[RE-wrenches] Fuse sizing in battery circuits

[Garrison Riegel]

Hi Ray and All,

250.166 says the GEC must be sized as specified in (A) Not smaller than the
neutral conductor, or (B) Not smaller than the largest conductor supplied by
the system, except as permitted by (C) through (E).

A water main [as in 250.52(A)(1)] is not listed as an exception in (C)
through (E). So if the GE is a water main wouldn't the GEC "need" to be 4/0,
if the battery cables were 4/0?  Not saying it makes sense, especially if
the water main is 3/4", but this has always made me wonder.

Thoughts?

Garrison Riegel
Project Manager | Solar Service Inc
[p] 847-677-0950 | garrison at solarserviceinc.com

NABCEP Certified PV Installation ProfessionalT


-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Ray Walters
Sent: Tuesday, April 16, 2013 12:52 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Fuse sizing in battery circuits

Hi Drake;

Read down a bit more and 250.166(C) and (D) limit the size of the GEC to
#4 or #6 max., depending on what electrode is used.
This used to not be the case, and systems in the 90s had 4/0 cable to a 5/8"
electrode: which just like your 1/2" pipe example was absolutely ridiculous.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 4/16/2013 9:31 AM, Drake wrote:
>
>
> So, in a standard battery system, with a charge control, ground fault 
> protection and an array, the DC system will likely need grounding. If 
> the DC system is grounded, then the battery cables are grounded also.
> In 250.166 (B) it says the grounding electrode conductor (GEC) shall 
> not be smaller than the largest conductor supplied by the system.
>
> If the battery cables are "supplied by the system" doesn't this imply 
> that the GEC should be the size of the battery cable?  This is the 
> logic that has led some inspectors to require a 4/0 copper wire to be 
> bonded to a 1/2" water pipe. This is, of course, technically absurd.

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