Ok to use 12g power cord on 225 amp Lincoln?

If not someone should tell Lincoln not to use 12g wire attached to a 50 amp plug.
I'm sure there is some excuse Lincoln can use 20 amp wire in a 50 amp welder.


The gray wire goes To a clothes dryer.

10g wire.
What guage copper measures 3/16 ?

This is what 225 amp Lincoln uses for welding cables.
How many amps can 3/16 copper wire handle if you are going by CODE?,
I only use 105 amps to weld 1/8 rods.
I don't weld thick metals.
I may go to 120 or 135 setting to warm up the rod and metal for a very short time.
That us to hot for a 1/8 rod.


When I get someone to watch the amprobes when I'm welding. I would like a know what the prime and secondary currents are at the 105 amp setting.

I've been using 10g wire and 30 amp breaker forever on my 12g Lincoln and see no signs of heat stress on the 10 or 12g wire.

I don't attempt to weld half inch metal.
Can someone post a link to the Lincoln's duty cycle?

If I recall the welder is not a commercial grade welder..
Duty cycle decrease greatly at full amps.

Someday I'll like to open the welder and see what guage wire is used to make the transformer and is it copper?

If you get inside the welder please post pictures and measure wire diameter.

Please post the actual current when you are welding.

Biggest question would be what is the exact model of your welder?

From that we would get the duty cycle %, which is the heart of your question, more or less.

Paul

Look up the NEC section on welder supply wiring. I was surprised the first time I did. It's all about duty cycle. My compliant welding receptacle is 10ga from a 30 amp breaker to 50a socket. Using an old 230A Miller AC/DC stick machine. Usually at 90-110A

All the welders I've looked at have what most would consider undersized factory cord/plug sets. Again, duty cycle.

It shows 50 amps
Yet the power cord is rated at 20 amps
12g wire.


Shouldn't
50 amp wire be 6g, not 12g.

Duty cycle on the classic AC-225-S "tombstone" welder is 20% on 60Hz at all amperages, according to the manual.

"Duty Cycle
(For Codes 11604 and below). The 60 Hz welders are rated 20% duty
cycle and the 50 Hz welders are rated 15% duty cycle for the welding
current shown on each switch position.
(For Codes 11674 and above). The 60 Hz welders are rated 20% duty
cycle and the 50 Hz welders are rated 13% duty cycle for the welding
current shown on each switch position.
Duty cycle is based on a ten minute period. This means that the arc
can be drawn for 2 minutes out of each ten minute period (with a
20% duty cycle unit) without any danger of overheating. If the welder
is used for more than 2 minutes during several successive ten minute
periods, it may overheat. Be sure to leave the unit "on" during each
10 minute period to let the fan motor run for adequate cooling.
Overheating reduces welder life"

So, it appears that you can weld 15-20 seconds out of every minute. 15-20% duty cycle.

The 80% rest time allows the supply wires and transformer to cool.

So their wires meet their specs.

If you try to continuously weld with it, you will melt things. And it will be your fault, as the specs tell you how much you may use the welder.

Paul

Duty cycle is based on a ten minute period. This means that the
arc can be drawn for 2 minutes out of each ten minute period
(with a 20% duty cycle unit) without any danger of overheating.

So you can burn one stick, sit down for 8 minutes before burning
another stick?

I thought the duty cycle depended on amps used..

Thanks.

(quoted from post at 12:03:50 10/18/22) I thought the duty cycle depended on amps used..

Click to expand...

In reality, it does, or at least it should. Think about it, though. It's much easier for the customer to understand to just make blanket statement of 20% duty cycle at all settings. It's also better for warranty claims, in theory. Of course most people pay no attention to the duty cycle and just run rod after rod after rod.

I was once told that the circle around the 70 on older models indicated the "100% duty cycle" setting.

I think you are right.
I use 90 or 105 amps and only stop to
install a new rod.
I've never seen smoke coming from 12a wire

Never Tripped 30 amp breaker.

