connecting OutBack for generator support was Converting Off-Grid OB to Gri

[John Raynes]

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Don't forget the FX's "ac1/gen input limit" amps setting.  I've found that 
tuning that setting is an absolutely essential part of every FX job we've 
done that included a generator.  Everything we sell is installed at 
elevations of 6000-10,000 ft, and we have to assume not only generator 
de-rating, but that the fuel mixture probably wasn't well-tuned for the 
elevation at which it will be used.  So I'm used to generators wheezing and 
generally sucking wind at first, unless they're way oversized.

I make it a point to do some testing with large, gradually increasing loads 
(my heat gun goes on every site visit, whether I need it or not), and 
listen for the point that things start to bog down, then set the limit 
setting below that level so there's some headroom.

That prevents the "slow-down, disconnect, re-connect, slow-down" cycle that 
William mentions, but it doesn't completely solve the problem if there is 
going to be more load than the generator can handle.  At the very least, 
having the limit clamp is better than trying to deal with generator 
overload-driven disconnects.  The biggest challenge I have in those cases 
is getting the customer to understand that the inverter worked exactly as 
designed, and the problem is with the generator and/or the loads.  Thank 
God for Fluke meters.

The Mate is also excellent in telling me what went wrong if there is a 
disconnect.  Too bad I never seem to be able to get my customers to learn 
how to successfully navigate the menus, though.

John Raynes
RE Solar
Torrey, UT


At 11:56 AM 2/25/2007 -0800, you wrote:

>Todd:
>
>I hope you are aware that the Outback FX inverter does not provide 
>"generator support," that is, the capability for the inverter to sync to 
>and add to the output from a current limited AC source.
>
>Consider a small generator with, say, only 12 amps AC capability.  Should 
>the loads exceed that 12 amps, an SW inverter would start inverting and 
>assist the generator in powering any loads above the programmed 12 amps.
>
>In this same case, the Outback FX would transfer loads entirely to the 
>generator and, if the loads exceed the 12 amps, the generator would 
>overload.  The generator would slow down or the voltage would decrease 
>until either the frequency or the voltage falls out of tolerance and the 
>inverter would disconnect from the generator.  The generator voltage and 
>frequency then return to normal and, after the delay, would be reconnected 
>by the inverter.   Repeat this scenario until someone intervenes.
>
>If your loads are ever larger than your AC source, you are out of luck 
>with an FX.  This is a significant failing of the Outback, in my humble 
>opinion, and one I hope they remedy soon.  I understand this is due to the 
>basic topology of the FX inverter and the fact that there is only one main 
>transformer, and it can perform only one function at a time.
>
>No disrespect intended to Outback.  The Outback FX line and BOS components 
>has many shining features that remedied many other defects in the SW 
>inverter line.  Chris Freitas, please correct me if any information above 
>is not accurate.
>
>The race is on, at least in my view, to see if Outback can correct this 
>short coming before the Xantrex XW series is unveiled.
>
>Respectfully,
>
>William Miller
>
>
>At 10:05 AM 2/25/2007, you wrote:
>
>>I hope Christopher answers these questions. I have a grid tied Outback 
>>system with generator support coming up next year and need to get it 
>>clear how this can be done. The ONLY thing I liked better about the SW 
>>than the FX was that is had provisions for two AC inputs.
>>
>>Todd
>
>
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