Ray
Couple of thoughts on your application. We used to use the sunny islands a
lot, challenge is they are only 120 volt so we needed to have two or add a
transformer, which proved problematic with the grid tied inverters and hertz
ranges.
So now we use the Outback 4048 and 8048 radians ( 8048 cost close to the
same as a Sunny Island ) is 240, no transformer needed and a simple relay to
break the main neutral on the enphases will shut them off when the voltage
goes too high if the grid goes down and there is no load.
Outback also has their load center that has the circuitry built in to shut
off the enphases. Keep it all ac, make it an AC coupled application, the
enphases should work very well partnered with the radians. The radian hooks
to the main service panel on AC in. AC out runs to the critical loads panel
and you can run the enphase system right into the critical loads panel.
While power is up the system works just like a grid tied system with the
battery portion and radian in standby. When the power goes down, not a
flinch, everything in the critical loads panel is hot, with the battery
system and the grid tied system. Very nice setup
peter giroux
ASAE
----- Original Message -----
From: "Ray Walters" <r...@solarray.com>
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Sent: Monday, August 17, 2015 4:10 PM
Subject: [RE-wrenches] AC Coupled with Generator
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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