[RE-wrenches] DC Series Fusing in inverters

[Jerry Shafer]

We have not had any issues with fuses blowing in the field without cause.
If a module has a ISC for 9.44 a 15 amp fuse is plenty but it sounded like
the sunpower string was being combined elsewhere then you need to use the
lug in the middle of the SMA combiner fuse holders its there to bypass the
fuses altogether. You still need protection somewhere in the system between
the modules and inverter with few exceptions.
Jerry



On Thu, Feb 6, 2014 at 10:51 AM, Steve Jefferson <
Steve.Jefferson at sma-america.com> wrote:

>  Morning Wrenches,
>
>
>
> SMA disconnects come with 15A fuses. If required by the module, you can
> bump the series fusing to a maximum of 20A.
>
>
>
> If you are combining the string before the disconnect, you need to land
> the combined input on the terminal labeled "Combined". This terminal is
> located in the middle of the series fusing terminals.
>
> Do not land a combined input to the standard fuse block and put a 20A (or
> greater) fuse in it, this could over amp the fuse terminal, resulting in a
> fire.
>
>
>
> Thanks
>
>
>
> SMA America, LLC
>
> Steve Jefferson
>
> Service Line Supervisor
>
> 3925 Atherton Ave
>
> Rocklin, CA 95765 - 3714
>
> U.S.A.
>
> Tel:  +1 916 625 3185 (direct)
>
> Fax: +1 916 625 0871
>
> Mobile: +1 916 622 4253
>
> Email: *Steve.jefferson at SMA-America.com <Steve.jefferson at SMA-America.com>*
>
> www.SMA-America.com <http://www.sma-america.com/>
>
>
>
> [image: cid:image001.png at 01CF1CFA.FE18BEB0]<http://www.youtube.com/watch?v=yQWzPuyqhzo&feature=youtu.be>
>
>
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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 *Kirpal Khalsa
> *Sent:* Thursday, February 06, 2014 10:12 AM
> *To:* glenn.burt at glbcc.com; RE-wrenches
> *Subject:* Re: [RE-wrenches] DC Series Fusing in inverters
>
>
>
> Jason...as you know, the fusing should match the max series fuse ratings
> of the module requirements per the module manufacturer....If strings are
> individually fused and combined before the fused disconnect box then the
> fuses often need to be changed from the factory supplied 15A fuses....Note
> the maximum allowed by SMA per the disconnect limitations per string of
> their disconnect.....Fronius used to supply metal slugs that fit in the
> fuse holders if no fusing was required on the input.....
>
> Didn't some of the Evergreen modules call for 20A series fuses?
>
> Good luck..
>
>
>   Sunny Regards,
> Kirpal Khalsa
> NABCEP Certified PV Installation Professional
> Renewable Energy Systems
> www.oregonsolarworks.com
> 541-218-0201 m
> 541-299-0402 o
>
>
>
> On Thu, Feb 6, 2014 at 9:56 AM, Glenn Burt <glenn.burt at glbcc.com> wrote:
>
> I think I just read that SMA has changed their long-standing 15A per
> string fuses to 20A.
>
> You might look to see if it applies to existing systems.
>
> Hope it helps.
>
>
>
> Glenn
>
>
>
> *From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
> re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Jason Szumlanski
> *Sent:* Thursday, February 06, 2014 12:50 PM
> *To:* RE-wrenches
> *Subject:* [RE-wrenches] DC Series Fusing in inverters
>
>
>
> SMA inverters typically come with 15A KLKD fuses pre-installed. I have
> seen a bunch of blown fuses recently (after cold weather)... It seems that
> some dealers are just assuming the 15A fuse is okay for series strings and
> not doing the calculations. I've been finding quite a few Evergreen systems
> or parallel connected two-string SunPower systems that should have 20A
> fuses per NEC 690.8. The problem does seem to be worse where inverters are
> exposed to direct sunlight, presumably from fuses that no longer meet their
> ampacity rating due to heat.
>
>
>
> Anyone else run into this frequently?
>
>
>
> Jason Szumlanski
>
> Fafco Solar
>
>
>
>
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