Good to know.
Most YT sparkies think because it has a 50 amp receptacle you need 50 amp breaker and 50 amp wire. Some debate if that's 8g or 6g.

Soooooo 10g wire, 30 amp breaker wired to a 50 amp receptacle, and the power goes to the transformer via 12g wire is code?
Is this nuts or what?

Must be a fairly new one. Mine has 8 ga for the plug and 0 for the stinger. The ground lead is somewhat smaller, maybe 2 ga. It 40 yrs old though. I bought it new at a welding supply. I have noticed they have cheapened them up. Only every shut down once, using 7/32 7024 without stopping for an maybe an hour except to add new rod. Only shut down for about 4 minutes. Was running I think 180 amps. 4 ga supplies the plug 25 ft from breaker.

Good afternoon good neighbor George, GREAT TOPIC for us sparkies, thanks for posting.

While this subject may be a bit confusing for some (Not all) non electricians and non engineers, FWIW I consider it very basic and easy so will explain how I was taught in school and several NEC Seminars and Workshops and practiced for many years. NOTE that's NO guarantee it's still correct !!!! codes change but it is how I was taught by the NEC experts and actual board members at the time who conducted those seminars, a couple that come to mind as I best recall were Joe McPartland (EC & M Magazine) and Mile Holt, here goes:

To size the conductors per the NEC when I last practiced power distribution, I:

1) Computed the Maximum Continuous Current the load can draw.....
2) Specified the Conductors to have a MINIMUM AMPACITY of at least 125% of the MCC

EXAMPLES if the MCC was 16 Amps, the minimum wire ampacity would be 1.25 x 16 = 20 Amps = 12 Gauge
if the MCC was OVER 16 Amps, I specified the next wire size or 10 Gauge

THAT BEING SAID

1) What current an AC Buzz Box Welder draws from its Primary input circuit DEPENDS ON WHAT THE SECONDARY WELDING CURRENT IS Well Duh If youre welding at 50 amps you dont draw near as much primary input current as if you're welding at 225 Amps EVERYBODY HERE KNOWS THAT IM SURE..

2) As far as overcurrent protection on the primary input wiring, its common to use a THERMAL MAGNETIC CIRCUIT BREAKER and those can trip EVEN AT CURRENT LESS THAN LABELED ON THE THERMAL SIDE GIVEN LONG ENOUGH TIME. Thats where DUTY CYCLE COMES INTO PLAY. EXAMPLE thats one reason why on a 20 amp circuit the MCC being 80% or 16 Amps WILL NOT CAUSE THE BREAKER TO TRIP OUT ON THERMAL However if you were to draw 18 or 19 amps long enough it could over time still trip ...I can not say what breakers designed specific for certain welders may now be ????????????

FWIW When and where I practiced per the NEC as I recall at the time (may have since changed) if I were to install a 50 Amp Receptacle I SPECIFIED 50 AMP WIRE AND A 50 AMP BREAKER. If the actual load was less that was not a problem BUT NEVER MORE. If I designed a branch circuit that terminated in a 50 Amp receptacle, I at that time (maybe changed since???) would NOT have wired it with 20 amp wire but 50 amp wire AGAIN MAYBE ITS SINCE CHANGED NO WARRANTY check it out for yourself, don't necessarily do what I did back then lol

While some may think they know more than the NEC board of experts (maybe they do, if so take it up with them not me lol) and want to do different and have got by fine for years or want to take shortcuts or do it half or how they think best YOU GET NO ARGUMENT FROM ME, GO FOR IT its YOUR business YOUR risk YOUR choice, wire it as you well please, I support a persons free choice on their own property yayyyyyyyyy

REGARDLESS I still advise, suggest and politely would ask everyone here when sizing conductors for welders or anything else to consider USE WIRE THAT HAS A MINIMUM AMPACITY OF 125% OF THE LOADS MAXIMUM CONTINUOUS CURENT Do NOT take MY word for it, if in doubt consult the NEC and professional current practicing electricians and engineers, doing so could save a life.

