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Solar on single phase of 3 phase house

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Tarquinbob

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Joined
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I live in france and my house is wired as 3 phase. I currently have 4x400W panels connected to a hoymiles 1600W grid tied micro inverter connected on a single phase. In France, for installations of less than 3kW you can inject back in on a single phase and the Linky smart meter is clever enough to sum up the usage on all 3 phases and if the sum is less than what is being produced on a single phase then the net usage is zero and I inject the excess for free to the grid.

I'd like to add a battery to the system as my main power usage is actually at night because as is typical in most French houses my hot water is from an immersion heater running on overnight cheap rate electricity. I've been looking at AC coupled systems, but haven't seen anything that would do what I want it to do. Basically I'd like to find a meter that acts like the smart meter that monitors all 3 phases and only if there's a net export use the surplus to charge a battery.

Does anyone know of something like that that exists and doens't cost a fortune?

The alternative that I've been thinking about is to use another grid tie inverter that's just fed by a battery and get a connect 2 of the panels to a charge controller to charge the battery during the day and then let the battery dishcharge overnight and let my house smart meter handle the phase balancing.

As I live in the south of France and can regularly end up exporting 5-10kWh a day, even on my small install, it seems a shame to waste so much energy. I can't sell the excess because it's a DIY system so I'm just iving it away to the grid for free.

P.S. I know someone is going to say why don't I just convert my house to single phase, but I'd quite like to keep the 3 phase for some woodworking machinery that I have and also for future use for faster charging if I ever get an electric car. Also, siwtching the immersion heater to day wouldn't really work for me either unless I fit significantly more panels which I don't have the space for as the rest of the roof get's too much shade from trees.

Cheers,

Phil
 
I have a similar "problem" that I'm resolving by switching some loads to an off-grid-with-grid-backup system.

As you asked about AC coupling with charging only when total balance of 3 phases is positive (towards export). Victron ESS manual mentions a setting called Multiphase Regulation (when you have a single phase victron/PV setup and 3 phase grid/loads), but they describe it as being used to make the total zero.

So for example (victron ESS on L1 and a smart energy meter et340 on 3 phase building supply) there are following loads:
L1 100w, L2 400W, L3 200W

ESS will send 700W out so the grid meter sees L1 -600W, L2 400W, L3 200W net 0. This uses the battery i believe. There is nothing in the manual about the opposite charging the battery when there is too much energy. It is kind of logical it would do it, but I learned to never assume.

If you consider Victron I'd ask your distributor (preferably in writing like email so you have basis for returning it over 14 days later if it doesn't perform).

Victron is not cheap, but it's not most expensive either. If I was doing an AC coupled system I'd use Victron.

Another thing to bear in mind is that the way all AC coupled systems work is with some delay (5s etc). So when you switch on your 3kW electric kettle the first few seconds will be pulled from the grid probably. Likewise with quickly raising solar production.

If there is anyone on this forum who uses such AC coupled system it would be very interesting to ask what happens if the battery is full, load is low and there is full sun. Then you power on a big load. How quickly Victron tells your AC inverter to start supplying, that is the question?

An integrated system doesn't suffer from this delay to such extent. A much better system would be to get a hybrid inverter (you can buy one for one phase and if wanted buy more of them to add more power or add extra phases). They too(depending on type) support load meters for zero export. As you're covering your use on other phases with export you'd probably legally have to limit yourself to EU certified devices the most popular of around here are Deye.
 
Tarquinbob said:
I live in france and my house is wired as 3 phase. I currently have 4x400W panels connected to a hoymiles 1600W grid tied micro inverter connected on a single phase. In France, for installations of less than 3kW you can inject back in on a single phase and the Linky smart meter is clever enough to sum up the usage on all 3 phases and if the sum is less than what is being produced on a single phase then the net usage is zero and I inject the excess for free to the grid.

