question

I don't want to step on anyone's toes who have already given their feedback, however I started using Victron equipment with 0 prior experience about 2 years ago now. I started with a single Compact Multiplus 2000, and some DIY batteries. I love that you can scale up their equipment, and to date, have thus far scaled up my system to a combined split-phase+parallel system with a total of 4 CMP 2000's (2 in parallel on each phase) for a combined output of up to 6400 watts...

I was very intimidated when first attempting a split-phase setup, using just two CMP 2000's about a year back now, however with just a couple online videos, I was able to navigate though VEconfig pretty darn easily and setup the both in a 180* split which is what we use here in the US.

The biggest issue with these "complex" setups is getting the wiring right, as you really are supposed to have identical lengths and sizes going from the battery to each inverter/charger. All this really means is, if one of your two inverter/chargers is a little further away from the battery, the other one will need to be left with a little additional slack so the runs are the same length. I don't feel like this is rocket science to get done right.. You just need a tape measure.

Split-Phase+Parallel gets a bit more complicated beyond this, as you then need to match the AC wiring side. If you are using only 1 inverter/charger per phase, this is not needed.

Apart from the wiring itself, yes, technically there is the potential for overload on one phase.. But so is there with your connection coming from the grid.. If you are not familiar with how split-phase 180* electric works, the principal is rather simple:

Say you have 100A 240V service coming from the grid - by definition, this should allow you 24,000 watts of loads. However, this gives you 100A 120V on one phase angle, and 100A 120V on the other phase angle. It is possible, if your house was wired poorly, for all your 120V loads to end up on 1 phase angle. If this were to happen, the main breaker of your house would trip if you used more than 12,000 watts at any one given time.

The way it works with a split-phase Victron system is identical, but on a smaller scale. I have 4x CMP 2000's with a continuous load rating of 1600w, which should give me 6400w total technically. But since this is split up between two phases, the maximum 120V power I could draw, from a single electric circuit, would only be 3200 watts. What I can do instead however, is draw 3200 watts 120V from the outlets in my kitchen, 3200 watts from the outlets upstairs since those two circuits are each on different phases. Or I could take 1600 watts from the kitchen, 1600 watts upstairs, and 3200 watts 240V from my EV charger, all at the same time.

All this means is your electrician with have to do their best to balance any 120V circuits you are connecting across the two phases available.. Again, not rocket science, it's pretty simple math/common sense. The issues with something like this tend to come from having something like 6 120V circuits, on a small system. Even if they are split up 3-and-3 on the two phases, you might be running a 1800 watt heater on 1 circuit, and a 1800 watt vacuum cleaner on another circuit. If those two just to happen to both be on the same phase, your system (in my case at least with 3200w max per phase) would overload and shutdown. This would be even though I'm only using 3600 watts, on what is technically a 6400 watt system.

My advice here - either oversize your inverter/chargers, buy more VA's than you think you need... OR, just be mindful not to run any extremely large 120V loads if the grid fails.. I use a little home-automation to make sure no 120v heaters or anything are running if the grid goes down.