Circuit breaker for welder

I am about to install a sub panel for the welder but I do not what size of breaker to use. The data on the old Marquette welder is long gone. It is a Marquette 180 Amp AC stick welder. What would be a good guess for a circuit breaker?

Depends if the breaker is being sized for only short circuit protection or for thermal protection. Two different factors that are frequently confused.

2 pole 50 amp. DH

Cant really say not knowing the welders actual current draw, but many older 225 amp 240 volt AC buzz box stick welders used a 50 amp branch circuit and 50 amp 240 volt two pole circuit breaker (with a 50 map receptacle into which the welder was plugged in)........You first consider the load, then size the feeder wires appropriately, then size the circuit breaker to protect the feeder wiring, like if its 50 amp rated wire, then one could use a 50 amp breaker. Many old straight 240 VAC AC buzz box stick welders require 3 wires ran to their receptacle, 2 hots (L1 & L2 Red n Black) plus an Equipment Grounding Conductor (Green/Bare). If the welder is equipped with a 40 amp plug, then you could get by using a 40 amp rated receptacle and 40 amp wiring and a 40 amp breaker, but it may well have a 50 amp plug in which case Id run 50 amp branch circuit wiring and breaker. You may want to just run a 50 amp branch circuit anyway for later upgrade use.

John T

If it still has the power plug on it, size your breaker and wiring for the plug. Like John sez, 50 amp is pretty standard for 240V welders and you'll be all set if you decide to replace it or buy a MIG machine.

Old lincoln 180 amp welders drew 37.5 amps maximum.they were designed to run on rural lines.I have 40 amp fuses on my welders line. the welder is a 150 amp.I do use my Lincoln 225 amp that has a 50 amp maximum draw on jobs that are too much for the old 150 amp welder.No problem for 45 years.Insurance companys go nuts if you mention fuses now.You have to use breakers.Federal Pacific went bankrupt because a lot of their circut breakers didnt open.Your wire size will tell you what the amperage of the breaker will be.

Do what the guys have said. If you had the data on it it's surprising how small you can go when you also consider the duty cycle.

There's a section in the electrical code on welders.

Dusty

The duty cycle of a welder plays absolutely no part in the selection of a circuit breaker. The duty cycle may be used to select the conductor size per NEC Article 630. For welders with low duty cycle, the supply conductors have opportunity to cool while the welder is idle.

Its been years since I was a designer, but back when we specified fuses quite often. Seems a fuse link will melt and be more reliable then a mechanical circuit breaker in which a few things have to all happen n come together AND ALL WORK...However being out of the trade so long Im not up with trends and the latest specs or NEC

John T

FWIW Nuttin actually, I agree with you both... The breaker size is determined by the ampacity of the conductors (they protect the feeders from excess current, overheating and insulation degradation) buttttttttttt depending upon the Duty Cycle (as posted) smaller conductors may suffice in which case the breakers would then also be smaller. I dont see either of your posts in disagreement with that I dont think???

Love this sparky chat as an old retired EE but its been too long n Im as rusty as an old nail on the NEC grrrrrrrrrrrr lol

Take care now, you sparkies

John T

I found many photos of burned wire insulation connected to circuit breakers, set copies to an insurance agent who said they would not insure a house with fuses.Ive found stuck circuit breakers and some that made the lights blink.When I did tv work I replaced a lot of circuit breakers.most were touchy and tripped for no reason.

Doesn't the shape of the male plug on the welder determine the size of breaker? What I'm trying to say is that dryer cords and electric ranges, as well as welders have certain shaped plugs. When you go to the hardware store to get the "female" version of the matching plug, it will say 40 amp or 50 amp, or whatever size it might be. I might be wrong, but that is how I have hooked up some electrical things and nothing has burned down.....yet.

You are partially correct c-man. But ultimately the breaker can't be oversized for the conductor wire coming out of the breaker panel going to the receptacle. For example, if you put a 50 amp breaker on #14 wire, the amperage draw could heat the wire hot enough to cause a fire where the wire is close to a combustible such as wood studs in the wall. Usually the excess heat causes the plastic in receptacles and light sockets to melt, short out, and start a fire. Theoretically breakers are designed to detect heat as well as amperage to cause it to trip. Too small wire could cause it to trip all the time or the heat will first generate at a weak spot such as a receptacle or maybe a pinched spot in the wire or where a nail got to it and a fire could result before the breaker picks up the heat.

You might check the conductor size of the dryers and ovens you have hooked up for piece of mind. Technically the safety factors built into wire runs and such along with intermittant use and low heat settings may protect you for a while. Stick a brisket in the oven in the oven for 12 hours and go off and leave it may result in something you didn't want.

I found that the plastic in old electrical stuff like receptacles breaks down over time (just like in cars and pipe) and should be replaced. I run some high wattage bulbs in a couple lamps and every few years the heat causes those sockets to short and fail. (no fires yet) I've looked at ceiling fixtures and found baked wiring just from using 100 watt bulbs when they are rated at 60 watts max. Same for the 100 watt rated ones. Just stuff to stay on top of.

Yes, 20 Amp circuts are 12 guage wire, 30A is 10 guage, 40A is 8 guage and 50A is 6 guage, all copper if I remember correctly. Would have to get out a book to be sure.

If you plan to stay with the old Marquette, then you need a 40 amp double (240 V) breaker and 10 gauge wire to provide the power from the main panel. If you have a long wire run of maybe 75 ft, then use a #8 wire to the welder, but the same 40 amp breaker.

If it was mine, I'd wire for a 50 amp circuit with #8 (or #6 for a long run), so as to be ready for a welder upgrade when the old one dies. But the new welders usually have a 4 prong cord, 2 hots(black and red), an neutral (white) and a ground (green). If you are buying new electrical cable, then that is what you should use.

Paul in MN

Your numbers are right.Since I have a long run of number 8 wire I use 40amp fuses.Ive run my welders since 1966 with no problem.My Lincoln 225 has a range cord on it using the old 50 amp crow foot style.New lincoln 225 welders have a number 12 wire in the line cord.Dosent make sense.CHEAP CHEAP.50 amp draw on 20 amp wire.

John, disagree about the breaker. The breaker MUST be able to supply the required amperage. Articles 630 and 430 have plenty of examples where the overcurrent device has rating greater than that of the conductors. Particularly read Article 630.12(B) 2008 NEC. I stand with my previous post.

Many of the responses to this thread are just wrong. Article 630 in the NEC addresses electric welders. In the 2008 NEC it fills less than 3 pages. I suggest reading and following it. For those who have the original instructions with their welder, if the welder is UL Listed, the NEC requires that those instructions be followed.