I may be missing something here...... but, for a manual switching solution, why
not use two standard 600V DC discos. Put the PV to the top of both, load side of
one goes to the battery inverter, load side of the other to the grid tied
inverter. Turn one off, turn the other one on. Not as elegant as a transfer
switch, maybe more expensive, but seems dirt simple and available now.

Dick Ratico
Solarwind Electric



--- You wrote:
Could you use the old Dankoff trick of running through 2 poles  in series of a
300 v rated switch? That used to be approved, before we had all these 600 v
rated equipment.

R. Walters
ray@solarray.com
Solar Engineer




On Nov 7, 2011, at 1:16 PM, Larry Crutcher, Starlight Solar Power Systems wrote:

> Ray,
> Yes, the idea was for a low cost way to add battery backup to existing high
voltage PV grid tie systems, not new construction.
> 
> The second inverter does not need to be able to sell since that is handled by
the grid tie inverter. It simple passes grid power to loads and maintains the
battery. That means any off-grid inverter/charger or even low cost separate
inverters and chargers may be used, a very economical solution. However, the
idea may be of no value because it appears no one makes a transfer switch.
> 
> Larry Crutcher
> Starlight Solar Power Systems
> 
> 
> 
> 
> On Nov 7, 2011, at 11:32 AM, Ray Walters wrote:
> 
>> Just curious, what's the advantage of switching at the array vs. just using a
Sunny Island or Outback system? Seems this would cost more, and have less
efficiency, since you would still have the battery float losses, backup inverter
idle losses, in addition to the 2nd grid tie inverter losses. Are there site
specific conditions driving this that I'm not understanding?
>> I've done quite a few GT systems w/ battery backup, so I'm always up for new
ideas though.
>> 
>> Ray
>> 
>> 
>> On 11/7/2011 12:15 PM, Larry Crutcher, Starlight Solar Power Systems wrote:
>>> 
>>> Hi Glen, 
>>> That model is a disconnect switch. What the system needs is a 4 pole
transfer switch, automatic or manual, to connect the PV source to the charge
controller.
>>> 
>>> Hello Gary Willit, 
>>> Yes, you've grasped my concept precisely and I agree, getting a high voltage
DC transfer switch may nix this design. Sounds like a product for Midnite Solar
to build.
>>> 
>>> 
>>> 
>>> Larry Crutcher
>>> Starlight Solar Power Systems
>>> 
>>> 
>>> On Nov 6, 2011, at 1:42 PM, Glenn Burt wrote:
>>> 
>>>> Siemens makes a line that are UL listed.
>>>> Their VBII series like HNF361PV - 30A
>>>>  
>>>> -Glenn
>>> 
--- end of quote ---

