While I know there aren’t many in the Victron community with this situation, I know I’m not the only one (because I saw literally ONE person ask a question about it in an old post). I assume I won’t be the last one that will attempt this either, so I thought I’d share my experience so far and what I plan on doing moving forward. I’ll also try to post updates until I have the system complete and configured properly (to fit my needs). I’m hoping someone will find this helpful if they find themselves in a similar situation. I would also love to hear what others are doing with this same service.
Most homes have one service panel that feeds the entire home. When the builder was putting in our electric system, they saw that I had an EV and I told them that I tend to use a lot of power, so they decided to have TWO 200 amp service panels installed “just to be safe”. It seemed like a good idea, but it created a lot of challenges when it came time to design an ESS for it. Both panels are serviced from two feeds that are connected/bolted to the utility meter (according to my electrician)
Something like this:
My goal was to back up as much of the house as possible with solar/inverter/batteries. I also had to make sure that any equipment I chose would pass the scrutiny of any permitting/inspection required by local/state requirements (which in large part means it must be UL listed)…I began my research/data gathering by having my electrician install 4 CT clamps on L1 and L2 in both panels so I could monitor my power usage on each individual line (turned out to be over a one year period) to see the how much power we ACTUALLY use.
With this data in mind, my first idea (which I submitted for permitting) was to try and backup the whole home using two 5kVA MultiPlus-IIs configured in split phase on each eclectic panel (4 inverters total) that would be connected to one battery bank. The permit packet I submitted got rejected a few times for various reasons (most notably, issues in the “one-line” diagram). I met with my electrician and discussed my plan and what was going on with the permits. He said that while the design may work, he wouldn’t recommend it because doing so would be “derating” the panels. By this he meant that each panel is rated for 200 amps total, where L1 and/or L2 could pull up to 200A (individually or combined). The 5kVA models allow for 95A of grid pass through. So while I’d have nearly 200A of grid pass-through in total, I would still be limited to the 95A on each line, where the panel would technically allow for more than 100A on each line. The other problem was that the 5kVA model was still pending UL Listing (and still is as of this posting), which likely would be prohibited for my permit.
Back to the drawing board: After much thought, I decided that the best way to proceed was to turn one of the two service panels into a “critical loads” panel. I created a spreadsheet with a diagram/list of all the existing circuit breakers in each panel, and then moved them around to separate the critical and non-critical loads. I would then backup the 200A critical loads panel with solar/inverters/batteries, and then later on, add grid-tied solar to the non-critical panel. My only available option was to use the 3kVA Multiplus-II since there is a UL Listed version of it, but it only has a 50A grid pass-through.
By installing 8 inverters (4 in parallel in split-phase configuration with 4 others in parallel), I am able to get up to 200 amps of grid pass-through (400A combined) and 9.6kW of inverted power on each line (more than plenty to support all our critical loads).
Here is a diagram I made to try and illustrate the final/currently deployed design for what I’m calling “Phase I”:
You can also check out the photos I posted in the “Show us your system” topic here:
I got all the documents I needed for my permit application from GreenLancer. I also got a structural engineering firm to give me a certified document with wind and snow load calculations for the solar panels mounted on my chicken coop (which was also required for the permit) from GreenLancer as well.
My electrician helped with updating/correcting the one-line diagram on the permit packet after I pitched him the new design idea. Once I submitted the packet with the new design containing a proper one-line drawing to reflect it, it was approved with no further troubles. The electricians also did all of the AC wiring (as you could imagine) which included moving all of the circuits, installing the 2 new sub-panels and wiring them to the inverters.
I did everything else myself which saved me A LOT of money. I learned almost everything I needed from watching hours and hours of YouTube videos over that year of gathering the power data. I couldn’t possibly name all the channels, I’m sure everyone who’s searched will come across the same ones (Will Prowse, Dave Poz, Andy [off-grid garage], etc) and all those guys are great. But I’d like to give a special shout out to Projects With Everyday Dave, because he’s the only one that I found that actually shows you step by step on how to set up ESS helpers and a bunch of other stuff I found extremely helpful for this project.
After the system went live, it took longer than I’d like to admit to get all the settings configured and dialed in. I took my time exploring every menu and option while making adjustments here and there. It’s running great, but it’s not quite where I want it just yet. What do I mean by that? I’ll explain below.
