Dust Collection Grounding

ScottR

ScottR

AzB Silver Member
Silver Member
As an amateur woodworker, I have read and heard conflicting viewpoints about whether a central dust collection system needs to be grounded to prevent static electricity fires.

I'd really appreciate the thoughts of all of you guys with years of experience. Do you ground your duct work? Thanks in advance.
 
ScottR said:
As an amateur woodworker, I have read and heard conflicting viewpoints about whether a central dust collection system needs to be grounded to prevent static electricity fires.

I'd really appreciate the thoughts of all of you guys with years of experience. Do you ground your duct work? Thanks in advance.
Click to expand...

No, I use PVC duct work and tried grounding to the collecter by running copper wire but what I found is all that it did was to clog up my duct work about every two minutes. Since PVC and ABS are insulaters it does no good to run the wire on the outside of the pipe. I started reading articles on the subject and most said that theoretically static electricity could start a fire, but that actually, there has never been a documented case where this has happened. I've been using my system for over ten years with no problems.

Dick
 
If you run metal pipe instead of plastic there is no need for a ground wire. I use a flexible pipe with wire reinforcement for the connection to the machine. Just bare the wire so that it makes contact with metal, beter safe than sorrry. Jim
 
Scott to anser you'r ? all dust collectors should be grounded regardless plastic or metal check wood working mags or e mail one they can help... It's really important and does't cost much considering the alternative....RAY p.s. you'r avatar is great.....
 
I am using a cyclone Tempest for over a year without grounding, never had a problem. Haley had told me that he didn't think it was an issue, and only clogs the pipes. I went without grounding and have had no issues.

How good is your shop insured?

:-)
 
The thing is, like Dick says above, I have never heard or read of any actual cases of fire from dust collection static electricity. I understand it in theory and I also know that it is inexpensive to do. On the down side, many people have talked about the grounding wire clogging their ducts.

Sometimes you can't find one right answer, huh?

p.s. Mr. Petree . . . . what's insurance??? :p
 
rhncue said:
No, I use PVC duct work and tried grounding to the collecter by running copper wire but what I found is all that it did was to clog up my duct work about every two minutes. Since PVC and ABS are insulaters it does no good to run the wire on the outside of the pipe. I started reading articles on the subject and most said that theoretically static electricity could start a fire, but that actually, there has never been a documented case where this has happened. I've been using my system for over ten years with no problems.

Dick
Click to expand...

Dick, it is true that PVC is considered as an insulator to normal electricty but what causes the problem with dust colectors is Static Electricty.
PVC is excellent for generating this type of electricty.
Dry wood dust moving thru the PVC tubes can build up a heafty charge and a static spark in the wrong place at the wrong time could cause an explosion or fire.

The best tube to use is either metal or the soft plastic stuff with the wire embeded in it.
Both types can be grounded to prevent the build up of a charge.

I often feel the discharge when I am using the shop vac to clean wood dust off my equipment and happen touch a grounded piece of metal.
The hose is plastic but it sure does a good job of making and conducting that charge.

But ... like another guy said ... it aint a problem till it happens.
 
ScottR said:
The thing is, like Dick says above, I have never heard or read of any actual cases of fire from dust collection static electricity. I understand it in theory and I also know that it is inexpensive to do. On the down side, many people have talked about the grounding wire clogging their ducts.
Sometimes you can't find one right answer, huh?
p.s. Mr. Petree . . . . what's insurance??? :p
Click to expand...

Why run the ground wire on the inside???
Wrap it around the outside one loop about every two feet or so.

Insurance?
That is something you think you have until you need it!

Willee
 
WilleeCue said:
Why run the ground wire on the inside???
Wrap it around the outside one loop about every two feet or so.

Insurance?
That is something you think you have until you need it!

Willee
Click to expand...

Wire on the outside only protects you from getting a small shock when you come in contact with it (at least for pvc). To prevent static buildup from arcing on the inside, the wire must be run on the inside and should grounded at both ends. The inside of the system is where most of the fuel source would be ie dust cloud, small wood particles, and where the theoretical hazard lies.

The potential hazard of cutting through a piece of metal and creating a hot ember that smolders within the collection system and starts a fire may be higher than the static discharge theory. I think there are 2 or 3 documented cases of fires caused from this type of hazard, but none from the static discharge.

Even if conditions were right for an arc, what would be the fuel source? Some people don't buy into the combustion of a dust cloud. You guys don't soak your coco in gasoline do you? turning fronts from righ lightered pine stumps?

Would the odds of a cue maker cutting a couple of fingers off while he is alone in his shop and nearly bleeding to death before getting to the hospital be greater than the odds of the never documented static dust cloud fire/explosion? How many here use metal gauntlets while cutting wood?

Just more thoughts from someone who just bought a big dust collector and hasn't yet decide which way to go himself...

