20 amp circuits tripping, WTF?

[SS350Sport]

Need some help guys. Sorry for the long read but I'm lost.
I finished my detached 26 x 30 a few months ago. I have a 200 amp Square D service at the garage with UFER ground, neutral & ground tied, 100 amp breaker feeding the house (house had an existing 100 amp service, ground and neutral split). At the garage I have 3, 20 amp circuits, two of them have GFI's at the begenning of the run with 4 outlets each (20amp recepticles), the other 20 amp circuit feeds six T8 lights & the garage door opener. I bought a Miller 140 Autoset MIG welder (Input PowerRequires 1-Phase power 115 V, 20 Amps 60Hz Rated Output90A at 18 VDC, 20% duty cycle Welding Amperage Range 30 - 140 Amps) and have been using it off and on I used it one day for over a hour teaching my son to weld and there was a lot of starting and stopping along with varying the voltage. Afew days ago I bought a Dewalt 4 1/2" 10 amp hand held grinder. I plugged it in and pulled the trigger a few times to make sure it worked then started to use it after about 20 seconds the breaker tripped, the GFI stay engaged. I reset the breaker and continued using it for 30 min. or more no problems. This weekend I put a C Notch in my truck and was using the welder, grinder and a new Miller 375 X-Treme plasma cutter (Input Power115 - 230 V 1 Phase, Input Amperage Circuit Requirement A 120 volt, 20 amp (min.) - 30 amp recommended or 230 volt, 15 amp (min.) individual branch circuit, Rated Output at 104° F (40°C) 27 A at 92 VDC, 35% Duty Cycle (240 V input)). The welder and plasma cutter kept tripping the 20 amp circuit breakers on all three circuits. The tripping was not consistant sometimes it would trip right away and other times let me complete the cut or weld with out tripping. I checked all of the connections, they are tight. What would you guys suggest looking at?

 

[georgiadave]

Are you sure they are ground fault breakers? Arc fault breakers are notoriously sensitive.

 

[SS350Sport]

The GFI's are outlets. Outlets at the beggining of the circuit, per my inspector. The 3rd circuit DOES NOT have a GFI at all. The two GFI's are holding, it's the actual breaker in the service panel tripping.

 

[rinny_tin_tin]

Need some help guys. Sorry for the long read but I'm lost.
I finished my detached 26 x 30 a few months ago. I have a 200 amp Square D service at the garage with UFER ground, neutral & ground tied, 100 amp breaker feeding the house (house had an existing 100 amp service, ground and neutral split). At the garage I have 3, 20 amp circuits, two of them have GFI's at the begenning of the run with 4 outlets each (20amp recepticles), the other 20 amp circuit feeds six T8 lights & the garage door opener. I bought a Miller 140 Autoset MIG welder (Input PowerRequires 1-Phase power 115 V, 20 Amps 60Hz Rated Output90A at 18 VDC, 20% duty cycle Welding Amperage Range 30 - 140 Amps) and have been using it off and on I used it one day for over a hour teaching my son to weld and there was a lot of starting and stopping along with varying the voltage. Afew days ago I bought a Dewalt 4 1/2" 10 amp hand held grinder. I plugged it in and pulled the trigger a few times to make sure it worked then started to use it after about 20 seconds the breaker tripped, the GFI stay engaged. I reset the breaker and continued using it for 30 min. or more no problems. This weekend I put a C Notch in my truck and was using the welder, grinder and a new Miller 375 X-Treme plasma cutter (Input Power115 - 230 V 1 Phase, Input Amperage Circuit Requirement A 120 volt, 20 amp (min.) - 30 amp recommended or 230 volt, 15 amp (min.) individual branch circuit, Rated Output at 104° F (40°C) 27 A at 92 VDC, 35% Duty Cycle (240 V input)). The welder and plasma cutter kept tripping the 20 amp circuit breakers on all three circuits. The tripping was not consistant sometimes it would trip right away and other times let me complete the cut or weld with out tripping. I checked all of the connections, they are tight. What would you guys suggest looking at?

