120 volt plasma cutter trips breaker

[3rdgendslmech]

Hey guys a while back I bought a Cornwell plasma cutter for a little body work project on my truck. It worked fine as most of the cuts were pretty short. It's a 16Amp output and you have give it an air supply.
I noticed the other day (this also happened one other time) that if you're cutting thicker metal 1/4 to 3/8 you can only cut about 3-4 inches before it trips the breaker.
Right now I'm in the middle of replacing some wear plates on a skid steer bucket and I'll only cut 2 or 3 inches and let the torch cool. It works, I really need to upgrade to a bigger machine since I've gotten into some bigger jobs.
The circuit in my pole barn it's running off of is 20 amp 12 gauge wire probably about 25-30 feet from the panel.
Should I run a dedicated circuit with 10 gauge wire and use a 10 gauge extension cord?

 

[sberry]

It really doesn't need a bigger wire, it needs a bigger breaker.

 

[alfredeneuman]

There might some additional info in the manual. If not, why don't you ask them for a solution? I doubt that you are the only guy that's had that problem.
http://corporate.cornwelltools.com/Contact_Us/Contact_Us.php

... after all the problem might be with the plasma cutter itself

 

[Captain Spaulding]

Input power is 20A at 120V. No surprise the breaker trips.

 

[sberry]

There isn't any good way to do this. You can try a 30 and see if it holds its own thermal but,, this should be on a dedicated circuit and not used for other tools. My helper wired it and used 10 wire and a 30, I would have used 12, the 10 just lets it hog more power. It's the only circuit in the place like it. I forgot it was there testing a welding machine a while back, would have tried it.

 

[Lassen Forge]

Don't replace the breaker with a higher ampacity rated one without first replacing the wire... the breaker is there to protect your building wiring - too many amps through insufficient wire, and that wire heats up.

 

[sberry]

The wire won't overheat, it's a calculated load with limited duty cycle. The main concern is restricting this modified circuit to this tool, unsafe to use other equipment on it.

 

[nadogail]

IMHO, the plasma cutter will work better on a dedicated circuit.

 

[sberry]

It would t work any better on a dedicated than a general provided the general doesn't have otheroad on it. What/where the dedicated is good is that any modification to it is to one outlet.

 

[3rdgendslmech]

I'm gonna run a dedicated circuit with 10 gauge wire and a 25 amp breaker and see what happens. I'm not really a fan of using a 30 amp breaker on 12 gauge wire. At the time nothing else was on this circuit. I'm guessing it's too long of a run.
If I get a little bit of time I'll put my meter on it and see how many amps it's pulling when I'm cutting.

 

[sberry]

The issue is the outlet. It can be used with other equipment. In some circumstances 12 wire [in pipe, 10 cable] can be used to 50A for welding equipment. A 30 is good on a 12 for this, some 14 in pipe is allowed. The 10 won't hurt.

 

[sberry]

The machine will burn up before it overheats the wire in this case. The reason the 20 is on a 12 for genergy circuits is there is multiple outlets, example would be 2 heaters plugged in to different recepts on the same wire. They can run continious, would overheat it,, or could. With a wire to a dedicated outlet it's the applied load,, the calculated load that protects it, the breaker simply becomes an off/on and short circuit interuption. Assuming a single outlet, either 15 or 20,, a correctly wired appliance can't overload the wire.

 

[3rdgendslmech]

I didn't get a chance to use play with it much today. I fired up my big welder and air arced the last 4 feet of weld.
What I did look at was the cord from the machine is made of 14 gauge wire.

 

[AngryBeaver]

a 20 amp thermal breaker is only good for 16amps continuous use. that plasma cutter is more than the breaker can handle on thick steels. this is very common on 120v plasma cutters. that machine is likely pulling 18-20 amps during the thicker cuts tripping the breaker. my old blue point is the same way. will cut 100' of 1/8" steel just fine. get up to 1/4" it'll trip a 20amp breaker after 2-3 minutes of continuous cut.

 

[Bert_]

a 20 amp thermal breaker is only good for 16amps continuous use. that plasma cutter is more than the breaker can handle on thick steels. this is very common on 120v plasma cutters. that machine is likely pulling 18-20 amps during the thicker cuts tripping the breaker. my old blue point is the same way. will cut 100' of 1/8" steel just fine. get up to 1/4" it'll trip a 20amp breaker after 2-3 minutes of continuous cut.

