question

Hi,

I wasn't aware the UK had split phase electricity I thought it was only 3 phase/single phase.

By split phase do you mean like they have in the US 120v across L1 and N and then 120v across L2 and N with L1 to L2 240v? Or by split phase do you mean 3 phase (only asking because i wasn't familiar with spit phase in UK)?

1. I believe Victron does have a split phase 2x120v model. MultiPlus-II 2x 120V - Victron Energy, if that is what you meant.

If you mean 3 phase (more common in UK) you can also achieve this but with 3x Multiplus ii (or quatro etc)

Some further details on both setups (this looks quite dated so you might be better off checking the manuals of whatever inverter charger you go with as that will definitely be the most up to date):

Parallel, split- and three phase VE.Bus systems [Victron Energy]

2. I believe in both cases a common battery is required (someone please correct me if i'm wrong on that).

3. Yes Victron has several pre set battery settings for various battery chemistries (however i personally tweak mine slightly).

I believe Pylontech battery BMS can also communicate with victron venus os/cerbo gx systems to transfer useful data like battery capacity etc.

If you go for a battery that doesn't have supported BMS communication with victron system then you'll likely need a smart shunt to monitor battery state of charge.

Hi Matt,

Thanks for your response.

Yes, dual phase 180 degrees out of phase.

L1-N 220v L1-L2 440v

Do you know if it is possible to run the inverters in split phase configuration with independent (unbalanced) loads?

Thanks

Chris

Ahh i see, thats really unusual for my area.

I suppose there's two potential setups.

1. Completely distinct setups per phase, easiest to setup but probably more inefficient and pretty sure you'd need dual batteries in that scenario.

2. The other option (which i think is what you're after) is traditional split phase. This will use a common battery (and need equal length leads/resistance to each inverter, some further details can be found in links below).

Victron has a professionals course on setting up these systems (I've not attended one though), but here's some useful links to get started:

7. Multiphase regulation - further information (victronenergy.com)

Parallel, split- and three phase VE.Bus systems [Victron Energy]

Previously you used to have to setup a veBUS and have the multiplus chained together with RJ45 cable. Then in vebus software you could select 180degree split phase however I think there's a new way to set this up using veconnect

I'm not familiar with this and there doesnt seem too much detail in the manual online (i imagine because they want folk to use the professional course given it's a bit more of a complex system)

Page 25 has some small detail on using Victron connect instead of Vebus software: VictronConnect - VE.Bus Configuration guide (victronenergy.com)

Hi Matt,

Thanks for your advice.

It would appear you only require equal cable lengths when running inverters in parallel configurations to ensure balanced inverter loading.

Sounds like option 2 maybe suitable, but I wonder if anyone can tell me if this configuration can feed unbalanced loads?

As in more loads on L1 than L2?

Someone correct me if I'm wrong but I believe it is able to do that, assuming loads on each leg are less than one of the inverters max output.

ie say you've got 2x5kva they couldn't power 8kw on L1.

Thanks Matt

I had a look through the training which supports your answer, I'm still a little uneasy as the training was referring to the inverters setup in off-grid mode.

My setup will be on-grid so I'll need the grid tied output to support unbalanced loads, it's possibly exactly the same thing with a simple answer, but it could equally be a Gotcha which bites me in the butt later on.

Joys of venturing to new products, but I'm sure it'll be worth the effort.

Hi @50Hz

I'm far from a professional when it comes to anything more than single phase however personally Off-grid mode would have been the one I'd have been more worried about. On grid in my head will just be simpler in regards to unbalanced loads.

My logic for saying that is if you take your current system for example, with no solar/batteries. You currently don't have to manage your loads perfectly across the 2 phases. Electricians will aim to balance loads across phases but they're not doing it extremely precisely just approximating.

And your proposed victron system is being added to both phases (equal load), my concern would be if i you've currently got unbalanced loads (ie lots of load on L1) that adding a victron system and not setting a correct current limit could draw too much from L1 if you charge from grid and push you over the limit of that phase. However with correct settings this can be avoided, and in my head doesn't add any additional worries regarding balancing the phases.

