[RE-wrenches] Combined Inverter Fuse sizing

Glenn Burt glenn.burt at glbcc.com
Sat Oct 24 19:22:46 PDT 2015


My bad, fat fingered another one.


Sincerely,
Glenn Burt
Sent from my 'smart' phone so please excuse grammar and typos.

-----Original Message-----
From: "Jason Szumlanski" <jason at floridasolardesigngroup.com>
Sent: ‎10/‎24/‎2015 18:27
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Subject: Re: [RE-wrenches] Combined Inverter Fuse sizing

Clarification - it's square root of 3, not 2, and if the Inverter Output
Current is specified on a datasheet for a 3-phase inverter, it would
already have the factor applied and that is the rating used to apply to
1.25x factor.

For example, Sunny Tripower 12,000 has a inverter output rating of:

12000 / 480 / sqrt(3) = 14.43 (listed as 14.5). Multiply the number of
inverters times 14.5 times 1.25 to get the combined OCPD and wire rating
required.



On Sat, Oct 24, 2015 at 8:39 AM, Glenn Burt <glenn.burt at glbcc.com> wrote:

> Two things,
> Combined OCPD sizing is based on the output current of the inverters, not
> the individual OCPD values.
> And in most 3 phase systems you will have a square root of 2 to factor
> into your calculations.
>
> Sincerely,
> Glenn Burt
> Sent from my 'smart' phone so please excuse grammar and typos.
> ------------------------------
> From: Allen Frishman <amfrish at aeonsolar.com>
> Sent: ‎10/‎24/‎2015 7:50
> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Subject: [RE-wrenches] Combined Inverter Fuse sizing
>
> Wrencher's,
> Quick question regarding sizing the fuse for a combined group of
> inverters.   If I have six 10KW three phase inverters each with a max AC
> current of 30A they each require a 3 pole 40 A breaker.   If I then take
> the combined output of the AC combiner panel I see two possible options for
> sizing the combined fuse size.
>
> 6 inverters x 40A breakers each = 240A so I need to use a 250A fuse
> 6 Inverters x 30A max output each = 180A x 1.25 = 225A Fuse
>
> Seems like both are acceptable options since all wire will be protected.
>
> All feedback is appreciated.
>
> *Al Frishman*
> AeonSolar
>
> *(917) 699-6641 <%28917%29%20699-6641> - cell*
> *(888) 460-2867 <%28888%29%20460-2867>*
> *www.aeonsolar.com <http://www.aeonsolar.com/>*
>
>
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