Fw: array disconnects and code compliance [RE-wrenches]

[Allan Sindelar, Positive Energy, Inc.]

Wrenches,
I forwarded Marco's request for Sunny Boy info to John Wiles. Below is his
response. While definitive, it repeats the answers that have already been
posted. The fille attachment isn't included as it is too big. SMA has it.
Allan at Positive Energy

----- Original Message -----
> Each ungrounded conductor in a power system is normally required to
> be protected from overcurrents from all sources.  Additionally,
> modules need to have reverse current protection as required by UL
> Standard 1703 and marked on the back of the module as the maximum
> series fuse.
>
> In a standard PV system (not SMA Sunny Boy) each series string of
> modules will require a series fuse that will normally provide the
> module protection and the conductor protection.  As strings are
> paralleled and conductor size increases, larger overcurrent devices
> are required to protect the conductors from reverse currents from
> backfeed from the utility-interative inverter or from the battery or
> other sources.
>
> The SMA Sunny Boy inverter is designed not backfeed currents into the
> dc circuits and the system usually uses only one or two strings of
> modules.  Since all wiring is sized at 1.56 of Isc, there are no
> sources of current in a one- or two-string Sunny Boy PV system that
> could damage modules or conductors.  No overcurrent device is
> required per NEC Section 690.9(A) Exception.
>
> See The attached SMA Guidelines for more information and HP Code
> Corners on the SWTDI web site URL below for additional information.
>
>
> >John, if you care to respond, I'll post your answer.
> >Allan
> >
> >----- Original Message -----
> >From: "Mangelsdorf, Marco" <mmangelsdorf at hei.com>
> >>
> >>  In order to be code-compliant, what is needed between the solar array,
or
> >>  combiner box, and the inverter in a battery-less system?  Does one
need
> >>  overcurrent protection in the form of a fuse or appropriately sized
> >circuit
> >>  breaker?  Or is an unfused disconnect acceptable?  The Sunny Boy folks
> >>  specify an unfused Sq. D HU361RB to act as the array disconnect before
> >going
> >>  into the inverter. I've done this with no problem from the local AHJ
but
> >am
> >>  now wondering whether an fused disconnect is Section 690 acceptable.
Any
> >>  observations?
> >>
> >>  marco

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