Obviously, you are overloading the breakers. Your breaker should be sized at 125% of your continuous load - so, for a 20A load, your breaker should be 25A anyway. Molded case circuit breakers (MCCBs) use an inverse time-current characteristic. Normally, a MCCB rated at 20A will eventually trip at 20A, but will take a longer time to trip than say at 25 A. Look at the trip curves that should have been packaged with your breakers and you will see that a 20A load is not indefinite. You may also have Chinese made breakers which are notorious for operating too near their rating - despite being UL listed.

The fact that your GFCIs are not tripping is a good sign.

For an auxiliary panel with a gnd rod fed from a main panel with split neutral/gnd and with its own gnd rod, I though you had to keep the neutrals/gnd split at the aux panel and no main gnding jumper?

 

[SS350Sport]

Thanks for the info. The breakers are Square D HOM. I'm suprised that the 10 amp Dewalt grinder would trip a 20 amp circuit.

 

[rinny_tin_tin]

Thanks for the info. The breakers are Square D HOM. I'm suprised that the 10 amp Dewalt grinder would trip a 20 amp circuit.

10 A is its continuous running current. Inrush current for a small motor can be six times its normal running current - so that perhaps coupled with too sensitive breakers can cause tripping. Feed the grinder via a 20A and see what happens then.

 

[ddawg16]

Make sure you have good breakers. Square D had a rash of counterfeit circuit breakers.

The below link is one of many about the problem.

Counterfeit Circuit Breakers

 

[Aceman]

Feed the grinder via a 20A and see what happens then.

He is? They're all 20 amp circuits....

I think you need to run some larger circuits for the equipment you're using. The circuit with the T8's on it(if they're 4 bulbers) draw an amp apiece for 6 amps total. Then you load it up with tools and it'll pop for sure.

If you had an amp clamp you could measure current to be sure that overloading(and not faulty breakers) is the problem.

 

[SS350Sport]

I picked up an AMPROBE (clamp type) from my father in law. I will look at the loading tomorrow.

 

[kenfath]

Are your GFI's rated for 20 AMPs? This sounds like a problem I had awhile back. The US made GFI's were stamped 20 AMPs but their package said they were 15 AMP. The air compressor would trip the 20 AMP circuit breaker. Replaced the GFI with a 20 AMP rated HF GFI and that solved the problem.

 

[SS350Sport]

Are your GFI's rated for 20 AMPs? This sounds like a problem I had awhile back. The US made GFI's were stamped 20 AMPs but their package said they were 15 AMP. The air compressor would trip the 20 AMP circuit breaker. Replaced the GFI with a 20 AMP rated HF GFI and that solved the problem.

I tried the welder and plasma cutter on the circuit with no GFI and that 20 amp breaker would trip as well. I'll get some actual AMP reading after work today and report back.

 

[rinny_tin_tin]

He is? They're all 20 amp circuits....

I think you need to run some larger circuits for the equipment you're using. The circuit with the T8's on it(if they're 4 bulbers) draw an amp apiece for 6 amps total. Then you load it up with tools and it'll pop for sure.

If you had an amp clamp you could measure current to be sure that overloading(and not faulty breakers) is the problem.

That is what I meant - run 30s, etc LOL

 

[SS350Sport]

Ok here are the results:
Miller 140 Autoset MIG = 1 Amp idling, 15 to 24 Amps while welding 3/16" full power.

Miller 375 X-treme Plasma cutter = 1 Amp idling, 18 to 30 Amps cutting 1/4" @ full power spiked to 41 at one point.

Dewalt 4-1/2" 10 Amp grinder = 6 to 24 Amps. 24 was bearing down on it HARD.

None of the breakers tripped today while running these tests. The three 20 amp circuits are all wired with #12 romex. What are my options?

 

[rinny_tin_tin]

Ok here are the results:
Miller 140 Autoset MIG = 1 Amp idling, 15 to 24 Amps while welding 3/16" full power.

Miller 375 X-treme Plasma cutter = 1 Amp idling, 18 to 30 Amps cutting 1/4" @ full power spiked to 41 at one point.

Dewalt 4-1/2" 10 Amp grinder = 6 to 24 Amps. 24 was bearing down on it HARD.

None of the breakers tripped today while running these tests. The three 20 amp circuits are all wired with #12 romex. What are my options?

Sounds like you should be running three 30A ckts instead of 20s - meaning, you will also need to upgrade your cable to #10.

