[RE-wrenches] Convert Grid Tie SW4048 to Backup System; Add New Inverter, AC Coupled

[Ray Walters]

We redid one in a very similar situation recently. In that case the 
customer wanted super backup and so we put in Grid tie Outbacks and a 
new battery bank, added modules, and kept the SWs as battery chargers 
from the generator. He had the option with bypass switches to use the 
SWs, if the Outbacks went out. This guy wanted a "keep the power going, 
no matter what" system, but I can't claim that was optimal.  The right 
answer depends on what the customer wants.
I probably wouldn't trash everything though as Jay suggested, since the 
existing modules are already racked and wired. (unless it's a bogus 
install, then yep, salvage it all)
You could probably easily rewire the parallel 48 v sets of modules all 
in series in 15 minutes in the combiner box to get the voltage up, and 
use a small GT only inverter, too. I guess it would also depend on how 
close the 2 different types of modules are in voltage or current, but it 
doesn't have to be perfect; as these were modules headed to the scrap 
heap otherwise.
In honor of modules that are well installed and still performing 
correctly, I do try and reuse them. Being able to brag: "these have been 
working for 30 years..." is great for the solar industry as a whole, but 
only if it makes sense.

Ray

On 11/17/2011 5:51 PM, jay peltz wrote:
> HI Richard,
>
> I'll chime in, although you won't like it.
>
> Dump the system and start over with a new battery less system and a genny as back up.
>
> Told you, you wouldn't like it.
>
> The SW parts are basically gone and it was a terrible  grid tied inverter anyway.
> The modules are usable but why at $1.5 watt keep them?
> Client doesn't want MX, so that means no batteries.
>
> You'll need a genny as back up anyway for long power outages during storms, so get a natural gas/propane unit as back up instead of batteries.
>
> OK you asked,
>
> jay
>
> peltz power
> On Nov 17, 2011, at 4:03 PM, Richard L Ratico wrote:
>
>> Hi Wrenches,
>>
>> This is a repost. No replies the first time, so I'm trying one last time.
>>
>> I may be "adopting" an eleven year old, Y2K, grid tie with battery back-up
>> system. It consists of 12 - Astro-Power 120 modules, installed in 2000, 12 -
>> Evergreen  EC-110 modules installed in 2004, only one MX60, which controls BOTH
>> sub-arrays, one SW4048 in SELL mode through a dedicated load sub-panel.
>> Existing, seven year old battery is shot (8-Trojan L-16). Initial bank of
>> unknown batteries was replaced after only four years.
>>
>> Recent long, nearby, utility outages have the client requesting a proposal to
>> include a new back-up generator and to restore the system selling to the grid.
>> Client may decide go straight grid tie to eliminate the batteries. They have
>> found the maintenance to be a hassle.
>>
>> My thoughts so far:
>>
>> 1)To take advantage of most of the existing hardware, I wonder if it makes sense
>> to try to improve the system efficiency by relegating the SW to a manual back-up
>> mode only, where, say, by means of a timer controlling grid availability through
>> AC1, it would only charge a smaller battery bank once a week. The battery bank
>> would be small,
>> a single string of either, sealed gel units or T-105s with the new Trojan
>> watering system.
>> 2) Provide new grid-tie inverter/s (appropriate string type or Enphase 190s) to
>> handle the net metering.
>> 3) Provide a way to AC couple the new inverter/s to the SW in the event of an
>> outage.
>> 4) Provide a new Honda 3000 inverter type generator connected to AC2 in the SW.
>> 5)Provide a way to lockout the grid tie inverter/s when the generator is
>> operating.
>>
>> Any thoughts or suggestions would be greatly appreciated.
>>
>> Thanks in advance,
>>
>> Dick Ratico
>> Solarwind Electric
>> Bradford, VT
>> _______________________________________________
>> Li
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