3-phase and solar - a problem?

My house has 3-phase coming in from the pole. I am looking to put a 7kW solar installation in and I am getting differing opinions on the impact of the 3-phase...

One installer says I have to do a complete rebuild of the system up to the pole, effectively removing the 3-phase.

The other installer insists it is no problem, when the inverter is feeding the grid it will simply feed one of the hot leads.

The city, believe it or not, has no opinion. They don't really want to voice an opinion one way or the other.

any ideas?


  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: 3-phase and solar - a problem?

    You may have 3 phase into the house, but are you using all 3 wires plus neutral. The meter is what may make/break the solar install. If it see's a draw on one phase and a supply on the other two. It may stop working or meter incorrectly.

    Your AC breaker box, is it single or 3 phase??
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: 3-phase and solar - a problem?

    What is the city? Why do you have 3 phase power at all? Was this a shop or industrial building ?

    Does the meter say 1 (single), 2 or 3 phase anywhere on it ?

    How many wires on your feed pole ? (or main breakers in your panel, single, double or triple) 1 bare cable, and 2 insulated ones twisted around it ?

    There are commercial, 3 phase inverters, so that should easily work.

    What does your electric company say - they have the final say over the city. ('cause the city can't pull the meter and cut your power)

    We need a bit more info to go on.
    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 ,

  • Solar GuppySolar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: 3-phase and solar - a problem?

    All the latest Xantrex GT series work with both 240 or 208 ( two legs of 3 phase ). One leg to neutral is 120 vac by the way, not 208 vac

    http://www.xantrex.com/web/id/1416/DocServe.aspx , notice both 240 and 208 is listed

    The only small down size of this is the power rating is slightly reduced as running at the lower voltage window reduced the VA rating

    Sounds like BOTH installers got it wrong, time to either educate them or find an installer that is better versed in GridTie solar
  • newenergynewenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: 3-phase and solar - a problem?

    Your house is probably 120/208 if it's 3 phase, but if it's 277/480 the SMA 6k or 7k will work (with 120/208 as well).
  • VicVic Solar Expert Posts: 3,185 ✭✭✭✭
    Re: 3-phase and solar - a problem?

    A house with 3-Phase is unusual ... must be in an industrial area, Live Work or similar.

    Usually, 3-Phase power in areas with substantial Split-Phase loads is configured as 120/240 VAC Delta,
    where the Neutral is at the center tap of one phase.
    This yields 120 VAC from CT to each leg, and 208 VAC neutral to the common point of the other legs.

    EDIT: Deleted my attempt @ a Phase Diagram using keyboard characters -- got scrambled as a post.

    I am an off-gridder, and do not know about the compatability of existing hardware in 3-Phase Grid Tied systems, but it must exist. Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: 3-phase and solar - a problem?

    Some additional information to ponder (ref 2005 NEC):
    690.63 Unbalanced Interconnection

    (A) Single Phase. Single phase inverters for photovoltaic systems and ac modules in interactive solar photovoltaic systems shall not be connected to a 3-phase power system unless the interconnected system is designed so that significant unbalanced loads cannot result.

    (B) Three Phase. Three-phase inverters and 3-phase ac modules in interactive systems shall have all phases automatically de-energized upon loss of, or unbalanced, voltage in one or more phases unless the interconnected system is designed so that significant unbalanced voltage will not result.
    OutBack Power System’s off-grid/backup inverters can be stacked in a 3-phase 120/208 VAC 60 Hz (U.S.) configuration (one inverter per hot leg, 10.8 kVA max total) operating from a PV system with a single battery bank. OutBack’s grid-interactive inverters cannot be stacked for 3-phase at this time.

    Jim Goodnight
    Eastern Regional Sales Manager
    OutBack Power Systems
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