Sunny Island and 3 phase 208

ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
I am not that well versed in dealing with 3 phase services, so bear with me...

Assuming that the utility is OK with it, can I connect two Sunny Islands to two legs of a 3 phase 208 WYE service hot to neutral? From the manual it looks like I can, but in the configuration menu of the master SI, would it be 3 phase or split phase?

Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,149 admin
    Re: Sunny Island and 3 phase 208

    Hmmm... Not sure...

    They list two units.. A 230 VAC nominal (202-253 volts). Unless they can adjust the voltage output down to the 208 mid-range...

    A a 120 VAC unit that is also listed as three phase compatible...

    Are you looking at one unit or multiple units (which may be the issue with 3-phase--the ability to shut down multiple units if one or more phases drop)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • rickrick Administrators Posts: 133 admin
    Re: Sunny Island and 3 phase 208
    ggunn wrote: »
    I am not that well versed in dealing with 3 phase services, so bear with me...

    Assuming that the utility is OK with it, can I connect two Sunny Islands to two legs of a 3 phase 208 WYE service hot to neutral? From the manual it looks like I can, but in the configuration menu of the master SI, would it be 3 phase or split phase?

    I'm not 100% sure, but you may have some problems trying to use two grid-tie inverters on only two of the three phases. I'm not sure if the Sunny Island will work in 3-phase mode if it does not detect the presence of all 3 phases. That would be ideal if it did. But here's what I'm thinking may happen if you use two SI inverters in single phase mode on two separate phases. Just to be sure we're on the same page, 3-phase power can be represented as 3 separate sine waves that are 90 degrees out of phase from phase 1 to phase 2 and 90 degrees out of phase from 2 to 3. If you connected a SI to two separate phases of a 3-phase system, I don't think the sine waves would be 90 degrees out of phase with each other. If this is the case, you could have problems if there are any shared neutrals in your building's wiring. If the signals are not out of phase and you're sharing a neutral across circuits from the two phases, you may cause the neutral to become overloaded. This can be extremely dangerous because there is no overcurrent protection on a neutral wire. Basically this is a recipe for a fire. If your building does not share any neutrals, I don't think you will have any problems associated with using two SI on two of the three phases. But again, this is just speculation. I don't know for sure. This would be a great question for the SMA forums or their tech support department.
    Website administrator for Northern Arizona Wind & Sun
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Sunny Island and 3 phase 208
    rick wrote: »
    I'm not 100% sure, but you may have some problems trying to use two grid-tie inverters on only two of the three phases. I'm not sure if the Sunny Island will work in 3-phase mode if it does not detect the presence of all 3 phases. That would be ideal if it did. But here's what I'm thinking may happen if you use two SI inverters in single phase mode on two separate phases. Just to be sure we're on the same page, 3-phase power can be represented as 3 separate sine waves that are 90 degrees out of phase from phase 1 to phase 2 and 90 degrees out of phase from 2 to 3. If you connected a SI to two separate phases of a 3-phase system, I don't think the sine waves would be 90 degrees out of phase with each other. If this is the case, you could have problems if there are any shared neutrals in your building's wiring. If the signals are not out of phase and you're sharing a neutral across circuits from the two phases, you may cause the neutral to become overloaded. This can be extremely dangerous because there is no overcurrent protection on a neutral wire. Basically this is a recipe for a fire. If your building does not share any neutrals, I don't think you will have any problems associated with using two SI on two of the three phases. But again, this is just speculation. I don't know for sure. This would be a great question for the SMA forums or their tech support department.
    I just spoke to one of their tech support guys. They said to connect each SI phase to ground and to set the master up as split phase in the setup menu.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Sunny Island and 3 phase 208

    by the way it would be 120 degrees out of phase and not 90 degrees just for the record.
  • rickrick Administrators Posts: 133 admin
    Re: Sunny Island and 3 phase 208
    niel wrote: »
    by the way it would be 120 degrees out of phase and not 90 degrees just for the record.

    True. I'm not sure what I was thinking when I wrote 90. Good catch.
    Website administrator for Northern Arizona Wind & Sun
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