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Discussion Starter · #1 ·
Going to install a welder circuit, I would just typically run #6 from a 2 pole 50 breaker to a 50 amp receptacle and not think about it. But this time I actually looked at the welder and noticed the plug on it says 20 amps. Then noticed that the plug that says 20 amps only fits into a 50 amp receptacle, I figured out where the 50 amps come from using the I max current of 22 amps at 200 percent then round up. But do all welders say 20 amps on the plug? It's kind of misleading I think.

The real question, there is already a 50 amp circuit where they want to use the welder, it has a 30 amp plug on it for a pressure washer, I think they upsized the wire and breaker since the pressure washer has a heater in it. Could I just mount a 50 amp receptacle next to the 30 and use the same feed? Both machines get seldom use and even if they did try and run them both, I would have a 50 amp breaker protecting the wire anyway. In a perfect world I would just bring over a new circuit but the panel isn't close by and it would be a challenge to do.


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I have a Hobart 210mvp, convertible from 240 to 120v. Silly me I read the directions.
There is 12 stranded in the cord, where you change the 50 amp plug over to 120v.
My directions say that I am only getting about 1/2 the amps when on 120v.
This welder draws 18 amps on 120v and 18 amp on 240v. I was very surprised, not a welder expert. Hobart has a scratch and dent page where you can get a returned and reverbished unit with orginal warrantee for less than a new one. Shipping is not all that bad.
I have an old Onan 6.5kw generator that I have rewired with a 50 amp plug fed by 20 amp circuit breakers and 2- 20 amp 120v GFCI outlets. I have tested the rig with the welder and it works just fine. Sometime out in the back 40 a person needs something portable. Least wise I do at times. I know that the welder takes most of the capability of the genny so it is single use. Weld or grind, not both.
At home I put in a 50 amp outlet with #6, just in case my buddy brings over his monster machine.

The only thing I see is the 30 is on a bigger circuit than it should be. Any chance you could put a 30 amp pull out between them?
 

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You don't know what might get plugged into that receptacle in the future, so to me that circuit for the recep must support the full voltage / load the recep is rated for. In other words you're not really installing a welder, you're installing a receptacle.
 

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The real question, there is already a 50 amp circuit where they want to use the welder, it has a 30 amp plug on it for a pressure washer, I think they upsized the wire and breaker since the pressure washer has a heater in it. Could I just mount a 50 amp receptacle next to the 30 and use the same feed? Both machines get seldom use and even if they did try and run them both
No and No
If the pressure washer has a heater in it, and it came with a 30 A plug, it gets a 30 A circuit.
Even if it was a 50A circuit, you couldn't tap off another receptacle for the welder unless you had an interlock.

Do it right, or don't put your name on it.
 

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No and No
If the pressure washer has a heater in it, and it came with a 30 A plug, it gets a 30 A circuit.
Even if it was a 50A circuit, you couldn't tap off another receptacle for the welder unless you had an interlock.

Do it right, or don't put your name on it.
Ok, so I kind of get what you are saying, but what really is the difference between putting these to receptacles on a circuit, and the receptacles in your living room? Each one of them has 2 15 amp outlets in them. You could plug 2 space heaters into one outlet and overload it.
He said in the OP that neither of them is used very often. Why would you need an interlock? I have put multiple welder receptacles on a circuit so that someone could move their welder around. It's one of those things that we tend to think of a machine like that needing its own circuit, but in reality is it any different from 120v 15 or 20A circuits

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We have several multiple receptacle 240 circuits at work. As long as the breaker is sized to protect the wire in the wall who cares. Anything you plug into it should be designed to not melt the plug off the cord. Guess the way I see it protection of the equipment cord etc should fall under the equipment overload design not the building wiring.
 

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Ok, so I kind of get what you are saying, but what really is the difference between putting these to receptacles on a circuit, and the receptacles in your living room? Each one of them has 2 15 amp outlets in them. You could plug 2 space heaters into one outlet and overload it.
He said in the OP that neither of them is used very often. Why would you need an interlock? I have put multiple welder receptacles on a circuit so that someone could move their welder around. It's one of those things that we tend to think of a machine like that needing its own circuit, but in reality is it any different from 120v 15 or 20A circuits

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Well, the 30 washer on a 50A breaker is a no go.