PS Yessssssssssss Duty Cycle is relevant and can affect how a Thermal Magnetic Circuit Breaker may be specified and operate......

Best wishes to all here, be wise be safe now, take care

John T

Duty cycle does depend on amps as well as time. Almost never do I get above 110a. Just don't need it, and if I do it is only for a very short period.

Usually the break when changing rod and/or position provided enough idle time for me.

All welders have an amp/duty cycle rating. Most publish it, but some just publish the rating at max. Which has little meaning for me, and I suspect most users.

JohnT
Is this true or false?
Look up the NEC section on welder supply wiring. I was surprised the first time I did. It's all about duty cycle. My compliant welding receptacle is 10ga from a 30 amp breaker to 50a socket. Using an old 230A Miller AC/DC stick machine. Usually at 90-110A.
Short answer only: True or false??

Dedicated welder supply circuits have their own rules under NEC.

What those rules are, I have never cared. My welder is cordless and will run 300A at 100 percent duty cycle.

Can you please post a link to the NEC section on welders?
I have no clue where to look.
This topic constantly comes up.
I think YT has its own rules.

Along the same lines, have you ever looked at the conductor sizes inside an electric range or an electric water heater vs. the code-required size of the wires that feeds them?

Electric Welders are Article 630 in the National Electric Code

If I remember correctly, that circled 70
said ''for thawing frozen pipes'' on the
old old Lincolns. That would fit the
100% duty cycle at 70 amps story. I
haven't used a Lincoln tombstone in 50
years, so my memory is dim.

My relatively new Hobart has a 12 gauge
primary cord.

So have you looked up Article 630 or not? Below you state that you have no idea where to find the NEC Code on welders, but above you mention being surprised when you've looked it up. Which one is it? You can argue all you want, your welder wiring is not up to code and should not be recommended for others. The fact that you've done it and had no issues has no relevance to whether or not it is up to code. I posted your specific violation yesterday, Article 630.11(A). It states that THE AMPACITY OF THE SUPPLY CONDUCTORS SHALL NOT BE LESS THEN THE I VALUE ON THE RATING PLATE. If I've missed anything I'm open to criticism but I believe this one is pretty cut and dry.

Your confusion comes from not reading all the posts below.
What I asked John came from
kencombs post below.
Are there special NEC codes for welders?

If so, please post the link to NEC welder rules..

Fair enough, I skimmed over the comments but didn't catch that. Yes, Article 630 Part II is specifically about Arc Welders. I'm looking at it right now. I have no idea if you can find it online, I've never needed to.

The duty cycle of the 225 lincoln is 20%.

Table 630.11(A) Duty Cycle Multiplication Factors for Arc Welders
Duty Cycle Multiplier for Arc Welders
Nonmotor
Generator Motor
Generator
100 1.00 1.00
90 0.95 0.96
80 0.89 0.91
70 0.84 0.86
60 0.78 0.81
50 0.71 0.75
40 0.63 0.69
30 0.55 0.62
20 0.45 0.55

So what does this mean?? I'm not a lawyer or an educated electrician.

Does it mean you multiply 50 amps By .45 = 22.5 amps?

If so, 10g wire and a 30 amp breaker are good to use and in compliance with NEC code ??

The power cord is 12g wire and 12g wire is rated at 20 amps.

A question for JohnT and/or licensed electricians,

Do the original power leads installed by a manufacturer (such as the power cord on a grinder, saw, welder, etc.) fall under the NEC, or the same NEC standards, for sizing as permanent wiring? I am thinking they don't but haven't found that printed anywhere today. Many tool power cords are a smaller gauge wire than they would be if the NEC code was applied for the maximum advertised amperage draw of the tool. I don't think the rating of a tool's attached power cord is the proper reference for sizing a circuit.

Yes it is on line. NFPA site has all the NFPA codes, and the electrical code is one of many.

