I am updating a mppt solar battery system to use a multiplus II 24v 3000kva and an ekrano GX. My ultimate goal being to make it into an ESS system and feed my unused solar energy back into my grid connection.
What I don’t clearly understand from the ESS manuals, is if I use this single phase 120v inverter that goes back to a single leg breaker, am I going to cause issues feeding back into a single leg of my split phase panel? I would think I could serve to balance out whatever load is on that leg, but to what extent? Could I technically send power back to the grid on one leg, while still consuming on the other?
Maybe I am over thinking this, but could someone help explain if there are issues with doing this? I have an autotransformer if it makes any sense at all to try to balance at some point.
I’m assuming you are in the US (Ohio), but please correct me if I’m mistaken.
You need to be aware of the legal issues feeding back power to the grid. Specifically, you will need an interconnection agreement with your power company to do that, and they may have requirements you may not be able to satisfy with Victron gear. At the very least, you will need to have a UL-listed Multiplus-II. Depending how difficult the power company is, you may need something in addition to using Grid Code “Other” in the ESS configuration, like a pair of utility meters, or just a new smart utility meter. This is true even if you don’t want to be paid for feeding back into the grid. You should contact your power company and carefully gather the info before making any decisions.
OK, now technically, feeding back on a single leg of 120V will work fine. In most US residential split-phase installations, you are billed for the combined L1 and L2 legs (hots) at 240V. The Neutral conductor is not metered. Any power you push back to the grid on L1 will be compensated for at the utility transformer secondary winding using the Neutral. The transformer is typically located on a pole near the house, or in a green transformer box on the ground.
Let’s say you export -500 W to the grid on L1, but the rest of the house is using 700 W on L2. The utility meter will read 200 W, so net, you are not exporting power to the grid. If you are able to balance the legs so that the net L1+L2 power is always positive, the utility meter will never see any power exported. As soon as that number goes negative, they will know (if you already have a smart utility meter, if they are checking, and if they care). Which is why getting an agreement in place first can be important.
There are also NEC rules about feeding back power into a breaker. See NEC 705.12, the 120% Rule.
Thank you very much for the clear explanation. That makes perfect sense to me, and sounds like that is not a concern fundamentally.
I am in Ohio, sorry I should have mentioned that. And thank you for the reminder on working with the electric company for approval. I did not plan on that part ahead of purchasing, but I am pausing now while I reach out to them. I do have a UL listed multiplus II so hopefully that will satisfy. Have there been power companies in the US that will refuse to work with Victron components? I guess I have thought of them to be one of the leading component makers, but maybe not recognized as much in the US? Just curious.
California does not approve victron grid-interactive ESS systems because they do not implement UL 1741-SB and are not on the allowed equipment list. Any other jurisdiction or power company requiring 1741 SB will also likely not approve the interconnect. Which is why you should ask first. Because the potential penalty for exporting power to the grid (even just a little) frequently results in a nasty letter or visit from the power company threatening to cut you off.
There is nothing wrong using Victron stuff without ESS as a big UPS for the house, since that is not considered grid-interactive. No agreement is necessary to do that, since the Multiplus is just a battery charger and load in that configuration. Lots of people do that.
However, installing ESS Assistant turns the Mutliplus into a hybrid inverter, and that’s when the power company can get hostile.
Not all power companies care, so it will depend on your local rules. Hopes this helps.
I believe the interconnection rules are set by the grid operator, not the utility (though I’m guessing the utility rules could be more restrictive than the grid operator rules).
If you want to run an inverter “in parallel” with the grid, I’m not aware of any grid operator in the US who doesn’t require UL1741 SB listing and also IEEE 1547 certs. I believe Ohio is on the PJM Interconnection, who do require IEEE 1547 for interconnecting inverter systems (see their manual here). The Victron system will work fine with grid code set to “other”, but is not good for overall health of the grid – which is why the IEEE 1547 specs exist.
For the Victron unit to meet the interconnection requirements, it would require Victron add a new IEEE 1547 grid code to the software, and also add the “supplement B” to their UL listing.
You can still connect the grid to the AC Input side of your Victron system, but without ESS installed and grid code set to “none”. The system would not be operating “in parallel” to the grid and therefore wouldn’t require an interconnection agreement (I fought this battle).
That said, if you have a grid connection, it’s more preferable to have an inverter that can parallel (so you can blend grid/PV/battery energy).
Thanks, I wish I would have asked these questions earlier, but such is life.
Im reading my local electric cooperative guidelines, and I see IEEE 1547 referenced, and ul 1741 but nothing about sa or SB.
Unfortunately the UL listed multipro II I got is listed to UL 458, not 1741 for some reason. But are you saying even if I switch to a UL1741 model, I still won’t likely be allowed to use it tied to the grid?
Correct, even with the UL1741 model you won’t be able to get an interconnection agreement. You can still proceed without an interconnection agreement, and connect the grid to the AC Input side of your unit (without ESS installed and grid code set to “none”).