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Old 01-30-2014, 12:35 AM   #1
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240 volt 3 wire receptical on new build


Hi all,

New to the site and looking for a little advice.

I moved to the US a few years ago and am not completely familiar with US Electrical code etc. But I was pretty used to working on electrics back in the UK.

Last year I had a new garage built by a contractor and I specified a couple of 240. V outlets as I wanted to run a compressor and a welder. Each are 30A. So I got myself a welder and when looking to plug it in I notice that the plug and receptacle don't match. after a little research I found out that the 240 outlets installed are nema 10-30. Is that even legal/to code? Looking on line all relevant reference seems to indicate that these were old and no longer used.

I had relevant permits and inspection of all work done at the time including the electrics so am wondering what happened.

I want to connect the welder but don't really want to cut the molded plug off and connect a new one. Can I replace a nema 10-30 with a bema 14-30 and not have the neutral? welder only uses 240 so the neutral would not be required as far as I can tell.

I am thinking I might have to contact the contractor again and ask them what's up, but if I can sort this myself then I want to. thanks for any advice.

Cheers
Lwlandy

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Old 01-30-2014, 01:23 AM   #2
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240 volt 3 wire receptical on new build


Welcome to the forum

I have no idea why they would install nema 10-30 receptacles. If your welder is 240 volt only it likely has a nema 6-30 plug on the power cord. 10-30's are common for electric clothes dryers prior to 1996.

I don't think you would want 14-30's as they are 3 pole 4 wire grounding with neutral. Can you give a link to your welder or post picture of the plug?

Take a look at this chart and match it up with your welder plug and tell us what you have.

http://www.westernextralite.com/resources.asp?key=69

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Old 01-30-2014, 01:32 AM   #3
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240 volt 3 wire receptical on new build


What kind of plug on the welder? The 10-30 is a 120/240v. I would think what you need is the 6-30 for 240v only??
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Old 01-30-2014, 06:26 AM   #4
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240 volt 3 wire receptical on new build


Quote:
Originally Posted by lwlandy View Post
...and I specified a couple of 240. V outlets
as I wanted to run a compressor and a welder. Each are 30A.
How specific were you when you "specified" ??
Did you give (did they ask) for a cut sheet or to see the welder?
Quote:
Can I replace a nema 10-30 with...
What is actually needed? Of course.
This is the reality more often than not.
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Old 01-30-2014, 04:41 PM   #5
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240 volt 3 wire receptical on new build


Thanks All,
Yes looks like I was wrong with the 14-30 it looks like the plug supplied is actually a Nema 6-50. Which confuses me even more.. As the welder is dual voltage and only draws less than 30 A on 240 V.
Below is from the manual: (Its a miller Syncrowave 210 by the way)
2 Plug − NEMA Type 5−15P
3 Receptacle − NEMA Type 5−15R
(Customer Supplied)
4 Plug − NEMA Type 5−20P (Optional)
5 Receptacle − NEMA Type 5−20R
(Customer Supplied)
6 Plug − NEMA Type 6−50P
7 Receptacle − NEMA Type 6−50R
(Customer Supplied)

So I can plug it in to my 110 Volt outlets, but I cant connect it to the 240 Volts as the supplied, (and from what I can tell) only 240 Volt plug available is for a 50A receptacle. So I guess now the question is can I just change the receptacle to the Nema 6-50 and just make sure that the 30 A Breaker is maintained? I cant see a problem with that from a technical perspective, but I am sure there would be issues with code compliance and if I ever sold the house, I would certainly not want the new owner to think they could simply replace the 30 A with 50 A Breaker based on the outlet..

Cheers



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Old 01-30-2014, 10:29 PM   #6
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240 volt 3 wire receptical on new build


Quote:
Originally Posted by TarheelTerp View Post
How specific were you when you "specified" ??
Did you give (did they ask) for a cut sheet or to see the welder?

What is actually needed? Of course.
This is the reality more often than not.
I didn't have a welder when I had the workshop built, and not knowing that there are multiple possible plugs I didn't think to ask/specify.