As I live in the south of France and can regularly end up exporting 5-10kWh a day, even on my small install, it seems a shame to waste so much energy. I can't sell the excess because it's a DIY system so I'm just iving it away to the grid for free.
Click to expand...
Dude, misconception.
The smart meter will record your excess as consumption, meaning you are being billed for exporting excess power, assuming if they are not coming over and fine you for exporting without permit.

In Germany, balkonkraftwerk only allows up to 800 watt export and one must register for such installation so that the local grid provider can re-program the meter not to register the excess as consumption. Consumers are not being compensated for any extra power being injected to the grid either.
 
I dont see what ac coupling will do on your 3 phase home, since your system is only capable of single phase.
Im unsure how you plan to use the battery.
 
Luk88 said:
I have a similar "problem" that I'm resolving by switching some loads to an off-grid-with-grid-backup system.

As you asked about AC coupling with charging only when total balance of 3 phases is positive (towards export). Victron ESS manual mentions a setting called Multiphase Regulation (when you have a single phase victron/PV setup and 3 phase grid/loads), but they describe it as being used to make the total zero.

So for example (victron ESS on L1 and a smart energy meter et340 on 3 phase building supply) there are following loads:
L1 100w, L2 400W, L3 200W

ESS will send 700W out so the grid meter sees L1 -600W, L2 400W, L3 200W net 0. This uses the battery i believe. There is nothing in the manual about the opposite charging the battery when there is too much energy. It is kind of logical it would do it, but I learned to never assume.

If you consider Victron I'd ask your distributor (preferably in writing like email so you have basis for returning it over 14 days later if it doesn't perform).

Victron is not cheap, but it's not most expensive either. If I was doing an AC coupled system I'd use Victron.

Another thing to bear in mind is that the way all AC coupled systems work is with some delay (5s etc). So when you switch on your 3kW electric kettle the first few seconds will be pulled from the grid probably. Likewise with quickly raising solar production.

If there is anyone on this forum who uses such AC coupled system it would be very interesting to ask what happens if the battery is full, load is low and there is full sun. Then you power on a big load. How quickly Victron tells your AC inverter to start supplying, that is the question?

An integrated system doesn't suffer from this delay to such extent. A much better system would be to get a hybrid inverter (you can buy one for one phase and if wanted buy more of them to add more power or add extra phases). They too(depending on type) support load meters for zero export. As you're covering your use on other phases with export you'd probably legally have to limit yourself to EU certified devices the most popular of around here are Deye.
Click to expand...
That's really intersting, I'll have to look into that Victron system, because as you described it, that sounds perfect for my neads. I would actually prefer not to export any surplus, so if the Victron can manage net zero injection, even better.

The main issue I have in my house is that the only place I have all 3 phases in one place is at the main breaker panel for the house. In order to balance the phases, I have L1 for downstairs circuits, L2 for the kitchen and L3 goes off to an auxiliary breaker panel for upstairs loads. My PV setup is curently connected to L3 on the upstairs loads (house on hill, so upstairs is ground level in the back garden and panels are on a patio roof), but the hot water tank is on L1 with no easy way to change it without ripping the whole house apart, otherwise I'd simply buy a hybrid inverter and put it on L1. There's also about 45m of cable between my solar installation and the nearest point I could break into L1, whereas it was only 5m to the nearest point that I could feed back in to L3.

I only installed the panels a few weeks ago and am otherwise super happy as I basically have no daytime electricity usage anymore, but my evening and overnight usage is still around 10-12kWh and I'd like to try and halve that with the addition of a battery.
 
AshleyL said:
Dude, misconception.
The smart meter will record your excess as consumption, meaning you are being billed for exporting excess power, assuming if they are not coming over and fine you for exporting without permit.

In Germany, balkonkraftwerk only allows up to 800 watt export and one must register for such installation so that the local grid provider can re-program the meter not to register the excess as consumption. Consumers are not being compensated for any extra power being injected to the grid either.
Click to expand...
No, it defintely doesn't count as consumption, you can see the total consumption on the meter and also how much you've injected into the grid. I can also see it on my electricity bill that my daytime usage is now just about zero.