This isn't continuous. A continuous load is defined as operating for 3 hours or more. That would be a reeeeeeally long cut

 

[AngryBeaver]

This isn't continuous. A continuous load is defined as operating for 3 hours or more. That would be a reeeeeeally long cut

you must not work in the electrical industry. We are not talking about "continuous" standby generators. And that continuous is rated for 4 hours or more fyi.

Continuous is anything more than a momentary start. a 20 amp breaker will start a compressor no problem. a 20 amp will not support a compressor pulling 17-18 amps running load on a 20 amp thermal breaker. It will however run off a 20 amp digital breaker, if you can find one in a residential system.

20 AMP deep fryer is a "continous load" and will require a 30 amp service to run it.

a 20 amp plasma cutter will not run on a 20 amp circuit cutting max capacity. Period, end of story.

 

[3rdgendslmech]

a 20 amp thermal breaker is only good for 16amps continuous use. that plasma cutter is more than the breaker can handle on thick steels. this is very common on 120v plasma cutters. that machine is likely pulling 18-20 amps during the thicker cuts tripping the breaker. my old blue point is the same way. will cut 100' of 1/8" steel just fine. get up to 1/4" it'll trip a 20amp breaker after 2-3 minutes of continuous cut.

Yeah I remember it doing this to me one other time at work when I was re skinning a front loader cab. To be honest, I'm not really impressed with any of the big 3 tool truck welders or equipment like that. At the time I was in a pinch and needed a welder and something to cut sheet metal. I dont like how the cord is 14 gauge. I dont like how the consumables are NOWHERE to be found except through the tool truck.

I've been looking into the LOTOS LTP5000D for my next purchase. A good friend of mine has a concrete buisness and purchased a few more skid steers. Concrete is hell on the buckets and everything else, so I need something bigger. It's not name brand but I know of 2 people that say it's a good product for the price for a DIYer.

 

[AngryBeaver]

Yeah I remember it doing this to me one other time at work when I was re skinning a front loader cab. To be honest, I'm not really impressed with any of the big 3 tool truck welders or equipment like that. At the time I was in a pinch and needed a welder and something to cut sheet metal. I dont like how the cord is 14 gauge. I dont like how the consumables are NOWHERE to be found except through the tool truck.

I've been looking into the LOTOS LTP5000D for my next purchase. A good friend of mine has a concrete buisness and purchased a few more skid steers. Concrete is hell on the buckets and everything else, so I need something bigger. It's not name brand but I know of 2 people that say it's a good product for the price for a DIYer.

I have spent more in consumables than my machine costs. I bought it six months old and used, and like you I need it for sheet metal and works great for that, but I need something that will do 1" plate, and not a sever cut.

I will never again buy a machine that uses specific parts. I will never again buy a machine that I get to get consumables through a truck. Hypertherm to Victor for me. something with local support... you get what you pay for.....

Good luck.

 

[sberry]

Evidently engineers are stupid and obviously don't know what cord to put on welding machines despite making millions of them.
Something else that seems to happen. When this stuff is new it works. Comps, chop saws these little welders work from a common circuit but as they age,,, valves leak, caps age, wire connections, all kinds of fussy little stuff adds to the problems. They barely work to start with.

 

[sberry]

I think Bert might be a master.

 

[BD1]

Buy a HYPERTHERM and your done. Made in USA, employee owned, and used on commercial plasma cutting tables.
I attended Fabtech show a few times.
HYPERTHERM is almost exclusively used on commercial tables. I asked them why Hypertherm ? They all said best in the business and they started by manufacturing machines for commercial use.


Sent from my iPhone using Tapatalk

 

[sparky 1971]

you must not work in the electrical industry. We are not talking about "continuous" standby generators. And that continuous is rated for 4 hours or more fyi.

Continuous is anything more than a momentary start. a 20 amp breaker will start a compressor no problem. a 20 amp will not support a compressor pulling 17-18 amps running load on a 20 amp thermal breaker. It will however run off a 20 amp digital breaker, if you can find one in a residential system.

