TIG tripping 120v GFCI when running 240v

[Dad Was A Racer]

Here's the details:
1. 2017 Miller Syncrowave 210 running DC TIG process @ less than 125amps
2. New shop building constructed in January this year, all fresh construction
3. LED overhead lighting hard-wired (no plugs) on dedicated circuit with GFCI breaker (code?)
4. Welder runs on dedicated 50a 240v circuit.

So here's what happens... When I try to TIG weld (1/8" stainless @ 125a DC) with the welder running on the dedicated 240v circuit, as soon as I "hit the gas" and ramp up the amps on the welder, the GFCI breaker on the lights' circuit trips and puts me in the dark.

If I switch the welder over to 120v (multi voltage plug), it doesn't trip the GFCI. I ran a loooong string of extension cords from the house to the shop and ran the welder off the house 120v and no GFCI trips.

So by my crude process of elimination, I would state that the welder is tripping the 120v GFCI breaker (only this one circuit) only when plugged into the 50a/240v outlet.

I'm aware of RFI produced by TIG machines, but why would this only be affecting the GFCI breaker that's on a different circuit than the 240v outlet, and not affect the GFCI when running on 120v?

 

[wyliesdiesels]

Are the lights hardwired or cord and plug connected to outlets?

If hardwired, then i have easy solution.

Switch GFCI breaker to regular breaker, then install GFVI outlet on first outlet in line of outlets.

 

[LXCam]

Did he run a dedicated ground to the welding recep, or just bond to the box?

 

[Dad Was A Racer]

Are the lights hardwired or cord and plug connected to outlets?

If hardwired, then i have easy solution.

Switch GFCI breaker to regular breaker, then install GFVI outlet on first outlet in line of outlets.

Lights are hard-wired.

 

[Dad Was A Racer]

Did he run a dedicated ground to the welding recep, or just bond to the box?

Need to check...

 

[wyliesdiesels]

Lights are hard-wired.

Lights dont need to be GFCI protected then.

Put them on a regular breaker.

And if you have enough lights to break them into 2 or more banks then i would do that and put them on separate breakers that way if one trips you have the other and are not left in the dark.

 

[Matt Matt]

My TIG welder I has a very similar odd pulse to it.

For many years it ran fine with no problems. Or no problems that I noticed. About eight years ago when I put in my RPC I wanted a little extra production, so I installed a ground fault circuit breaker. Every time I went to DC TIG it would Trip it at 150A. About five years ago I got one of those fancy touch taps made by moen. I found when I went to DC TIG and I hit about 150 A or higher my tap in the kitchen would turn on.

I have since put the welder on its own circuit with out ground fault. But the tap/faucet sometimes still turned on. I pulled the batteries from the faucet... i’ve been running trouble free for about four years. I think there was a small amount of DC current being sent into my ground.

 

[AntonLargiader]

That's super interesting. Just to fill out the info a bit more:

- what happens if you weld 120V from the wall outlets rather than from the house?

- you are definitely getting GFCI trips and not overload or AFCI trips, right? Just confirming.

- If you turn off the lights, do you still get the trip?

 

[Roundhouse]

I’d switch the GFI breaker to a normal one and if you have any outlets near water , replace those individual outlets with GFI outlets

 

[AntonLargiader]

Maybe in a wood shop it's different, but I would leave all of the receps on GFCI. In most fabrication environments there's a good risk of cross-chest shock with a bad tool and a metal workbench.

 

[Dad Was A Racer]

That's super interesting. Just to fill out the info a bit more:

- what happens if you weld 120V from the wall outlets rather than from the house?

- you are definitely getting GFCI trips and not overload or AFCI trips, right? Just confirming.

- If you turn off the lights, do you still get the trip?

Anton, no, it does not trip the GFCI breaker when running on 120v, whether from an outlet in the shop that's on the same panel, or from the house which is on a separate panel/transformer/etc. It only trips when running on the 240v shop feed.

The breaker trips off and I have to reset the handle. I cannot tell you if that's from a ground fault or an overload situation, as I do not know how to distinguish the two.

I need to turn the lights off and try the welder on 240v to test your theory...

 

[steel 35]

Wish I had a good answer.
I had the same thing except it was a dedicated 110 outlet for a freezer running through the same wall about 10" separation, Square wave 220 Only.
I learned to check GFCI every time I used the tig and it only happened like you say doing Stainless.
Good luck.