In France you have to register your installation with the enrgy grid (Enedis) and have your installation inspected for conformity, but there's no issue to export to the grid if under 3kW, in fact it's evem written into law.
 
My understanding
Supervstech said:
I dont see what ac coupling will do on your 3 phase home, since your system is only capable of single phase.
Im unsure how you plan to use the battery.
Click to expand...
I was thinking that if I had an AC coupled inverter that knows when there's net export across all 3 phases, then it could use the surplus to charge a battery and then when it's net import across the 3 phases it could power from the battery to try and make it net zero, but it would only have to be coupled on a single phase because my smart meter handles the net import/export for me in terms of billing.

My micro inverters don't try to do zero export, they just output the maximum all the time and if it's not consumed by the house then the surplus is simply exported to the grid for free. As it's a DIY system I can't benefit from feed in tariffs under the compulsory by back law as my system wasn't installed by an RGE certified installer and the other feed in schemes have a monthly subscription cost that wouldn't be worth my while as I don't actually export enough with my relatively small system.
 
Bonjour et bienvenue!

Tarquinbob said:
Does anyone know of something like that that exists and doens't cost a fortune?
Click to expand...

I guess that depends what you define as a fortune ;)

I have build an immersion diverter which uses data from my emonPi monitoring system (albeit on 1 phase) to determine when and how much energy to divert to the 3kW immersion heater. I previously posted more details here...
diysolarforum.com

Nuts and bolts of PV diverters

I have a 5.5KW (3.68KVA exported limited) SE setup with a Puredrive 10.2KWh ac coupled battery. This is my first year of operation and through the spring/summer, I've just left my 3KW immersion heater turned on all the time, cycling on the thermostat coupled to the heater. So far, this has...
diysolarforum.com diysolarforum.com

Suggest the solution would be to have a similar system, but monitoring all 3 phases; that could then tell you if you have net export or not and divert energy as required.
 
Tarquinbob said:
I was thinking that if I had an AC coupled inverter that knows when there's net export across all 3 phases, then it could use the surplus to charge a battery and then when it's net import across the 3 phases it could power from the battery to try and make it net zero, but it would only have to be coupled on a single phase because my smart meter handles the net import/export for me in terms of billing.
Click to expand...
That sounds do-able to me. It's a pity that you have micro-inverters rather than a hybrid string inverter.

In my mind you would "simply" need to monitor each of the 3 phases via an Eastron or Acrel type power meter, sum the 3 power readings into one value and use that value to feed the "net" power value to your hybrid inverter and/or AC coupled ESS.
 
SeaGal said:
That sounds do-able to me. It's a pity that you have micro-inverters rather than a hybrid string inverter.

In my mind you would "simply" need to monitor each of the 3 phases via an Eastron or Acrel type power meter, sum the 3 power readings into one value and use that value to feed the "net" power value to your hybrid inverter and/or AC coupled ESS.
Click to expand...
That sounds complicated and probably involves too much tinkering for my liking.

I should also mention that my main breaker panel is in my living room, so I don't want loads of additional boxes and wires around it or any noisy inverters with fans, which is why I went with the micro inverter route as that just goes to a small waterproof AC isolation box with surge protection outside and then just has a single 2.5mm2 twin and a 6mm2 earth back to the upstairs breaker box.

One system that's plug and play with my current setup that should cut down on my evening/ovenight electricity usage is the Zendure Solarflow one. I'd invest in that were it not for the fact that they only work with their own batteries which are quite expensive and I already own a few Lifepo4 batteries that I'd like to make use of.
 
