The premise
After Robbert published the video of wiring his three-phase Victron set into the meter cupboard, the comments lit up. Disagreements, sharper alternatives, missing context. He went through the recurring questions one by one and made a follow-up. This article is the debriefing.
The transfer switch is coming later
The most repeated comment: there's no automatic transfer switch in the install. Robbert filmed the project in small steps on purpose. Cramming the whole build into one video would bury the reasoning. The current state of the meter box is the configuration without a transfer switch. A separate side cabinet next to the original meter box already holds an extra earth-leakage breaker between grid and set. That cabinet has room reserved for the transfer switch, which will go in once the rest is stable.
Tools and the ten-point voltage check
Other commenters pointed out he didn't use the most ideal tools. He used his standard Fluke multimeter because that's what was on the bench. There are torque screwdrivers and dedicated low-voltage probes that are less error-prone. Fair point, noted.
A sharper one came from a viewer named Jaap: to prove a system is truly de-energised you need the ten-point measurement, not three. Robbert measured N to L1, N to L2, N to L3. If N and L3 are disconnected but L2 and L3 are still bridged somewhere, you'd read zero on N-L3 while 400 V is sitting between L2 and L3. Ten points covers every pair.
AC-in, AC-out 1, AC-out 2
A lot of confusion in the comments centred on the three AC ports on the Multiplus. They look similar, they're not the same.
| Port | When does it carry voltage? |
|---|---|
| AC-in | Grid voltage when grid is present; bidirectional |
| AC-out 1 | Always live: grid passes through, or inverter supplies it |
| AC-out 2 | Only live when the grid is present; drops on grid loss |
The point of AC-out 2 is load shedding. Put heat pumps, washers, dryers, big consumers on AC-out 2. Put critical circuits on AC-out 1. When the grid fails, the heavy loads drop, the battery doesn't drain in fifteen minutes, and the lights stay on.
Solar on AC-out 1, no extra energy meter
Several commenters asked why there's no separate energy meter for the PV side. The Multiplus has built-in metering on every phase. It can see grid-to-house flow and house-to-grid flow. If solar produces 1000 W and the house consumes 300 W, the Multiplus sees 700 W trying to push back to the grid. It catches it, redirects to the battery, and the export reads zero. Same logic in reverse for consumption.
Putting the PV on AC-out 1 has a second benefit. Solar inverters shut down during a grid outage by design, they're not allowed to feed back into a dead grid. But AC-out 1 keeps generating its own 50 Hz during an outage, so the inverters see a "grid", stay on, and keep producing. The Multiplus catches the energy and charges the battery.
Frequency shifting
If the battery is full during a grid outage and the solar inverters keep feeding in, where does the energy go? Victron uses frequency shifting. Connected to the grid, frequency is fixed at 50 Hz. Disconnected, the Multiplus runs its own frequency. When the battery gets full, it nudges the frequency up toward 53 Hz. Many solar inverters detect that shift and throttle or shut off. The mechanism only works in island mode, because on grid the frequency is not the Multiplus's to set.
Why he doesn't aim for exactly zero grid draw
A viewer asked: can the import be pushed to absolute zero? Robbert's answer: technically no, and you shouldn't try. There's always a small fluctuation, the inverter has reaction delay, a cloud passes, the dishwasher kicks on. Targeting zero means the system flips constantly between drawing 20 W and exporting 20 W, charging and discharging the cells for no reason. Victron's default is to pull a small offset, around 50 W from the grid, which absorbs the noise. In practice he sees 10 to 40 W of import on a stable moment. Negligible cost, much healthier for the cells.
The Victron 1.0 rule and the battery-capacity rule
A commenter named Rogéri pointed at the Victron 1.0 rule: maximum PV power must not exceed the VA rating of the inverters. Robbert runs 5 kVA Multiplus units, one per phase, with roughly 3 kW of PV per phase. That stays inside the rule on each phase.
There's a second rule: for every 1.5 kW of PV you should have around 4.8 kWh of battery capacity. He's not there yet. Right now one 16 kWh pack is connected, two of three solar strings are live, and one pack can charge at up to 5 kW. He's throttled the charge rate so the limit isn't crossed. The set is built for three packs, target 48 kWh, and a second and third pack are in the pipeline.
The emergency stop is the next addition
Another sharp comment from a commenter called Gertjan: the fire brigade assumes that throwing the main switch kills the power in the house. With a battery-backed system that's no longer true. Robbert plans to run a single loop from the Multiplus remote-input contacts through two emergency-stop buttons, one in the meter cupboard and one in the shed. Push either one, the loop opens, all three Multiplus units drop, and the whole house is dead. That's what the brigade needs.
What's next, beyond the comments
He's also building a per-cell temperature sensor module on an Arduino. Sixteen probes, one glued to each cell. If any single cell crosses 60 °C, the Arduino opens the same emergency-stop loop and the entire set shuts down. Standard BMS uses one temperature probe for the whole pack, which is slow to see a single bad cell.
He's also experimenting with hoverboard motors as wind generators. Cheap brushless DC motors, 3D-printed hubs and blades, the rectifier is a handful of diodes. The unit prices on second-hand hoverboards are low enough that the proof of concept costs maybe €50. The point isn't to compete with solar in summer. It's to see whether something can keep trickling in at night and in winter.
Takeaways
- AC-out 1 is always live, AC-out 2 drops with the grid: use it for load shedding.
- Solar on AC-out 1 keeps producing during a grid outage; the Multiplus catches the export.
- The ten-point voltage check is the only proper de-energise verification on a three-phase install.
- An emergency-stop loop through the Multiplus remote contacts kills the whole system in one push.
- Don't chase zero grid import: the cell cycling costs more than the residual 30 W.
