Home ESS with US 400A (2 x 200A Panel) Service - Lessons Learned/Current Progress

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.

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As I said, everything is working great. The issue I’m currently experiencing is that whenever I view the system in VRM, I only see the activity of the critical loads panel. Ideally, I’d like to see the power usage of the entire home within VRM (even though the non-critical loads are not backed up by anything.

After some research I found that in order to accomplish this, I would need to install an external grid meter, and change the ESS settings for “Grid metering” to “External” (instead of “Inverter/Charger”). I found a post where someone in a similar situation (400A service) was wanting to do grid metering as well but had troubles because of the large CT clamps required to do this. Someone replied with a great solution, which was to use a Carlo Gavazzi EM530 Split phase Energy Meter with two 250A CTs. Which could be connected to the Cerbo GX by using the Victron RS485 to USB cable.

My thoughts were that I should only connect it to the grid connection’s L1 and L2 to the non-critical loads panel. Since the inverters are connected to the critical loads panel (with no other external loads), the Victron system should already be aware of all of the critical power use, and with the addition of the external grid meter, it would also be aware of the power usage of the non-critical loads as well.

So I purchased and installed the energy meter and configured all the settings. There is a quick setup procedure that you go through in the beginning where the only setting you really have to change is to set it to “2P” for split phase metering. Once that’s done, you’ll want to adjust the “CT Ratio” setting to 50 (I couldn’t find that information anywhere and it took me a while to figure it out).

Now that it was working properly, I changed the ESS grid metering setting to “external” and it appeared to be working very well. I then realized that in VRM it was only showing me the grid information of the external meter (and not adding the external grid meter info to the inverters grid info as I hoped). This also caused some erratic behavior in charging/discharging as I’m sure the system is a little confused with this odd configuration. I changed the ESS grid metering setting back to “Inverter/Charger” for now so that it functions properly, and grid stats in VRM are still showing the external meter (sometimes it shows the inverters information instead depending on which one has a higher load I believe).

The good news is that all of that information is being pulled in to Home Assistant (HA), so I am able to create sensors manually that add the appropriate data correctly to paint a proper picture within HA

With this new information, here is my [current] plan:

I’m going to purchase an additional CG EM530 energy meter and install it on L1 and L2 of the grid feed to the inverters. I’m going to connect the second energy meter in parallel with the first one so I can utilize the same RS485 cable.

I read in the Victron ESS manual that you can connect multiple energy meters in parallel on the same RS485 cable. But that’s the ONLY thing it tells you about it. Will it add the values of the two external “grid meters” together? Or is it going to flip back and forth between displaying both values individually (kind of like it’s doing now)? I have seen this question asked a few times, but there have been NO replies as to how this will actually work. The energy meter isn’t cheap, especially when you factor in the cost of an electrician to install it as well. So I would hate to go this route only to find out that it won’t pan out as I hope (again).

Does anyone have any experience/insights/suggestions/thoughts about this?

I have a similar ESS setup with 2x 200A main panels, but I am gradually expanding.
Only one of the main panels is connected to the ESS right now.

However, I have two EM530 energy meters, one for each main panel.

I have two critical load panels coming from one of the main panels, with approved generator interlocks and 50A Locking Inlets. My Quattros are rackmounted and cabled over to the inlets to keep the setup “temporary”.

The Cerbo GX only appears to recognize one energy meter, it will not add up both of them for you. In my presently peculiar case, I want the ESS to push back power to the whole house, through the meter split into the other panel, but not export anything to the grid.

My solution was writing lots of python software to emulate a composite EM530 meter over a network socket, and have it do the power adding (which is not nearly as trivial as you might think). The emulated EM530 talks to the real two meters over network sockets. I use waveshare devices to convert from ModbusRTU over RS-485 to ModbusRTU over socket (not ModbusTCP).

I’ll have more comments later tonight. Hope this helps.

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@XFaktor

Hi where have you read that? just on per rs485 to usb victron converter according to the victron manuals

However Technically 2 is possible, but you would have to change the adress with the CG software ( only adress 1 or 2 is supported) and have to terminate the last one in line

2 meters will not add up measurements, They will be separate in the system

It took me a while to find where I saw that and it was located in the installation and configuration of the ET112 energy meter (a different device but similar communication):

I saw an option to adjust the modbus address on the EM530 in the settings of the device so this should be simple to do manually. The datasheet of the EM530 also shows how to wire the communication cables so the meter can be designated as the “last device” on the line:

But it’s good to know that they wouldn’t be added together. Seems like a good option for a future update: Aggregate selected energy meters.

Really interested to hear more about your solution. I tried to follow up on one of your previous posts in the old forums but it wouldn’t allow any new replies. Making a virtual grid meter sounds like a cool idea.

Out of curiosity (I’ll never truly grasp US power installs I guess):

  • How do you pull in a 200A line ? What kind of cable is that ?

I’ve just requested a hefty grid connection in Belgium for 2x 400V tri phase 32A.
For this feed in from the street I’m planning a cable of 4x25mm² / 3AWG (N+L1/L2/L3).
Anything above 63A is an industrial connection here (got a tri phase 400V 160A connection at the business) so 200A for a home connection really blows my fuse (pun intended).

200A Service Entrances in USA
4/0 AWG = 107 mm^2 Aluminum
3/0 AWG = 85 mm^2 Copper

Need three conductors: L1, L2, N

Commercial Properties typically get 3 phase 208V/120V.
Residential Properties typically get 200A Split-Phase 240V/120V.

Edison was first, so we are stuck with this system.
The rest of the world got to do a clean design.