20 AMP deep fryer is a "continous load" and will require a 30 amp service to run it.

a 20 amp plasma cutter will not run on a 20 amp circuit cutting max capacity. Period, end of story.

You should probably look up the definition of a continuous load in the NEC.. I am pretty sure Bert is a master. He knows a whole lot more than I do. I also have a master's license, but don't consider myself a master.

A 20 amp breaker should support a 20 amp load. That's why it's a 20 amp breaker. It is limited to less than three hours by the NEC. I have seen a few cases where a breaker was at or almost at 100% capacity or a little more 24/7. All I was able to say is that it should have tripped a long time ago.

Has anyone considered that this may be a weak breaker? Could it possibly be a GFCI breaker and it isn't tripping on overload, but could have a problem with the machine?

 

[Bert_]

you must not work in the electrical industry. We are not talking about "continuous" standby generators. And that continuous is rated for 4 hours or more fyi.

Continuous is anything more than a momentary start. a 20 amp breaker will start a compressor no problem. a 20 amp will not support a compressor pulling 17-18 amps running load on a 20 amp thermal breaker. It will however run off a 20 amp digital breaker, if you can find one in a residential system.

20 AMP deep fryer is a "continous load" and will require a 30 amp service to run it.

a 20 amp plasma cutter will not run on a 20 amp circuit cutting max capacity. Period, end of story.

Let's crack open the code book...


You mention a compressor but that is a motor and follows a whole different set of rules. Not sure why you would even mention that.

 

[AngryBeaver]

you should consult your book to see why a 20 amp thermal breaker trips at 16.8 amps on a continuous load. by continous, I mean more than 10 minutes.

if you can't figure that out, you are not a master anything. a thermal breaker is only rated at 80% of its rating for continous use.

thanks

 

[Bert_]

you should consult your book to see why a 20 amp thermal breaker trips at 16.8 amps on a continuous load. by continous, I mean more than 10 minutes.

if you can't figure that out, you are not a master anything. a thermal breaker is only rated at 80% of its rating for continous use.

thanks

It won't trip, but I guess the manufacturers are wrong about their own breakers also. Ge says a thql will hold it's rated current indefinitely. Actually if you look closely it will slightly over rated current for at least the 16 minutes that this graph covers.

 

[nadogail]

Buy a HYPERTHERM and your done. Made in USA, employee owned, and used on commercial plasma cutting tables.
I attended Fabtech show a few times.
HYPERTHERM is almost exclusively used on commercial tables. I asked them why Hypertherm ? They all said best in the business and they started by manufacturing machines for commercial use.


Sent from my iPhone using Tapatalk

I have been bailed out by Hypertherm's Tech support more times than I can remember. Their aid and assistance enabled me to return my employers plasma cutter to service and they made me look good.

If and when I buy a plasma cutter with my own money I will first look at a Hypertherm.

 

[walrus]

It won't trip, but I guess the manufacturers are wrong about their own breakers also. Ge says a thql will hold it's rated current indefinitely. Actually if you look closely it will slightly over rated current for at least the 16 minutes that this graph covers.

A GE definitely will hold, you can arc weld with the wires in my experience with GE

 

[sparky 1971]

you should consult your book to see why a 20 amp thermal breaker trips at 16.8 amps on a continuous load. by continous, I mean more than 10 minutes.

if you can't figure that out, you are not a master anything. a thermal breaker is only rated at 80% of its rating for continous use.

thanks

This and post #16 are bad information. The only true part is a breaker is supposed to be at 80% for continuous use per the NEC. Continuous use is three hours or more. That is straight out of the book you say should be consulted. I have personally seen a 20 amp breaker humming along just fine with 22 amps worth of load on it. It was in a 24hr diesel shop in the summer time and every one of the techs had a 30" fan among other things plugged into the columns down the center of the building. I wasn't there for that, I was trying to find another circuit using my amprobe and happened across that particular breaker. I ran two more circuits for the columns while I was there to alleviate any potential future problem. Oh yeah, these were Square D QO breakers.

