Inverter Monitoring & Canceling Meter Legs [RE-wrenches]

[Kirk Herander, VSE]

>   Last month I proposed a meter wiring scheme for battery-based,
> grid-tied systems (like an SW or Outback) that had grid AC input passing
> thru one leg of a standard 4-contact meter, and inverter AC output
> passing in the opposite direction thru the other leg. Straight pass-thru
> power from the grid to the loads would be ignored, the two currents
> cancel each other out. But any renewable power input or grid power use
> by the inverter would be registered accordingly. Considerable, but
> inconclusive discussion ensued...we need hands-on experience, which I've
> got now.
>
>   It Works. With inexpensive, standard 4-contact J5 type meters, it DOES
> work. I currently have two of them running. One is monitoring a Trace
> SW5548, the other is monitoring an Outback GVFX3648 (serial #GFX00001,
> thank you very much Robin and Christopher!) The only trick is when
> running an AC meter on 120vac systems, there's a small pair of screws on
> the back of the meter holding down a connection tab. Loosen them, rotate
> the tab open, and run a ground or neutral wire to the screw with the
> captive tab. (Caution, the other screw is connected directly to one of
> the power contacts.)
>
>   I'm running cheap rebuilt Hialeah meters, two different mfr. brands.
> One's a GE, the other's a Sangamo(sp?). They run backwards when the
> inverter is selling power, forwards when the inverter is battery
> charging, and don't move at all at night when the inverter is simply
> passing grid power directly to the loads. It's a simple solution folks.

Doug,

OK - but don't we want the meter to only register Solar-generated AC? We
want the meter running forwards, not backwards when selling to the grid,
right? See if you agree with my wiring to do this.

meter socket line lug #1 - to AC1 input
meter socket load lug #1 - from utility AC
meter socket line lug #2 - from inverter AC output
meter socket load lug #2 - to critical loads

example #1 - 5kw of critical loads, 4kw of solar generated(1 hour duration)
---  5kwh is moving the meter forward from the inverter AC out to critical
loads
---  1kwh is being supplied from the grid to AC1, moving the meter backwards
---  net registered on meter = 4kwh (solar AC generated)

example #2 - 5kw of critical loads, 6kw of solar generated(1 hour duration)
---  5kwh is moving the meter forward from the inverter AC out to critical
loads
---  1kwh is being supplied TO the grid from AC1, moving the meter forwards
also
---  net registered on meter = 6kwh (solar AC generated)

I'll try it again with the 2S meters. I couldn't get it to work before, but
probably forgot to isolate the tab screws and connect the neutral on Sangamo
EZ read meter I used.

Kirk

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