Tarquinbob said:
The main issue I have in my house is that the only place I have all 3 phases in one place is at the main breaker panel for the house. In order to balance the phases, I have L1 for downstairs circuits, L2 for the kitchen and L3 goes off to an auxiliary breaker panel for upstairs loads. My PV setup is curently connected to L3 on the upstairs loads (house on hill, so upstairs is ground level in the back garden and panels are on a patio roof), but the hot water tank is on L1 with no easy way to change it without ripping the whole house apart, otherwise I'd simply buy a hybrid inverter and put it on L1. There's also about 45m of cable between my solar installation and the nearest point I could break into L1, whereas it was only 5m to the nearest point that I could feed back in to L3.

I only installed the panels a few weeks ago and am otherwise super happy as I basically have no daytime electricity usage anymore, but my evening and overnight usage is still around 10-12kWh and I'd like to try and halve that with the addition of a battery.
Click to expand...
I understand now why you'd look into AC coupling first. The fact you can export without being a "prosumer" (that's what they call people with a certified grid-tie setup and the contract to sell electricity to the grid here) works in your favour. In many countries including here in Poland(and based on the previous reply Germany) you're not allowed to export 1W if you don't have the right contract etc. Before I signed it I didn;t even have a bi-directional meter.

For some reason Victron ESS manual says their system has to be on L1. I don't quite understand what difference does it make, but that's what they say. So if you choose ESS you may need to swap L1 and L3.

Tarquinbob said:
I should also mention that my main breaker panel is in my living room, so I don't want loads of additional boxes and wires around it or any noisy inverters with fans, which is why I went with the micro inverter route as that just goes to a small waterproof AC isolation box with surge protection outside and then just has a single 2.5mm2 twin and a 6mm2 earth back to the upstairs breaker box.
Click to expand...
Do you have space for a Victron Multiplus II and a battery? It doen't have to be located near the main panel, but it will need to be between the supply and the PV (micro)inverter.
Tarquinbob said:
One system that's plug and play with my current setup that should cut down on my evening/ovenight electricity usage is the Zendure Solarflow one. I'd invest in that were it not for the fact that they only work with their own batteries which are quite expensive and I already own a few Lifepo4 batteries that I'd like to make use of.
Click to expand...

I had a quick look. The battery is probably one of the main profit items for the makers of the system.

I'm guessing what you need is something like a Tesla powerwall, but using your own batteries. If you don't really care about the UPS feature it is perfectly find, as I understand it, to have all the loads on the supply side of the Multiplus. The only thing that definitely has to be connected on the output side is the current micro inverter.

Please verify this with the dealer before you decide on spending any money. My "knowledge" of Victron is from researching manuals from when I was considering it for myself. Sometimes what's written in a manual and reality is diffrent. Perhaps there is something else that doesn't require remodelling others will suggest?
 
Would like to have a variable load that could be set to the desired wattage, but most are just switchable on/off.

There are hybrids that use CT around wires at meter, can be set to shave imports and exports. They could limit export to your allowed level, and you could install more PV which would only supply household loads.

There are several AC coupled batteries as well as battery + PV. Tesla Powerwall of course (newer model has PV input). SMA Sunny Boy (battery), Sunny Boy Smart Energy and TriPower Smart Energy (battery + PV) which is 3-phase.
Each of these can disconnect from grid and provide backup to some loads, TriPower being AIO but others needing external transfer switch.

Sunny Boy Smart Energy | SMA Solar

The SMA Sunny Boy Smart Energy single-phase hybrid inverter is the two-in-one solution for the generation and flexible use of solar power at home.
www.sma.de www.sma.de

www.sma.de

Sunny Tripower Smart Energy | SMA Solar

www.sma.de www.sma.de



Those are big names and more expensive Several cheaper hybrids can do the same. Usually easier to move PV onto them than to interact with GT PV inverter, especially for backup operation.

The hybrids will be a less cluttered install. But most will still have cable to battery, except some like Tesla which have battery in same package. Battery fires happen, should be less likely with top names (although LG had multiple recalls) so I would favor locating any lithium chemistry some distance from the house.
 
Hedges said:
Would like to have a variable load that could be set to the desired wattage, but most are just switchable on/off.

