The code provisions regarding conductors in parallel [2011, 310(H)(I)] are very
specific and make complete sense. When installed correctly, in larger sizes, 1/0
or greater, as permitted, there is very little likelihood of significant
difference in resistance or any other problem. This is done safely and routinely
every day all over the US and probably the world. In larger sizes there are
substantial practical and economic advantages to using parallel conducors. In
smaller sizes these advantages don't apply. The explanatory text in the Code
Handbook explains this more completely than I can here.

Dick Ratico
Solarwind Electric

--- You 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@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@lists.re-wrenches.org [mailto:
> re-wrenches-bounces@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...****
--- end of quote ---