[RE-wrenches] parallel OCPD

[Chris Mason]

I believe that current flow through two parallel conductors
is inherently balanced by ohms law. I think the reason the NEC
prohibits parallel cables below 1/0 is to stop contractors taking
shortcuts, using two conductors just because it was what they had.
electrically it works fine. At some point you have to be able to use two or
more conductors.

On Wed, Sep 26, 2012 at 9:16 AM, mac Lewis <maclewis1 at gmail.com> wrote:

> Good points.  I would think a more dangerous situation would be the case
> that you often have with large parallel feeders landing on a single OCPD.
>  If one wire has a little less resistance, it will always run hotter than
> the other, and you could easily overheat a wire that is protected by that
> large OCPD.
> Thanks
>
> On Wed, Sep 26, 2012 at 6:48 AM, Jeff Irish <jeff at hudsonsolar.com> wrote:
>
>>  Code issues aside, even two seemingly identical runs each with breakers
>> would have at least slightly different resistances, causing the lower
>> resistance run to take more than half the total current, tripping the
>> breaker in that run, then causing a tripping of the breaker in the other
>> run.****
>>
>> ** **
>>
>> Jeff Irish****
>>
>> ** **
>>
>> *From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
>> re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *mac Lewis
>> *Sent:* Tuesday, September 25, 2012 9:16 PM
>> *To:* RE-wrenches
>> *Subject:* [RE-wrenches] parallel OCPD****
>>
>> ** **
>>
>> Hello wrenches,****
>>
>> ** **
>>
>> Does anyone understand why you are not allowed to have
>> parallel separately protected runs of wire.****
>>
>> For example, say I need 120A from point A to point B, why doesn't the
>> code allow two runs of #6 breakered at 60A each.  Its probably obvious, but
>> not to me...****
>>
>>
>> ****
>>
>> ** **
>>
>> -- ****
>>
>> ** **
>>
>> ** **
>>
>> ** **
>>
>> Mac Lewis**
>>
>> "Yo solo sé que no sé nada." *-Sócrates***
>>
>> ** **
>>
>>
>> --
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>>
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>
>
> --
>
>
>
> Mac Lewis
>
> *
>
> "Yo solo sé que no sé nada." -Sócrates
> *
>
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-- 
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
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