[RE-wrenches] DC Series Fusing in inverters

[Steve Jefferson]

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<mailto:Steve.jefferson at 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 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<http://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<mailto: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> [mailto: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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