Uniphase inverter in three phase building

quique
quique Solar Expert Posts: 259 ✭✭
in Solar Beginners Corner #1
I have a building which has a three phase main service panel which feeds 2 sub panels which are single phase.

Could I install a Fronius uniphase inverter at those subpanels?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,660 admin
    #2
    Re: Uniphase inverter in three phase building

    It depends...

    You probably need to contact your utility first... In Northern California, there is something like a 10 kWatt limit in balancing three phase power (as I recall). If your system is over 10 kWatt, you may have issues and need access to more phases.

    Also, there are various ways of wiring delta and Wye three phase power--You would need to understand how the building is wired and ensure that the Fronius can interface correctly (and all inverters probably need to drop their output if one or more phases fail)...

    Are you thinking of doing this yourself, or using an electrical contracting firm that knows solar?

    -Bill "way out of my depth" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • quique
    quique Solar Expert Posts: 259 ✭✭
    #3
    Re: Uniphase inverter in three phase building

    Already checked and no, the phase limit is not an issue.

    As for the install, we have a solar company, we saw the project today so we're wondering about it.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #4
    Re: Uniphase inverter in three phase building
    quique wrote: »
    I have a building which has a three phase main service panel which feeds 2 sub panels which are single phase.

    Could I install a Fronius uniphase inverter at those subpanels?
    Not sure about the Fronius, in terms of whether it needs any jumper or software setting to be made, but 208V is a lot like 240V for most purposes. The big question is what it does in monitoring the neutral.
    UL requires inverters for split phase (120/240) configuration to monitor the two line to neutral voltages to make sure that they are equal within a certain tolerance. For a phase to phase installation on three phase, the line to neutral voltages will still be equal in amplitude, just not opposite in phase.
    So that probably will not be an issue either.

    For Enphase microinverters, AFAIK the only difference between 120/240 single phase and 208Y/120 three phase is in the model of trunk cable that you attach them to.
    It is always worth looking to see if there is a configuration setting which needs to be different.
    A single-unit three phase inverter, on the other hand, is going to be good only for a three phase connection.
    SMA SB 3000, old BP panels.
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