[RE-wrenches] Fuse sizing in battery circuits

[August Goers]

Ray,



Thanks for the note and I see your point about "operating at greater than
50 v". Does anyone else have an opinion on the operating voltage for
batteries? I know that NEC 480.2 defines the nominal battery voltage as 2
volts per cell for lead-acid and I believe I have a code interpretation
book lying around that states that this is what you apply to 250.162 but I
don't have much info other than that.



Best, August



*From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Ray Walters
*Sent:* Monday, April 15, 2013 1:48 PM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] Fuse sizing in battery circuits



Hi August;

250.162(A) says "operating at greater than 50 v", which a 48 v nominal
system operates most of the time at over 50 v, at least when solar charging
and/or selling back.
We used to get dinged many years ago for using breakers rated at 50v dc on
48 v systems.  John Wiles used to insist we use the highest possible
voltage (Voc of modules on coldest day)
Personally I prefer ungrounded systems, so I'm not saying there's anything
wrong from a safety stand point, just that inspectors here don't see it the
same way.


R.Ray Walters

CTO, Solarray, Inc

Nabcep Certified PV Installer,

Licensed Master Electrician

Solar Design Engineer

303 505-8760

On 4/15/2013 2:20 PM, August Goers wrote:

Hi Drake,



The Sunny Island System runs at 48 V nominal so I don't believe 250.162(A)
applies. We have some really savvy inspectors in the Bay Area and they were
happy for us to be ungrounded since we're operating at 48 V. Yes, the
actual voltage might go above 50 V when charging but I believe it is the
nominal voltage that the code cares about.



Best,
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20130416/75e280a1/attachment-0004.html>