Offgrid vs onGrid.

I thought it might also be useful to shed some light on off-grid vs on-grid with a victron system. (If you already know this please disregard but it might be useful).

When you say on-grid there's a few ways to configure this. Which might calm your worries regarding phase balancing.

1. Have the grid plug into ACIN and then have all your loads on AC1 OUT or AC2 OUT (assuming you have multiplus/quattro). In this configuration the grid passes through the inverters to your loads and if loads are on AC1 OUT they will continue to be battery powered when grid goes down or is disconnected automatically, whereas AC2 out disconnects when grid goes down. If your loads are less than the maximum the inverters can provide I'd suggest wiring this way as it allows for a more flexible setup ie if grid goes down you still have all your loads without needing to setup transfer switches or separate "critical load" circuits etc.

2. However you're also able to put loads on ACIN and as long as you have a grid meter installed (so victron system knows how much is being import/export) the victron system is then able to calculate how much power to output on ACIN to cover those loads on ACIN (using the meter data). This however doesn't allow you to power loads on ACIN if grid goes down as there's obviously a risk of shocking someone down the line on the grid if you export power. This option is better if your loads are greater than the inverters output, and your grid rarely goes down.

This link might be useful just for the diagrams for visualising the above:

https://www.victronenergy.com/live/ess:quick-installation-guide

The diagrams are single phase and also include (AC coupled) grid tied inverters in the pictures however the concepts still apply to multi-phase and without the PV inverters, and might explain victron systems better.

Hi Matt,

Sounds like I'm worrying about nothing, my concern is based on typical 3-phase inverters, which typically only provide a balanced output.

It seems, since the Victron setup is effectively an inverter per phase, it is exactly that - 2 independent inverters with their output sync'd depending upon phase separation.

The installation will have load limiting in place so no worries about exceeding max demand but thanks for the prompt.

It would be nice to connect loads via the AC out, but unfortunately, the inverters are in a separate building to incoming supply which makes cabling expensive and messy. We shall utilise 1 of the backup ports which will be fed to the source of the installation and offered in via a manual changeover switch.

Following more research and discussions, turns out it is better to wire the system up as AC coupled, then connect additional AC inverter (with frequencey response) to one of the output ports of the Multiplus. Unfortunately, Multiplus are not G99 compliant so Quatros would be needed at extra cost. The G100 is take care of by the AC coupled inverter.

I'm begining to realise that perhaps my usercase is not well suited to Victron products since a standard hybrid inverter (G99 & G100 compliant) connected to each phase could take care of all of my requirements in 1 package for a fraction of the cost and less space. The only drawback is I wouldn't be able to use a common battery.

Needs thought

Hi,

I've seen a few threads recently about G99 compliance of multiplus. I'm not sure if that's a recent change to non compliance but I did see a lot of folk mentioning it recently. I'd keep an eye on the forum as that seems to be changing regularly. This was the thread that caught my eye. I've not read through recently but seems a hot topic atm

Multiplus UK G98 G99 non-compliance update - Victron Community (victronenergy.com)

I'm in a similar situation where the inverters aren't close to grid input, I'm single phase, so I've considered running 4 cores out to where the inverters are, 2 cores for grid and then 2 cores back for AC1Out back to the house so i have the benefit of battery power if grid goes down.

Only down side is a big enough wire at 4 core is so bloody expensive

There's definitely far cheaper solutions. I had a similar headache when designing my current system. I just liked the idea of the built in transfer switch victron had (even though I'm currently not using it). I spent ages trying to pick a system but eventually came back to victron as it seemed to have all the features, and I could integrate everything in one system (that wasn't dependent on some dodgy looking cloud service).

Happy to share more info on my (single phase) setup if you have other queries. Best of luck on the designing/planning phase (I hated that part, just wanted to get to installing)