5 kW grid-tie...Do I need a combiner box?

I'm installing a 5 kW system on my house. I have 5 strings of 5 Sanyo HIP200BA3 modules and 2 SMA 3000US 3250 Watt inverters in Western Colorado. My wire run from array to inverters is 50' max. I plan to put 2 strings in one inverter and 3 in the other.
My question is this: If I combine strings at the array and bring them down to the inverters, they will over power the inverters. Is there a way to disseminate into 5 strings again before going into the inverters or should I just bring down 5 sets of wires?

All help is greatly appreciated :)

Comments

  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: 5 kW grid-tie...Do I need a combiner box?

    You will probably have to fuse each of the array that are grouped as a parrallel x 3, the isc would exceed the manufactures short circuit rating
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: 5 kW grid-tie...Do I need a combiner box?

    Have you already bought these ?

    A single Xantrex GT-5 would work, and I think you can combine in the terminals of the inverter (manual says 3 strings, but it looks like it will take 6 for GT5 - any owners have any say on it ?)

    Local code may have other ideas about combiner boxes, DC fuses, wire runs etc...

    Sizing Tool:
    http://www.xantrex.com/support/gtsizing/disclaimer.asp?lang=eng
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2
    System2 Posts: 6,290 admin
    Re: 5 kW grid-tie...Do I need a combiner box?

    Yes, I already have the components. Just curious about running 5 sets of wires down to the inverters...is that the best way to get the maximum wattage from the array?
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: 5 kW grid-tie...Do I need a combiner box?
    Ecoguy wrote: »
    Yes, I already have the components. Just curious about running 5 sets of wires down to the inverters...is that the best way to get the maximum wattage from the array?

    Well, if you are feeding 2 inverters, you only need 2 sets of wires. But they have to be larger. You may find better prices for 5 sets of wire @ 12ga, then 2 sets @ 8ga

    And then combine next to the inverters, where it's easier to work (or replace a fuse) You may want to look at the 3/2 split in a year, maybe find which string has lower current (or shade) and use that one for the 3rd string on a inverter. Why pack 3 high performing strings on 1 inverter, it will get even hotter.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: 5 kW grid-tie...Do I need a combiner box?

    You can't do this in 4 strings? Already bought the panels and they don't divide by 2? Voltage limitation?

    Overpower the inverters?

    The SMA 3000 takes two strings, so if you have 3 you're gonna have to combine.

    Could you post more details, including what you've already bought and what you're flexible about?
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: 5 kW grid-tie...Do I need a combiner box?

    Another reason NOT to use sanyo HIT's they are typically 50-60V panels and require more strings than regular Si panels on any decent sized array

    For example, my 5kW array has 2 strings of 15 Evergreens in series for 5100 watts. Sanyo needs 5 strings for the same power
  • System2
    System2 Posts: 6,290 admin
    Re: 5 kW grid-tie...Do I need a combiner box?

    I have the SMA DC disconnect with each inverter which is supposed to accept up to 4 strings and then combine to 2 going into the inverter. According to SMA's sizing program for my location, 3 strings of 5 modules will not overpower...so, 3 strings in one inverter and 2 in the other, right?
    When I originally configured this system, I went by the sizing program, the module info, and selected inverters. I didn't give much consideration to the connection of module strings with MC connectors to less expensive wiring for the 50' run. So I am now confronted with figuring this out.
    Here's what I'm thinking now...
    Using 2 junction boxes under the arrays (one for 3 strings, one for 2), I will connect the MC cables to #10 wire and run through metal conduit in the attic and down the outside wall to the disconnects. One conduit will carry 3 strings and one will have 2. This wire size should more than accomodate temp derating for a hot attic, conductors per raceway, etc.
    Then connect at the inverters and everything is great, right?
    I thought my biggest problem was figuring out how to bring the array wiring down to the inverters, but the more I look into it, the more confused I get.
    Is this the best way to do this with the equipment I already have?
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: 5 kW grid-tie...Do I need a combiner box?

    You can't just wire three arrays in parrallel without fuses. Your solar panels have a maximum current and putting them in parrallel with one string faulted exceeds that current ( two strings will be sending current into the third )

    The inverter may have connections for 4 strings, that doesn't mean anything as you have to meet the PANELS UL listed ratings.
  • System2
    System2 Posts: 6,290 admin
    Re: 5 kW grid-tie...Do I need a combiner box?

    Each string will have a 6 Amp fuse in the DC disconnect (3.83 module Isc X 1.56). The max input Isc for the inverter is 24 Amp.