 

[Dad Was A Racer]

I have done some more tests and eliminated some questions and errors in my original assessment... The lights are on their own circuit, but protected by a GFCI breaker. I have no idea why lights need a fault-protection circuit, and I assume that code requires it. I have THREE 50a/240v plugs in my shop that are all on the same circuit. I tried plugging the welder into the other outlets and get the same response, step on the gas, it trips the breaker on the lights. Since the lights and the welder are on two separate circuits, one's 120v, the other 240v, and it ONLY trips the GFCI when the welder is running on 240v (not on 120v), I can safely assert that the issue is in the 240v circuit. But why would it trip the 120v GFCI on the lights, and not trip the 240v welding circuit if there was in fact a short of some kind?

 

[MoonRise]

On 120V input the Syncrowave (or any other 120/240V dual input welder) is limited on the output power.

The welder will only give you 'full' power on 240V power.

On 120V input, the Syncro will only go to 125 amps in TIG mode and 90 amps in DC stick mode.

On 240V input, it will go to 210 amps in TIG mode and 150 amps in stick mode.

Without running some type of oscilloscope monitoring on the lighting circuit, or some pretty sensitive voltage monitoring (as in tracking a 5 millivolt RFI-induced voltage signal among the 120V GFCI circuit), I would suspect you are dealing with some induced voltage on the 120V circuit from the welder's high-frequency arc start.

See pages 30-something (depending on your machine's serial number) in the manual on HF interference and some possible ways to minimize it.

 

[wyliesdiesels]

I have done some more tests and eliminated some questions and errors in my original assessment... The lights are on their own circuit, but protected by a GFCI breaker. I have no idea why lights need a fault-protection circuit, and I assume that code requires it.

As i previously explained, hardwired lights do NOT need to be GFCI protected.

You could remove the GFCi breaker and put a regular breaker in its place.

What brand of breakers do you have BTW?

I have THREE 50a/240v plugs in my shop that are all on the same circuit. I tried plugging the welder into the other outlets and get the same response, step on the gas, it trips the breaker on the lights. Since the lights and the welder are on two separate circuits, one's 120v, the other 240v, and it ONLY trips the GFCI when the welder is running on 240v (not on 120v), I can safely assert that the issue is in the 240v circuit. But why would it trip the 120v GFCI on the lights, and not trip the 240v welding circuit if there was in fact a short of some kind?

A GFCI does not care about shorts. The only thing a GFCI cares about is current balance between hot and neutral. If there is a short between the hot and neutral wont care or trip. This is because GFCIs are not OCPDs

However, you have a GFCI breaker and so you its a little more complicated.

 

[KenC]

Are the conductors for the two circuits near each other for any appreciable difference?

Thinking an inductance issue maybe? High current flow on the 240v is creating an inductance current on the 120v line.

I agree with just replacing the GFCI breaker with a normal one as it's not needed. Or, just for fun move it to the other buss in the box, and/or reroute the wiring in the box to get max seperation between the two circuits.

 

[Mavigogun]

I wonder how this resolved. It’s not uncommon for folks to confuse the neutral and ground- maybe a contributor?

 

[ssdave]

.....

 

[wyliesdiesels]

My guess why it happens on 240 and not on 120, is that on 120 it's on the opposite leg than the lights, so no current carrying conductors in common.

On 240, it's on both legs, and thus has to have a common connection to the lighting. An alternate explanation is that the additional power on the 240 volt circuit makes the tig change what it is putting out for RF interference, and that is the difference why it doesn't happen on 120.

The welder is inducing a current somehow in the lighting circuit, which the GFCI interprets as a mis-balance, and trips on. Tig is known to interfere with sensitive electronics, so this should not be a surprise.

As already explained, just take out the GFCI on the lights. Not required by code or for safety, if only the lights are on the circuit.

If the lights plug into a receptacle then a GFCI is required. only way around this is to hardwire the lights.

 

[Samh]

Had something similar at my old shop with my syncrowave 350. One thing I did that lessened it, was making sure my points were adjusted within spec. Made it less likely to happen, but still did. I had wondered if mine was due to the proximity of the welder the that specific gfci, as it didn’t do it to the other two in the shop.