[RE-wrenches] DC conductor line loss numbers

[Jerry Shafer]

Wrenches
I have 3 engineering firms and one in-house engineer that only use 1%
because in the NEC it is stated as a suggestion and not a requirement but
they take this as a must not exceed instead,
I cant change CC as it will be remotely monitored via the Outback
connection, the Engineers refuse to make any changes to the 1% and still
stamp the drawings. This is what I have found in my research it came from
Mike Holt


Contrary to common belief, the NEC generally doesn't require you to size
conductors to accommodate voltage drop. It merely suggests in the Fine
Print Notes to 210.19(A), 215.2(A)(4), 230.31(C), and 310.15(A)(1) that you
adjust for voltage drop when sizing conductors. It's important for you to
remember that Fine Print Notes are recommendations, not requirements
[90.5(C)].

The NEC recommends that the maximum combined voltage drop for both the
feeder and branch circuit shouldn't exceed 5%, and the maximum on the
feeder or branch circuit shouldn't exceed 3%. This recommendation is a
performance issue, not a safety issue.

Jerry

On Wed, Jul 22, 2015 at 11:28 AM, Starlight Solar Power Systems <
larry at starlightsolar.com> wrote:

> Jerry,
>
> A long distance wire run is practical now days using a high voltage
> controller. Have a look at Schneider and Morningstar 600Vdc controllers.
> Not sure what you mean "by nothing can be changed but wire size” but you
> will have to rewire the strings into series and protect the wire run.
>
> Larry Crutcher
> Starlight Solar Power Systems
>
>
>
> On Jul 22, 2015, at 10:37 AM, Jerry Shafer <jerrysgarage01 at gmail.com>
> wrote:
>
> Wrenches
> Some time back there was discussion on the conductor size and efficiency
> rating requirement for long DC runs.
> What I am looking at is this, 400 feet of MCM 400 to keep the line loss at
> or below 1% per NEC code for an off grid application, cost vs return is not
> acceptable. 2/0 is less than 2.5% and the cost is far less. Specs are 4
> strings of 3, 250 watt modules feeding one Outback FM 80 charge controller.
> There are lots of things I can do like SMA instread, or 200 VDC charge
> controller but nothing can be changed except the wire gauge. Does anyone
> recall a thread with this topic.
>
> thoughts ??
> Jerry
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