View Full Version : Getting shock from welder - 2 problems or 1?

07-13-2006, 10:33 AM
I was getting a mild shock from touching the frame of a TIG welder, even with it turned off. Obviously one problem is a short to ground. It would seem to me though that if it was properly grounded it would be impossible to get a shock. Yes or No?

Or could it be that a little resistance in the ground circuit would allow you a little tingle?

This welder just came back from being repaired after it caused the electrical box on the wall to catch on fire. It had melted the ground wire yet never blew a fuse. To me that indicates either too large a fuse or wiring too small. But I am not in maintenance so I was ignored on that subject.

07-13-2006, 10:35 AM
Red tag it and report it. Stop using it.

07-13-2006, 11:14 AM
A shock with the power off would indicate a problem in the incoming wiring, perhaps a strand of the hot wire touching the frame of the welder.

It would also indicate a problem in the integrity of the grounding system. Not only the welder needs to be inspected, but the wall box's grounding should be inspected. There is an open in the ground system somewhere.

07-13-2006, 11:18 AM
I did tag both the welder and the wall outlet.

07-13-2006, 06:30 PM
Red tag is good but I thik OSHA requires it be locked out with a key type lock if you know of an issue like this. Lock them both out. This way, the tag doesnt come up missing and if someone cuts the lock, they will get the brunt of the fine.

Just trying to keep us all safe.

As for the issue, call an electrican and have it looked over. Small price to pay for the avoidance of an injury.

Good luck

07-14-2006, 03:35 AM
Could be more than one problem. If there's juice on the case even when the power switch is off, there could be a problem with the wiring to the outlet for the welder. That would be if the black and white wires are backwards. This goes for 110 vac wiring. If the tig welder is 220 (probably) and the welders power switch doesn't switch both hot leads, then any short or conductive path is still free to put juice on the case. The only thing that's 'off' is the completed circuit to the welders transformer. If the power switch opens both hot leads, then troubleshooting is easier. Something between the welders power wire and the switch is allowing juice to flow to the case. Probably a damaged power wire, or grommet where it enters the case.

If the power switch only opens one hot lead, then anything within the welder that is wired has the potential (sic) to leak juice to anything that would conduct that juice to ground. If the outlet box is properly wired and the connections are good, then the fact that it burnt up says that the welder likely passed a lot of current through the ground wire. It's likely that a stray metal shaving got inside and is the culprit. It could be pretty much anything though, so if a good visual inspection doesn't show up somehting obvious, then it's a job for a repair person. I have to suggest in that case that this really isn't a job for a typical electrician , but more for an electronics tech.

Herm Williams
07-14-2006, 01:20 PM
Had that happer recently. the ground wire connector had come loose and shorted to a hot wire. direct connect to 440 on the case welded the overhead hoist cable to a punch press. no one hurt but the cable had to be replaced on the hoist. since that bypassed the machine circuit breaker the main 200 amp power was routed directly to ground. lot of arcs and sparks.

07-14-2006, 05:40 PM
I was getting a mild shock from touching the frame of a TIG welder, even with it turned off.

Unplug it and don't use it! This advice might save your (or someone else's) life!

This welder just came back from being repaired after it caused the electrical box on the wall to catch on fire.

Obviously the job isn't complete. If it were me, the machine would go back for them to do the job right.

Also, I'd check to see if the ground was good at the receptical. If not, and there is a fault, you don't have a pathway to ground. A breaker or fuse may not clear, and this could also be the cause of your fire.

07-14-2006, 06:28 PM
I am sure that every one who has worked in industry has a horror story or two like this. One place I worked found out that they had a neutral and hot wire switched in their system when a worker went to drill a hole in the head of a floor model drill press with a hand electric drill. As soon as he got a couple of inches away it drew an arc to the drill bit. That ruined the hand drill (welded some gears together) and the underwear of the man doing the work. In large plants, changes to the wiring sometimes get done in a hurry and potentially deadly mistakes are made. Shortly after that, they got a plug tester and checked all the 110vac outlets for this kind of thing and found several others.

Jim (KB4IVH)

07-14-2006, 09:38 PM
You have a open ground problem. If you have an Digital or analog volt meter with an Ohms scale it is easy to check. With the meterleads not touching the scale should be flashing or reading very high. Touch the meter leads together and the meter should read 0 or very close to 0, this indicates low resistance or a complete circuit. With the welder disconnected put one lead of the ohm meter on the plug ground lead and the other lead on the welder metal cover or screw, make sure it is a bare metal surface, the meter should read no more thn 1 ohm 0 is even better. If it reads more than 3 or 4 then you have a faulty ground in the welder. If it is close to 0 then the welder is ok. If so , then make sure the power is turned off at the circuit breaker and plug the welder into the plug and put one meter lead on the welder bare metal surface and put the other meter lead on a metal electrical box cover. The meter should again read 0 or close to it. If it does you have a faulty incoming power ground and you need to call an electrician. Just because you are not getting a tingle on other equipment does not indicate there is not a ground problem. Don't leave it unchecked, you can be electrocuted on less than one amp in the right circumstance, the floor is wet, you are sweaty and touch a good ground. I have been working in Medical Electrical/ Electronics for 35 years and I have been involved in investigations of electrical shock.