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Is this scheme valid to save weight, add flexibility and

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brianrobertwood(at)gmail.
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Posted: Fri Dec 26, 2008 4:50 pm Post subject: Is this scheme valid to save weight, add flexibility and

Yep, you are right about that. Small wire=high-resistance=heat which leads  

to smoke. How hot would a run of #4 get if it were shorted out (batt+ to  

ground)? Would it smoke the insulation?



Brian in Brazil



Em Fri, 26 Dec 2008 22:10:55 -0200, Robert L. Nuckolls, III  

<nuckolls.bob(at)aeroelectric.com> escreveu:

 	  Quote: 	
		  > I think the safest course is to avoid any smoking wires, either one foot

> or twelve feet, I think either one would probably kill you.



     Without a doubt, the smoking of wires with insulation

     of any pedigree produces a most disagreeable atmosphere.

     But at the same time, let's made a distinction between small

     wires that are ROUTINELY protected and fat wires that are

     not. Small wires are very likely to smoke when driven by

     high current sources. FAT wires are generally few in number,

     installed with special care and more likely to burn away the

     faulting intrusion than to burn and become an emitter of smoke.

     Small wire protection is generally takes the form of breakers or

     fuses (I prefer fuses cause they're light, cheap, fast

     and take up minimum panel space on airplane). Had the #22 wire

     cite above been thoughtfully protected, the outcome of the

     experience would have been much less exciting.



         Bob . . .



         ----------------------------------------)

         ( . . .  a long habit of not thinking   )

         ( a thing wrong, gives it a superficial )

         ( appearance of being right . . .       )

         (                                       )

         (                  -Thomas Paine 1776-  )

         ----------------------------------------


	


-- 

Brian R. Wood

JH Manutencao

Anapolis. Goias, Brazil

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CamLight

Joined: 19 Dec 2008
Posts: 11

Posted: Fri Dec 26, 2008 5:23 pm Post subject: Re: Is this scheme valid to save weight, add flexibility

 	  brianrobertwood(at)gmail. wrote: 	
		  Yep, you are right about that. Small wire=high-resistance=heat which leads  

to smoke. How hot would a run of #4 get if it were shorted out (batt+ to  

ground)? Would it smoke the insulation?



Brian in Brazil



Brian R. Wood

JH Manutencao

Anapolis. Goias, Brazil 	




I've run 300A through #4 synthetic rubber insulated welding cable (105 degrees-C rated) for several minutes without the insulation smoking or failing.  It did get VERY hot though. 



A lot depends on the insulation.  PVC is often rated at 85-degrees C. and will smoke a lot sooner than 400 degree-C rated fiberglass insulation. The "fusing current" level, at which the copper will melt and the wire acts like a fuse, is around 800A.

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John M.
Owner
CamLight Systems

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