[RE-wrenches] Fuse sizing in battery circuits

[Drake]

Are AC coupled systems with no DC loads exempted 
from the grounding rules of DC coupled, battery 
based systems and the rules of DC grounding?



>This is from the Sunny Island Manual:
>"External grounding of the negative pole of the 
>batteries is possible, because the batteries
>and the grid side are galvanically isolated within the Sunny Island.
>• Dimenssion the cross‑section of the 
>protective conductor sufficiently. Thus you are
>ensuring that in the event of a fault the high 
>currents occurring can be discharged with
>an external grounding.
>• If groounding of the negative pole of the 
>battery is necessary, assemble this outside of
>the Sunny Island.
>
>As far as I am aware, the NEC code is kind of 
>vague on grounding battery banks (please correct 
>me if I am wrong), it is more of a AHJ requirement.
>
>There is no reference to ground (DC side) inside the SI.
>
>SMA America, LLC
>Steve Jefferson
>Supervisor, Service Line
>6020 West Oaks Blvd, Suite 300
>Rocklin, CA 95765 - 3714
>U.S.A.
>Tel:  +1 916 625 0870
>Fax: +1 916 624-2445
>Service Line +1 877 697 6283 (Toll Free)
>Email: steve.jefferson at sma-america.com
><http://www.sma-america.com/>www.SMA-America.com
>
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>From: re-wrenches-bounces at lists.re-wrenches.org 
>[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of August Goers
>Sent: Wednesday, April 10, 2013 2:13 PM
>To: RE-wrenches
>Subject: Re: [RE-wrenches] Fuse sizing in battery circuits
>
>Steve,
>
>So if we wanted to ground the negative would we 
>literally run a ground wire to one of the 
>battery terminals? Is there anything in the NEC 
>that governs this? What are the deciding factors 
>when deciding to ground the negative or not?
>
>As a separate note, I've noticed that the 
>negative battery terminals measure 0 volts to 
>ground on a Sunny Island setup once everything 
>is connected without any extra grounding added. 
>I thought that there must be some reference to 
>ground happening in the Sunny Island but apparently I'm wrong.
>
>Thanks, August
>
>From: 
><mailto:re-wrenches-bounces at lists.re-wrenches.org>re-wrenches-bounces at lists.re-wrenches.org 
>[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Steve Jefferson
>Sent: Wednesday, April 10, 2013 9:56 AM
>To: RE-wrenches
>Subject: Re: [RE-wrenches] Fuse sizing in battery circuits
>
>If the Batt negative is not bonded to ground, 
>then yes SMA recommends fusing both Positive and Negative.
>
>Also, the negative is not bonded to ground internally in the Sunny Island.
>
>SMA America, LLC
>Steve Jefferson
>Supervisor, Service Line
>6020 West Oaks Blvd, Suite 300
>Rocklin, CA 95765 - 3714
>U.S.A.
>Tel:  +1 916 625 0870
>Fax: +1 916 624-2445
>Service Line +1 877 697 6283 (Toll Free)
>Email: <mailto:steve.jefferson at sma-america.com>steve.jefferson at sma-america.com
>www.SMA-America.com
>
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