Anyway, back to the original post. Is there possibly something else plugged into the circuit that you aren't aware of? Maybe a beer fridge that you don't notice isn't working when the breaker trips. If it's a dedicated circuit, I would start to think weak breaker or there is something wrong with the machine. Maybe it's a gfci breaker and it's actually tripping because of a ground fault. If it has a factory 15 or 20 amp cord cap on it, there is no reason a 20 amp circuit couldn't handle it as long as there is nothing else running on that particular circuit and the machine is designed for it.

I did google Cornwell plasma cutter and one 120 volt unit came up. The specs say it is a 16 amp unit....but it's rated to cut 1/8". It may be asking too much out of the machine to cut the bigger stuff. I have no idea how a plasma cutter works, so feel free to beat me up over the previous sentence.

 

[wyliesdiesels]

Hey guys a while back I bought a Cornwell plasma cutter for a little body work project on my truck. It worked fine as most of the cuts were pretty short. It's a 16Amp output and you have give it an air supply.
I noticed the other day (this also happened one other time) that if you're cutting thicker metal 1/4 to 3/8 you can only cut about 3-4 inches before it trips the breaker.
Right now I'm in the middle of replacing some wear plates on a skid steer bucket and I'll only cut 2 or 3 inches and let the torch cool. It works, I really need to upgrade to a bigger machine since I've gotten into some bigger jobs.
The circuit in my pole barn it's running off of is 20 amp 12 gauge wire probably about 25-30 feet from the panel.
Should I run a dedicated circuit with 10 gauge wire and use a 10 gauge extension cord?

Not sure why no one else mentioned this but assuming this is the model you have, you are exceeding the rated capacity of the cutter.

Its only designed to cut up to 1/8"

no wonder it trips the breaker.

http://corporate.cornwelltools.com/webcat/products/MMWP125I-%2d-120V-Inverter-Plasma-Cutter.html

Cuts mild steel up to 1/8”...

a 20 amp thermal breaker is only good for 16amps continuous use. that plasma cutter is more than the breaker can handle on thick steels. this is very common on 120v plasma cutters. that machine is likely pulling 18-20 amps during the thicker cuts tripping the breaker. my old blue point is the same way. will cut 100' of 1/8" steel just fine. get up to 1/4" it'll trip a 20amp breaker after 2-3 minutes of continuous cut.

That is completely false. A breaker is good for its rated ampacity.

And the OPs usage is NOT continuous. Do you have a code book handy? Go look up the definition....

you must not work in the electrical industry. We are not talking about "continuous" standby generators. And that continuous is rated for 4 hours or more fyi.

thats a bit ironic when you dont even know the definition of continuous. your own sentence can be thrown right back at you.

Not sure why you brought up standby generators. Has NOTHING to do with this thread.

Continuous is NOT 4hrs.

Since you obviously dont have a codebook I'll quote it for you (FYI you can access it for free online):

Continuous Load A load where the maximum current is expected to continue for 3hrs or more.

Continuous is anything more than a momentary start. a 20 amp breaker will start a compressor no problem. a 20 amp will not support a compressor pulling 17-18 amps running load on a 20 amp thermal breaker. It will however run off a 20 amp digital breaker, if you can find one in a residential system.

20 AMP deep fryer is a "continuous load" and will require a 30 amp service to run it.

Wrong again

And motors are a different animal than a plasma cutter. False equivalency.

a 20 amp plasma cutter will not run on a 20 amp circuit cutting max capacity. Period, end of story.

what you failed to see here is that the OP is using the cutter beyond its design limit which is 1/8" mild steel. this is why its tripping.

you should consult your book to see why a 20 amp thermal breaker trips at 16.8 amps on a continuous load. by continuous, I mean more than 10 minutes.

if you can't figure that out, you are not a master anything. a thermal breaker is only rated at 80% of its rating for continuous use.

thanks

you are wrong again.

you should really consult the codebook on what a continuous load is. I posted it above for you in case for whatever reason you couldnt find it yourself.

first you claimed it only applied to standby generators, then you claimed it was more than 4hrs and now you say its more than 10minutes. you've contradicted yourself over and over here. We obviously know who ISNT a master here and its not bert.

Even the breaker manufacturers have white papers that contradict what you say. The egg is on your face.

Thanks

 

[Bert_]

A GE definitely will hold, you can arc weld with the wires in my experience with GE

Ge or not isn't going to make a difference. Most of the major manufacturers residential stuff will have similar trip curves.