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#169478 - 10/05/07 06:43 PM hooking up a miller welder??
kojunho Offline
Member

Registered: 03/11/06
Posts: 27
Loc: bay area, ca
my buddy just bought a miller tig welder and wants me to run a circuit for his welder. i was checking out the owners manual and it recommends using a 80a breaker w/ 8awg copper conductors. should i up the wire size to 6awg or go with the manufacturers recommendation?? anyone w/ experience hooking up welders?? i looked in 630.11 but couldn't interpret it.
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#169484 - 10/05/07 07:23 PM Re: hooking up a miller welder?? [Re: kojunho]
electure Offline

Member

Registered: 12/24/00
Posts: 4225
Loc: Fullerton, CA USA
You should be fine with the manufacturer's recommendation.
It looks like they've just taken into account the duty cycle of the welder and applied the proper multiplier.

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#169514 - 10/06/07 06:39 PM Re: hooking up a miller welder?? [Re: electure]
Active 1 Offline
Member

Registered: 02/22/03
Posts: 684
Loc: Grayslake IL, USA
Looking at the specs it says:
Min Grounding Conductor #8
with a footnote (4) size per 310.16

Why would they size the EG using 310.16?
Why do they call for the EG to be the same size as the current carrying conductors? Extra safty or a mistake?
I would say it should be sized per 250.122.

Also it lists the unit as:
Drawing 54 amps at rated output
Use #8 min input conductors
With the same footnot size per 310.16

If I look at 310.16 #8 is good for 55 amps if you could use the 90 degree column. In the 75 degree column it is only good for 50 amps.

I agree you can derate it for duty cycle per 630.11.
It does not list the duty cycle on this page. And still why would they say size per 310.16 with no mention of derating. Would derating the conductors per duty cycle be concidered by some as failing to follow manufactures instructions.

To me it just looks like the manufacture stumbled with the NEC when printing the manual.

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#169520 - 10/07/07 06:59 AM Re: hooking up a miller welder?? [Re: Active 1]
PE&Master Offline
Member

Registered: 02/25/06
Posts: 138
Loc: TX, USA
Stick with the owners recommendations. They know what the equipment needs better than anyone. I'm sure they didn't guess at wire size of grounding requirements. Unfortunately everything in life will not make sense.

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#169551 - 10/08/07 02:21 AM Re: hooking up a miller welder?? [Re: PE&Master]
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2331
Loc: Vienna, Austria
On the other hand... oversizing the feeder will only harm the owner's wallet. Technically it will increase the life expectance of the wire since the insulation temperature will be lower. And NO, I'm absolutely not sure if the people printing a tech manual really know what they're doing.

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#169555 - 10/08/07 04:57 AM Re: hooking up a miller welder?? [Re: Texas_Ranger]
gibbonsseabee80 Offline
Member

Registered: 10/10/05
Posts: 40
Loc: Chesapeake, VA
Kojunho,
Just curious of the model of the Miller Tig. I would like to read the manual. I looked at a couple of Maxstar models on the website. The manuals seem to be on the money with ground and sizing recommendations. It seems like like the sizing recommendation in your post is based on motor sizing rules. I have hooked up welders and used to clean the Miller hard-wired welders at my last shop. Really wierd, but with todays technology anything is possible.
_________________________
Brian Gibbons

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#169564 - 10/08/07 08:36 AM Re: hooking up a miller welder?? [Re: gibbonsseabee80]
JValdes Offline
Member

Registered: 06/03/07
Posts: 308
Loc: South Carolina
Would it be a violation to use #8 awg on a 80 amp breaker?
60c wire max is 40 amp column 1
75c wire max is 50 amp column 2
90c wire max is 55 amp column 3
No derate calculated.

The equipment conductors can be whatever the manufacturer wants to use. As they calculate at diferrent wire temps.

If it were my welder, I would use a 60 amp breaker with #6 wire and 90c or 75c wire. My first thought was a 50 amp breaker but your load is 54 amps.

The manufacturer may be considering the high inrush current when you start welding. (thus 80 amp breaker)?

The manufacturers care nothing about the code. What you do for the hook up is in your lap, not theirs.

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#169566 - 10/08/07 09:13 AM Re: hooking up a miller welder?? [Re: JValdes]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
Welders are in article 630. The rules allow fairly small conductors for a low duty cycle welder.
You can never go wrong using 310.16 but that will be more wire than you need in most cases, particularly for the typical homeowner welder. I used 310.16 for mine but I knew I might be using that outlet for other things, another consideration when you turn Harry Homeowner loose with an extra circuit.
_________________________
Greg Fretwell

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#169709 - 10/12/07 06:59 PM Re: hooking up a miller welder?? [Re: gibbonsseabee80]
kojunho Offline
Member

Registered: 03/11/06
Posts: 27
Loc: bay area, ca
 Originally Posted By: gibbonsseabee80
Kojunho,
Just curious of the model of the Miller Tig. I would like to read the manual. I looked at a couple of Maxstar models on the website. The manuals seem to be on the money with ground and sizing recommendations. It seems like like the sizing recommendation in your post is based on motor sizing rules. I have hooked up welders and used to clean the Miller hard-wired welders at my last shop. Really wierd, but with todays technology anything is possible.

the welder is a miller syncrowave 200. im thinking about using the time delay fuses instead of the 80a breaker. 80a breakers aren't easy to find. by the time i get home the supply houses are closed. if i hook it up using the 60a time-delay fuses, would i still run 8awg from the panel to 60a time-delay disconnect, and use a 40a breaker in the sub-panel?? my foreman tells me to run 6awg but want to see what others have to say

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#169712 - 10/13/07 03:26 AM Re: hooking up a miller welder?? [Re: kojunho]
electure Offline

Member

Registered: 12/24/00
Posts: 4225
Loc: Fullerton, CA USA
The characteristics of the welder itself will not be changed.
The wire size will remain the same with the exception of the equipment grounding conductor, which with a 60A overcurrent protection could, by NEC, be reduced to a #10.

You've just had an easy hundred or two years of combined experience explain this to you.

Are you sure you want to put that 40Amp breaker in the subpanel? You've now gone from a matter of the manufacturer's recommendations at 80A OCPD with #8 to a 40A OCPD with #6??

Does your foreman have any reason that he can cite for the increased conductor size to #6? That's just nonsense.


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