HI Drake, What sort of multi stage relay control are you using?
jay peltz power > On Aug 21, 2015, at 5:27 AM, Drake <[email protected]> > wrote: > > I'm considering an AC coupled system with Enphase that would shed inverters a > group at a time, ending up with one still charging until the set point is > reached. > > At 12:56 AM 8/21/2015, you wrote: >> Hi Folks; >> >> I've done more research on the whole AC coupled issue, and one flaw I found >> with both the Sunny Island and the Radian is that they can't really do a >> full 3 stage charge for the batteries in off grid mode. >> They detect that the batteries are full and disconnect the AC coupled GT >> inverters, but this is about as subtle as the very early charge controllers, >> and amounts to 1 stage charging. This is fine for temporary outages, and >> when the grid comes back, the batteries get a good 3 stage charge. But >> these folks are really wanting a design that could be taken off grid >> permanently. Also as you my recall, the GT PV system is Enphase, so we >> can't use the more sophisticated controls that SMA offers for the Sunny >> boys. >> I hate to say it, but I might be back to a diversion load with PWM >> controller. Not elegant, but we could get 3 stage charging. >> Every time I look at AC coupled setups, I just want to start over with >> charge controllers. >> >> R.Ray Walters >> CTO, Solarray, Inc >> Nabcep Certified PV Installer, >> Licensed Master Electrician >> Solar Design Engineer >> 303 505-8760 >> On 8/17/2015 9:39 PM, Mac Lewis wrote: >>> Hi Ray, >>> >>> With that size grid-tied system, you would want to use a battery based >>> inverter(s) near the (6.7/0.8) 8000W range. >>> >>> The frequency shift of the Sunny Islands will work with kicking out the >>> enphase inverters but you wouldn't get the same output ramping that it >>> would offer if it was a Sunny Boy grid-tied inverter. The Sunny Island can >>> effectively solve your generator backfeeding because there is a reverse >>> current sensor that will disconnect the AC input at whatever level you >>> want, 50 mA is default I think. You may need to give the Sunny Island >>> generator start control for this however. >>> >>> You can read about it here on page 137. >>> >>> http://files.sma.de/dl/15216/SI4548-6048-US-BE-en-21W.pdf >>> <http://files.sma.de/dl/15216/SI4548-6048-US-BE-en-21W.pdf> >>> >>> You'll need to give the Sunny Island a digital signal that tell it whether >>> its connected to a generator or a grid as outlined in the manual. >>> >>> This is where the Radian is nice because it has two AC Input terminals. >>> >>> Sounds like an interesting project. >>> >>> Good Luck. >>> >>> >>> >>> >>> On Mon, Aug 17, 2015 at 8:36 PM, Jerry Shafer <[email protected] >>> <mailto:[email protected]> > wrote: >>> >>> I cant see this working well without some battery based inverter >>> Jerry >>> On Aug 17, 2015 10:10 AM, "Ray Walters" <[email protected] >>> <mailto:[email protected]>> wrote: >>> 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 <tel:303%20505-8760> >>> >>> ______ >
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