Welder??

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  #1  
Old 10-31-04, 04:51 PM
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Welder??

For my Miller Synchro electrical wiring it states:

60 hertz-110 circuit breaker-110
min conductor 6 gauge with 74 amps input

Other than maybe "surge", why would you put a 110 amp breaker on a 6 gauge wire drawing 74 amps??

John1
 
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Old 10-31-04, 04:59 PM
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Because it's a welder.
Welders have their own set of codes. Following the manufacturers instructions is the safest bet. Especially for a big name like Miller.

You're going to have to hard wire this thing as there are no plug/receptacles for 110 amps. You will need to use a 200 amp disconnect unless the breaker is within sight.
 
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Old 10-31-04, 05:14 PM
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Nothing wrong with following the installation instructions.

A welder is essentially a controlled short-circuit. Your Miller sounds like it's 100% duty cycle, which means you could keep that arc struck constantly and the machine will tolerate it.

Miller most likely has found that any smaller circuit breaker will prematurely fail, so they specify a larger one.

How long will your wire run be? You may want to consider up-sizing the conductors if your run is much longer than, say, 50 feet.
 
  #4  
Old 10-31-04, 10:28 PM
u2slow
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Originally Posted by John1
Other than maybe "surge", why would you put a 110 amp breaker on a 6 gauge wire drawing 74 amps??
Any machine with windings (i.e. motors, transformers) have an inrush current significantly higher than the running current. That will be why they spec a 110A breaker.

I only have a Canadian code book, but #6 tops out at 65A. I would guess the manufacturer is taking into account the duty cycle. Perhaps full output of the machine is only possible for a few minutes at a time?
 
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Old 11-01-04, 03:36 AM
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It's all in NEC Art.630. Although I do not like to apply this article to residential installations.
 
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