Breaker/outlet Amps for Thunderbolt 225/150 AC DC

[Spudland_Dave]

this may seem a little sketchy to some people who have never heard of it, but i can tell you that it is a common occurrence.

Seen it done and heard about it before, Totally understand what you say...but IMO buying 6ga wire and a 50A breaker is cheaper then buying/building a new house. I'm not gonna take a chance with the safety of my family over 50 bucks of cable.

Do it right or dont do it at all :thumbsup:

 

[lostcause]

Seen it done and heard about it before, Totally understand what you say...but IMO buying 6ga wire and a 50A breaker is cheaper then buying/building a new house. I'm not gonna take a chance with the safety of my family over 50 bucks of cable.

Do it right or dont do it at all :thumbsup:

yeah, i hear ya, but to be honest, you probably already have this same thing going on in your house somewhere already, but just don't know it. like i said, my old welder says right on it: 230v, 50a, 60hz, 1 phase... but it has a 12/3 cord from the factory. if you own a stick welder, check yours out. i bet its the same thing. from what i understand, this is also common in hvac equipment and particularly electric motors. these items have a huge startup load, but the continuous operating draw is not that high, so they have wiring that is sized for the continuous load but may require a breaker much larger. you may find this if you have any sort of central heating or air conditioning. those companies undersize the wires because they know it's not necessary to go any larger, and it saves them a few bucks each time, multiplied by thousands of times.

 

[yomax4]

Hmmm. I would not go with 12ga wire for Any Welder. 115v or 230v. If you must go with 12ga, Buy a 115v unit. 8ga or 6ga only for the 230v units. Electric motors are a bit different. They draw much less on 230v. Buy 6ga with a 50amp breaker and Welder up!!:thumbsup:

 

[lostcause]

Hmmm. I would not go with 12ga wire for Any Welder. 115v or 230v. If you must go with 12ga, Buy a 115v unit. 8ga or 6ga only for the 230v units. Electric motors are a bit different. They draw much less on 230v. Buy 6ga with a 50amp breaker and Welder up!!:thumbsup:

you're not reading... i DID NOT use #12 wire, the manufacturer did. basically, whoever was building welders for sears/craftsman back in the 70's (as a guess on the age of it) used 12/3 cord on a machine that they state as being 230v, 50a, 60hz, single phase. cord is slightly different than nm cable, but i'm trying to illustrate the point about duty cycle. the manufacturers know what the max the machines can draw, and yes, it's more than you would normally put on that size conductor, but a welder is governed by a duty cycle, and it will not draw 100% of the time. they know this and are willing to put their name (and money) on the line, so it's a pretty good bet it's correct.

as far as my comments about electric motors, you kinda missed the point again. it doesn't matter whether the motor is wired for a 120v or 240v circuit... the point was that they generally draw higher when they start up. the manufacturers know this initial draw is temporary, and they may tell you that you need a #10 wire, but a 50a breaker. again, big business with money to lose in a lawsuit is saying it's ok to do it.

ok, i did a quick look... do a google search for table 630.11 and look at the duty cycle multipliers.

hate to keep beating a dead horse, but a lot of people think their rule of thumb is the only correct way, but i like to review all options and then choose what looks best. this other forum thread has some well written information: http://www.selfhelpforums.com/archive/index.php/t-8169.html

 

[Mark @ Everlast]

Section 630 in the NEC specifically deals with the wiring issue. They have a table (which I don't have the full copy of) that tells you what multiplying factor you need to apply to the particular duty cycle of your welder. I do know that for a 60% duty cycle multiply the rated amps of the welder by .78 and use the results to match to the rated wire gauge that equals the result. There are some nuances in there, and its quite detailed. I am not an electical expert, but an electrician can look it up for you, just tell him you need to wire it according to section 630 of the NEC.

 

[mustangsallysdad]

I just put in a new welding circuit in the shop...disconnect (60A), circuit breaker (50A).

