Hi Dan

Can you provide any documentation on this?  

Thanks Jay
Peltz power. 


Sent from my iPhone

> On Jan 28, 2016, at 8:52 PM, <d...@energysolarnow.com> 
> <d...@energysolarnow.com> wrote:
> 
> While Brian T.  is correct that fusing is not required for string-to-string 
> overcurrent protection with two strings into two channels, there is another 
> reason to require fusing.
> Transformerless inverters like Fronius Primo have no transformer to provide 
> AC-DC isolation, so a ground fault can allow excessive AC current from AC 
> neutral to enter the DC side and fry inverter components. Transformerless 
> inverters need fuses on both DC positive and DC negative legs to protect the 
> inverter in case of ground fault.
> This is why both DC+ and DC- are switched and PV wire is required for DC 
> connections-- to protect the inverters, not just the PV modules. 
> This is also why SMA, for example, no longer has any fuses in their 
> disconnect switches but requires a separate fused DC combiner box with fuses 
> for both positive and negative circuits.
> I have had inverter damage with another inverter brand that only had fuses 
> for the DC+. They now provide fuses on both legs.
> 
> Don Barch
> Energy Solar
> 
> Date: Wed, 27 Jan 2016 17:31:22 -0800
> From: Brian Teitelbaum <bteitelb...@aeesolar.com>
> To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
> Subject: Re: [RE-wrenches] fusing requirement for 4 strings run to a
> Inverter with 2 MPPT's
> Message-ID: <7b344022a97655195ced29e564a31...@mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
> 
> Al,
> 
> 
> 
> As long as you only have a max of two strings going into each of the
> separate MPPT channels, no string fusing is needed. So with four strings,
> two on each MPPT input channel in the inverter, no string fusing is needed.
> This is one of the big advantages to having multiple MPPT channels in GT
> inverters.
> 
> 
> 
> No need to run separate conduits either. All four PV string circuits can be
> run in a single conduit, as long as the conduit is properly sized for wire
> fill, of course.
> 
> 
> 
> 
> 
> Brian Teitelbaum
> 
> AEE Solar
> 
> 
> 
> 
> 
> *From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On
> Behalf Of *Allen Frishman
> *Sent:* Wednesday, January 27, 2016 6:12 AM
> *To:* re-wrenches@lists.re-wrenches.org
> *Subject:* [RE-wrenches] fusing requirement for 4 strings run to a Inverter
> with 2 MPPT's
> 
> 
> 
> Wrenchers,
> 
> What is the requirement for fusing 2 strings per MPPT? Specifically for
> an inverter like the Fronius Primo that has no integrated fuses. If you
> run 2 strings to each MPPT do you need to fuse each string? In this case
> there is a total of 4 strings which would need to be fused if using a
> single mppt.
> 
> 
> 
> If the home runs are run in separate conduits from the array to limit the
> strings in the conduit to 2 per you still have all 4 strings together in
> the inverter.
> 
> 
> 
> All thoughts and feedback are 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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