electricdist
Member
Why does a tig welder operating at 240v 4 wire system trip the gfci receptacles(general purpose 120v) as soon as arc is drawn?
tig welder kicking gfci receptacles
- Thread starter electricdist
- Start date
- Status
Re: tig welder kicking gfci receptacles
So the welder isn't plugged into one of the receptacles it trips?
I'm taking a guess here, but if you are welding something connected to the building ground, and if there is a second neutral-ground bond somewhere, then some of the current from the welder might find its way back through the receptacle's neutral, tripping the GFI.
Steve
So the welder isn't plugged into one of the receptacles it trips?
I'm taking a guess here, but if you are welding something connected to the building ground, and if there is a second neutral-ground bond somewhere, then some of the current from the welder might find its way back through the receptacle's neutral, tripping the GFI.
Steve
john m. caloggero
Senior Member
Re: tig welder kicking gfci receptacles
Steve, sounds like a the correct answer.
Steve, sounds like a the correct answer.
electricdist
Member
Re: tig welder kicking gfci receptacles
No,the welder is plugged into a single circuit that operates at 240v,it has nothing else on that circuit.
I assume there is enough leakage thru the welders circuit coming back thru the ground ,that the GFCI senses that causing those to trip.Just needed someone to confirm that.Thanks
No,the welder is plugged into a single circuit that operates at 240v,it has nothing else on that circuit.
I assume there is enough leakage thru the welders circuit coming back thru the ground ,that the GFCI senses that causing those to trip.Just needed someone to confirm that.Thanks
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: tig welder kicking gfci receptacles
First of all, why would you assume there is any leakage current flowing anywhere?
Secondly, the GFCI only senses current in the phase and neutral conductors of the circuit that it is serving. It does not sense current in any equipment grounding conductor. It does not even need an EGC to protect its circuit.
Finally, in order for the GFCI to trip, it has to "believe" that there is a difference between the current flowing in its phase conductor and the current flowing in its neutral conductor. I can think of three ways that can happen. Steve mentioned one of them. But that relies on a wiring error being present somewhere in the building. The second is if there really is a ground fault present in the circuit that the GFCI is protecting. But that would trip the GFCI every time you turn it on, not just when you run the welders. The third way, and the one my money is on, is the large magnetic impulse from the welder interferes with the magnetic pick up coils of the GFCI device, and fools the device into believing that there is a fault in its own circuit.
Did you notice that you did not get confirmation?
First of all, why would you assume there is any leakage current flowing anywhere?
Secondly, the GFCI only senses current in the phase and neutral conductors of the circuit that it is serving. It does not sense current in any equipment grounding conductor. It does not even need an EGC to protect its circuit.
Finally, in order for the GFCI to trip, it has to "believe" that there is a difference between the current flowing in its phase conductor and the current flowing in its neutral conductor. I can think of three ways that can happen. Steve mentioned one of them. But that relies on a wiring error being present somewhere in the building. The second is if there really is a ground fault present in the circuit that the GFCI is protecting. But that would trip the GFCI every time you turn it on, not just when you run the welders. The third way, and the one my money is on, is the large magnetic impulse from the welder interferes with the magnetic pick up coils of the GFCI device, and fools the device into believing that there is a fault in its own circuit.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: tig welder kicking gfci receptacles
I'm with your third one too as if the service has any kind of a voltage drop when the tig is arcing, this high frequency event will show an imbalance in the current coils, GFCIs are design (newer ones) to filter out short duration HF events but any long term event as in the welding it will see as a fault and trip. The reason they have the time delay (u sec's) is to filter nuisance tripping from normal switched motor and coil loads, but in electrical terms a second is a long time and it cant filter out it or it would also filter out a ground fault.
I'm with your third one too as if the service has any kind of a voltage drop when the tig is arcing, this high frequency event will show an imbalance in the current coils, GFCIs are design (newer ones) to filter out short duration HF events but any long term event as in the welding it will see as a fault and trip. The reason they have the time delay (u sec's) is to filter nuisance tripping from normal switched motor and coil loads, but in electrical terms a second is a long time and it cant filter out it or it would also filter out a ground fault.
electricdist
Member
Re: tig welder kicking gfci receptacles
This is not my problem,I am asking this question for someone else, so I really don't have the particulars.I am trying to resolve his situation so he can still use his GFCI protected circuits.
Some welders operate with reversed polarity,could this be an issue?
This is not my problem,I am asking this question for someone else, so I really don't have the particulars.I am trying to resolve his situation so he can still use his GFCI protected circuits.
Some welders operate with reversed polarity,could this be an issue?
- Status