In the UK, we have one plug for 240v up to 13A and then one plug for 16A, one for 30A etc. I incorrectly assumed the same would be the case here in the us.
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Old 01-31-2014, 01:19 AM   #7
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240 volt 3 wire receptical on new build


Quote:
Originally Posted by lwlandy View Post
Thanks All,



Yes looks like I was wrong with the 14-30 it looks like the plug supplied is actually a Nema 6-50. Which confuses me even more.. As the welder is dual voltage and only draws less than 30 A on 240 V.

Below is from the manual: (Its a miller Syncrowave 210 by the way)
2 Plug − NEMA Type 5−15P
3 Receptacle − NEMA Type 5−15R
(Customer Supplied)
4 Plug − NEMA Type 5−20P (Optional)
5 Receptacle − NEMA Type 5−20R
(Customer Supplied)
6 Plug − NEMA Type 6−50P
7 Receptacle − NEMA Type 6−50R
(Customer Supplied)

So I can plug it in to my 110 Volt outlets, but I cant connect it to the 240 Volts as the supplied, (and from what I can tell) only 240 Volt plug available is for a 50A receptacle. So I guess now the question is can I just change the receptacle to the Nema 6-50 and just make sure that the 30 A Breaker is maintained? I cant see a problem with that from a technical perspective, but I am sure there would be issues with code compliance and if I ever sold the house, I would certainly not want the new owner to think they could simply replace the 30 A with 50 A Breaker based on the outlet..

Cheers


The 6-50 is a 240v ONLY plug/receptacle.

But I'm confused now that you say the welder is "dual voltage". Does it run on 120/240? If so, then you would need a 10-50 plug and receptacle.

Can you take a pic of the plug, please?

Also, what information is on the metal spec plate attached to the welder?

I wouldn't suggest a higher rated receptacle on a lower rated breaker for the reasons you give.
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Last edited by sirsparksalot; 01-31-2014 at 01:24 AM.
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Old 01-31-2014, 07:45 AM   #8
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240 volt 3 wire receptical on new build


Quote:
Originally Posted by lwlandy
In the UK, we have one plug for 240v up to 13A and then one plug for 16A, one for 30A etc. I incorrectly assumed the same would be the case here in the us.
Here in the US, we don't like to make things so simple
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Old 01-31-2014, 10:00 AM   #9
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240 volt 3 wire receptical on new build


I've worked with several of the welders like the OPs. They are indeed dual-voltage and will adjust themselves to whatever voltage is supplied.

The cord on the welder is a sort or pin-type and you buy whatever end that matches your receptacle.

The trick here is the max welding amps and duty cycle. The max welding amps is much lower if the machine is run on 120. Higher if it's on a 20 amp 240 circuit, and higher still if it's on a 50 amp 240.

Given that the wire run to the 10-30 receptacle is almost certainly #10, I would recommend replacing the 10-30 receptacle with a 6-20 (20 amp, 240 volt) and changing the breaker to a 2 pole 20 amp.

20 amps at 240 volts will allow about 150 amps of welding current, more for a short time.

Rob

P.S. These new welders are getting better; I recently ran a bunch of circuits for a fabrication shop and the welders would accept anything from 480 3 to 208 1, all automatically switched.
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Old 01-31-2014, 04:03 PM   #10
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240 volt 3 wire receptical on new build


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Originally Posted by micromind View Post
I've worked with several of the welders like the OPs. They are indeed dual-voltage and will adjust themselves to whatever voltage is supplied.

The cord on the welder is a sort or pin-type and you buy whatever end that matches your receptacle.

The trick here is the max welding amps and duty cycle. The max welding amps is much lower if the machine is run on 120. Higher if it's on a 20 amp 240 circuit, and higher still if it's on a 50 amp 240.

Given that the wire run to the 10-30 receptacle is almost certainly #10, I would recommend replacing the 10-30 receptacle with a 6-20 (20 amp, 240 volt) and changing the breaker to a 2 pole 20 amp.

20 amps at 240 volts will allow about 150 amps of welding current, more for a short time.

