[RE-wrenches] Invert first?

Larry Brown sunmountain at netstep.net
Sun Oct 2 13:03:43 PDT 2011


Eric,

We have had excellent results doing these with Sunny Boys and Sunny  
Islands.  It is more pricey but if you have a high end customer and  
want a a reliable, trouble free (?) system, we have had no wrinkles or  
call backs with this approach. We have inverted at the array in the  
past and sent AC to the critical loads sub panel at the house and from  
there to the Sunny Islands and then either the main service panel or  
done a tap between the main service panel and the utility meter. If  
you do a tap then you need an AC fused disconnect before the tap.  But  
you could also run DC from the array to the house, if it is a new  
system, and then invert to AC.
This is also a good approach if a customer wants to add battery back  
up to an existing grid tie system. There is some rewiring but it is  
not at the array.  The output of the grid tie inverter in an AC  
coupled system needs to land in the critical loads sub panel rather  
than the main service panel where it probably now lands.

Magnum has a good schematic on their website showing how this is done  
using a MS-PAE battery based inverter and a grid tie inverter

Larry Brown
Sun Mountain
Nabcep Certified PV Installer


On Oct 2, 2011, at 12:15 PM, Eric Thomas wrote:

> Wrenches,
>
> We are designing a super high end grid-tied w/ battery backup system  
> for a customer. Array will be ~15kW; pole or stand alone structure  
> mounted; 250' from home/batteries. My question is: does it make any  
> sense to invert the power at the array and use this ac to make the  
> long run to the batteries THEN connect to a typical battery charger  
> rather than a dc charge controller? Im mostly concerned with huge dc  
> conductors making this run across the property. Havent delved into  
> the specific design enough to size said conductors yet, or specify  
> any equipment, but wanted to know if im barking up the wrong tree ir  
> not.
> Thanks for the insight.
>
> Eric Thomas
> Founder
> Solar Epiphany LLC
> NABCEP Certified PV Installer
> WA Electrical Contractor # SOLAREL911NR
>
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