Dan and others,
Thanks for the comments. The answer from Dan is what I was needing:
"For two parallel runs of different sized conductors, add the circular mil area
for both conductors, then using a wire table (such as a pocket guide), find the
gauge closest to the total CMA to get the AWG equivalent."
Perhaps I should have explained that the PV system voltage is under 50 volts
and that all conductors are bonded with terminal blocks at both ends. The
current will distribute itself across the two conductors.
Just a side note for those concerned with the NEC and RV wiring: After years of
wire installations in nearly every recreational vehicle made, I can assure you
that not one RV is in total compliance with NEC. Some of the DC wiring
performed by manufacturers is downright dangerous with long cable runs or many
branch circuits with no circuit protection at all. Very scary.
Larry
----- Original Message -----
From: Exeltech
To: RE-wrenches
Sent: Wednesday, February 02, 2011 10:26 AM
Subject: Re: [RE-wrenches] Parallel wire runs to increase size
NEC 310.4 permits parallel conductors of 1/0 or larger. Conductors
smaller than 1/0 are permitted, but with stipulations.
Nick's assertion "most if not all of the current will flow on the
larger wires" is incorrect. The current will be shared proportionately between
two paralleled conductors commensurate with their individual resistances.
The original query related to recreational vehicle PV DC-side
installation, and referenced installation of a "second PV", implying only one
existed initially. This would thus fall outside the bounds of the NEC, but
shouldn't be interpreted to mean some of the common-sense aspects of the NEC
aren't to be considered.
Dan
--- On Wed, 2/2/11, Jason Szumlanski <ja...@fafcosolar.com> wrote:
From: Jason Szumlanski <ja...@fafcosolar.com>
Subject: Re: [RE-wrenches] Parallel wire runs to increase size
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Date: Wednesday, February 2, 2011, 11:15 AM
Nick,
Can you cite a code section that supports this. (not challenging you
– it makes sense and I agree)
I have been wondering about SMA’s recommendation to parallel two 1/0
cables for a Sunny Island. If the wire sizes and lengths are identical, is this
acceptable?
Jason Szumlanski
Fafco Solar
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Nick Soleil
Sent: Wednesday, February 02, 2011 12:05 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Parallel wire runs to increase size
You shouldn't parallel wiring that way. That is not acceptable by
code, and it is unnecessary. If the #10 is not sufficient just replace it.
Due to the fact that the larger wiring has much less resistance, most if not
all of the current will flow on the larger wires.
Nick Soleil
Project Manager
Advanced Alternative Energy Solutions, LLC
PO Box 657
Petaluma, CA 94953
Cell: 707-321-2937
Office: 707-789-9537
Fax: 707-769-9037
----------------------------------------------------------------------
From: "Starlight Solar, Larry Crutcher" <la...@starlightsolar.com>
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Sent: Wed, February 2, 2011 8:00:07 AM
Subject: [RE-wrenches] Parallel wire runs to increase size
Wrenches,
Some of our business involves repairing poor PV solar installations
on recreational vehicles. So often we wind up installing a roof junction box
and running a second PV to controller wire and then replacing the controller to
battery wire size. For instance, we may find a 10 gauge wire run to the
controller. We then add #8, #6, #4 or even 2 gauge and parallel to the #10
depending on power and distance of the run. My question: Is there a calculator
or chart that will tell me what the combination of any two wire sizes equate
to? example: #10 + #4 = X
Thanks.
Larry Crutcher
Starlight Solar Power Systems
powered by STARLIGHT™
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
