This may happen to you if your RV has a Victron Multiplus II Inverter Charger and you plug into a standard household GFCI outlet. Don’t worry, it’s not caused by a bad installation.
It usually does not happen right away and may not even happen at all. It may even take a few minutes based on charging or power load levels. When it does happen, the GFCI breaker trips, shore power goes out, and your Inverter takes over just as if you’re back off-grid, because now you are. You’ll eventually check the GFCI plug, reset it and the shore power comes back on. AND then it happens again leaving you scratching your head.
This happened to me a number of times in the past before I figured it out. Let me explain what’s going on here and tell you how to avoid it.
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Explanation
If you don’t have a Victron Multiplus II Inverter Charger, then none of this will apply to you. This will only affect those of us with a Victron Multiplus II Inverter Charger in our RV, van or camper as part of a larger off-grid power system. This issue may occur when using the Multiplus Power-Assist feature while powered from a GFCI outlet.
What is Power Assist? The Victron Multiplus Power-Assist feature lets you limit the amount of electrical current it will draw from a shore-power connection. Any additional power required above the limit will be provided by the Multiplus inverter and batteries. This is very useful if you want to plug your RV into a standard household outlet without overloading it.
GFCI electrical outlets are on most outdoor and garages in North America. They have a built-in safety device that functions as a very sensitive “shock protector.” If it detects even a tiny bit of electricity leaking (4-5 milliamps, an extremely small amount), it immediately turns the power off to keep you safe.
Your Victron inverter was made in Europe, and in Europe they allow up to 30 milliamps of leakage before tripping. So the Victron Multiplus is built to be a bit less sensitive than GFCI electrical outlets in North America.
When the Tripping Happens
When you’re only using shore power (normal pass-through mode), everything is usually fine. But with Power-Assist enabled with an active shore power connection, the Multiplus also goes into inverter mode to make up any power difference. This automatically creates an internal connection between the ground and neutral wires. The ground-neutral bonding is normal and necessary for an off-grid setup. But here’s where we might start tripping.
When the Multiplus ground-neutral relay transitions to inverter mode while on shore power, a small amount of current may leak (often around 8 to 10 milliamps). That’s more than the 4-6 milliamp limit of the North American GFCI outlet rating, so the outlet trips.
For some reason, it is most common in the Victron Multiplus II 2 x 120V model inverter.
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What Is The Solution?
None of these are perfect, but here are the main fixes used by Victron users.
Update the Multiplus Firmware
To date, there have not been any firmware upgrades that resolve this issue directly. But some have reported the problem going away after updating the Multiplus firmware.
Don’t Use GFCI Outlets with Power-Assist (Recommended)
Use a circuit that does not have GFCI protection. I went with this solution and have a non-GFCI outlet for the RV. So, this will definitely resolve the issue, but it may be difficult with newer homes given that recent electrical code changes require GFCI protection in exposed areas.
30A and 50A outlets in RV parks generally don’t have GFCI protection. So use your 30A or 50A cord or a 15A to 30A “Dog Bone” Adapter to convert a standard 15A plug to a 30A plug. This is what I do when in an RV park.
Don’t Use Power-Assist
This may be a last resort and will require you to monitor and self-regulate your power consumption in order to keep it under the rated 15A or 20A circuit limit. If your RV draws too much power, you’ll likely (hopefully) trip a breaker in the main electrical panel.
Change the Automatic Ground-Neutral Bond Setting in the Multiplus
Tell the inverter to stop making its own ground-neutral connection while on shore power. This is not something you can do through the mobile app or Cerbo GX though. You will need to connect a PC/Laptop to your Multiplus to make this change. Perhaps only do this when you’re going to be on limited shore-power for an extended period.
That ground-neutral bond is needed for safety while the inverter is working in off-grid mode. So be sure to turn it back on when disconnecting from shore-power.
Bottom line
This is a known “quirk” between European inverters and North American GFCI outlets. Most people just avoid Power-Assist on regular outlets or use the bigger pedestal outlets.