 

[SS350Sport]

Do they make a 30 amp outlet that is layed out like the 20 amp outlets? or can I just use HD 20 amp outlets? I don't want to have to change plugs on the welder.

 

[mrb]

thinking out loud here:
I would open every box between the panel and the last outlet and see if you have any bad connections anywhere.

A 20amp breaker will hold for quite a while at 24a.

Its not the breakers, and its not your tools. Something else is wrong.

Also, measure the voltage as close as possible to the load, while under load. It is possible you have severe voltage drop from a bad utility connection somewhere.

 

[SS350Sport]

thinking out loud here:
I would open every box between the panel and the last outlet and see if you have any bad connections anywhere.

A 20amp breaker will hold for quite a while at 24a.

Its not the breakers, and its not your tools. Something else is wrong.

Also, measure the voltage as close as possible to the load, while under load. It is possible you have severe voltage drop from a bad utility connection somewhere.

I'll do that his weekend.

 

[mrb]

another thought, where did the breakers come from? Did you buy them off ebay a few years ago when there was that huge flood of counterfeit SQD stuff? At $5 a breaker, might make sense to just replace them to rule out the breakers being defective.

 

[SS350Sport]

Bought them at Electrical wholesale supply, A local electrical supplier. I'm pretty sure they are not counterfeit.

 

[Charles (in GA)]

The original poster said he is using Square D Homeline, and the counterfeit breakers were of the standard Square D QO series, not the Homeline series.

http://www.cpsc.gov/cpscpub/prerel/prhtml08/08151.html

Charles

 

[mrb]

The original poster said he is using Square D Homeline, and the counterfeit breakers were of the standard Square D QO series, not the Homeline series.

http://www.cpsc.gov/cpscpub/prerel/prhtml08/08151.html

Charles

good catch, thanks

 

[rinny_tin_tin]

Do they make a 30 amp outlet that is layed out like the 20 amp outlets? or can I just use HD 20 amp outlets? I don't want to have to change plugs on the welder.

No & No

Here are your choices

http://www.generatorjoe.net/html/web/outlet/quailplug.html

Perhaps you can rewire your equipment for 240, then you don't need to change out your cable - but then need to move to 2 pole breakers.

Your GFIs are fine, and your 20A breakers are fine and you won't find any miswiring. Your breakers are just overloaded.

 

[sberry]

If this is a dedicated circuit you can use a 20A outlet for a 120V welder with a 30A breaker without issue. A wire right from the panel to this labeled outlet, welder only. I wouldn't change the factory plug on the machine. When you modify a circuit for a dedicated tool like this you cannot have other outlets accessible for general use connected to it.
My chop saw is an example, 30 a breaker on a 12 wire and a 15A recept. After repeated starts it trips a 20 so its on its own modified circuit. This is a common issue with air comps, motors and 120V welding, sometimes you got to bite the bullet and run a wire and since I needed to do that its likely I would have anything running from 240V that I could.

 

[rinny_tin_tin]

If this is a dedicated circuit you can use a 20A outlet for a 120V welder with a 30A breaker without issue. A wire right from the panel to this labeled outlet, welder only. I wouldn't change the factory plug on the machine. When you modify a circuit for a dedicated tool like this you cannot have other outlets accessible for general use connected to it.
My chop saw is an example, 30 a breaker on a 12 wire and a 15A recept. After repeated starts it trips a 20 so its on its own modified circuit. This is a common issue with air comps, motors and 120V welding, sometimes you got to bite the bullet and run a wire and since I needed to do that its likely I would have anything running from 240V that I could.

Are you sure about that? A 20A receptacle is only listed for 20A max service

 

[walrus]

One might be able to run a 30 amp breaker on a piece of no. 12 for a dedicated motor circuit but I doubt its legal going to a 15 amp recept.

 

[Aceman]

210.21(B)1 Exc. 2
630.11(A)
630.12

These articles list the requirements for sizing conductors/breakers for welding receptacles.

IMO, the best way to handle this and get the full potential out of the machines is to convert them over to 240v if possible. Then run properly sized branch circuits for both of them and be done with it. To me, it looks like Miller tried to make both machines work on 120v for the hobby welder who isn't looking to run them at full output. For serious welding though, you really need the 240v to get the full potential out of them. Honestly, I don't think you'll be happy trying to make them work on 120v.