50 Amp receptacle in barn with 50 Amp 240 Service?

I don't know but I run my 65amp welder on a 50 amp circuit all the time. I do not recall ever tripping a breaker. Most of the time you WON'T run your welder at its max setting. Maybe never depending on the work you do. If the breaker trips you stop welding and reset the breaker. I do not know how your sub panel is setup, but the welder circuit should be on its own breaker even if its the same size as the incoming circuit.
Its "probably" ok, but I have not seen the barn. However to give you an idea. Go add up the current limit of all the circuits in a house. Its almost always much more than the main breaker on the service entrance. My shop has a 100amp sub panel feeding it, and off that sub panel are two more sub panels. One is 100 amps, and one is 60 amps. The only time I recall tripping one of the main breakers was when I accidentally shorted a transformer while repairing a machine.
MAKE SURE YOUR WIRING IS UP TO THE TASK. DO NOT SKIMP. FOR "NORMAL" SHOP WELDING IT SHOULD WORK, AND YOU CAN PROBABLY EVEN LEAVE THE LIGHTS ON.

I don't know but I run my 65amp welder on a 50 amp circuit all the time. I do not recall ever tripping a breaker. Most of the time you WON'T run your welder at its max setting. Maybe never depending on the work you do. If the breaker trips you stop welding and reset the breaker. I do not know how your sub panel is setup, but the welder circuit should be on its own breaker even if its the same size as the incoming circuit.
Its "probably" ok, but I have not seen the barn. However to give you an idea. Go add up the current limit of all the circuits in a house. Its almost always much more than the main breaker on the service entrance. My shop has a 100amp sub panel feeding it, and off that sub panel are two more sub panels. One is 100 amps, and one is 60 amps. The only time I recall tripping one of the main breakers was when I accidentally shorted a transformer while repairing a machine.
MAKE SURE YOUR WIRING IS UP TO THE TASK. DO NOT SKIMP. FOR "NORMAL" SHOP WELDING IT SHOULD WORK, AND YOU CAN PROBABLY EVEN LEAVE THE LIGHTS ON.
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I run a Lincoln Square Wave 175 welder at about 120A through a 50A breaker (240V) in a 200A panel (electric heat). The breaker hasn't tripped yet, even when rods stick. 120A has been good for up to 1/2" plate with 1/8" 7018 rods.
My 50A AC arc welder draws less than 20A at 120V. I've measured it carefully because I converted it into a variable voltage battery charger, and operate it short-circuited to test circuit breakers. Some from Amazon degraded after the first trip. For power calculations the expected arc voltage is 20~25V and the efficiency is around 60~70% at line voltage, due to the transformer's simple lossy current limiting design. The efficiency is much higher at lower input voltages where the core doesn't saturate.

I run a Lincoln Square Wave 175 welder at about 120A through a 50A breaker (240V) in a 200A panel (electric heat). The breaker hasn't tripped yet, even when rods stick. 120A has been good for up to 1/2" plate with 1/8" 7018 rods.
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At 100% efficiency 120A at 25 arc volts would equal only 12.5A through the breaker at 240V. The Lincoln has active SCR control and I haven't measured its efficiency because welding projects don't appear to affect my home electric bill.

Isn't a "rule of thumb" 50% efficiency for copper-and-iron transformer machines 90%+ efficiency for inverter welding machines ? So start with your calculation (/ (* 120 25) ;; 3000 ;; W 240.0) ;; 12.5 ;; Amps then double the Amps assumed at the wall-socket ie. 25A if is a transformer machine.
That inverters are so efficient is rather obvious from the welds you can run without ever tripping the breaker.

Isn't a "rule of thumb" 50% efficiency for copper-and-iron transformer machines 90%+ efficiency for inverter welding machines ? So start with your calculation (/ (* 120 25) ;; 3000 ;; W 240.0) ;; 12.5 ;; Amps then double the Amps assumed at the wall-socket ie. 25A if is a transformer machine.
That inverters are so efficient is rather obvious from the welds you can run without ever tripping the breaker.
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My largely home schooling in electrical engineering missed that part.
The idling power loss in the 50A buzz box transformer measured 1/4KW at 120V in and 1/2KW at 130V in. The no-load magnetizing current is proportional to input voltage up to 90VAC, then rises rapidly as the core goes into saturation. They are made that way to limit the welding current, as when an electrode sticks. I needed to know because a Powerstat variable autotransformer sets the output voltage and excessive current will burn out its contact brush.
This is the tool that measures AC current without having to disconnect the wire.
I have the UT210E because it also measures DC current and reads low enough to check the power-off drain from a car battery.

I helped you on something? I am pleased with myself!
The info you cite is great. So I'd got the numbers about right just by hearsay judged plausible by observation...
Best wishes Rich Smith

I helped you on something? I am pleased with myself!
The info you cite is great. So I'd got the numbers about right just by hearsay judged plausible by observation...
Best wishes Rich Smith
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I appreciate help on the things I don't know. That's why I ask questions and post links to the references I find. My scientific education was more concerned with the means of uncovering new information, by literature search or experiment, than over-filling my head with details of accepted knowledge. R&D is all about what you don't know yet.
Apparently that's a fundamental difference between science and liberal arts.

