The welder and the GFCI.

Status
Not open for further replies.
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Call today about a GFCI receptacle tripping when a small portable welder was used. These small welders are used about everywhere and never had a problem we know of. When the ground lead was attached to the auger of the grain system the GFCI would trip within a second or two of the arc being struck. Remove the ground lead and attach it to an isolated plate, strike an arc and things are good. The welder was missing the EG prong from the cord...so I put a new cord end on. I had no real hope for that solution but it worked fine. Any one care to explain why?
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Call today about a GFCI receptacle tripping when a small portable welder was used. These small welders are used about everywhere and never had a problem we know of. When the ground lead was attached to the auger of the grain system the GFCI would trip within a second or two of the arc being struck. Remove the ground lead and attach it to an isolated plate, strike an arc and things are good. The welder was missing the EG prong from the cord...so I put a new cord end on. I had no real hope for that solution but it worked fine. Any one care to explain why?

No, but I'll stand by!:lol:

I really just wanted to comment on the thread title.
It sounded like the title of a book or short story.:)
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
With no reference to earth the GFI would not see any leakage to earth, so clamping to an isolated plate would not cause a trip..... like putting a GFI on a two wire circuit. You need an actual ground/earth fault to make it trip.

With the ground prong missing there would be a potential difference between neutral and earth; assuming there is a connection between the grain auger and earth. As such, in the case of every grain auger I have seen, it would be impossible to avoid.
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
With no reference to earth the GFI would not see any leakage to earth, so clamping to an isolated plate would not cause a trip..... like putting a GFI on a two wire circuit. You need an actual ground/earth fault to make it trip.

With the ground prong missing there would be a potential difference between neutral and earth; assuming there is a connection between the grain auger and earth. As such, in the case of every grain auger I have seen, it would be impossible to avoid.

I understand how the isolated welding would not trip the gfci...but not how adding an EG to the welder will prevent it from tripping the GFCI when the welding is not isolated.

The auger is part of a multi bin set up and I see no way how it could not be at the same potential as the neutral. To much steel let alone the EGs pulled to motors.
 

ELA

Senior Member
Occupation
Electrical Test Engineer
May not have anything to do with differential currents. But instead may have to do with high frequency radiated or conducted EMI.
The arc from a welder produces a broad band EMI emission.

High frequency interference has been known to nuisance trip a GFCI.


When you change the grounding path (and/or shielding effectiveness) the high frequency currents take different paths, or the amount of radiated and thus induced currents changes.
 

lakee911

Senior Member
Location
Columbus, OH
I would speculate that current from the welder was leaking through the floor causing the trip, but when you added the earth connection for the welder, it had a least path of resistance through the earth connection which the GFCI could then account for and not trip.


like putting a GFI on a two wire circuit. You need an actual ground/earth fault to make it trip.

Actually, that's not how a GFCI works. You can put GFCI protection on a 2-wire circuit (if you label it as such) and it will be just fine. You don't have your earth connection, but if your current-out doesn't equal your current-in plus or minus a small tollerance (roughly 5mA for personnel safety) it will trip.
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
May not have anything to do with differential currents. But instead may have to do with high frequency radiated or conducted EMI.
The arc from a welder produces a broad band EMI emission.

High frequency interference has been known to nuisance trip a GFCI.


When you change the grounding path (and/or shielding effectiveness) the high frequency currents take different paths, or the amount of radiated and thus induced currents changes.

Thank you.
 
Status
Not open for further replies.
Top