[RE-wrenches] fusing requirement for 4 strings run to a Inverter with 2 MPPT's

[Bradley Bassett]

That document refers to 2008 NEC 690.9 code which has the exemption that is
used for grounded inverters. Section 690.35 for ungrounded systems just
refers back to 690.9 for over-current protection. So I do not see any
indication that two strings on an ungrounded inverter could not have the
same exemption applied to it, which I think is largely standard practice
with a few AHJ's not accepting it. There was nothing that I saw in the
document that would indicate otherwise.

Brad

On Fri, Jan 29, 2016 at 11:34 PM, <don at energysolarnow.com> wrote:

> Hi Jay-
> Here is a somewhat dated Engineering Bulletin from Solar World with nice
> diagrams.
>
> Mark-
> NEC requires transformerless inverters to be handled differently than the
> ones with transformers.
> Neither DC+ or DC- is grounded, so there no ground fault fuse inside the
> inverter.
> Both DC+ and DC- are fused external to the inverter.
> Both DC+ and DC- are switched by the DC Disconnect.
> PV wire is required to better ensure against ground faults since they
> become so catastrophic.
>
> Don Barch
> Energy Solar
>
> Jay <jay.peltz at gmail.com> wrote:
> >
> >Hi Dan
> >
> >Can you provide any documentation on this?
> >
> >Thanks Jay
> >Peltz power.
>
> >"Mark Byington" <markb at cobaltpower.com> wrote:
> >
> >"Transformerless inverters need fuses on both DC positive and DC negative
> >legs to protect the inverter in case of ground fault."
> >
> >
> >I could be wrong, but my understanding is that TL inverters are no
> different
> >than transformer type inverters in terms of DC fusing requirements - no
> fuse
> >required for one or two strings in parallel; fuses required on + and -
> leads
> >for 3 or more strings in parallel.
> >
> >
> >Mark Byington
> >
> >Cobalt Power Systems, Inc
>
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