Sorry. Its actually 200amp output. Reccomended breaker is 65 amp. Never made any sense to me since it came with a 50 amp plug on it brand new from Miller.

I bought a UT210E after your recommendation and it was useful but I now find it doesn't work any more. It turns on and responds to the selection switch and buttons and on resistance or voltage it shows its working when you connect an item to test and then just displays 0.000 which is all it does in any mode now. I can't see anything wrong internally and new batteries had no effect so it looks like its dead or at least of no use whatsoever.

I bought a UT210E after your recommendation and it was useful but I now find it doesn't work any more. It turns on and responds to the selection switch and buttons and on resistance or voltage it shows its working when you connect an item to test and then just displays 0.000 which is all it does in any mode now. I can't see anything wrong internally and new batteries had no effect so it looks like its dead or at least of no use whatsoever.
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Sorry. There is a lot of info on line about them, including calibration and hacking the code. I haven't tried any of it.

I've just started to look at it but haven't found any useful stuff yet. I wonder as it has firmware if it's trashed its calibration settings, I've seen that sort of behaviour on a number of occasions where the device would occasionally write to places it shouldn't do to ill effect.

Sorry. Its actually 200amp output. Reccomended breaker is 65 amp. Never made any sense to me since it came with a 50 amp plug on it brand new from Miller.
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Don't ask me to make sense of it.

I've just started to look at it but haven't found any useful stuff yet. I wonder as it has firmware if it's trashed its calibration settings, I've seen that sort of behaviour on a number of occasions where the device would occasionally write to places it shouldn't do to ill effect.
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I have several of Uni-T's products. My impression is that they are bright young guys with lots of good ideas but are a little short of practical experience on implementing them reliably. Several times I've noticed that new electrical engineers don't always know how real-life components deviate from the theoretical ideal.
I learned when I was in the testing business, measuring those things. Many of the parts I've bought on line don't quite meet their specs. That was true of Radio Shack too, but surprisingly some were much better than specified, like a "50V" rectifier bridge that tested OK to >500V.
I have another brand of Chinese DC voltage/current/power meter that goes haywire if connected to solar panels, apparently from the marginal operating voltage at dawn and dusk.
Then again I found a bug in an Intel IC's reset circuit and a Texas Instruments computer's microcode. The latter got me promoted to Engineering.

I've got a UT70B IIRC DVM as a back-up to my Beckman DVM, the UT70B has the RS232 which is handy for data logging from time to time. Can't fault the UT70B no problem so far and I've had it for a number of years.
I've turned up the odd bug in a MS 16bit Windows time function where it would report a day earlier at the roll over of midnight from time to time, easy to write code to test it, other Windows time functions had the bug reported but not the one I was using.
I know a guy that turn up a serious bug in an Arizona Microchip processor and he reported it and as a thank you they gave him the development tools he was using.
I have a Newall DRO on my lathe and from time to time it trashes some settings, normally but not always the X axis linear error compensation, thankfully the trashed value is so large that if you move the carriage 1mm it says 10mm so it's obvious. A worse one was a Ubinetics GSM modem which would occasionally trash its radio calibration data and as the company was no more due to the poor product it bricked the modem. Turned out from some testing it was one AT command used to gracefully close the transmission which was at fault so we removed its use as we had that option others that used commercial comms software weren't so lucky.

...A worse one was a Ubinetics GSM modem which would occasionally trash its radio calibration data and as the company was no more due to the poor product it bricked the modem. Turned out from some testing it was one AT command used to gracefully close the transmission which was at fault so we removed its use as we had that option others that used commercial comms software weren't so lucky.
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Back when I had dialup with a low monthly data allowance I wrote a program that extracted new connection data from the modem log and reported current total usage. It had to parse for several AT commands because the protocol didn't seem to be strictly defined or implemented.

Jim - I did research which earned me a Doctorate (PhD). It didn't get me a career because * the project organisation collapsed and mine turned into a solo effort with no-one there for the outcome * my scientific endeavours have been "pilot studies" making a lot of pragmatic progress in the first early stages of the subject timeline, lacking the highfallutin' theory squeezing the n-th nuance out far towards to the highly-developed near-horizontal "right-hand-side" of the subject's progress vs. timeline graph So some similarities - apart from you had career success in an entrepreneurial culture :-)