4/0 AWG or 3/0 AWG for a residential connection shiver
What kind of wire is in the street if service entries are 200A ?
At 120V you guys must be pulling in Amps like crazy.
And losses go by Amps² :frowning:
So happy to have 230/400V tri phase over here.

We had 120V here ages ago but luckily we kicked that out.
In some old sections we still have 230V tri phase without neutral (sort of like split phase) here, but those are slowly getting replaced as well.

My industrial 3x 400V 160A connection pulls in 4x 250mm² (no idea how that calculates in AWG) aluminium here, 500m to the high voltage cabinet at the curb.
Typical residential connection in Belgium is either 230V 40A single phase or 3x 400V 20A to 32A.
Thanks for the info, time for bed now here :slight_smile:

Yes we are better of in europe,
here in the netherlands 3x35A is the standard max in houses, 6mm2 is enough :slightly_smiling_face:

Here is my code documentation for the composite emulated EM530.
I don’t know if we post code here, maybe in Modifications section.
The house is divided into two pieces: Main House, Addition, each having their own Main Panel.

# -------------------------------------------------------------------------------------------------------------------
# Implements a server class to emulate a composite Carlo Gavazzi EM530 Energy Meter device,
# which is actually composed of two separate physical EM530s,
# summing up the power, current, and energy values of both devices.
#
# This is to support USA 400A Split-Phase Service, which is divided up into
# two main panels rated 200A each. There is one EM530 with a pair of CTs in each main panel.
#
# This class communicates with both real EM530s, and aggregates the grid data into a
# single emulated EM530 device. However, voltages are taken only from the first energy meter.
#
# This allows the Victron Cerbo GX to see the emulated energy meter as a single entity for purposes
# of ESS grid metering. Effectively, any excess PV power available will be fed into the total house
# using both main 200A panels, instead of just the one supported by the default Venus OS.
#
# Because the house is metered in two places after the Utility meter, Energy Meter 1 must
# always be functional. Energy Meter 2 is optional, but when connected, power can be diverted
# to the addition as well. It is NOT POSSIBLE to use only Energy Meter 2, because the ESS is connected
# to the main house. The energy direction for the addition would be backwards in that configuration.
# Adding both meters together cancels out the backfed power, yielding a true measure of grid power usage.
#
#   Energy Meter 1  = Grid Power - ESS Backfed Power
#   Energy Meter 2  = Grid Power + ESS Backfed Power
#   Composite Meter = Grid Power
#
# The client connects transparently using TCP port 1502.
# However, this is ModbusRTU over TCP, not ModbusTCP.
# The emulated EM530 is configured as Slave Address 1.
#
# Only Cerbo GX messages are currently handled, despite other registers being available on the EM530s.
#
# On the Cerbo GX, the following creates a virtual serial port that Venus OS can use:
#
#    socat -x pty,link=/dev/ttyV0,raw tcp:192.168.169.20:1502 > /dev/null 2> /dev/null &
#    /opt/victronenergy/dbus-cgwacs/dbus-cgwacs /dev/ttyV0
#
# These commands are individually rolled into custom services in /opt/vicronenery/service for automatic use.
# -------------------------------------------------------------------------------------------------------------------

Oh man this is great! It might be nice to start a new topic specific to emulating a meter or adding multiple meters together. Posting the code would be super helpful.

A couple of questions off the top of my head:

  • How are the EM530s wired for communication (2 separate USB cables, 1 cable w/ parrallel, etc)?
  • Are you plugging the USB cable in to a raspberry pi or some device that’s running the code to read the meter values and then transmit the new values to the Cerbo GX?

You can answer these in the new post if you like. I think compiling this information in one place would be useful for many. Thank you for all the info thus far!

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Back to your topic:
Can you explain this in more detail? Specifically the erratic behavior?

If you want to see the inverter info on the dash board when ESS is using a grid meter, you can’t, but in Advanced you can make a custom plot to show the inverter input and output power. Unless I misunderstood.

I have my “Grid setpoint” set to 400w to try and ensure I don’t export any power to the grid. I don’t have a net metering contract with my power company so my meter charges me for any power that gets fed back.

When I had “Grid metering” set to “External meter”, there were a couple times where I saw the system showing that it was exporting over 1000 watts to the grid! I think it was occurring when I had large AC loads on the EM530 and solar coming in too. I didn’t leave the setting on for very long because seeing those values made me nervous so I changed it back to “Inverter/Charger” right away. Before switching back I tried changing the setting on weather to back up all loads or only critical loads. Neither option seemed to have any affect on this.

In either situation, VRM wants to display grid values from only one meter (internal or external but not in any combination). This is mostly fine since all the proper values are still being captured by the Cerbo GX and then imported in to Home Assistant. I can then add the inverter’s grid power readings (feed 1 from the utility meter) to the EM530’s power readings (feed 2 from the utility meter) and then add them together to get the true total grid usage.

This means that what is being displayed in the VRM dashboard isn’t as accurate as my dashboard in Home Assistant. I’m ok with this as long as the system functions properly and I can still get the data as I do. Unfortunately, it seems someone without Home Assistant or any programming skills wouldn’t be able to get the whole picture of their home’s power use in VRM if they have more than one grid feed/meter.

If I’m understanding your solution correctly, I’m thinking that maybe I can plug unplug the EM530’s USB cable from the Cerbo GX and plug it in to a Raspberry Pi Zero that can run a modified version of your python code which will read the data from the EM530, pull the inverter’s grid data, do the math and then transmit that data to the Cerbo as the only external grid meter it would be aware of. If this is possible, VRM would have accurate info to display and hopefully the better information will keep the odd power import/export glitch from happening.