Unfortunately it is not searchable, nor can you copy and paste from it. They want to sell copies.

Look in chapter six.

Your welder your call but you know you shouldn't. Yes it will work as long as you don't use the high amperage settings. By the same standards your stove will work on 12 g also as long as you don't turn all the burners on high. I wouldn't recommend that either.

Can't really comment on the wire that came on the welder as my Lincoln is an industrial with a 100% duty cycle. The cord on it is huge.

Finally found a link to the welder info
http://thenecwiki.com/2021/02/article-630/
Not on the official NFPA site, but an exact copy.

You need to look above that in the code book. That multiplication factor table is used when the I value is not on the rating plate. At least that is how I interpret it. I took several years of code classes, but the welding section was not one that we focused on.

Dad's welder looks almost identical to that except his has the old steel pointer on it. We weld as we wish. I have welded with it for hours on end in the past till the stinger was so hot I had to wrap a rag around it to continue. I never checked the wire size but knowing dad it is at least the 50 amp supply with I think close to the 10or8 gauge wire in the pigtail that came with the welder. This welder is close to 60 years old now and still works fine. I usually weld in the 145-180range on it for most welding. Seldom turn it below 145. I welded up track rails on the Cat with it as a kid learning to weld spent hours doing that with only the rod change for a break on it. I only stop when welding bigger jobs to let the stinger cool to hold on to.

Far as I know per the NEC when I practiced (may be changed by now no warranty) if you wire a branch circuit to feed a 50 Amp receptacle YOU NEED TO USE 50 AMP WIRE notttttttttt 12 Gauge nottttttttttttt 10 Gauge. I believe that remains correct and if I (then and would still now) specify wiring a 50 amp receptacle IT WILL USE 50 AMP WIRE But use 12 Gauge if you like !!!!!!!!!!!

No way would I wire a 50 amp receptacle with ONLY 12 gauge wire BUT I SUPPORT YOUR DECISION IF YOU WANT TO

I am NOT saying what the code says about what size wire is needed to power a welder that draws x amps and at what duty cycle THATS A DIFFERENT QUESTION ask the welder manufacturer not meeeeeeeee lol

I AM SAYING unless code has changed the absolute MINIMUM wire to be used must have an ampacity of at least 125% of the circuits Maximum Continuous Current AND THAT HOLDS TURE FOR WELDERSS OR ANY ELECTRIC LOADS

SOOOOOOOO I SAY THE ABOVE IS TRUE and Im stickin to that unless and until Im shown the NEC says different

ONCE MORE feel free to wire YOUR welder with any size wire you like GO FOR IT regardless if it meets code or not ITS YOUR RISK YOUR CALL not mine not the NEC I am NOT telling you what to use got it ????

There ya go. I say this is all TRUE but all are entitled to other opinions with all due respect

John T

JohnT
Is this true or false?
Look up the NEC section on welder supply wiring. I was surprised the first time I did. It's all about duty cycle. My compliant welding receptacle is 10ga from a 30 amp breaker to 50a socket. Using an old 230A Miller AC/DC stick machine. Usually at 90-110A.
Short answer only: True or false??

MY RESPONSE:

Far as I know per the NEC when I practiced (may be changed by now no warranty) if you wire a branch circuit to feed a 50 Amp receptacle YOU NEED TO USE 50 AMP WIRE nottttttttt 12 Gauge nottttttttttt 10 Gauge. I believe that remains correct and if I (then and would still now) specify wiring a 50 amp receptacle IT WILL USE 50 AMP WIRE....... But use 12 Gauge if you like !!!!!!!!!!

