[RE-wrenches] Outback AC coupling Sunpower?

[Ray Walters]

The Outback rep got me some good info, and I'm liking the Radian with 
the Remote controlled breaker to control the GT inverter when the grid 
is out.  I've heard of quite a few problems related to the Sunny Island 
frequency controlled system.
My question is can off grid inverters like the Magnum be AC coupled?  
I'm trying to get the price down, and still handle the 240 vac input 
from the GT inverter.
I penciled out the Radian and I was topping $10k before installation.   
This customer is hoping for a solution under $10k, and closer to $5k if 
possible.  I think an elegant lower cost solution for Grid tie with 
battery back up is in order.  A Radian Lite?
For backup, it could even be mod sine, as it wouldn't be much worse than 
generator power or the average UPS setup.


R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 7/30/2013 2:59 PM, Ray Walters wrote:
> Hi All;
>
> I know AC coupled systems have been covered before, but I have a new 
> issue:  positive grounding.  A customer with an existing 8kw Sunpower 
> system wants to add backup.   He was put off by the high cost the 
> Sunny Island, so I was steering him towards a single Outback VFX 
> coupled to just one of his 3 inverters.  The issue is how will the VFX 
> work with positive grounded inverters.  I'm assuming that since the 
> two inverters will only be connected by AC, that the positive vs 
> negative grounding of their separate DC systems will not matter.  Any 
> experience with this particular scenario: Sunpower system AC coupled 
> to an Outback?
> Also, would I even need a GVFX, since the inverter would only be used 
> during outages  (which might allow a generator to be used later as 
> well)  A VFX should still AC couple to the GT inverter during an 
> outage, right?
>
> Thanks as always,
>