Grid Tied Installation Size Projects

quique
quique Solar Expert Posts: 259 ✭✭
in Solar Beginners Corner #1
Hi,

I was wondering, because Ive installed my Fronius 3kW system at home, and Ive seen Fronius Residential inverters go as high as 12kW.

What would be necessary for larger installations? I imagine the 2 options are larger inverters or series of inverters.

What is the largest series of 12kW inverters installed together that you guys have worked on?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Grid Tied Installation Size Projects

    Actually the main limitation is the service capacity. As in the NEC 120% back-feed rule limiting a 200 Amp service to 40 Amps of solar (9600 Watts). A 250 Amp service could have 50 Amps of solar (12000 Watts). Another limit is that some utilities restrict any install to less than 10 kW.

    In theory you could have a 250 Amp 3-phase service with 12 kW on each phase totaling 36 kW.

    If a line-side tap was used then a typical household could in theory back-feed 48 kW (limited by the service transformer and wiring). This may one day be the norm.

    Since a GTI syncs to grid there's no limit to how high you could go because all the inverters would synchronize (except for certain problems with them generating HD on the lines which could throw some inverters off - it gets crazy technical at that point).
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  • quique
    quique Solar Expert Posts: 259 ✭✭
    #3
    Re: Grid Tied Installation Size Projects

    Thanks but I meant more in terms of installation requirements.

    For example, perhaps when you get to systems over 50KW you need or should install X.

    Or over 100KW use Y?

    For example, residential installs use inverters such as fronius or SMA which run up to 11KW. After that, instead of stringing more than 10 units for a 110KW system, use central inverter stations from fronius or some other manufacturer.

    That kinda thing :-)
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    #4
    Re: Grid Tied Installation Size Projects

    I do not have any information on large commercial installs... If you have other installations in your area--I would try to find out what they use. At least you will have other installations nearby and, hopefully, better support/service if you do an installation.

    For large systems like this, you will probably need to hire an electrical engineering firm--They should be able to give you manufacturers that they recommend.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #5
    Re: Grid Tied Installation Size Projects
    Cariboocoot wrote: »
    If a line-side tap was used then a typical household could in theory back-feed 48 kW (limited by the service transformer and wiring). This may one day be the norm.

    Since a GTI syncs to grid there's no limit to how high you could go because all the inverters would synchronize (except for certain problems with them generating HD on the lines which could throw some inverters off - it gets crazy technical at that point).

    +1
    According to the NEC (not so confident about Canada), if you use a line side tap (also called a supply side tap) and connect to the service wires directly where they enter the main panel or upstream from that point you are limited only by the service size. So for a 200A service you could do a 200A backfeed.
    Part of the reason for this is that the POCO conductors running from their transformer to your service point are not subject to the NEC.

    Now the resulting higher voltage present at your service point because of power going out and not in, that is indeed a can of worms when the backfeed approaches the service rating. If you share a transformer with other users in the same area, then your backfeed could also increase the voltage they see if the POCO transformer is undersized (OK, let's just say conservatively sized.)

    In a thread from last year involving, I believe Puerto Rico, a large PV installation at a Coast Guard base actually drove the voltage for everyone in the area higher than tolerable.
    SMA SB 3000, old BP panels.
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  • DanS26
    DanS26 Solar Expert Posts: 268 ✭✭✭
    #6
    Re: Grid Tied Installation Size Projects

    The Fronius product line has 1 phase inverters up to around 11 to 12 kW. Larger than that you need to have 3 phase service. Hanging three transformers outside your house is cost prohibited for most homeowners.
    23.16kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED Pro System monitoring
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  • HX_Guy
    HX_Guy Solar Expert Posts: 296 ✭✭✭✭✭✭
    #7
    Re: Grid Tied Installation Size Projects

    Fronius' largest 240V inverter is the 11.4 model which has a maximum output of 11,400w AC and can take as much as 13,100w DC input. Their 12,000w inverter is for 277v which I believe is only in commercial applications?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    #8
    Re: Grid Tied Installation Size Projects

    277 VAC is line to neutral voltage for a 480 volt 3 phase "Wye" (Y or Star) power system.

    Very common voltage for industrial lighting.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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