 

[patrick_g]

breakers and duty cycle aren't really the issue. your breaker must be able to resist the entire current draw that you are putting on it, otherwise it will trip. the downsizing issue is about the wire you use between the box and machine. this is where you can downsize due to duty cycle. normally, a 50a load requires #6 wire, but wiring does not fail instantly the way that a breaker trips instantly when overloaded. the wire will get hot over time and then eventually cause failure and possibly a fire.

since welders generally have a duty cycle (10%-60% generally), meaning that they will only work (draw current) for so many minutes in a row. because of this, the current draw will cause a smaller wire to heat up, but not to the point of failure. when the machine hits its duty cycle the draw stops, and the wire will cool down. a properly sized smaller than normal wire will work fine for this application.

this may seem a little sketchy to some people who have never heard of it, but i can tell you that it is a common occurrence. i have an older craftsman 30a-230a welder, and the power cord that the manufacturer put on it is a 12/3. normally people consider a #12 wire to be good for only 20a, i can guarantee the welder draws more than 20a at times. as you can see the manufacturers are already doing the wire downsizing, so it is perfectly common and safe. i think i remember reading somewhere that most common stick welders will operate safely on 10/2 nm cable.

again, this is just my layman's description of what happens. if unsure, always consult a professional. i do know that to meet code, you need some special sort of labeling on any circuit where the wire is downsized due to duty cycle.

I never tripped the 50 amp breaker and I never run a load wire that isn't sized to safely carry the breakers full output steady state forever and sometimes I go a size bigger (can't hurt and it sure doesn't cost much for the peace of mind. I can't guarantee I would never use the outlet for anything with a higher duty cycle than whatever or that I won't exceed the duty cycle recommendations.

Pat

 

[Spudland_Dave]

yeah, i hear ya, but to be honest, you probably already have this same thing going on in your house somewhere already, but just don't know it.

We built 4 years ago so I still remember ...I'm super **** about details. I can guarantee none of the hardwiring is like that.. got 6GA for the oven/stove and 10 ga for the Dryer.... 12 ga for all recepticles, 14 ga for lighting. All Copper. Same goes for the plumbing, cost for copper back then was stupid, but I just didnt trust Pex....

Now...for the cords that plug into the house wiring, everything is the way it left the factory...I'm gonna go look at my miller next time I'm out there.

 

[captaincrab55]

you're not reading... i DID NOT use #12 wire, the manufacturer did. basically, whoever was building welders for sears/craftsman back in the 70's (as a guess on the age of it) used 12/3 cord on a machine that they state as being 230v, 50a, 60hz, single phase. cord is slightly different than nm cable,

Let's review that 12/3 cord, maybe we can't... Without knowing the TYPE of insulation used on the cord, one can't say how many amps it's rated for.. My Dad and I had one of those Sears welders, it was a 1969 Christmas present...

Trust me, this isn't the spot to de-rate... Let's say one installs copper 10 NMB wire on a 50 amp breaker with a 50 amp receptacle. It may very well work fine with a duty rated piece of equipment connected to the circuit... At a latter time someone may try to use a piece of equipment on that circuit that's not duty rated.. It's a potential Fire Hazzard

BTW, When one makes a statement that something was wired to the latest National Electrical Code, it's wired to a minimum standard.....

 

[lostcause]

Now...for the cords that plug into the house wiring, everything is the way it left the factory...I'm gonna go look at my miller next time I'm out there.

that's what i'm talking about. cords and manufacturer supplied leads for hardwired appliances. they will be supplied to what is needed for code and safety, but they won't overdo in the form of overalls with belt and suspenders approach that i see a lot. i'm not saying that you or anyone who has the slightest glimmer of a clue about wiring would size and install inappropriately.

Trust me, this isn't the spot to de-rate... Let's say one installs copper 10 NMB wire on a 50 amp breaker with a 50 amp receptacle. It may very well work fine with a duty rated piece of equipment connected to the circuit... At a latter time someone may try to use a piece of equipment on that circuit that's not duty rated.. It's a potential Fire Hazzard

it's a pretty safe bet that anyone who has even heard of conductor size reduction for welders has also noticed the wording stating that you need to label that circuit accordingly to prevent the misuse that you are worried about. people are reading one line and going off without looking at everything here. i'm not advocating conductor size reduction, i'm just pointing out that it is acceptable, and it DOES work without burning your house down. like everything, it has to be used correctly. if you don't label it as required, and someone uses it incorrectly, then you half-assed the job. no different than using 20a breakers with #14 wire. you can't legislate against all human error.

i only was pointing this out because i see so many people posting replies in this type of threads with doom and gloom telling people they are going to set the world on fire if they do something a certain way when they often don't know what they are talking about. heck, do a search and you will see a pile of people saying that you need a white neutral for a 240v circuit. others think that the green ground is also the neutral. a fairly small number probably know that in a 240v circuit, the red and black wires are actually the neutrals as well as the hot leads.

yes, the bulk of people wiring a 50a welder breaker will use #6 copper, and that's fine and probably a good choice. i'm just pointing out that if you CAN (SAFELY) use a smaller conductor to power a welder if it meets the duty cycle requirements.