Got Welder need wiring Advice ASAP!

[Inspector507]

Guys,
Keep in mind, welder overcurrent protection and overcurrent protection for conductors to welders is determined in Article 630 of the NEC®. You can toss out all the numbers in 310-16.
Its all determined by the amperage of the unit and the duty cycle of the welder.

 

[bnixon]

You just went WAY over my head! /forums/images/graemlins/shocked.gif

What does that mean to me? I have a 20% Duty Cycle 50 amp max draw unit.

 

[Anonymous Poster]

At the risk of complicating what has been a superb treatise on branch circuit wiring, /forums/images/graemlins/tongue.gif I might take exception to the idea of using DUAL ELEMENT fuses in that welder circuit. My experience with DE fuses in these kinds of applications is that they RUN HOTTER than the equivalent NON fuses do. This is after looking through the lens of an infrared camera at electrical equipment for the last 13 years. If I see a DE fuse used on lighting, for example, it is hot-hot-hot. Does that welder have THAT KIND of inrush that it would require Dual Element fuses??? /forums/images/graemlins/crazy.gif Another very minor point....always install fuses so you can READ the labels. If you do that, you'll always have the correct end in the correct fuse clip when encountering panels with reject-type fuse clips. /forums/images/graemlins/tongue.gif

 

[Inspector507]

It means the same thing I said posts ago........you'll be okay.

 

[uhmgawa]

</font><font color="blue" class="small">( Guys,
Keep in mind, welder overcurrent protection and overcurrent protection for conductors to welders is determined in Article 630 of the NEC®. You can toss out all the numbers in 310-16.
Its all determined by the amperage of the unit and the duty cycle of the welder. )</font>

Funny, I glanced at that a few days ago and wrongly assumed
it pertained only to commercial group-welder installations.
You are correct. The NEC allows derating the required
conductor ampacity for an installation of individual welder
per feed where the welder has under 1 hour time rating as
follows:

D/C % Multiplier
100 1.0
90 .95
80 .89
70 .84
60 .78
50 .71
40 .63
30 .55
<=20 .45

Thus for a welder drawing 50A at it's maximum output power,
but only rated for a duty cycle of 40% at this setting,
the required conductor ampacity is 50A * .63 = 31.5A.
With that bit of NEC legalese aside the minimal conductor
size required is essentially a function of allowable voltage
drop.

Nice catch.

 

[Inspector507]

Maybe the Chief Inspector actually knows the NEC® /forums/images/graemlins/grin.gif

 

[Anonymous Poster]

Inspector507,
Thanks for the clarification.

Uhmgawa,
Thanks for the info.
DaveL

 

[Anonymous Poster]

CJDave,
I guess I've always used dual element fuses on inductive loads. I wonder why the FRN style fuses run so hot?
DaveL

 

[Anonymous Poster]

I've never really figured that out, but suspect it has to do with cross-sectional area in the links themselves. /forums/images/graemlins/tongue.gif Using time-delay fuses in non-motor circuitry and using reject-type fuses......that is any dual-element fuse with an "R" as a suffix......in clips which are not made to accept type "R" fuses are the two biggest snafus that I see in fuse applications. /forums/images/graemlins/frown.gifOften the type "R" fuse doesn't fit the fuse clip very well and gives away some much needed contact area which contributes to hot spots at the fuse clip. /forums/images/graemlins/tongue.gif