Ray, The battery-based inverter in an AC-coupled system should not be grid-interactive. The grid passes through the BB inverter to the grid-direct inverter(s). The BB inverter is there to create a stable grid-like signal for the grid-direct inverters when the grid is not present, and to manage the batteries. Thus, the pass-through AC capability of the BB inverters normally (there is a complicated work-around) must be able to handle all of the PV AC output, when loads are low. You probably are aware, but to make it clear in this thread: the system needs to have some method to protect the batteries from overcharging, as a result of the grid-direct inverter output when the grid is down and loads can't use all the solar energy available. With the Sunny Islands it's done by a signal that reduces output from the Sunny Boys without disconnecting them. With Outback and others it's done with a installer-designed relay that disconnects the grid-direct inverter when the battery voltage gets to a set point. We haven't done an AC-coupled system with the Radian, yet. Sounds like the remote controlled breaker is Outback's approved and listed way to do it. About time.
-Kelly Kelly Keilwitz, P.E. Principal Whidbey Sun & Wind Renewable Energy Systems NABCEP PV Installation Professional WA Electrical Administrator ke...@whidbeysunwind.com PH & FAX: 360.678.7131 On Jul 30, 2013, at 4:23 PM, Ray Walters <r...@solarray.com> wrote: > The Outback rep got me some good info, and I'm liking the Radian with the > Remote controlled breaker to control the GT inverter when the grid is out. > I've heard of quite a few problems related to the Sunny Island frequency > controlled system. > My question is can off grid inverters like the Magnum be AC coupled? I'm > trying to get the price down, and still handle the 240 vac input from the GT > inverter. > I penciled out the Radian and I was topping $10k before installation. This > customer is hoping for a solution under $10k, and closer to $5k if possible. > I think an elegant lower cost solution for Grid tie with battery back up is > in order. A Radian Lite? > For backup, it could even be mod sine, as it wouldn't be much worse than > generator power or the average UPS setup. > > > R.Ray Walters > CTO, Solarray, Inc > Nabcep Certified PV Installer, > Licensed Master Electrician > Solar Design Engineer > 303 505-8760 > > On 7/30/2013 2:59 PM, Ray Walters wrote: >> Hi All; >> >> I know AC coupled systems have been covered before, but I have a new issue: >> positive grounding. A customer with an existing 8kw Sunpower system wants >> to add backup. He was put off by the high cost the Sunny Island, so I was >> steering him towards a single Outback VFX coupled to just one of his 3 >> inverters. The issue is how will the VFX work with positive grounded >> inverters. I'm assuming that since the two inverters will only be connected >> by AC, that the positive vs negative grounding of their separate DC systems >> will not matter. Any experience with this particular scenario: Sunpower >> system AC coupled to an Outback? >> Also, would I even need a GVFX, since the inverter would only be used during >> outages (which might allow a generator to be used later as well) A VFX >> should still AC couple to the GT inverter during an outage, right? >> >> Thanks as always, >> > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Change email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org >
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