using single phase inverters in a three phase building

Good evening all,
I live in Kingston Jamaica where we have a Delta Grid, so our single phase installations are 110v between phases (110+110=220vac) and our three phase is 110vac-110vac-190vac (high leg). No manufacturer makes a three phase inverter which will interconnect with the delta grid unless you put a transformer with delta/star which adds about $3-4k usd to the bill. My question is for a 25kw PV system can i use five 5000w single (split phase) phase inverters on the two 110 legs and not connect anything to the 190vac leg ..

sincerely,

Robin

Comments

  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: using single phase inverters in a three phase building

    You can use single phase inverters on the two 110 legs, yes. But the power company may not be OK with the imbalance that will cause on their system (unless most of that energy will actually be going to feed your own 110v loads on site.)
    Most of the major GTI manufacturers I have looked at (including SMA) offer individual inverters that are designed to wire between two hot lines (which in your case would be any two) at a voltage of ~ 220 or 240 volts. Using those you could connect to the high leg (just not from the neutral) as well as to the 110/220 legs.
    Some of these inverters may, so satisfy some regulator requirements that may not apply in your case, be designed so that they need a center point reference input even though they will not be delivering any current to it. That would be the center tap in the case of 110/220 single phase and the neutral in the case of 190Y/110 three phase (which is not what you have...)
    SMA SB 3000, old BP panels.
  • reckless1
    reckless1 Solar Expert Posts: 29
    Re: using single phase inverters in a three phase building

    Thanks inetdog...


    robin
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: using single phase inverters in a three phase building
    inetdog wrote: »
    You can use single phase inverters on the two 110 legs, yes. But the power company may not be OK with the imbalance that will cause on their system (unless most of that energy will actually be going to feed your own 110v loads on site.)
    Most of the major GTI manufacturers I have looked at (including SMA) offer individual inverters that are designed to wire between two hot lines (which in your case would be any two) at a voltage of ~ 220 or 240 volts. Using those you could connect to the high leg (just not from the neutral) as well as to the 110/220 legs.
    Some of these inverters may, so satisfy some regulator requirements that may not apply in your case, be designed so that they need a center point reference input even though they will not be delivering any current to it. That would be the center tap in the case of 110/220 single phase and the neutral in the case of 190Y/110 three phase (which is not what you have...)

    I'll just add that some of these high leg arrangements are open delta with a much smaller transformer driving the high leg than the other two. In those situations the power company may not even want you to interconnect with the high leg.
  • Rudy
    Rudy Registered Users, Users Awaiting Email Confirmation Posts: 1
    In a grid tie system (220/380, Y, Argentina), is it possible to connect a delta output inverter (no grounded) or iIam obligated to use an inverter with a Y output? My idea is the delta should not be a problem, connected to the phases of the Y system. which are at 380 volts, but I want to be sure. In the Y system I only have single phase loads. Evntually a 3 phase electrical motor. Thanks for your help. Rudy.
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,731 ✭✭✭✭✭✭
    If you want to be sure you will need to check what is customary or required by the utility.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • daveund
    daveund Registered Users, Users Awaiting Email Confirmation Posts: 1
    i have a 3 phase pump service and the voltage is 240-240-240- 120-120-208 ( Delta). I want to connect a two single phase 240 volt SMA inverters . Can I just connect to the two phases that do not have stinger A-B & A-C Leaving B-C alone and still get reverse rotation at utility meter.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Welcome to the forum Daveund,

    I would suggest you start your own thread/discussion if you need to continue to go into detail about your system (avoids confusion with Q&A from original poster).

    I guess you are in the USA, possibly in California?

    To answer your question--I am pretty sure that the meter will properly record your energy consumed and produced....

    However, there are other issues that you may come across.

    First is that some (few, many, all?) may have a maximum 3 phase imbalance of 10 kWatts when feeding power back to the utility.

    Second is that you may find that you need to insure that if there is a phase drop, that the multiple inverters are safely shutdown (either external relays, or with shutdown control logic for the separate inverters).

    Third is that whatever the "meter reads", will depends on how the utility has programmed them (many/most meters in California seem to be "smart" meters these days). While the meter can read power draw and backfeed, the utility may program something called "revenue guard). This is to prevent people feeding energy back into the grid (via solar, etc.) and to prevent people taking a meter and "installing it upside down" (i.e., installed correctly for 3 weeks of month, upside down for 1 week a month to run meter backwards and steal energy).

    The utility will probably install a new meter anyway coded to your rate plan (time of day, logging energy sold to utility with a different "register" than power purchased from utility--All depends on rate plans).

    In California, they are in the process of overhauling GT solar rate plans.... As I understand, California would basically let GT Solar run the meter backwards when feeding GT solar to grid, and run the meter forwards when buying from grid... Basically buying/selling energy at a single "retail" value.

    The new rate plans (to be implimented in a few months?) will only buy power from GT solar at something like $0.085 per kWattHour). And selling to customers can be as high as $0.40 to $0.50 during peak times).

    As to how much money you can safe with GT Solar--You may need to talk with an engineer or other expert about how the new rate plans would affect...

    And if this is a commercial account (farm, industrial, etc.)--GT solar was already a fairly confusing mess regarding billing (in times past, roughly 50% of bill was $/kWH, and other 50% of bill was "15 minute per month peak energy flow"--Which with GT solar could dramatically affect your billing... I.e., you consume energy 24 hours per day, and solar only feeds back ~6 hours per day--For 100% energy offset, your GT solar would be something like 4x the average pre-solar 15 minute peak. And this could cause the electric bill to be higher with GT solar vs without GT solar).

    Again, some of these issues where in times past (more than a decade ago)... But with billing/rate plans continuing to change--You need to make sure your system energy usage/generation actually is financially viable and you don't get blindsided with your actual billing.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • GreenAirCyprus
    GreenAirCyprus Registered Users, Users Awaiting Email Confirmation Posts: 1
    daveund said:
    i have a 3 phase pump service and the voltage is 240-240-240- 120-120-208 ( Delta). I want to connect a two single phase 240 volt SMA inverters . Can I just connect to the two phases that do not have stinger A-B & A-C Leaving B-C alone and still get reverse rotation at utility meter.
    This is something I also tried and worked pretty well. It's a good way to go around this problem.