Minimum string size for Solectria 3000w grid-tie inverter?

 hey tracy and welcome to the group,

 sounds like an exciting project! i was exposed to a great quote the other day that popped to mind when i read your posting.

"I have a plan so cunning you could put a tail on it and call it a weasel."

--From Black Adder

 although the phrase conjours up a humorous image, it is not meant to be derogatory in the least. in fact i see your plan as perfect in every way.

 couple possible issues/roadblocks

1. have to nail down solectria on the low limit specs- there should not be any. i know we can do it (run a small/even tiny array) with the xantrex gt's and the sunnyboys. but the solectria string tool won't let us go to less than 1.1kw- i suspect it is just an issue with the sizing tool? not 100% sure though.

 in an effort to find out i requested clarification from the fine folks at the company.

on 3-31 i sent the following to the east coast tech link:

"hi folks,
 
question. will the pvi3000 run with a very small array?   example, pv array of only 250 watts stc with voc well within the operating window? the string sizing tool only goes down to 1.1kw
 
thank you, dave"

on 4-1 sent this request to the west coast tech link:

" hi allison,
 
 a quick question if i may?
 
will the pvi 3000 run with a very small array?
 
example...a 250 watt stc array with the voc well within our operating window?
 
great string sizing chart! well done, however we only go down to 1.1kw as the smallest array.
 
thank you, dave"

  no response from the company yet.. we shall see, it may take a few of us to hold them down while you go through their pockets looking for the secret information!

2. your local utility may have a minimun allowable grid tie contract. here we need 2 or 2.5kw (depending on who you ask) for a net metering contract. *see below

3. there will be placard issues..aka signs for your current system parameters.

4. should pre-plan for the final system size. at least as far as conduit and "home run" wire size.

  a. i would bypass the built in pv combiner (per manufacturers instructions) and do a combiner box(s) at the array. with properly rated (watch the voltage ratings) equipment.

  b. "home run" the conductors from pv combiner to the inverter.

5. did you notice that those kaneka GSA-60  modules have a preferred orientation? we want the "laser" lines pointing in the up/down direction with an inclination of at least 10 degrees. (some of the thin film designs have "polarization" issues, resulting in an odd photon cancellation phenomenon?)

6. we want to be sure that module (gsa-60) is going to still be around and available for the future expansion of the system!

 not really much help. but wanted to at least give you some kind of feedback and get the ball rolling.

kind regards, dave

edit: added caveat #6 ..bet there are many more as well.

*update 4/11 -seems the rules have changed here in ct and i can net meter with no lower limit. sweet.

There was a time Tracy when Alt-E didn't seem to mind web links to competetors posted in their forum and, I greatly admired and respected them for that, but I think that has change over time. Understandably, I mean what with the economy here in America and around the world going to the dogs. Its dog eat dog. I wish I could tell you all here, where to go to get a package deal of;
52   GSA-60 KANEKA 60 WATT MODULE   
1   MNPV16 COMBINER BOX   
13   8AMP 600VDC KLKD FUSE AND HOLDER   
1   DELTA DC LIGHTNING ARRESTOR LA602DC   
1   SB3000US SUNNY BOY 3000W INVERTER     
1   DU221RB SQUARE D AC DISCONNECT 30 AMP     
1   DELTA AC LIGHTNING ARRESTOR LA302R   
13   MC 3 Cables 30 ft
for just under $6,500. but I suppose that would disrespectable to Alt-E. I mean they are gracious enough to have this forum.

Have I every told about my paternal grand parents that used to live in Miami, Florida many years ago? Have you every been there? Its been a long time ago since I was there. It was the late 60's when we, my mom and dad and brothers and sister and I, would all load up in a station wagon and drive all night to visit them. If my memory serves me correctly it wasn't too far from 511 NE. 15 street. I remember they had a huge mango tree in their back yard. But then again in Miami who doesn't? Their both gone now, God rest their soul. I miss my Poppy and Nanny.
Oh, look at me blabbering on! I have to get ready for Easter Sunday dinner with the in-laws... So long.

for our forum friend thomas,
thanks for your continued support of the forum, as more and more places can sell gear, the number of folks that can miss the devil in the details grows.

for the "package" that you listed, it is noteworthy to me that 8a fuses are supplied, being that kaneka modules have a 7a max series fuse size.

i am no stranger to the occasional mistake myself, but these are the errors that raise an eyebrow. I would suggest that any electrical work that is often described in the forum, be undertaken with due care and planning from the paper stage to the integration stage.  much like the sandwich you described so well in the earlier post, what you see may not be what you get, let alone what you need, regardless of the place one acquires it.

anyway, the burger post made me laugh, thanks for the continued support of the forum.

cheers,

james
altE staff

Thanks everyone for all of the help.

I've been trying for the last two months to get a definitive answer back from Solectria about this very issue. My concern is that they may attempt to void the warranty or something else if they deem this to have been running "out-of-spec". The voltages/wattages going into the unit (albeit low) would be stored in the unit so that is easy to determine.

I'm trying my best to stay within the operating parameters of the inverter so as not to damage it. On the other hand, I don't want to wait another 2 years to be able to afford the extra 2.8kw of panels to start getting some sort of payback.

Obviously, after an investment of this magnitude, it would be nice to offset at least *something*, *anything* at the git-go. My house, when idle, draws about 230 watts (wall warts, idle loads, etc).

I've emailed and called Solectria (left voice mail) and they never seem to have time for the "little guy". I wish I would have known this prior to purchasing the inverter since I would have chosen a more customer-friendly manufacturer.

I'm sure many others here might consider a similar start to PV, which would benefit AltE and Solectria right away (through increased sales) but I guess we'll be left in the dark (excuse the pun) with regard to the lower operating limits of the inverter.

On another note, the price-per-watt for the Kaneka GSA60 panels can't be beat but watch out for the cost-per-watt for the Unirac mounting solutions! I figured that the cost for mounting each module is about the same cost of the module itself when you figure the "D" clamps, railing, standoffs, etc. I've already committed to this course but something to think about if you're following a similar path.

It would be really nice if Solectria could improve their customer support and/or sizing tool.

Oh, forgot to mention; Yes, the wiring runs, etc have been designed for the final setup (3000w total).

Thanks again for the replies and hope Solectria gets back soon with some answers

 update: six emails and two voice mails.

for those reading and wondering, this is the sort of information we are looking for on the pvi 3000



these are the low limit performance charts for the pvi 1800 and pvi 2500.

http://www.altestore.com/mmsolar/Others/PVI1800_2500_Installation_and_Operation_Manual_Rev1.04.pdf

 we see the 1800 does well down to 300 watts and drops off the chart at ~100 watts. the pvi 2500 does well down to 500 watts and drops out at about 150 watts. if we use the trend of those charts we should still be on line with the  pvi 3000 down to about 200 watts or so.

 i don't see any way of damaging the unit with low input as that would be a normal occurrence with snow/weather/low light conditions. i understand your concerns in regards to the warranty and excuses for voiding it. could be a chance that alte may have your back covered with post #4? i would like to see that company return some answers to repeated query's none the less!

kind regards, dave