Shop Vac dust collection

[DickB]

Perhaps it would be best to first concentrate on the configuration that started this thread: a shop vac connected to a Carvewright. I myself strayed away from that with the reference to PVC - sorry.

I suggest that there are three reasons to consider grounding:

1. Equipment damage: prevention of ESD (electrostatic discharge) damage, particularly to the Carvewright.
2. Safety: prevention of fire or explosion.
3. Comfort: prevention of a static shock to one's person.

Anyone who has used a shop vac to collect sawdust can attest that static electricity is generated. This is caused by the sawdust particles moving through the shop vac hose.

Regarding point 1, static charge collecting on the hose can be transferred to the Carvewright. Sawdust moving within the Carvewight itself may also generate a static charge. Without additional grounding, charge can accumulate since the ground on the power plug is not electrically connected to the machine's metal frame and head. An external ground wire added to the machine and/or head can provide a path for static charge to be dissipated, reducing the chance of a damaging ESD event to the machine. This would I suggest include an externally-induced charge, such as when opening the cover to change bits, even if no vacuum system were employed.

There have been anecdotal reports on this forum of users who have experienced electronics failures of their Carvewright machines using ungrounded shop vac setups, and those who have experienced no failures using the same setup. This does not surprise me. However, static electricity is definitely generated in the shop vac hose. In my view, grounding the Carvewright to drain off any potential static charge is a wise preventative move.

Now on point 2, I do not believe that there is a significant risk of explosion or fire in using a shop vac. Millions are sold and in use, connected to other equipment or not, and incidences are rare - I don't believe that I've ever heard of one. If it were necessary for shop vacs and hoses to be grounded for safety reasons, certainly manufacturers would do that. If you read 200k's reference, it also comes to the conclusion that the use of PVC does not present a significant safety risk.

On point 3, 200k's reference suggest that this is the reason to run a ground wire inside the hose or PVC. I'll not repeat the reasoning here, but note that it is argued that an internal ground wire does not eliminate static charge, but rather provides a shorter path to ground for an electrical discharge, making contact with a spark less uncomfortable. Again, back to the shop vac application, due to the length of hose, an internal ground wire is probably not required for comfort reasons.

I understand that the code that I cited does not apply to home shops. I did not intend to imply that it does, sorry for any confusion. I intended only to cite it as a reference regarding the effectiveness of a bare copper wire in a PVC pipe in eliminating static discharge. I believe it not recommended in large commercial applications because it is not effective at eliminating static charge under conditions where explosion may be possible.

In any case, the statement that a bare copper ground wire needs to run through the hose where it is in contact with the moving dust particles to be effective is not technically accurate, and that was meant to be the gist of my earlier post.

[fwharris]

Perhaps it would be best to first concentrate on the configuration that started this thread: a shop vac connected to a Carvewright. I myself strayed away from that with the reference to PVC - sorry.

I suggest that there are three reasons to consider grounding:

1. Equipment damage: prevention of ESD (electrostatic discharge) damage, particularly to the Carvewright.
2. Safety: prevention of fire or explosion.
3. Comfort: prevention of a static shock to one's person.

Anyone who has used a shop vac to collect sawdust can attest that static electricity is generated. This is caused by the sawdust particles moving through the shop vac hose.

Regarding point 1, static charge collecting on the hose can be transferred to the Carvewright. Sawdust moving within the Carvewight itself may also generate a static charge. Without additional grounding, charge can accumulate since the ground on the power plug is not electrically connected to the machine's metal frame and head. An external ground wire added to the machine and/or head can provide a path for static charge to be dissipated, reducing the chance of a damaging ESD event to the machine. This would I suggest include an externally-induced charge, such as when opening the cover to change bits, even if no vacuum system were employed.

There have been anecdotal reports on this forum of users who have experienced electronics failures of their Carvewright machines using ungrounded shop vac setups, and those who have experienced no failures using the same setup. This does not surprise me. However, static electricity is definitely generated in the shop vac hose. In my view, grounding the Carvewright to drain off any potential static charge is a wise preventative move.

Now on point 2, I do not believe that there is a significant risk of explosion or fire in using a shop vac. Millions are sold and in use, connected to other equipment or not, and incidences are rare - I don't believe that I've ever heard of one. If it were necessary for shop vacs and hoses to be grounded for safety reasons, certainly manufacturers would do that. If you read 200k's reference, it also comes to the conclusion that the use of PVC does not present a significant safety risk.

On point 3, 200k's reference suggest that this is the reason to run a ground wire inside the hose or PVC. I'll not repeat the reasoning here, but note that it is argued that an internal ground wire does not eliminate static charge, but rather provides a shorter path to ground for an electrical discharge, making contact with a spark less uncomfortable. Again, back to the shop vac application, due to the length of hose, an internal ground wire is probably not required for comfort reasons.

I understand that the code that I cited does not apply to home shops. I did not intend to imply that it does, sorry for any confusion. I intended only to cite it as a reference regarding the effectiveness of a bare copper wire in a PVC pipe in eliminating static discharge. I believe it not recommended in large commercial applications because it is not effective at eliminating static charge under conditions where explosion may be possible.

In any case, the statement that a bare copper ground wire needs to run through the hose where it is in contact with the moving dust particles to be effective is not technically accurate, and that was meant to be the gist of my earlier post.

Dick,
Very well stated sir!

[mcQ]

The fact that to be effective a bare wire needs to run through the duct work and hose did not just come from me.
Every ground kit sold whether from Rockler, Shop Fox, Grizzly, Woodcraft all have instructions that the wire must run through the hose and duck work to be effective.
See the attached instruction sheet I copied from Rocklers site and posted earlier today.
I would trust that the companies manufacturing and selling dust collection equipment including the ground kits are more knowledgeable than most of us.
Why not just follow these manufactures instructions running the wire inside and if you want go ahead and also wrap the outside for extra insurance.

[DickB]

We seem to be repeating ourselves. I'm not arguing that the aforementioned grounding kits are not effective at reducing static discharges to the person. I am asserting that they are not necessary or effective for explosion or fire reasons. I am also asserting that they do not work on the principle of dust particles coming in contact with the copper wire.

[mcQ]

Regardless of how the ground works they are effective at reducing static discharges to both a person as well as the CarveWright machine and because of this are a good precaution to prevent damage from static.
Also, I see no reason not to install the ground kit per the instructions included in the kit.