2 separate PV systems connected to the same service

slurry bowl
slurry bowl Registered Users Posts: 34 ✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
After reviewing NEC 690 and 705 I cant seem to find anything prohibiting 2 separate systems from being connected to the same service.
Where it is interesting is that we could install them with their own respective disconnects and have both interconnect at the same terminal box after the meter but it would be much easier for us to interconnect at 2 different locations (obv both systems having NG bond and on LINE SIDE with their own discos. One at the terminal box and one at a gen. auto transfer switch. Utility is Ameren in IL. Any input or advice on this appreciated. THANKS
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  • MichaelK
    MichaelK Registered Users Posts: 236 ✭✭✭
    edited November 2020 #2
    Are you talking about connecting the inverter output of each system to the mail breaker panel?  That could potentially be a BIG no-no depending how you do it.  Unless the two inverters are communicating with each other, the two sine-waves would be out of phase with each other, causing destructive distortion. 

    What might work if no-one besides you ever works on the system is wiring one 120V inverter hot to L1 only, and the other inverter to L2.  BUT, you could never use a dual-pole 240V breaker because of the same distortion problem.

    I think you are going to be far better off if you just get split-phase inverters that are designed to do this and can be paralleled.  Schneider and Outback both make those. 
    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
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  • slurry bowl
    slurry bowl Registered Users Posts: 34 ✭✭
    edited November 2020 #3
    MichaelK said:
    Are you talking about connecting the inverter output of each system to the mail breaker panel?  That could potentially be a BIG no-no depending how you do it.  Unless the two inverters are communicating with each other, the two sine-waves would be out of phase with each other, causing destructive distortion. 

    What might work if no-one besides you ever works on the system is wiring one 120V inverter hot to L1 only, and the other inverter to L2.  BUT, you could never use a dual-pole 240V breaker because of the same distortion problem.

    I think you are going to be far better off if you just get split-phase inverters that are designed to do this and can be paralleled.  Schneider and Outback both make those. 
    thanks for the response. These are large scale systems which always use SMA 240 split-phase inverters. 6 inverters on one system and 12 on the other. I am familiar with phasing and these systems always "handshake" and match wave forms. always. this is not an off-grid system! thanks though. I am not aware of any 120V inverters for the net metering market! I was simply looking for NEC references regarding multiple PV systems under one service.
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