TEMPORARY LIGHTS

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jimwalker

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TAMPA FLORIDA
Just how many amps could a 12-2 take before it would actually set on fire or open a conductor? And what would happen first ? fire or open conductor ? We did find that at 19.7 amps the wire was getting warm.We are trying to keep several 2x4 layin running for the next week till power can get turned on.
 
Re: TEMPORARY LIGHTS

80% of 20 ampps for continuous loads. Next size breaker 20 amps you should be fine Mr. Walker. As long as you are using the proper size breaker neither should occur.
 
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Yes i know 80% but we are in a jam and this is temp.for next week while construction finishes.We are not concerned about breaker triping.We just need to push this 12-2 to a non fire limit.
 
Re: TEMPORARY LIGHTS

The insulation of the cable will melt long before the metal conductor melts/burns off . By the time the metal conductor opens, the cable and the house will be gone. :(

The ampacity of a cable varies greatly depending on how it is cooled. If you put a cable in free air (e.g. holding it between you hands ;) ) the ampacity is about twice (a very rough figure) of what it is if you put it in the middle of a wall full of insulation. Furthermore, there is a slight difference between two and three current carrying conductors. Thirdly, the cable will fail with time. If the cable is disgarded after a few weeks the ampacity is higher than if it is intended to be used for years. Conclusion: A soon to be discarded, single phase cable on the outside of a wall can take a lot more current than a permanently installed 3-phase cable in the middle of an insulated wall.
 
Re: TEMPORARY LIGHTS

527.2 All Wiring Installations. Except as specifically modified in this article, all other requirements of this Code for permanent wiring shall apply to temporary wiring installations.
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Originally posted by jimwalker:
... We just need to push this 12-2 to a non fire limit.
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What is the specific modification of Art 527 that permits this?
 
Re: TEMPORARY LIGHTS

Originally posted by jimwalker: And what would happen first ? fire or open conductor ?
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Fire would happen first. The fire would start in whatever materials are in contact with the wire, not in the wire?s insulation system.
We did find that at 19.7 amps the wire was getting warm.
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How about trying a 10-2? Protect it with the same 20 amp breaker, and give it the same 19.7 amps, and it will not get as hot.
. . . but we are in a jam and this is temp. for next week while construction finishes.
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Come on, Jim. I have read too many of your posts to believe that you would sacrifice your professional regard for safety for a reason no more valid than expediency.
 
Re: TEMPORARY LIGHTS

310-16 specs the conductor ampacity at 30 amps but referes us( * )to the FPN which states that we can not use a breaker (per code) that exceeds 20 amps.

It is a judgement call on your end. Another option it to take out a few of the lamps so that the circuit is not so overloaded.

Just my $0.02
 
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if i was in full charge this situation would never got created to start with.It was my suggestion in the beginning to run 10-2 but they wanted to save a few dollars.No i do not feel good about this overloaded situation and have asked a few times to do something to correct this.The problem is not being able to prevent subs from turning on rooms and causing the overload.This was some poor planing to deal with rooms that are too dark and with our weather in last 2 weeks being very rainy the matter has become worse.My question was just to see if anyone else ever pushed # 12 to the max and at just what point should we say no.Keep in mind the temp.in this building is about 90 most of the day.I am concerned but this is out of my control.
 
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I don't understand why #12awg cannot be loaded to 20 amps It's not the wire that requires the de-ratting to 80% it is the breaker. and if you had a breaker that had a 100% rating it would be ok then right? look at 210.20(A) exception for the most part #12 has a 25 amp rating for de-rating purposes. so I don't think the wire would fail as it wouldn't reach it's failure temperature of 90deg.c

[ August 07, 2004, 01:32 AM: Message edited by: hurk27 ]
 
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Bob it is turning it self off every couple hours and gets a 1 minute break before resets.Where are them federal pacific breakers when we need them ?
 
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We made it without flames. But next time maybe they listen and spend a little extra.I retired that that 30 amp breaker today :) :) :)

[ August 18, 2004, 06:26 PM: Message edited by: jimwalker ]
 
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