sdkubota
Platinum Member
6 gauge conductors are required to carry 50 amps. Stuff isn't cheap either.
Home AC Welder Breaker ???
- Thread starter Beltzington
- Start date
6 gauge conductors are required to carry 50 amps. Stuff isn't cheap either.
joshuabardwell
Elite Member
6 AWG?
LD1
Epic Contributor
Yep, 6awg aint cheap. BUT...there is an exception to the 6ga/50a rule for welders.
The NEC has a section just for welders. IF it is a dedicated circuit used ONLY by the welder, you can use smaller wire. I "think" you can go as low as 10awg for a 50a welder circuit.
The NEC has a section just for welders. IF it is a dedicated circuit used ONLY by the welder, you can use smaller wire. I "think" you can go as low as 10awg for a 50a welder circuit.
joshuabardwell
Elite Member
The thinking here is that, because a welder is seldom (if ever) designed for 100% duty cycle at its highest rated amperage, you don't need to run heavy enough cable to handle 100% duty cycle at that amperage. For example, if you were going to run a 50-amp electric motor on a given circuit, you would need to use #6 wire because the motor would be expected to be run continuously. But for a 50-amp-draw welder (say, output amperage between 40-140 amps), it may only have 20% duty cycle at any output over, say 100 amps. So there's no expectation that it would ever actually draw 50 amps for any significant length of time. This means that the wire would have time to cool down.
The relevant table of the NEC is 630-11(a). That table gives a derating percentage for each duty cycle percentage. For example (I am just making up these numbers), at a duty cycle of 20%, you might be allowed to derate the max amperage to 60%. So if your welder drew 50 amps max, which would normally require a #6 wire, you would multiply that by 0.6 to get 30 amps, and put in the equivalent wire gauge to handle 30 amps. You would still use a 50 amp breaker, however.
Unfortunately, I cannot for the life of me find a copy of 630-11(a) online, so I can't actually give you the multipliers for the duty-cycle percentages.
Again: this is only for dedicated circuits that only the welder will ever be used on.
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joshuabardwell
Elite Member
BTW, this all assumes that the operator of the welder is obeying his or her machine's duty cycle. With high-tech welders, they will automatically cut off when they are overheating. But with older, low-tech welders, you can happily keep welding until they burn up. And if you have derated your wire based on the welder's duty cycle, it may be the case that the wire in your wall is the first thing to go. The wires' amp ratings (as I understand it) are based on the melting temperature of the wire's insulation. So once you exceed the amp rating of the wire, you potentially melt the insulation, cause a short, or who knows what else after that. If you're lucky, you pop the breaker. If you're un-lucky, you burn down your house. So, moral of the story: obey your welder's duty cycle!
k0ua
Epic Contributor
Or do what I did and run #6 AWG from the breaker to the outlet, (it was less than 10 foot) and I made up an extension cord using SO cord (very flexible multi strand wire ) and I used #10 AWG in the SO cord. My new welder cannot draw over 31 amps at full bore, so I am pretty safe, It never even gets warm. But if I ever do put on a welder that needs the 50 amps I am covered from the outlet to the breaker and would just need a more heavy duty extension cord or monitor the usage and temp of my lighter duty extension cord.. But I would recommend running the #6 AWG wire in the wall, because running wire is something you want to do once, and you know the wire is not liable to melt before the 50 amp breaker pops.
James K0UA
James K0UA
joshuabardwell
Elite Member
I think this is really good advice. I have been thinking for a long time about putting in a backfeed receptacle for my generator instead of using the extension cords that I use now. I recently realized that, by putting in the welder outlet, I had more or less already done the work, except that it had the wrong receptacle on the end of the wire. If I had put in smaller wire, I wouldn't have the option of using the existing run for a generator (continuous load). I was really glad when I confirmed that the wire in the wall was six-gauge. But my run was really short (about 4'). I might have felt differently if I was running 220 all the way out to my barn or something. 6/3 is approximately double the cost of 10/3!
caver
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If your welder nameplate has a rating I1eff you use that rating if not use this table below per 2011 NEC.
Duty Cycle Multiplier
100 1.00
90 .95
80 .89
70 .84
60 .76
50 .71
40 .63
30 .55
20 or less .45
Buckgnarly
Platinum Member
Exactly what I did, but I ran #8 in my 25' extension cord and only about a foot for the outlet from the box. I'd rather put the money into the extension cord than the wiring for the outlet. Another suggestion I picked up is to make 2 shorter extension cords as opposed to one long one. Much easier to handle and the two can be added if really needed.
OP
Beltzington
Platinum Member
Well he knows the error of his ways now with 3 of us telling him the same thing
James K0UA
Well I just pulled the cover off my panel and found the three of you where correct, can't get both legs of 115 from a single c/b slot. **** you all. Since I have no other available slots looks like I will be doing all my welding at my property where I have several unused slots on my 200-amp service. Unfortunately my new plugin is 50-miles from where I sleep. I hope you are all happy!