No way would I wire a 50 amp receptacle with ONLY 12 gauge wire BUT I SUPPORT YOUR DECISION IF YOU WANT TO

I am NOT saying what the code says about what size wire is needed to power a welder that draws x amps and at what duty cycle THATS A DIFFERENT QUESTION ask the welder manufacturer not meeeeeeee lol

I AM SAYING unless code has changed the absolute MINIMUM wire to be used must have an ampacity of at least 125% of the circuits Maximum Continuous Current AND THAT HOLDS TURE FOR WELDERS OR ANY ELECTRIC LOADS

SOOOOOOO I SAY THE ABOVE IS TRUE and Im stickin to that unless and until Im shown the NEC says different

ONCE MORE feel free to wire YOUR welder with any size wire you like GO FOR IT regardless if it meets code or not ITS YOUR RISK YOUR CALL not mine not the NEC I am NOT telling you what to use, got it ????

There ya go. I say this is all TRUE but all are entitled to other opinions with all due respect

John T

Hey Good Neighbor George, I TOLD YA SO and here's proof........

Electrical or Legal questions draw more responses and opinions, both lay and professional, than any other topics and I thoroughly enjoy them yayyyyyyyyyyyyyyyy

This draws out more than gas prices or EV topics lol

Take care George I love your interesting threads, keeps the place busy

John T

I think your 12g wire would heat up about as fast as the welding rods. Might work in an emergency but wouldn't last very long.

The receptacle has to be fed with the proper wire size for the amps. https://www.cerrowire.com/products/resources/tables-calculators/ampacity-charts/

Plug wire on the welder is irrelevant.

I run drops for my welder. Welder requires 50amps. So I use 6ga outdoor wire for all drops. It's slightly higher than needed, but voltage drop is within an acceptable range at the distance I run.

You can't cheap out on wire.

I saw this electrical thread and didn't want to be the only one not to post so here I are. Slice any way you please but the fact is those old tombstones can't be burned up regardless what NEC thinks about them.

JohnT

I AM SAYING unless code has changed the absolute MINIMUM wire to be used must have an ampacity of at least 125% of the circuits Maximum Continuous Current AND THAT HOLDS TURE FOR WELDERS OR ANY ELECTRIC LOADS.

Me electrician doesn't use 125%, he says wires and circuit breakers should only be used at about 80-85% of their max rating. Again these rules apply to Maximum Continuous Current.


The 225 Lincoln is not rated at Continuous use, they are rated at 20% duty cycle..

Would you like to wager, a meal at TX roadhouse, the transformer's primary wires are not bigger than 12g?

The cables are 3/16 diameter, .1875. Is that a 7 g wire?
How much current can a 3/16 copper handle?

Do you think the secondary windings are made of 3/16 wire or larger?

To protect a 10g wire use a 30 amp breaker? Yes or NO

Can you use a power transformer, unlike an electric motor, safely work on less input voltage (IR loss) and not burn up?
Yes or NO


George

My dad had an antique lincoln. All copper. It use an iron core that controls the magnetic coupling between the primary and secondary. That welder was 100% duty cycle. Next to bullet proof.
Someplace I read the older 225 lincolns had copper windings (not sure of duty cycle) and the new ones have aluminium transformers. (not 100% sure)

Anybody who has checked the wire gauge on power cords for shop equipment or home appliances has probably found them to be undersized. But the NEC doesn't dictate the size of power cords; the manufacturer does. In the case of your welder, the engineers at Lincoln probably figured out the welder will trip its thermal protection long before the 12 gauge power cord overheats.

I use a 12 gauge extension cord on my 170 amp MIG welder. It's never been a problem even on the highest settings, but I can't weld very long at max voltage and wire speed before the thermal switch trips.

None of that changes the requirements for wiring a 240V/50A outlet. It needs to be wired for 50 amps: AWG 10 wire (minimum) and a 50 amp breaker.

> None of that changes the requirements for wiring a 240V/50A outlet. It needs to be wired for 50 amps: AWG 10 wire (minimum) and a 50 amp breaker.

Should have said AWG 6 wire (minimum), not 10!

Its fun helping you understand this George, keep those questions coming and I will answer them for you.

