Confused about series/parallel using four FXs

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Confused about series/parallel using four FXs

Postby mikedodd on Fri Oct 07, 2011 8:43 pm

Hello, everyone. I'm new to solar power, and trying to gather the information I need to put together a 10KW grid-interactive system.

Reading the FX SERIES INVERTER/CHARGER FX/ VFX/GTFX/GVFX/MOBILE Installation Manual, I see that four FXs can be connected together to provide 14.4 KW.

Q1. Since I need 10KW, I'd like to connect three FXs, but I don't think that's possible, because I need to feed both legs of a 240V panel. Am I correct that I can't do this, and need four FXs providing 7.2KW on each leg? What if one leg in the box is connected to smaller loads than the other leg? Could I then use three FXs, with 7KW on one leg and 3.5KW on the other? Or is that just a Bad Idea?

Q2. Looking at the connection diagram on page 30 of the manual, I see a "required X-240 transformer. On page 26, the manual says, "Series/parallel stacking requires an FW-X240 Auto Transformer and must use “OutBack” stacking programming. I don't understand how this transformer works. It looks like the red/neutral leg is connected to the black/neutral leg through the transformer.

Okay, so what? Since the legs are in phase, the transformer just sits there. I can see that if, say, the two red-leg inverters went down, the black-leg inverters would supply power to the red leg through the transformer. Is this its only purpose? What if I don't care? How often will two inverters on one leg fail? Why is the transformer required? Would the system not work if it were omitted?

Thanks for any information on thee to questions.

--- Mike
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(ANSWERED) Re: Confused about series/parallel using four FXs

Postby mikedodd on Sat Oct 08, 2011 6:33 pm

Never mind. I think I figured out what I need to know by downloading and reading a bunch more FX user manuals. It looks like I must use four inverters, so I've down-sized them to 2.5KW each, instead of 3.5KW. Saved a few bucks.

I read in one of the manual that the transformer is for "balancing" the inverters. Not sure quite what that means, but I'll plan on using a transformer.

Regards,

Mike
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My RE system: Just getting started. Trying to identify and size the needed components.

Re: Confused about series/parallel using four FXs

Postby SteveHiggins on Tue Oct 11, 2011 6:27 am

Mike...

Just sent you an EMAIL...
Steve Higgins
Technical Services Director- Surrette Battery Company

\
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Re: Confused about series/parallel using four FXs

Postby dragoner on Sun Nov 06, 2011 10:57 pm

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