Kelly
 
WilleeCue said:
Why run the ground wire on the inside???
Wrap it around the outside one loop about every two feet or so.

Insurance?
That is something you think you have until you need it!

Willee
Click to expand...

Willee, I understand about static electricity. That is the reason that I said that PVC or ABS or any other type plastic is an insulater. Since it is an insulater the grounding wire must be run on the inside of the pipe where the static electricity is occuring for a ground to be of any use. Wrapping a wire around the outside of the pipe does not help at all as the plastic insulater ( the walls of the pipe itself ) are between the static and the ground.

Dick
 
WilleeCue said:
Why run the ground wire on the inside???
Wrap it around the outside one loop about every two feet or so.

Insurance?
That is something you think you have until you need it!

Willee
Click to expand...
I was kidding about the insurance. Honestly! :D
 
rhncue said:
Willee, I understand about static electricity. That is the reason that I said that PVC or ABS or any other type plastic is an insulater. Since it is an insulater the grounding wire must be run on the inside of the pipe where the static electricity is occuring for a ground to be of any use. Wrapping a wire around the outside of the pipe does not help at all as the plastic insulater ( the walls of the pipe itself ) are between the static and the ground.

Dick
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Dick, it is true that the charge is generated on the inside of the pipe by the sawdust brushing the PVC but the fact is if you touch the outside of it you still get a zap.
How do you supose the charge gets from the inside to the outside if the PVC is a good insulator?
I think the explanation has someting to do with high voltages not acting the same way low voltages do.
A grounded wire wraped around the outside will drain the static charge just as good as one ran inside the PVC pipe.

Kelly_Guy, I think there has been plenty of documentation that flamable dust in the air at the right ratio will ignite with great gusto.
Grain elevators have exploded because of dust clouds.
 
While we are talking about dust fires, has anyone ever noticed that sometimes bandsawing hardwood you get smoke?
I often worry about a smoldering bit of wood entering my dust collecting system and setting the saw dust in the collector on fire.
The real worry is that it would smolder for hours and unoticed before breaking out in flames at two o'clock in the morning.
 
WilleeCue said:
While we are talking about dust fires, has anyone ever noticed that sometimes bandsawing hardwood you get smoke?
I often worry about a smoldering bit of wood entering my dust collecting system and setting the saw dust in the collector on fire.
The real worry is that it would smolder for hours and unoticed before breaking out in flames at two o'clock in the morning.
Click to expand...
I've never noticed smoke when bandsawing. I'll pay closer attention.
 
WilleeCue said:
Dick, it is true that the charge is generated on the inside of the pipe by the sawdust brushing the PVC but the fact is if you touch the outside of it you still get a zap.
How do you supose the charge gets from the inside to the outside if the PVC is a good insulator?
I think the explanation has someting to do with high voltages not acting the same way low voltages do.
A grounded wire wraped around the outside will drain the static charge just as good as one ran inside the PVC pipe.

Kelly_Guy, I think there has been plenty of documentation that flamable dust in the air at the right ratio will ignite with great gusto.
Grain elevators have exploded because of dust clouds.
Click to expand...
Aren't grain elevator fires/explosions caused by the build up of heat, not static electricity? Or were you just speaking about the flammability of airborn dust?
 
WilleeCue said:
Dick, it is true that the charge is generated on the inside of the pipe by the sawdust brushing the PVC but the fact is if you touch the outside of it you still get a zap.
How do you supose the charge gets from the inside to the outside if the PVC is a good insulator?
I think the explanation has someting to do with high voltages not acting the same way low voltages do.
A grounded wire wraped around the outside will drain the static charge just as good as one ran inside the PVC pipe.

Kelly_Guy, I think there has been plenty of documentation that flamable dust in the air at the right ratio will ignite with great gusto.
Grain elevators have exploded because of dust clouds.
Click to expand...

Of all the sources that talk about grounding PVC that I have read, even the ones who feel it is a waste of time say if there is a real hazard, the grounding wire must be run on the inside.

No insulator is perfect, and over time voltage leakage will charge the outside of the PVC. You are a conductor, and when you come in contact with it you get the arc. Even if that discharge is enough to overcome the insulation of the PVC and affect the charge on the inside, that is not the same as the grounding wire on the outside. A grounding wire wrapped around the outside will keep you from getting the little shocks by keeping the buildup from happening on the outside, but it will not keep the buildup from happening on the inside. Too much insulation to achieve that.

I did not know that about grain elevators, thanks.
Kelly
 
ScottR said:
Aren't grain elevator fires/explosions caused by the build up of heat, not static electricity? Or were you just speaking about the flammability of airborn dust?
Click to expand...

The airborn dust inginted by a spark from any source is what I was refering to.
Could be someone striking metal with a hammer, equipment starting up, faulty electrical wiring, or even a static discharge.

In the case of dust collectors it is static electricty that most likely makes the spark.
 
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