Rob

P.S. These new welders are getting better; I recently ran a bunch of circuits for a fabrication shop and the welders would accept anything from 480 3 to 208 1, all automatically switched.
Thanks Rob,

Yes exactly right the welder cable has a proprietary end that then allows a specific 120 or 240 V plug to attach. But the only supply 1 of each with the welder and the 240 one looks like it is a 6-50. As you say I could change the receptacle for a 6-20, but the welder is rated at 210 amps output at under 30 A input. I have 30 A supply and I am needing to weld some 1/4" Steel and Aluminum which will likely be at the top end of the current rating.

One thing I thought of that might be the best option all round, though its not perfect, is to make a custom extension with a Nema 10-30 one end and a Nema 6-50 female the other end to allow the welder to plug into it. This way I wont change the wiring or Breaker/Receptacle at all and as long as I remove the extension then no one else would be any the wiser..
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Old 01-31-2014, 08:55 PM   #11
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240 volt 3 wire receptical on new build


Quote:
Originally Posted by lwlandy View Post
One thing I thought of that might be the best option all round, though its not perfect, is to make a custom extension with a Nema 10-30 one end and a Nema 6-50 female the other end to allow the welder to plug into it. This way I wont change the wiring or Breaker/Receptacle at all and as long as I remove the extension then no one else would be any the wiser..
Depending on how you interpret the code, this may or may not be compliant, but it is completely safe.

I would get a dryer cord with a 10-30 plug, and connect the other end to a 6-50 receptacle.

This way you can leave the existing installation as it is, and you have only one connection to make; at the 6-50 receptacle.

The possible code violations I can see is that you're using a technical neutral/ground as a grounding means. No hazard whatsoever, but it might be a violation.

Also, you're now feeding a 50 amp receptacle with a 30 amp circuit. The code says it needs to be fed with a 50. But since it's not part of the permanent wiring, I doubt that the code would apply.

Rob
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Old 01-31-2014, 11:54 PM   #12
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240 volt 3 wire receptical on new build


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Originally Posted by micromind View Post
Depending on how you interpret the code, this may or may not be compliant, but it is completely safe.

I would get a dryer cord with a 10-30 plug, and connect the other end to a 6-50 receptacle.

This way you can leave the existing installation as it is, and you have only one connection to make; at the 6-50 receptacle.

The possible code violations I can see is that you're using a technical neutral/ground as a grounding means. No hazard whatsoever, but it might be a violation.

Also, you're now feeding a 50 amp receptacle with a 30 amp circuit. The code says it needs to be fed with a 50. But since it's not part of the permanent wiring, I doubt that the code would apply.

Rob
Thanks Rob,

I think I will actually do that, but I will contact the original contractor. As I pulled one of the wall plates off today to see how the receptacle was wired and it is connected with two hots and earth with the neutral looped back in the wall. so it doesn't look like it was wired to code in any case.

But the extension should work as you say.
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Old 02-01-2014, 04:11 PM   #13
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240 volt 3 wire receptical on new build


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Originally Posted by micromind View Post
I would get a dryer cord with a 10-30 plug, and connect the other end to a 6-50 receptacle.

This way you can leave the existing installation as it is, and you have only one connection to make; at the 6-50 receptacle. Rob
Huh? I don't understand!

A 10-30 plug with the leads attached to a 6-50 receptacle? What are we doing, cutting the plug off the 10-30 and hardwiring to the welder?

Still don't sound sound to me.
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Old 02-01-2014, 04:28 PM   #14
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240 volt 3 wire receptical on new build


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Originally Posted by sirsparksalot View Post
Huh? I don't understand!

A 10-30 plug with the leads attached to a 6-50 receptacle? What are we doing, cutting the plug off the 10-30 and hardwiring to the welder?

Still don't sound sound to me.
This doesn't affect the welder cord at all; the item in question is nothing more than a 10-30 male to a 5-50 female adapter.

The 10-30 male plugs in to the existing 10-30 receptacle, and the welder plugs in to the 6-50 female.

I suggested using a dryer cord because it already has the 10-30 male attached, and all that needs to be done here is connect the other end of the dryer cord to a 6-50 cord connector or more likely, a 6-50 receptacle.

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