Welding Machine Grounding
- Thread starter Generic
- Start date
- Status
- Location
- Massachusetts
I would not ground the table and am not following your issue about the grinder.
- Location
- Massachusetts
Generic said:
That cable is not 'ground' it is 'work' and if I recall is not bonded to the buildings grounding system until someone attaches the clamp to a grounded item.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
If the ground cable from the welder isn't connected to anything will the welder work?
- Location
- Massachusetts
infinity said:
:smile:
Thats what I am pointing out.
If you leave the 'work' lead isolated there will be no complete circuit to any thing from the electrode lead.
Welding table
Welding table
I have seen a metal encased grinder laying on a metal table which has a conduit feeding a receptacle that is bolted to the table fry because the person forgot to attach the welding machine ground to the table and started to weld. I want to avoid this happening again, however the client wants to have the 110V receptacle mounted on the table and the table legs encased in the concrete floor.
Welding table
I have seen a metal encased grinder laying on a metal table which has a conduit feeding a receptacle that is bolted to the table fry because the person forgot to attach the welding machine ground to the table and started to weld. I want to avoid this happening again, however the client wants to have the 110V receptacle mounted on the table and the table legs encased in the concrete floor.
- Location
- Massachusetts
Well that is a problem.
There is no way to 'fix' what you see happening with grounding wire.
Why?
Keep in mind the transformer in the welder is the source of the welding current.
If you were to connect the table to the buildings grounding system and someone forgets to attach the work clamp to the work and the welder has an internal work to ground connection then the current path for the entire welder current would be through the buildings equipment grounding conductors and finally back up the supply cord of the welder.
How long do you thing the branch circuit grounding conductors will tolerate 100-200 amps of welding current?
Now that said I suspect there is something you overlooked when you saw the grinder fry.
Either the work lead was connected to something else grounded (like a nearby EMT, building steel, a water pipe, etc.) or the welder itself had a fault from case to the work lead in that case the path would be back through the branch circuit EGC to the grinder and through the table to the electrode.
It should not hurt anything to ground the table but grounding the table is not the answer for the condition you described.
The only way to make a permanent fix is to permanently connect a full sized lead from the table to the welders work lead.
You could do that in addition to the work clamp in case they need to weld off the table sometimes.
There is no way to 'fix' what you see happening with grounding wire.
Why?
Keep in mind the transformer in the welder is the source of the welding current.
If you were to connect the table to the buildings grounding system and someone forgets to attach the work clamp to the work and the welder has an internal work to ground connection then the current path for the entire welder current would be through the buildings equipment grounding conductors and finally back up the supply cord of the welder.
How long do you thing the branch circuit grounding conductors will tolerate 100-200 amps of welding current?
Now that said I suspect there is something you overlooked when you saw the grinder fry.
Either the work lead was connected to something else grounded (like a nearby EMT, building steel, a water pipe, etc.) or the welder itself had a fault from case to the work lead in that case the path would be back through the branch circuit EGC to the grinder and through the table to the electrode.
It should not hurt anything to ground the table but grounding the table is not the answer for the condition you described.
The only way to make a permanent fix is to permanently connect a full sized lead from the table to the welders work lead.
You could do that in addition to the work clamp in case they need to weld off the table sometimes.
Last edited:
Welding
Welding
Ok, I tried to simplfy the situation.
The entire situation:
There are 4 welding machines next to a wall. 5-10 feet away are 3 metal tables with metal legs encased in concrete. Each table has a 110V receptacle in a metal box bolted to the metal table fed with a conduit also in the floor encased in concrete. The client wants to be able to weld on any of the 3 metal tables with any of the 4 welding machines.
How would you wire this keeping in mind that the person may forget to attach the welding machine ground clamp. I thought the metal table could be permantly grounded to building steel and the welding machine frame also permantly grounded to the same spot of the building steel ground. However, doesn't that go against the FPN under welding machine secondary grounding section of the code (I'm going by memory, I don't have a code book with me). Also, what if more than 1 welding machine is in use at the same time? Sorry this is so long and confusing.
Welding
Ok, I tried to simplfy the situation.
The entire situation:
There are 4 welding machines next to a wall. 5-10 feet away are 3 metal tables with metal legs encased in concrete. Each table has a 110V receptacle in a metal box bolted to the metal table fed with a conduit also in the floor encased in concrete. The client wants to be able to weld on any of the 3 metal tables with any of the 4 welding machines.
How would you wire this keeping in mind that the person may forget to attach the welding machine ground clamp. I thought the metal table could be permantly grounded to building steel and the welding machine frame also permantly grounded to the same spot of the building steel ground. However, doesn't that go against the FPN under welding machine secondary grounding section of the code (I'm going by memory, I don't have a code book with me). Also, what if more than 1 welding machine is in use at the same time? Sorry this is so long and confusing.
- Location
- Massachusetts
In my opinion the safest and easiest method would be to attach a permanent full size lead directly from the table(s) to each of the welder(s) 'work' connection.
More than one welder could be used at the same time.
This FPN
Is reminding us that ideally the work lead should remain isolated from the buildings electrical system.
In your case, with the receptacle box mounted to the table it is not possible to remain isolated.
More than one welder could be used at the same time.
This FPN
Is reminding us that ideally the work lead should remain isolated from the buildings electrical system.
In your case, with the receptacle box mounted to the table it is not possible to remain isolated.
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
Not really if they're DC welders 
.
OTOH, the welding machine maunfacturer may have a problem with bussing the work/common terminal between multiple machines. (In theory, the welding current source should be completely isolated, so any "grounds" are created by the user. OTOH, I once saw someone park the machine in the 2nd floor garage of a building, drop a lead from the roof (12th fl) to the machine, and use the sprinkler pipe as the work lead. Good thing the building electrician didn't come around, that guy had a low idiot threshold.)
.OTOH, the welding machine maunfacturer may have a problem with bussing the work/common terminal between multiple machines. (In theory, the welding current source should be completely isolated, so any "grounds" are created by the user. OTOH, I once saw someone park the machine in the 2nd floor garage of a building, drop a lead from the roof (12th fl) to the machine, and use the sprinkler pipe as the work lead. Good thing the building electrician didn't come around, that guy had a low idiot threshold.)
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