[RE-wrenches] Fuse sizing in battery circuits

[Ray Walters]

First, a water main is no longer allowed to be used as the primary 
grounding electrode by itself, it needs an additional electrode added to 
it 25053(D)2. You still are required to bond to it 250.104(A)1,  but it 
doesn't count as the electrode.  Also, 250.166 (C) specifically lists 
pipe as one of the exceptions.

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

On 4/16/2013 1:06 PM, Garrison Riegel wrote:
> 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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