[RE-wrenches] 3 Phase With 2 Inverters?

[penobscotsolar at midmaine.com]

Hi Holt,
   We installed a commercial system a year ago for the National Park
Service that was designed by a competitor (?) and signed off on by an
engineer. It consisted of 13.2 kw of pv and two Fronius 7000 watt, 208
3 ph. inverters. It sounds a lot like what you are dealing with. I
questioned the engineer on it and he said because the facility was so
large (it was a large research and visitor "campus" for Acadia National
Park with 20+ buildings)the transformer would never see the imbalance
and therefore was not a problem. Fronius agreed, but prefaced that with
the fact that it still was "not recommended". I can say that we have
had no issues or complaints at all since the installation in August of
2011 and they monitor it continuously. It would have been a far better
design to use three Fronius 4.5 inverters at 3 ph. I drafted a letter
(CYA letter) to the powers that be about my concerns (transformer
imbalance) and they chose to go ahead with the installation. Nothing
like government work.......many more stories about this installation
than anyone has time for here.....

Daryl DeJoy
NABCEP Certified PV installer
Penobscot Solar Design



> We were asked to inspect a  GT system installed by others. Service is 208
> 3ph with two (?) Fronius IG 4500 208v inverters. The inverter panel is 3ph
> with two 2pole breakers - one each side of the buss bar in a A/B, B/C
> configuration (??). Called Fronius and they said it would work, but they
> "don't recommend it". No other information was given as to why they don't.
> My electrician is very uncomfortable with doing work on this system as is
> (ME TOO!), so I am wondering if I might be able get some ammo to convince
> system owner to add a third inverter to get the system right. What
> problems might/will be encountered in this system if not modified? BTW -
> inverter LCD screens were crapped out, so we couldn't readily see if
> system was functioning properly....from metering, we think not.
>
>
> Holt E. Kelly
> Holtek Fireplace & Solar Products
> 500 Jewell Dr.
> Waco TX. 76712
> 254-751-9111
> www.holteksolar.com
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