

[tfischer]

Just as a point of clarification -- since fire is mentioned several times in this thread:

If you suck up a spark (e.g. from cutting through a nail), having a perfectly grounded system is not going to help you. The only way it would help is if the spark were caused by static electricity -- and like others have said, this isn't likely to happen.

-Tim

[lcm1947]

Good point tfischer. Thanks.

[Jim-Iowa]

I have been studying this subject quite a lot.
There are arguements that not grounding is to risk fire.
And arguements that that is a lot of nonsense.
There is a very good scientific review on the subject on Bill P site, that states grounding will not effectively work in a pvc system.
I read that only two instances of home shop fire being attributed to static discharge. They were in Arizona & New Mexico, areas where there is very low humidity.
Low Humidity is never a problem in Iowa so I am not overly concerned.
And since I built Zero Boundary Fence in Housing developments in Austin back in 1984. I don`t think you will have to worry about low humidity there either.

[lcm1947]

Thanks Jim for your reply. And yes you are right we pretty much have high humidity here in Austin so if that is a factor then we shouldn't have to worry about it here. So it looks like a non-issue after all everybody's help. Appreciate it guys.

[LinuxRandal]

A friend of mine got a little paranoid after I believe it was a 20/20 story about a grain bin explosion. He said they used sawdust to demo some explosion. I missed the whole thing.
You would really have to cut a lot of wood at one time or let your dc go to build up an explosive charge, as most home runs are short enough that the dust doesn't stick around the pipe. But my friend said better safe then sorry, and he ran some old copper wire he had lying around to a ground connector on the cold water pipe of the house. I had told him about the old carpet tubes from the store next door to my work. He dumpster dived them and used them for the dc.