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Old 02-11-2020, 11:15 AM
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Sberry Sberry is offline
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Default Wiring welders and other equipment

I see a quite a bit of confusion about wiring welders, wire and breaker size. There is a difference between thermal overload and short circuit interruption. While some overkill is ok the way its presented makes it obvious there is a bit more study needed.
Very rarely other than 120v general circuits does the breaker protect the wire from overload, the applied load of the device does or further internal ocpd may, some of it in the fashion of a power strip where it protects the wire ahead of it.
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Old 02-11-2020, 11:28 AM
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I am going to simply add pieces as I walk by my puter or sit for coffee, its easier than keeping a continuous thought.
But equipment may be wired different if its hard or a recept. Other than welders which have a special code section other circuits need to match wire recept and breaker for 2 reasons. It tells the user it is adequate for appliances that come 30A plug,,,, and as importantly it is to insure it has a limited opcd, so a 30 has a 30. Many tools may require or allow 30 but come with 14 wire, the tool is protected by other means, part of the tool maybe further protected or load calculated but requires short circuit from the breaker. Buzzer welders, electric ranges, compressors and other special equipment is and may be tailored with internal wire sufficient for this rather than add further devices.
You see this with motor leads and controls. We built a cooler a while back, my guy used light control wires etc, load of 11A and we wanted to use it on welder circuits so its all 240 and we added a 20A breaker to it and upsize the cord to 12 to a welder plug, can plug in to welder circuits to 50A.
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Old 02-11-2020, 12:48 PM
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We got some good code nitpickers but wouldn't mind seeing some "why" so to speak which are the fundamentals of circuit design. The only reason I do it at all is I want something and welding wiring and piping is a way to get it.
I missed the computer revolution. I was right n it and had a barn fire which took me about 4 years to recover. Business that would have benefited fast were done then and I missed the wave and not an engineer and don't care to work in sophisticated trouble shooting, some are natural, I hate all that stuff.
So,,, I had a nice little collection or job pics I had, I even looked for negatives but was in a desk got burned. I had hoped to scan them in 91. I knew I couldnt call someone for every circuit and I wired a lot wrong due to the lack of testing and I could fool other people by design etc. It took a couple years for me to beat someone to the answer on a forum till I had a couple relevant duh moments to stuff now an instinct.
I am an installer and I want to make it compliant and worthy of inspection. As the truck inspector said after a reman we did,,, absolutely no reason not to get it inspected. Anything I work on or for my first instinct is to size and insure adequate ground. Look for floating cans. Lots of diy copy 1 panel to the other and bond the second or leave it floating. In some cases a bond could be preferable to ungrounded. Hence the advent of the GFCI.
So excellent in the advent of interruption from equipment from wired improperly or loss of ground fault pathway.

Last edited by Sberry; 02-11-2020 at 01:07 PM.
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Old 02-11-2020, 01:13 PM
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I see some boogers. My neighbor has nice place and uses 12/2 for a dryer. He is a smart guy but simply glazes over when a guy trys to work on the concept the wire needs to match the outlet. Always on the long end of a circuit with another hundred foot shit strung on thru power strips and 3 ways with ground missing on the plug.
Considers gfci a nussiance and the exact poster child for why they got it.
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Old 02-11-2020, 01:43 PM
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So the code has a bunch of math gibberish that is over my head and its easier to try and remember it but basically circuits up to 30 need a wire as big as the other conductors and some circuits to 60A and or 6 wire need 10.
Its tempting to want to simply upsize at every turn but not always a great idea as other parts then not compliant etc. This may include the machine plugged in to it in regards to internal fault protection.
Anyone remember an old timer was an electrician Hank on the Hobart Miller,,, well he had finally come to the conclusion of hook it up to a 10 cable and weld away, worry about what if later, had all modest equipment and knew it wouldn't over heat it, simple as that.
Welders in the compact 240 class non inverters work rather well with 12 cord. They allow 50 ft of 14, I put it 50 ft of 12. Give him 2 outlets where he was gonna use 1 and both will make direct machine plug available vs a cord across the whole building. Wired both outlets to the same breaker. Not daisy chained.
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Old 02-11-2020, 01:44 PM
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My observations: Most in the trade wire for the load. Most DIY's either over-kill or under-kill. Rare is the inspector who is well versed in all trades.
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Old 02-11-2020, 02:03 PM
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I believe other than a welder outlet the conductors must match the outlet as well as the breaker. Yes as to wire for load when its hard wired. Especially air comps and air cond for this crowd. Some installers over wire due to the reduced stock on wheels. Before a guy changes a breaker from 15 to 20 on every 12 wire he sees insure that there isn't 14 extensions and even some under sized wire isn't so much a concern provided the installation is limited thru hard wire such as lights.
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Old 02-11-2020, 02:13 PM
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Something else to consider is the minimum ground conductor may apply as part of a cord or cable as long as its as big as the current carry conductors, could need to upsize under some circumstance. Note in some of the old 240 compacts they used to allow 14 conductors and required a 12 ground. The new DVI have a fuse in the adapter to allow a device with 14 cord to be plugged on to common 50A welder circuits.
The 120V end simply removes it and rewires for 120 and allows the premiss circuit breaker provide fault protection in to and within part of the machine. Think of the adapter on the dvi as a 30A breaker in the line.

Last edited by Sberry; 02-11-2020 at 02:19 PM.
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Old 02-11-2020, 02:20 PM
nelstomlinson nelstomlinson is online now
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Sberry, the one nit I would pick after a quick skim through what you wrote is that the NEC does call for the breaker to protect the wire, so wire size is determined by breaker size. The breaker does NOT protect the equipment fed by the circuit - that is why there are fuses or something inside the equipment.

NEC 210 is the section that tells us things like what conductor size to use for branch circuits, NEC 630 is the section that covers welders and how to select a smaller conductor size for them.
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Old 02-11-2020, 02:30 PM
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Quote:
Originally Posted by nelstomlinson View Post
Sberry, the one nit I would pick after a quick skim through what you wrote is that the NEC does call for the breaker to protect the wire, so wire size is determined by breaker size. The breaker does NOT protect the equipment fed by the circuit - that is why there are fuses or something inside the equipment.

NEC 210 is the section that tells us things like what conductor size to use for branch circuits.
There are also exceptions for motor and compressor circuits that have fuses or other OCPD at the unit, the breaker is there for short circuit protection of the circuit and the fuses are there for overload protection of the unit and the circuit. The motor tables allow us to size the breaker well above what the circuit conductors are rated for, there are even exceptions to the exceptions, (ie if it still trips at startup you may go to the next size up).
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