[RE-wrenches] Old dual SW4048 system problem

[R Ray Walters]

We are finishing an upgrade on a similar system with a pair of SW4024s.
I decided to keep the SWs for generator charging, and as a backup's backup.
We then added a pair of Outbacks GVFXs for sell. The SWs only get powered up for generator charging, or if the Outbacks quit.
Interesting thing about this arrangement, is that you could sell generator power to the grid. Obviously stupid, but it would work.
The customer was an electrical engineer and he liked the concept of not pulling out the SWs.
 
R. Walters
ray at solarray.com
Solar Engineer




On Dec 2, 2009, at 11:44 AM, Jeff Yago wrote:

> Called in to trouble shoot a dual Trace SW4048 system that we did not install. 
>  
> Yes, I know, and we almost never work on systems we did not install, but client was desparate and installer was long gone.  System has about 6 kW solar, 17 kW generator, 16 L-16 batteries, and is set up to "SELL" solar to grid.  Generator has separate automatic grid/gen transfer switch, so AC1 of both inverters conneted to grid supplied panel, AC2 of both inverters connected to inv/gen panel, and both inverters supply an emergency loads panel.  
>  
> I am convinced this system may have never worked correctly as client had no idea of programming, setpoints, or how system was to work.  I found inverters programmed with mostly defaults, but they were set up for SELL mode.   If only AC2 is supplied from grid/gen transfer switch, system works perfectly in normal and battery backup mode supplying emergency loads panel.  However, if I would turn on the breaker feeding grid power to both AC1 inverter inputs, one inverter would go off line in about 2 minutes and required switch to off then back on to re-start, and will not stay on line with power on AC1.  
>  
> There was a pull dis-connect located right next to inverters to only dis-connect AC1 power to inverters which may have been originally installed when the contractor had the same problem, and if so, this means the system never sold any solar power to grid and never did anything since the inverters were holding batteries at float except when there was a power outage.
>  
> If it was not for sell mode, they could leave AC1 dis-connected and everything would work just fine, but its my understanding that SELL mode only feeds power out on AC1 although this is not clearly stated in the owners manual.   We have checked L1 & L2 phasing of all AC1 and AC2 inputs and outputs, but are thinking there may be some type of backfeed issue out in the three separate cir. bkr. panels resulting in the inverter supplying output power to its own input, but so far have not found problem.
>  
> Any ideas?
>  
> Thanks,
>  
> Jeff Yago
> 
>  
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