Jim - I did research which earned me a Doctorate (PhD). It didn't get me a career because * the project organisation collapsed and mine turned into a solo effort with no-one there for the outcome * my scientific endeavours have been "pilot studies" making a lot of pragmatic progress in the first early stages of the subject timeline, lacking the highfallutin' theory squeezing the n-th nuance out far towards to the highly-developed near-horizontal "right-hand-side" of the subject's progress vs. timeline graph So some similarities - apart from you had career success in an entrepreneurial culture :-)
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The only Space project I was privileged to work on shut down after the lead scientist/promoter found a better opportunity elsewhere. It was one of many that was born in a home workshop. They brought me in as electronic tech and I had to prove I could handle optics and machining as well. The Ph.Ds designed with what they could buy off the shelf while I made or custom-ordered whatever I wanted, including a connector for 25um x 125um gold IC bonding ribbon.
Many of the Ph.D theses I've read tend to demonstrate that the author has the potential to do serious research, but they and their advisors lack practical experience.
I think I was most useful when I brought my wide but not that deep multi-disciplinary knowledge to a researcher whose education had concentrated in one field.
A good example, though not a thesis, is Rossi's E-Cat. It was made from brazed copper pipe fittings and he either didn't know or hoped others wouldn't that hot hydrogen reduces copper oxide to copper atoms and carries them downstream. The copper found in the nickel wasn't proof of nuclear transformation. "Given numerous other scientific inconsistencies ? such as the ratio of isotopes in the supposed copper "fusion product" being identical to that in natural copper..."
Iron, nickel and copper are in the region of greatest nuclear stability. Lighter elements can release energy by fusion and heavier ones by fission. They are the end products, the burnt-out ashes of stellar fusion. Imagine what wondrous civilizations might have lived in the light released from what ended as a chunk of iron. Invert the graph to show energy that fusion or fission can release.
The Cruise Missile/Drone/UAV began as a private project that eventually collapsed. The story shows how small details like who happens to be involved can make or break a project. If it worked they could get funding, and if they had funding they could make it work.
The effort wasn't wasted, Sperry and Doolittle gave us IFR flight. Hap Arnold wrote that by the time it was ready the exhausted Germans had no worthwhile targets left within its range.
Re the parachute, they had existed since 1797 but wouldn't (yet) reliably open in free fall. Their container was attached to the fuselage or observation balloon basket and the falling pilot's weight pulled them out evenly. That was no good if the plane was burning or tumbling, and if it wasn't they might glide down. jsw

The comment I can make is from other "interactions" with people in academia. I saw ways of getting at profound scientific issues through "windows" which practical workshop techniques made available. Shuffling scientific ideas - what would be valuable to know - against what was possible to do, in the end I saw very specific "alignments" where what would be useful was possible.
Basically though, I scared people finding totally unfamiliar techniques which looked demented to onlookers.
Okay - something like three decades have passed, so - here goes...
I wasn't supposed to hear this very experienced industrial metallurgist say to my supervisor "So now then who's insane?! :-)" after a technique I proposed worked (using a "shaper" to machine steel in a bath of liquid nitrogen, to keep the weld hydrogen immobile until ready to get it to reveal its location / distribution in the resulting sample).
That experienced metallurgist had faltered to a stop with his jaw dropped coming into the machine shop, with cold steam pouring off the table of the shaper. Explaining I was machine steel in liquid nitrogen, he responded
"I can see what it is that you are doing! What I cannot believe is that someone would actually *do it*!!!" (I wish I could convey the intonation) He knew what I was researching, and had lent me the "Welding steels without hydrogen cracking" publication. So seeing the shaper with cold steam pouring everywhere, he could see in a glance exactly what leap of logic I had made in trying to get in at the issue.
Yes. A team comprising only one type of person has no significance.

The comment I can make is from other "interactions" with people in academia. I saw ways of getting at profound scientific issues through "windows" which practical workshop techniques made available. Shuffling scientific ideas - what would be valuable to know - against what was possible to do, in the end I saw very specific "alignments" where what would be useful was possible.
Basically though, I scared people finding totally unfamiliar techniques which looked demented to onlookers.
Okay - something like three decades have passed, so - here goes...
I wasn't supposed to hear this very experienced industrial metallurgist say to my supervisor "So now then who's insane?! :-)" after a technique I proposed worked (using a "shaper" to machine steel in a bath of liquid nitrogen, to keep the weld hydrogen immobile until ready to get it to reveal its location / distribution in the resulting sample).
That experienced metallurgist had faltered to a stop with his jaw dropped coming into the machine shop, with cold steam pouring off the table of the shaper. Explaining I was machine steel in liquid nitrogen, he responded
"I can see what it is that you are doing! What I cannot believe is that someone would actually *do it*!!!" (I wish I could convey the intonation) He knew what I was researching, and had lent me the "Welding steels without hydrogen cracking" publication. So seeing the shaper with cold steam pouring everywhere, he could see in a glance exactly what leap of logic I had made in trying to get in at the issue.
Yes. A team comprising only one type of person has no significance.
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Love it!!
I had the less spectacular equipment to operate electronics in liquid nitrogen.
Chemists and physicists are encouraged but not required to learn hands-on experimental technique. In industry they may have to be a team of one.
I've seen evidence that mechanical engineers gravitate toward racing and electrical engineers toward amateur radio if they are inclined to build things. Otherwise the EEs I worked for depended heavily on techs to create what they wanted and fix their personal devices, and to clean up after they did try to do something themselves.
At Segway the mechanical engineers all knew how to operate the CNC machine tools, usually crowding me onto the manual ones. Doing weird things was formalized into Frog Days.
As brilliant and well educated as he is, John didn't know how to fabricate and join sheet metal until I showed him press-in PEM nuts.