I know what you're saying with the recept's, but when you're wiring a known load that means you are intentionally overloading the circuit. Honestly can't think of a code ref for that but just something I would not do (for a customer)

I look at it this way ... It's why we wouldn't ditch interlocks for multiple motors on a circuit, and just have the customer only run one at a time.
 

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Well, the 30 washer on a 50A breaker is a no go.

I know what you're saying with the recept's, but when you're wiring a known load that means you are intentionally overloading the circuit. Honestly can't think of a code ref for that but just something I would not do (for a customer)

I look at it this way ... It's why we wouldn't ditch interlocks for multiple motors on a circuit, and just have the customer only run one at a time.
As long as the breaker is sized to protect the wire in the wall and the receptacle, ie 50 amp breaker with 50 amp wire with 50 amp receptacle, who cares what they plug into it? Protection of the corded equipment is up to the manufacture at that point, right? The washer should have internal overload protection to limit it to 30 amps and if it shorts out the 50 amp breaker should still catch it. Or am I missing something?
 

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As long as the breaker is sized to protect the wire in the wall and the receptacle, ie 50 amp breaker with 50 amp wire with 50 amp receptacle, who cares what they plug into it? Protection of the corded equipment is up to the manufacture at that point, right? The washer should have internal overload protection to limit it to 30 amps and if it shorts out the 50 amp breaker should still catch it. Or am I missing something?
The pressure washer does not have a 50A receptacle. It has a 50A breaker, with #6, on a 30A receptacle
 

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If the receptacle itself is only rated 30 amps vs the washer being rated 30 amps then that could be an issue, I would think anyway. Seems like you could still add another 50 amp plug on the same circuit.
 

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Coming from a maintenance guy I would probably just switch the plug on the washer to the same 50 amp plug as the welder and put a 50 amp recep in the existing spot and move on. But I don't work on paying customers stuff.
 

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Discussion Starter · #13 ·
Just to update, it looks like there are actually two receptacles on that 50 amp circuit to accomadate them using the washer on the other side of the shop, both receps are 30 amps. I think I‘m going to look at this like some have said, a 50 amp branch circuit with multiple outlets that anything can be plugged into. I do have a problem though leaving the 30 amp outlets on there, just seems wrong, like putting a standard outlet on an old dryer circuit without changing the breaker or something. Maybe just a fusible pull out will take care of that.

Thanks for all the input.
 

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Agree. The problem here is a 30a receptacle with 50A protection. The only time you are allowed to use a lower rated receptacle on a higher protected circuit is the very specific exception of multiple 15A receptacles on a single 20A breaker. The best fix at this point is as others have described, switching the plug on the washer to a 50A NEMA 6-50 plug, matching the welder, then replace the existing 30A receptacles with NEMA 6-50's fed from the 50A breaker with #6. Makes for a safer setup, and gives the ability to plug either the washer or the welder in to either location.
 

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Discussion Starter · #18 ·
Just to give an update, this project is dead. It was for my day job as a maintenance electrician, the guys in the fleet garage shop somehow came into possession of a welder they wanted to use so I was trying to help them out. Well I went and bought everything this morning to add a fusible pullout and receptacle and Frankenstein it in on the cheap. But when I took the existing 30 amp plug off the wall it only had #8 to it. The circuit has #6 at the breaker so I dug around and found a 10kva buck/boost transformer somewhere in the middle. Looks like they’re boosting 208v up to 225v. I said game over, I don’t feel comfortable trying to force this one in, tell the bosses we need some money to do it right and bring a new 50 amp circuit over. (Little things less than $200 I can just approve on my own, that’s why I was trying to avoid a new circuit.)

So next time I’m at the supply house I’ll sneak a 2 pole 30 in there and replace the 50 amp breaker that’s there now.
 

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As long as the breaker is sized to protect the wire in the wall and the receptacle, ie 50 amp breaker with 50 amp wire with 50 amp receptacle, who cares what they plug into it? Protection of the corded equipment is up to the manufacture at that point, right? The washer should have internal overload protection to limit it to 30 amps and if it shorts out the 50 amp breaker should still catch it. Or am I missing something?
What's missing is a machine's owners manual may specify a certain OCP despite the molded cord-plug attached. (Very common with welders.)

In this case, both the welder and washer sound like could each be happy with a 30A circuit.

I would say the approach for installing a circuit changes once the equipment is known/on-site. After all, the work we're doing is to power a piece of equipment; not simply to have a receptacle to stare at.
 
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