1) Me electrician doesn't use 125%, he says wires and circuit breakers should only be used at about 80-85% of their max rating. Again these rules apply to Maximum Continuous Current

George, you were a teacher right?? Did you teach math ?? The 125% and 80% rules accomplish the same result !!!!!!!!! its how you use it !!!!!!!!!

a) If the MCC is 16 Amps and you size the conductors to have a minimum ampacity of 125% THATS 20 AMP WIRE 16 x 125% = 20 IE if the MCC is 16 you have to use 125% greater wire which is 20 amps

b) If you use 20 amp wire the max current is 80% of 16 Amps 80% x 20 = 16 Amps

SAME RESULT (80% and 125% rules) it depends on which way you use it THERES THE ANSWER IF YOUR ELECTRICIAN DOESNT EXCEED 80% OF CURRENT HE HAS ALSO USED THE 125% RULE just in reverse

2) The 225 Lincoln is not rated at Continuous use, they are rated at 20% duty cycle..

That being the case their internal wiring ampacity may be less than if they were rated for 100%

3) Would you like to wager, a meal at TX roadhouse, the transformer's primary wires are not bigger than 12g?

NO WAY what you and most (so dont feel bad George) non electricians non engineers dont understand is
THE AMPACITY OF SINGLE CONDUCTORS IN FREE AIR IS MUCHHHHHHHHHHHHHHH GREATER than if jacketed or
in conduit. A single 12 gauge wire all alone in air has a MUCH higher ampacity then if its in a
jacket or cord or conduit and if in conduit how many wires and what size conduit

4) The cables are 3/16 diameter, .1875. Is that a 7 g wire?
How much current can a 3/16 copper handle?

The current it can handle is a function of wire size,,,,,,,Type class and physics/chemistry of its insulation ,,,,,,Temperature,,,,,,,,,,,,If its in free air orrrrrrrrr in a jacket or enclosure or raceway and if so how many conductors in what size enclosure

5) To protect a 10g wire use a 30 amp breaker? Yes or NO

NO you protect the wire based on its ampacity ....If its rated (depends on if in free air or jacketed or in raceway or enclosure and temperature and insulation and how many enclosed conductors) at 30 amps in that case YES use a 30 amp breaker

6) Can you use a power transformer, unlike an electric motor, safely work on less input voltage (IR loss) and not burn up?
Yes or NO

YES it will NOT burn up iffffffffff its windings and internals are all sufficiently rated to handle the max current and effectively dissipate the heat generated on BOTH its Primary and Secondary. If the input voltage is less so will the output voltage be less,,,If the input is higher so wil the output be higher,,,,,

GEORGE, do not feel bad if you dont understand all this. Its IMPOSSIBLE for me to explain or for you to understand in a few sentences here WHAT CAN TAKE YEARS OF STUDY to comprehend, but hey I try my best and am glad to help you and will continue to do so

FWIW per NEC when I practiced (may be different now it changes every 3 years so no warranty) if I specified the conductors that fed a 50 amp receptacle, they had to have at least 50 amp rating NOTTTTTTTT 20 NOTTTTTTTTT 30. NOTE thats NOT to say if it only takes 20 or 30 amps to serve a load you have to use 50 amp wire WHAT A WELDER OR OTHER LOAD REQUIRES IS NOT THE SAME AS WHAT THE CODE MAY REQUIRE TO FEED A GIVEN RECEPTACLE

You DO NOT need any of our permission or the NEC to wire anything however you please GO FOR IT. Its YOUR life YOUR risk YOUR building. All I can do is try my best to help and educate you and the other fine gents here in electrical safety and theory to maybe prevent a fire or electrocution NOTTTTTTTTTTT TO ARGUE WITH OR FIGHT, ONLY TO HELP

Best wishes good neighbor, I hope this helps but again I can NOT explain nor can you be expected to understand what takes years of study and experience to comprehend SO YOURE OKAY Have a good day neighbor. Instead of us boring the others to tears feel free to e mail me [email protected] your questions and I will try my best to help you without hogging up the forum lol

John T

Easy to install. Comes with attached 6 ft. (1.8m) input powercable and NEMA 6-50P plug

Lincoln says welders come with a 6g 50a plug.
Mine is 10g and 50a plug powercable.
The welder was a Christmas gift.
I think this welder was purchased at sears or lowes.
I'm wondering if my welder was built cheaply for the weekender welder and sold at box stores.