There are hybrids that use CT around wires at meter, can be set to shave imports and exports. They could limit export to your allowed level, and you could install more PV which would only supply household loads.

There are several AC coupled batteries as well as battery + PV. Tesla Powerwall of course (newer model has PV input). SMA Sunny Boy (battery), Sunny Boy Smart Energy and TriPower Smart Energy (battery + PV) which is 3-phase.
Each of these can disconnect from grid and provide backup to some loads, TriPower being AIO but others needing external transfer switch.
Click to expand...
The key issue, the way I understand it is, are any/all/none of the above able to sum usage on all 3 phases and act accordingly while being connected to only one phase?
 
Yes, that is the key issue.

The utility meter likely logs total kWh only, summing what's coming in (and hopefully going out) other legs.

An inverter with CT likely (most certainly) only pays attention to the phase(s) it also has electrical connections to. In the US, we use split phase (2 legs 180 degrees apart) and some models also work with 2 out of the 3 legs of 3-phase, popular in condos and apartments.

My Sunny Boy Storage connects to split phase but uses external WattNode 3-phase meter. Presently I have that connected to split phase with 2 CT.

It is possible a hybrid on a single phase that uses external 3-phase meter like WattNode could utilize and seek to limit usage on all 3 phases. But since those are reported separately by WattNode, its software may or may not.

A 3-phase inverter, or one sold to be used with 3 individual for 3-phase, is more likely to do what you want.
There are several cheap brands supporting 3-phase as well as the name brands.
 
This video shows exactly what I want to achieve, just a shame that the equipment in that video is quite expensive and I'd never get the ROI with my quite small PV setup.


Edit to add, on this video it doesn't show a connection between sunny boy storage and the sunny boy inverter. Does that mean that in theory the sunny boy storage could just be plugged in to any existing solar system. It looks to me that it's behaving as an AC coupled inverter with exactly the feature I was looking for.
 
Last edited:
Hedges said:
It is possible a hybrid on a single phase that uses external 3-phase meter like WattNode could utilize and seek to limit usage on all 3 phases. But since those are reported separately by WattNode, its software may or may not.
Click to expand...
(y) - that is the principle I was referring to in post #9 where I said...
SeaGal said:
In my mind you would "simply" need to monitor each of the 3 phases via an Eastron or Acrel type power meter, sum the 3 power readings into one value and use that value to feed the "net" power value to your hybrid inverter and/or AC coupled ESS.
Click to expand...

I understand that may be too complex for the OP (as he noted), but relatively simply for someone with some IT/software skills to achieve using a RPi and two RS485 to USB adaptors and some python code. For others reading this thread, a good start would be to use some of the code that @peufeu created to implement a MITM RS485 interface between an Eastron power meter and Solis inverter - see:-
diysolarforum.com

Solis S5: Various issues

Hello everyone! This is in France. The house has three phase power for the heat pump. I installed a Solis S5 hybrid inverter (S5-EH1P-6K-L) with two Pylontech US5000 and of course solar panels. It's a single phase inverter, I don't need three phase backup. My main reason for choosing this one...
diysolarforum.com diysolarforum.com
 
SeaGal said:
(y) - that is the principle I was referring to in post #9 where I said...


I understand that may be too complex for the OP (as he noted), but relatively simply for someone with some IT/software skills to achieve using a RPi and two RS485 to USB adaptors and some python code. For others reading this thread, a good start would be to use some of the code that @peufeu created to implement a MITM RS485 interface between an Eastron power meter and Solis inverter - see:-
diysolarforum.com

Solis S5: Various issues

Hello everyone! This is in France. The house has three phase power for the heat pump. I installed a Solis S5 hybrid inverter (S5-EH1P-6K-L) with two Pylontech US5000 and of course solar panels. It's a single phase inverter, I don't need three phase backup. My main reason for choosing this one...
diysolarforum.com diysolarforum.com
Click to expand...
I think I undersold my skills as a tinkerer, this is what's currently sitting on my desk. It's more that solar just isn't my hobby and I just want something to work that's closer to a plug and play system that I can install and let me get back to my actual hobbies of 3D printing, CNC machining and laser cutting and incrporating some fun electronics, mostly for my kids or as teaching aids for my whife who's a primary school teacher.

