[RE-wrenches] Add-On to DGT, string inverter, w/Different Modules on 2nd string

jay jay.peltz at gmail.com
Thu Jun 23 15:44:53 PDT 2016


HI Ash,

You don’t give a lot of data to the system, tilt, orientation, probably its 12 in series ( probably?), location, or room available for added modules, how difficult to add new wires or are the wires off the roof large enough to handle another string of modules, does the inverter have good ventilation if its going to be worked hard.

So depending on answers to all that, I might consider just adding 12 more 190 watt 72 cell/44voc modules in parallel.  
I’d check with SMA to see if that is going to be any issue with the inverter as that is up around 4000 watts.
or you could remove 2 modules and then make 2 sets of 10 modules, which would be around 3550 watts. 

I’m just not a big fan of removing already installed working parts.  


jay

Peltz power







> On Jun 21, 2016, at 12:47 PM, Ash Bowersock <Ash.Bowersock at rgsenergy.com> wrote:
> 
> Good day RE Wrench crew,
> I’ve got a client whom installed a 2kW array with a 3kW SunnyBoy inverter a number of years back. Due to the age of the system I assume it is single MPPT. The client oversized his inverter in the hopes of using it for this future expansion (and unfortunately his installer went along with it). The original modules were 12 SolarWorld 175’s I believe, and we would be looking at adding SolarWorld 280’s more than likely. To me it is clear that this is poor design practice and not something I am willing to do. My recommendation is a micro-inverter system that we tie in w/his existing using an AC Combiner. But the client wants to know exactly why we don’t want to just add a second string of 12 SolarWorld 280’s to his 6 year old SunnyBoy inverter.
> Can someone please give me a technical reason why mixed modules on a string inverter is “poor design practice”?
> The more technical and dry an explanation, the better ;) 
> If you can’t convince them, bore them to tears with the details.
>  
> Ash Bowersock
> Senior System Designer
>  <http://www.rgsenergy.com/>
> 833 W. South Boulder Road | Louisville, CO 80027
> tel 303.222.8387
> RGSEnergy.com <http://www.rgsenergy.com/>
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