HI Esteemed Wrenches:
I am consulting on a system I have never seen, that consists of a 6.7Kw
Enphase roof mounted system, and 2 backup generators. Each generator
has an automatic 200 amp transfer switch to back up its own 200 amp
panel. Both 200 amp panels are fed by a 400 amp service from the grid.
The Enphase PV backfeeds a subpanel in another building which then is
fed by a 2 pole 60 amp breaker in one of the 200 amp panels.
Currently they are having issues with the generators kicking out because
of the Enphase inverters. That part I understand: you can't backfeed a
generator, or its voltage regulation freaks out.
Now we get to the fun part: they want to create a third critical load
subpanel with loads selected from both 200 amp panels to be powered by
batteries and an inverter.
I am considering the Sunny Island since it makes the most sense with its
ability to signal the Enphase inverters to shut off when the batteries
are full. I also see this as a partial solution to the generator issue,
since normally the Enphase will be connected to the output side of the
Sunny Island. However, when the generator is used to charge, we will be
back to directly coupling the generator output to the Enphase.
Here are some possible solutions I'm considering:
1) Use a separate charger for the generator so that it will only feed DC
to the batteries, and not be AC coupled.
2) convert the PV back to DC with charge controllers, but that would
involve ditching and adding another conduit run between buildings.
3) Put the Enphase PV on a relay that would disconnect the PV when
charging with the generator.
4) Something I haven't thought of that one of you clever folks can
suggest......
As always, thanks in advance for all you responses,
--
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
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