In the photo is a sound box for a rocket taking off for my wife who is doing a project on space and the makings of a speed climbing timer with a wirleless stop button and timer display that will use ESPNow protocol if I can ever get it to work.
 

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Tarquinbob said:
I think I undersold my skills as a tinkerer, this is what's currently sitting on my desk. It's more that solar just isn't my hobby and I just want something to work that's closer to a plug and play system that I can install and let me get back to my actual hobbies of 3D printing, CNC machining and laser cutting and incrporating some fun electronics, mostly for my kids or as teaching aids for my whife who's a primary school teacher.

In the photo is a sound box for a rocket taking off for my wife who is doing a project on space and the makings of a speed climbing timer with a wirleless stop button and timer display that will use ESPNow protocol if I can ever get it to work.
Click to expand...
In this case I think @SeaGal 's reply is definitely something to look into :)

A digital 3 phase meter plus any hybrid inverter that can talk to a single phase meter over the network or via serial and a microcontroller/single board computer inbetween them could definitely work. One would have to write the script to take the data from the 3-phase meter, sum it and emulate a single phase meter output. It's not hard, but definitely requires some tinkering. This can be much cheaper than getting a device that implements it from the start.
 
Luk88 said:
One would have to write the script to take the data from the 3-phase meter, sum it and emulate a single phase meter output. It's not hard, but definitely requires some tinkering
Click to expand...
(y) @peufeu's Grugbus code, that I referenced above (and have used myself) abstracts the complexities of Modbus RTU into easy-to-use python objects. So yes, some tinkering and testing, but it looks like the OP has the skills if a plug-and-play solution is not forthcoming :)
 
 
kommando said:
MK2PVrouter
Click to expand...
... which is now owned by a french company where the OP is located (y).

There is also the Marlec iBoost product, though more expensive.

I was just wondering... does anyone know what happens if you could physically fit the 3 live feeds of a 3 phase supply through one single CT clamp? Would the resulting measurement be an accurate sum of the net flow through said clamp?
 
SeaGal said:
I was just wondering... does anyone know what happens if you could physically fit the 3 live feeds of a 3 phase supply through one single CT clamp? Would the resulting measurement be an accurate sum of the net flow through said clamp?
Click to expand...

The result is the same as if you just connected 3 CTs in parallell. It will sum, but the waveform will be messed up. How this will affect the equipment the CT connects to depends on the circuit inside. If it just changes it to a voltage and rectifies it with a big capacitor to smooth it out it will sum and one may get the outcome one wants. But I read some modern devices send the CT output to an AD converter (they digitise it as is) and then analyse the actual waveform. This will not work.

So the actual answer. It might work... or not. Sorry...
 
SeaGal said:
I was just wondering... does anyone know what happens if you could physically fit the 3 live feeds of a 3 phase supply through one single CT clamp? Would the resulting measurement be an accurate sum of the net flow through said clamp?
Click to expand...

That works for our split phase, with the assumption that voltage on second leg is equal and opposite (180 degrees apart). You just run the other wire through CT in opposite direction.

It would not work well with 3 phase because L2 and L3 are +/- 120 degrees from L1. It would sum the cosine (sine?) of the currents while subtracting the sine (cosine?).

In the event L2 and L3 currents were identical and in phase with their voltage, because the summed component of the vector is 0.5x its magnitude, you could put each wire through twice and would get the right total. But in general currents aren't identical so wouldn't work. Also wouldn't work if you had a 208 (or 400) volt resistive load between L2 and L3, because wouldn't be in phase.

1716558329567.png
 
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