The premise
After each video on the three-phase Victron build, Robbert circles back to the comments. This one collects the questions that came in on the install video and walks through what he's changing, what he's keeping, and why. The themes: meter-cupboard wiring choices, sizing the Multiplus, AC-coupled solar, and a bypass plan for maintenance.
Earth-leakage automat in the meter cupboard
A viewer (Petros) suggested replacing the standalone RCD with an earth-leakage automat. Robbert is using an EMAT three-pole + N 25 A unit. He hasn't had problems with it, but the comment threads have plenty of mixed reviews. Open question: if real-world reliability is as bad as some commenters say, he'll swap it for another brand.
Splitting the neutral instead of looping it
Several commenters pointed out that he daisy-chained the neutral from one Multiplus to the next on both the AC-in and AC-out sides. It works, but the cleaner setup is to split the neutral in a small terminal block and feed each Multiplus from there individually. Same on the output side. He's planning to redo this in a later video and grants the point.
Ferrules on fine-stranded cables
Jeller flagged missing ferrules on the soft cable terminations. Robbert agrees. His habit is to dry-fit cables in place first, then go back and crimp ferrules at the end. The downside is that mid-build adjustments are easier without ferrules, which is why he keeps doing it that way. By the time the install is finished, all the cable ends are properly crimped, but the video catches the half-built state.
Why a 25 A breaker on the AC out
Weiden en Sikkerbaard asked why he used a 25 A breaker when the 5 kVA Multiplus can deliver up to 40 A in PowerAssist mode. Robbert's answer: their household runs 2 to 3 kW per phase at peak, with short spikes to 3 kW for an oven or microwave. The 25 A breaker is what he had on hand and it covers actual usage. The cabling between the shed and the meter cupboard is 6 mm², which is rated for the full 40 A, so swapping to a 40 A breaker is a future option (for example, if he adds an EV charger).
Why 5 kVA over 3 kVA Multiplus
This one is straightforward.
- 3 kVA Multiplus: charges at up to 35 A. On a 48 V pack that's around 1700 W into the battery.
- 5 kVA Multiplus: charges at up to 70 A. On a 48 V pack that's around 3300 W.
Robbert's house has solar split across three phases:
- 3 kW on the back roof (phase 1)
- 3 kW on the back veranda (phase 2)
- 3 kW on the front of the house (phase 3, coming soon)
- An extra 6 panels on the shed via MPPT
- 6 panels on a small back veranda
That's around 3 kW peak per phase coming home. The 3 kVA unit cannot fully absorb that into the battery and the rest exports. The 5 kVA unit keeps everything local, which matters once net metering ends.
Why no extra energy meter
Every Multiplus has its own internal energy meter. Grid power passes through the Multiplus to the rest of the house, so the Multiplus already sees the full flow in both directions. The only extra meter Robbert is considering is one specifically for the solar inverters, to get a clean read on how much each string is generating.
Why solar is AC-coupled
Two reasons:
- AC carries over long distances without thick cabling. The roof-to-meter run doesn't need expensive solar DC cable.
- On AC-input 1 of the Multiplus, if the grid drops out, the solar inverters keep running on the Multiplus's output AC. They keep feeding the battery or the loads even during a grid failure.
Current can flow either direction through the Multiplus: panel power can push into the battery, and battery power can push back into the meter cupboard. That flexibility is the reason for the topology.
MPPT vs AC inverter
A common comment: "swap your AC inverters for MPPTs, they're more efficient." Robbert agrees on the physics. An MPPT converts panel DC directly to battery DC, avoiding the DC-to-AC-to-DC round-trip and its conversion losses.
The economics push the other way. He buys second-hand solar inverters on Marktplaats for around €40 to €60. The AC path needs no thick DC cables, no Class T fuses on long runs, no expensive MPPT box. The 45% efficiency improvement of an MPPT does not pay back the cost of replacing an existing AC inverter in any reasonable time. For new strings going directly onto the battery (the 6 panels on the shed), MPPT is the right tool. For existing AC-coupled strings, leave them.
Bypass switch in the meter cupboard
Kees en Bart Huigens asked whether Robbert is planning a bypass that routes the house directly to the grid, skipping the Victron entirely. Yes.
Right now the path is: main switch → RCD → Victron → back to the meter cupboard → distribution. If any Multiplus is offline for any reason, the house loses power. A bypass switch lets him route the house directly from the main switch to the RCD without going through the Victron, so he can service the inverters safely while the rest of the house keeps running.
He's already added an extra sub-cabinet next to the existing meter cupboard. The earth-leakage automat lives there. The bypass switch goes in the same cabinet.
Internet for the Cerbo
Toon asked about emergency power for internet. The Multiplus already handles that. When the grid drops, the entire house runs from the battery, including the router. He's deciding between running an Ethernet cable from house to shed for the Cerbo or using its built-in Wi-Fi. Both work. The choice is logistical, not electrical.
Transformer hum under phase imbalance
Sparkelende asked about transformer noise from the Multiplus when phases are unbalanced. Robbert plans to cover this in a later video, with thermal-camera footage of hotspots and noise analysis. Possible fixes if the hum is annoying: rubber damping behind the transformer plates, or replacing the cooling fans with ones that can spin continuously at low RPM instead of cycling.
The precharge button (preview)
Robbert previewed the precharge button that will go into the upcoming Lynx Shunt build. The reasoning is the same as the soft-start trick from earlier videos: when a Multiplus first connects to a full battery, the empty input capacitors pull a hard spark. A 6 V bulb wired across the main switch acts as a resistor, slowly charging the capacitors. When the bulb dims out, the caps are full and the main switch can close without a spark, without contact damage, and without stressing the BMS.
Takeaways
- The neutral chain across multiple Multiplus units should be split at a terminal block, not daisy-chained.
- Sizing the breaker to the actual household load is fine; oversized cabling leaves headroom for later upgrades.
- The 5 kVA Multiplus is the right pick when each phase produces 3 kW of solar and you want to store it locally.
- AC-coupled solar is cheaper to deploy and gives you a fallback when the grid drops; MPPT is for new dedicated strings into the battery.
- A bypass switch in the meter cupboard is worth planning before you need it.