It works for me using a 1/8 rod, 105 amp setting, 30 amp breaker and 10g wire.

A power transformer can operate safely on less input voltage caused by IR loss.

I use a dimmer on my old battery charger. No damage to transformer. Decrease input voltage and decrease output voltage. It's that simple.

My son may come over this weekend. He wants to learn how to weld. It takes 2 people to measure the primary and secondary currents..One person to weld and the other to read the amprobes.
I may attempt to measure the primary voltage too, measure IR loss.

> My son may come over this weekend. He wants to learn how to weld. It takes 2 people to measure the primary and secondary currents..One person to weld and the other to read the amprobes.

I think you'll be surprised at the peak current your welder draws. Let us know how it goes.

Mark,
Peak primary current in 91 amps. Peak out current is 210 a on the 130 a setting. I want to know the continuous welding current
Peak current on my central 2.5 ton AC is more and it's wired with 30 amp and 10g wire.
Peak current on a 4 hp electric chainsaw is 74 amps.
Running amps is 15a.
Peak AC compressor current is more important than peak current on a transformer. I've never seen a residential AC (not hP) wired with more than 30a and 10g.

You would be surprised if you measure a refrigerator's the starting current.

I'll bet you I could put a diode in series and weld with half waves powering the transformer. I see no reason to use half waves. I do have a diode that will easily handle the starting current

Less voltage to the transformer's primary will only influence the secondary voltage..NO DAMAGE,

Mark, Geo whoever, please follow the link I posted earlier. Pretty clear that welder outlets don't follow the normal rules.

I will say however, that any outlet so wired should be labeled as 'WELDER ONLY', no matter what the book says.

I have a big electric heater that could be plugged into my welder outlet. But that continuous load would really heat up my 10ga wire.

Air 240conditions/Heat pumps are another example of legal violations of NEC 240's normal rules. NEC 440 allows larger overcurrent protection for AC. 40A on 10ga is really common locally to prevent nuisance tripping. Good article here: https://iaeimagazine.org/electrical-inspections/overcurrent-protection-for-air-conditioning-and-refrigeration-equipment/

Use whatever gauge wire you want.

Maybe after the house or barn burns down the fire inspector will not find the 10 gauge wire feeding the 50 amp outlet.

And maybe your insurance company will not deny coverage.

(quoted from post at 09:56:27 10/19/22) Mark, Geo whoever, please follow the link I posted earlier. Pretty clear that welder outlets don't follow the normal rules.

I will say however, that any outlet so wired should be labeled as 'WELDER ONLY', no matter what the book says.

I have a big electric heater that could be plugged into my welder outlet. But that continuous load would really heat up my 10ga wire.

Click to expand...

ohn shoots the straight stuff in NEC. However, by my read, George isn't really looking for that, so I will help muddy the waters. 12 GA wire in free air can handle 41 amps (MIL-STD 5088). I wouldn't do this inside the walls of my structures. Further, the fusing current (where 12GA copper wire melts) is above 240 amperes. 1/8=0.125 (80% & 125%). Again, not in my house or garage, but did once upon a time long long ago, operate a garage door opener with power thru 18GA copper coated steel telephone wire strung thru the trees. What can or has been done does not in any way equate to what should be done and for sure won't meet NEC!
9

Geo-TH,In
2004 was the year my garage was built. My little welder required a 50 amp receptacle. 50amp breaker and the proper size wire to the receptacle. You can get away with smaller wire of course, as long as you ARE NOT using the welder to the MAX!c

The code does not cover cords from appliances, Most are probably not up to feeder ampacity.