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Old 06-06-2011, 08:22 PM   #1
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Wiring for 30/50 Amp


My shop is wired for 220 off a 30Amp breaker from the main box to a breaker box in my shop. The reason we didn't wire for 50Amp is because I hadn't used a heavy enough wire and didn't want to dig it up and start over. At the time I only needed 220 for my large compressor. It's about 30 feet away from the house.

I have a Lincon Arc Welder that will pull variable voltage, depending on manual settings. I normally use only 75 or less. The welder has a 125V plug on it.

What I want to know is what can I do to use the welder at the shop. I have a 50Amp outlet below the main box at the house, but don't want to weld everything over there or drag out my SUPER HD 50A extension cord.

Can I not wire a 50Amp receptacle from a 30Amp breaker? Or can I not use a 50Amp breaker on the 30Amp bars? (At the shop).

I'm probably not wording this correctly, but I hope you can understand what I'm trying to do

If I cannot do it, I'll just run 50Amps (overhead - no more digging) to the shop.

Any advice greatly appreciated.

Regards,

Jim in The Deserts of NM

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Old 06-06-2011, 09:06 PM   #2
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Wiring for 30/50 Amp


I operate my Millermatic 180 MIG welder from 30a breaker and #10 wire - works fine even on higher settings. I have a extension cord for the welder that converts from the 30a recept to the welder plug. When not using the welder other things use the 30a recept - such as a shop heater.

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Old 06-06-2011, 09:36 PM   #3
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Wiring for 30/50 Amp


Quote:
Originally Posted by vsheetz View Post
I operate my Millermatic 180 MIG welder from 30a breaker and #10 wire - works fine even on higher settings. I have a extension cord for the welder that converts from the 30a recept to the welder plug. When not using the welder other things use the 30a recept - such as a shop heater.
What type of plug is on your welder? I've attached a picture of the outlet I need to use.

I also have an extension cord to run 50A from the house box, but it's as big as your leg .

My real question is "what" breaker to put in the box in the shop. It has 220V, but at this point, I have only used a 30Amp breaker because the wire from the main box wasn't heavy enough (??) to handle 50 Amps. I think it was only 12 Gauge.

Many thanks,

Jim
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Old 06-06-2011, 11:19 PM   #4
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Wiring for 30/50 Amp


WEll...a 30 amp breaker should have 10 ga. wire....not smaller. If you truly have 12 ga wire you need to either change it or replace the breaker with a 20 amp. (and the welder just may work on the 20 amp breaker) And your welder always draws the same voltage, it's the output you are controlling, not the input. You said the welder has a 125v plug on it? Now I'm confused.
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Old 06-06-2011, 11:49 PM   #5
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Wiring for 30/50 Amp


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WEll...a 30 amp breaker should have 10 ga. wire....not smaller. If you truly have 12 ga wire you need to either change it or replace the breaker with a 20 amp. (and the welder just may work on the 20 amp breaker) And your welder always draws the same voltage, it's the output you are controlling, not the input. You said the welder has a 125v plug on it? Now I'm confused.
I don't know. That's what Cooper (maker of plugs and receptacles) told me. Not sure exactly what it meant. Anyway, the picture I included is the outlet I need to plug the welder into. I was thinking 30Amp, but they said it was a 50Amp. Still not sure what the 125 plug thing was all about. Actually, all this has my head spinning .

Regards,

Jim
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Old 06-07-2011, 08:04 AM   #6
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Wiring for 30/50 Amp


If you were to install the 50 amp receptacle off the panel that is fed by the 30, it would still be limited by the 30 amp breaker that feeds the panel.

Devices are shown with ratings of 125/250 volts even tho the system voltages are 120 and 240.
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Old 06-07-2011, 08:39 AM   #7
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Wiring for 30/50 Amp


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Originally Posted by desertjim View Post
I don't know. That's what Cooper (maker of plugs and receptacles) told me. Not sure exactly what it meant. Anyway, the picture I included is the outlet I need to plug the welder into. I was thinking 30Amp, but they said it was a 50Amp. Still not sure what the 125 plug thing was all about. Actually, all this has my head spinning .

Regards,

Jim
That is a 50A 125V receptacle (5-50R).
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Old 06-07-2011, 10:41 AM   #8
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Wiring for 30/50 Amp


Quote:
Originally Posted by Jim Port View Post
If you were to install the 50 amp receptacle off the panel that is fed by the 30, it would still be limited by the 30 amp breaker that feeds the panel.

Devices are shown with ratings of 125/250 volts even tho the system voltages are 120 and 240.
Thanks, that's what I've been trying to ascertain. I don't want to do anything that would damage anything.

I bought the welder used and the guy was using it on 30Amps, so I know it will work on 30A. It will just be limited in that respect.

So........doesn't that mean that I could use a 30A breaker in the box in the shop rather than a 50A breaker?

Regards,

Jim
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Old 06-07-2011, 03:11 PM   #9
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Wiring for 30/50 Amp


You can have a circuit protected by a 30a breaker - using #10 wire - going to the 50a recept appropriate for your welder.
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Old 06-07-2011, 03:22 PM   #10
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Wiring for 30/50 Amp


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Originally Posted by vsheetz View Post
You can have a circuit protected by a 30a breaker - using #10 wire - going to the 50a recept appropriate for your welder.
Why do I need #10 wire since my welder can run off 30A? Is it just for the proper configuration for the receptacle?

Thanks,

Jim
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Old 06-07-2011, 03:33 PM   #11
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Wiring for 30/50 Amp


A 30 amp circuit requires #10. A 50 amp would be #6.
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Old 06-07-2011, 04:25 PM   #12
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Wiring for 30/50 Amp


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Originally Posted by Jim Port View Post
A 30 amp circuit requires #10. A 50 amp would be #6.
Ok! I guess I ran #10 wire to the shop. Makes sense, since I know I have 30A out there. Thanks, Jim

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