Recommendation for replacement grid tie inverter

balee123balee123 Solar Expert Posts: 86 ✭✭
Hello all,

I'm looking for advice on a replacement Grid Tie Inverter(s) for my system. I am getting prepared mentally and financially for a replacement in the future. I understand that most, if not all, GT inverters these days have an input voltage range that is quite high (>220 V) compared to my current set up which is ~64 V (4 AP-100 12V panels in series), then paralleled into GT inverters (see below for description of system). The nice thing about my current system is that if one panel gets shaded, I only lose the output from one set of 4 panels. If I have to series connect a lot more panels for today's GT inverter input voltage ranges, I lose this feature, not to mention I would have to rewire the system. Microinverters don't seem economically worth it since each panel is only 100W. Any suggestion for a replacement inverter(s) or how to handle this when the day comes where I have to replace these inverters.............???

Andy

Background:

11 year old grid-tied system

2 paralleled mppt inverters: Xantrex STRX2500, Xantrex STRX1500

STRX2500 has a total of 28 AP-100 100W Astropower panels. 7 sets of 4 panels in series, then paralled into the inverter
STRX1500 has same panels, total of 16, 4 sets paralled into inverter.


AP-100 monocrystalline Panel Specs:

Vmp 16.1 V
Imp 6.2 A
Voc 20.1 V
Isc 7.2 A
Max. Series Fuse Amps 15

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,752 admin
    Re: Recommendation for replacement grid tie inverter

    You probably will be hard pressed to find any viable replacement parts for your system...

    My guess, you will need to purchase new panels (that now meet UL/NRTL Listing requirements--old panels probably do not) and new inverters that also meet the current GT Inverter UL/NRTL Listing requirements too.

    If you want to go with a per panel (low voltage) inverter--You can look at Enphase and similar micro GT inverters (I think you will need to match new/current production panels with these inverters):

    Enphase Microinverters for Grid-Tie Solar Systems

    Otherwise, there are some smaller GT inverters--but you would also need to (most likely) replace your panels too:

    Sunny Boy 700-US 700 Watt Grid Tie Inverter

    Obviously, there are lots of inverters in the larger sizes (3-10kW for residential).

    At least the solar panels are a lot cheaper these days than yours probably cost you:

    High Power Solar Panels - Over 100 Watts

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • balee123balee123 Solar Expert Posts: 86 ✭✭
    Re: Recommendation for replacement grid tie inverter

    Thanks so much for the reply. The panels and Inverter are UL listed. Inverter = UL 1741-1999 (first edition) and cUL listed to CSA C22.2 No. 107.1-95. I"m not sure why I would need all new panels. Is it only for the specific configuration I was talking about? If I didn't care about the potential shading issues with longer strings, could I do something like:

    2 x 22 panel strings and use a SunnyBoy SB5000 US?

    Thanks in advance.
  • BB.BB. Super Moderators, Administrators Posts: 30,752 admin
    Re: Recommendation for replacement grid tie inverter

    If the panels are listed to UL at 600 Volts--then they should be OK--Older panels tended to not be Listed originally and were typically rated to only ~70 VDC maximum (originally designed for battery based systems).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Solar Expert Posts: 1,963 ✭✭✭
    Re: Recommendation for replacement grid tie inverter

    This is easy.

    Just at the combiner wire each string in series so you have one long string. If you read my HP91 article, that's exactly what I did to compare the sunnyboys to the Sunties.

    That system now runs on a pair of Xantrex GT2.5 with the above rewiring. The bypass diodes handle the shading and only the shaded panel is lost as its a single string
  • balee123balee123 Solar Expert Posts: 86 ✭✭
    Re: Recommendation for replacement grid tie inverter

    Solar Guppy,

    Thanks for your reply. How do I find your HP91 article?

    Thanks
  • BB.BB. Super Moderators, Administrators Posts: 30,752 admin
    Re: Recommendation for replacement grid tie inverter

    Home Power Magazine Issue HP91 Oct/Nov 2002 (Index).

    Library or if you subscribe, I think you can read back issues on-line.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • balee123balee123 Solar Expert Posts: 86 ✭✭
    Re: Recommendation for replacement grid tie inverter

    Solar Guppy, thanks for the suggestion. That will work perfectly when the day comes to replace my inverter(s). I read your article...very interesting. I also had the same ST2500 swapped out for my current STRX2500 back in 2002 and Xantrex also came out and installed a monitoring device(s) for my system. At best, I still only seem to ever get ~65% of the STC rating of my system ( 2850 watts from a 4400 watt system). I've been a little disappointed over the years.

    May I inquire why you decided to go with 2 Xantrex GT2.5s instead of other inverters?, especially after reading your article.

    Question for all: are there any potential problems using a Sunny Boy Grid Tied inverter in parallel with either the STRX2500 or STRX1500?
    This is easy.

    Just at the combiner wire each string in series so you have one long string. If you read my HP91 article, that's exactly what I did to compare the sunnyboys to the Sunties.

    That system now runs on a pair of Xantrex GT2.5 with the above rewiring. The bypass diodes handle the shading and only the shaded panel is lost as its a single string
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Recommendation for replacement grid tie inverter

    "Question for all: are there any potential problems using a Sunny Boy Grid Tied inverter in parallel with either the STRX2500 or STRX1500?"

    i don't see a problem as long as they each have their own pvs.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,963 ✭✭✭
    Re: Recommendation for replacement grid tie inverter

    I redesigned the Software and some of the hardware on the old ST's, they became UPG's and were offered free swap to all ST owners in the spring of 2003. I transitioned into the GT program and later the XW program.In 2007, that system in HP91 system I used for the testing, no longer owned by me needed both all the KC-120's and the Suntie replaced ( one still worked ). Xantrex had an upgrade policy for $999 you could get a new GT to upgrade an old Suntie ... last I heard they still honored it if you called service on the 800 number. So the owner got the GT-2.5s, still running fine I am told

    The 5kw inverters have really come down in price, if you have the panels and can make two equal length strings, cost wise going with a GT5.0 or Sunnyboy 5kw would be ideal
  • balee123balee123 Solar Expert Posts: 86 ✭✭
    Re: Recommendation for replacement grid tie inverter

    Thanks to all for the info.
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