XANTREX Advice or Knowledge Requested

[LowGear]

I have 6 KW of solar plugged into a Sunnyboy 6000 inverter.  I had a pipe leak above it a month ago and still "No Problem".  The downside of these cast aluminum tanks is that when the grid goes down so do they.  If I have a full system lock out (I know there's a more accurate term but it's me) then how do I get that SMA 6 KW system to do something like run the dryer and water heater without going down the SMA Sunny Island route (doesn't add any PV capacity but costs almost as much as an XW unit)?  I expect to put about 3KW PV more in.

Can an Xantrex XW generate enough of a sinewave to fool the Sunnyboy into "islanding"?  What's the smallest XW nn48 made or is the 4548 it?  Would the XW 4024 be just as efficient and have the same battery performance?

Alternatives?

Casey

[Tom Reed]

It definitely might work. But how does the cost compare with the Sunny Island which we know works?

[mobile_bob]

it might fool the sunnyboy, but will the xantrex handle a back feed from the sunnyboy?

i don't know, that is why i ask

bob g

[Tom Reed]

Could be an expensive puff of magic smoke if not.

[mobile_bob]

if you were to want to test the theory, and i would not suggest you do until you can verify that it will work...
then i might suggest you insert an inline fuse holder with as small a fuse as you can find, perhaps a 5amp fuse or less

that way the fuse will blow if there is some incompatability issue, like out of phase or phase shift, or some other problem.

if it blew the little fuse, it might save something much more expensive to fix

i used this method many times when working in control panels without schematics to work with, sometimes you just get confused
by all the wires, all the same color and no identification where they go,  if i were in doubt i used an inline fuse holder and a small fuse
to do the connection first,  if the fuse held i had some assurance that what i was doing was not going to harm things irreparably, if it went flash/pop i knew real quick to back out of that idea in a hurry.

again i would not suggest doing this with your equipment until i could verify that it is safe to do so by both manufactures engineering departments, then i would still use the fuse as an extra layer of insurance, just in case i talked to a newbie engineer that wasn't clear what i was asking or turned out to be full of crap.

funny how they forget who you are when the smoke starts filling the room!  all of a sudden no one remembers talking to you, and no one remembers telling you or anyone that your scheme was safe to do!

good luck
bob g

[uber39]

Have a look through this UK forum http://www.navitron.org.uk/forum/
some blokes over there are using stand alone inverters to start the grid inverter, BUT there using smaller GTI's
      Ian

[Thob]

Crank up the Witte - let it be the "grid" and then the Sunny Boy can supply power???  Use a fuse - like Bob said!

[DanG]

I've asked the same question six or eight times and have never gotten the same answer twice; spoofing a grid-tie inverter using a pilot signal.

Two or so years ago Home Power Magazine had a featured system of an off-grid system showing a slaved 4000 watt 240VAC PV grid tie inverter working as a booster for high dedicated 240V loads. If memory serves me correctly they had it fed with one of their step-up transformers off of a paralleled set of 4000w inverters (8000w) so it was picking up loads on the 120V side also but with delays of wire length and transformer may not have been called on much. With that system the 240 kicking in sagged line voltage enough it was discernible so they spent more money!

I know I should have scanned the article and saved the hard-copy but I just had to laugh I'd finally seen it in print. I have a battery-less Trace 4048PV 240V grid-tie inverter I want to dedicate to a well pump...

[LowGear]

But how does the cost compare with the Sunny Island which we know works?

The XW is more money and while the SunnyIsland does provide for battery operation when islanding it doesn't provide for more panels.

Casey

I'll see about calling them.  Now how will this story go?  My great Aunt died and I inherited her XW4024 (is there a 4048?) and I want to know what would happen if I stuck it on my garage and ran it through the same main breaker box as my Sunnyboy 6000. 

[Tom Reed]

Dan, I remember that HP article too. Still have the magazine as I save them all and have an almost complete set. I don't remember to many details about how they accomplished the islanding though. IIRC the home owner was a Sunnyboy exec, so he might have had access to items the general public doesn't.

[LowGear]

OK.

Xantrex via Schneider contacted via email. 

Xantrex has a problem.  Xantrex.com does not acknowledge the grid tie section of their products.  You have to go to Schneider.  Apparently its either a 4548 or a 4024?

I'll let you know.

Casey

Northern Arizona Solar (pretty close) made it simple.  Pull the SunnyBoy and stick in an XW there as well.  Hey, it's only money!

[LowGear]

Schneider got back to me already - two hours - not bad.

1.  The tech doubted if I could get permitted for more solar than 6KWH - 25 Amps.  He assumed a 200 amp service.  I'm not sure I buy that. 

2.  XW unites are really designed as stand alone and I would have problems if I tried to coexist them (see next point). 

3.  Rather than buy two SunnyIslands (they're 120 volts each so a 240 system like mine needs two) I should feed my SunnyBoy into the XW on the output.  The XW would work as an island unit with the batteries but would not handle anymore line wattage (more panels) and I'd have to purchase the xw6048 to accommodate the SunnyBoy 6000 fully paneled as is mine.

I hate it when I don't get the answer I wanted.

Casey

[Tom Reed]

If I read that right either way is going to cost you $$$. 

[mike90045]

This has been discussed a lot, in the Arizona Wind Sun forums.   It's doable, but you need a very large battery bank to absorb the backfeed if the loads drop off, and the "grid" voltage will rise out of spec, and knock the inverters off line for 5 minutes.   The SB system uses a slight frequency shift in the "grid" to control or "throttle" the source, so it does not overload the system.  There has been some talk that XW is working on firmware that will allow some interaction, but nobody has built up a trial rig yet.

 Mike

3KW PV, xw6048, MS MPPT 60  controller, 48V 800AH Nife battery bank