L1/L2 imbalance - general questions

[KevinC_63559]

Hi all -

Energized my pair of Victron Multiplus IIs up yesterday with a partial critical load. The pair are configured to provide 240V AC, 120V per unit apparently coordinated to provide proper split phase between them.

Watching my Cerbo display, its kinda neat how they handle any imbalance. Since they are two semi-independent units, its no big deal if one provides 100w and the other provides 250w - both work at their optimal performance for their individual loads. When I throw 1000w of 240V demand on the system, each contributes 500w and all is good.

Made me wonder how the larger all-in-one 240V split phase inverters handle it? Do they internally have dual systems?

How does the utilities handle it? More importantly how does my utility meter handle it? (e.g. Am I charged at the greater leg amount? At the combined amount?)

Inquiring minds want to know! (And I figured somebody here probably does!)

Thanks in advance,

Kevin

 

[ricardocello]

More importantly how does my utility meter handle it? (e.g. Am I charged at the greater leg amount? At the combined amount?)

Your meter only looks at the L1 and L2 power in (and power out if you export power) by measuring the current and voltage on L1 and L2.
The neutral current is not measured. It goes back to the split-phase transformer on the pole or in a box.

If you use 100W on L1 and 250W on L2, you are charged for 350W, as you would expect.

More interestingly, with ESS installed, you can see -100W on L1 and 250W on L2, and you are charged for 150W.
Happens all of the time for me.

 

[aliarifat794]

Many split-phase inverters essentially contain two inverters operating out of phase with each other. This design allows them to manage imbalances between the two legs efficiently, similar to how your Victron units work.

 

[KevinC_63559]

Your meter only looks at the L1 and L2 power in (and power out if you export power) by measuring the current and voltage on L1 and L2.
The neutral current is not measured. It goes back to the split-phase transformer on the pole or in a box.

If you use 100W on L1 and 250W on L2, you are charged for 350W, as you would expect.

More interestingly, with ESS installed, you can see -100W on L1 and 250W on L2, and you are charged for 150W.
Happens all of the time for me.

Good to know. Alas my electric coop is pretty "solar unfriendly" (they only pay wholesale for produced power and require a separate meter they charge $60/month for. That's about 1300kws before you break even!). So I just work on reducing my load from them...

That said, adding solar to the system is my next step. Might be next years tax return that funds that effort... we shall see.