Wiring a welder circuit

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Old 07-17-08, 06:35 AM
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Wiring a welder circuit

Hello
This is my first post here and I hope that you folks can help me. I have a fair degree of electrical aptitude but I am kinda stumped with how to go about one of my projects. I have a 200amp GE main panel in my garage. I have appx 6 open slots and I already bought a 60 amp double breaker to install so I can wire up an old lincoln buzzbox welder. Installing in the panel isnt a problem, the wire size is. Nowhere can I find 4/3 romex cable as I believe that this is the minimun that I need. The welder, btw, is rated 240V/50amp...I just want a little heavier breaker just in case....
I read somewhere that 6awg THHN cable might work? I am a little confused as LOWES doesnt sell anything in the 4/3 romex venue. Can someone here tell me what wire options I am looking at?

Thanks a bunch!

Ben
 
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Old 07-17-08, 07:05 AM
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You don't need 3 conductor for a "pure" 240v circuit. If the distance isn't far you should be OK with 6-2.
 
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Old 07-17-08, 07:09 AM
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For a welder you can use smaller conductor sizes than would normally be allowed. Assuming that particular welder has a duty cycle of 40% (it may be lower) #8 conductors would be sufficient.

Further, you do not need three current-carrying conductors in the supply, but two current-carrying plus an equipment ground.
 
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Old 07-17-08, 08:07 AM
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Useally the arc welder have it own rules to deal with conductor size and with common resdential " buzzbox " typically use #8 THHN/THWN or UF or NM and you only need two hot conductor and equmient ground.

A quick side note if you use 8-2w/g NM or UF for some reason make sure you remarked the white conductor so you will know it is a hot conductor instead of netural.

Merci,Marc
 
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Old 07-17-08, 08:35 AM
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I agree #8/2g or #6/2g romex NM-B cable will be sufficient for your welder.
 
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Old 07-17-08, 08:36 AM
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Guys
Thanks for the Great replies
Now just to clarify, I can use either 6/2 NM (isnt this rated at 55amp?) even though my breaker will let 60 amp through? Is that why the duty cycle is important (because the welder won't be pulling max amps 100% of the time?

OR
I can use #8 THHN (also rated at 55amp?) I never used anything more than 12/2 or 14/2 romex. From what I understand, are both the 6/2 and #8 THHN wire stranded? I thought for most house wiring, solid core copper romex was the standard.

I was given 4 spools of #12 THHN stranded wire awhile ago, but since I saw it was stranded, I never used it for any of my house wiring projects. Instead, I went out and bought spools of 12/2 romex. I guess what I am saying here is that I am a little hesitant to use stranded wire when all of my house (at least what I saw so far), has the solid copper romex (either 12/2, 12/3 14/2 or 14/3)

Are my assumptions about stranded wire wrong (re: amperage capacity ratings) One last thing, if I decide to go the THHN route, what kind of conduit do I put it in? (armor I assume?)

Thanks again!!
 
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Old 07-17-08, 08:44 AM
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Above 30 amps, there is not a simple rule about how many amps that wire of a certain size can handle. So your comment about #6 being good for 55 amps simply doesn't apply to welders. Rules for applications above 30 amps are more complicated.

Stranded and solid are equivalent. Use them interchangeably. However, cable and individual wires are not equivalent, and the rules for installation and ampacity differ.

In most cases, DIYers will find that PVC conduit is easier to work with than metal. Just make sure the glue is fully dry before putting in the wire.
 
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Old 07-17-08, 12:01 PM
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Just to be clear the #12 you have can not be used for the welder circuit.
 
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