FWIW, I’ve figured it out. The issue is the MP2 creates a lot of capacitive leakage. If the unit is grounded at a different point than the AC panel, the leakage builds over time and “charges” the frame. I figured it out by running a ground cable from the MP PE bond to the AC panel PE bond underneath the trailer. I didn’t have the right connectors and didn’t scrape the frame’s paint away but even this loose connection was enough to have the GFCI operate for a few hours without tripping. I’m now ordering proper grounding lugs to permanently install and expect this to solve the issue.
I take it back. The problem isn’t resolved.
I ran a solid core 6 AWG (16mm2) copper ground wire from the same point on the frame where the AC distribution panel is grounded to the negative bus bar which is connected to the battery negatives and the chassis PE lug of the MP2.
I’m still measuring 110-120ma of current between L1 and the neutral wire. There is a second negative bus bar which connects some low current devices that aren’t being used (brakes and tow vehicle connection). This bus is also PE bonded and I decided to try lifting those grounds and connecting this bus bar directly to the main negative bus with an extra wire. This had no effect.
At this point, all circuits are grounded to the frame within a few inches of each other. The leakage is constant and the GFCI stays closed for about a minute before popping open. There are no other AC loads.
I’m at a loss. I have to assume the MP2 is leaking a massive amount of current somewhere as the same GFCI and same AC distribution panel worked just fine before, even with the multiple PE bonds at different parts of the trailer frame. It’s the only thing that makes sense.
What doesn’t make sense is why the breaker is only popping after a minute or so and not instantaneously.
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I have had the same problem for years. I did come up with a work around and do before you attach to GFI pwr. This is on a boat and should work the same. Mine is a MultiPlus 12/3000/120-50 120V
- Turn shore pwr off or unplug it.
- Turn all supply breakers off on boat. These are the breakers/devices the Victron is suppling..
- Put MultiPlus into “Charge only”
- Turn shore pwr on or plug it in.
- Wait until the battery charging starts , about a minute or two. You can hear the relay click on the unit.
- Put the device in “on” mode.
- Turn ac breakers back on.
This works 100% of the time. If I do NOT do the above steps I will trip the GFI breaker. I think the problem is the built in inverter and the GFI breakers. I wish Victron work correct the issue. I keep waiting for a firmware update or something.
I tried your method yesterday. Interestingly enough, it worked for about 12 hours and then the GFI tripped again. This is roughly about 11 hours and 59 minutes longer than its ever gone without tripping so I’m curious as to why this happened this way.
Its my understanding that the GFCIs only measure the difference between the leg (L1) and neutral (N) and only pass-thru the ground connection for safety. When the current of L1 - N >= 4ma, the circuit disconnects presumably because some current is flowing outside of the closed circuit. When I lift the ground connection, the GFCI will stay connected, unbothered by the current flowing through it. It only trips when the ground is connected.
So far, I haven’t been able to measure any current flowing in the ground connection but have measured unreasonably high current differences (leakage?) between L1 and N. This could be a limitation of my testing equipment and setup but still..
My theory is that a significant amount of this current leakage is dumped to ground when the grounding auto-relay in the MP2 first engages and then builds over a minute or less until the GFCI has had enough.
Your power-up sequence might change how much leakage is initially dumped when the auto-relay engages, or drop it to nothing, so that leakage takes much longer to build up and make the GFCI unhappy.
do you have the ground relay enabled on the multiplus? This will cause the shore power GFI to trip. So when you are attached to the shore power they have the ground and neutral connected and you should not on the multiplus, however if you are disconnected from shore power you should have it enabled. I get around this by connecting the ground and neutral internally on my generator. When I am connected to shore power there is no ground to neutral connection within my boat, just at the shore power source. When I transfer switch to generator and it turns off shore power. The generator is making the ground and neutral connection. This also corrects the issue I commented on above. Shore power supplies ground/neutral connection, multiplus if that is the only AC source (ground/neutral relay) or at the generator. There should only be one at a time.
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The ground relay in the multiplus is automatically disabled when on shore power or generator. In most mobile installations this relay should be left enabled enabled in the configuration. The multi will then switch it as necessary. The problem with GFCI and multiplus operation in NA has nothing to do with the relay.
They GFI will trip if it detects the ground and neutral are connected. The multiplus will turn off the replay if it senses shore power. The problem is that the gfi trips before the multiplus detects that it has pwr in to open the relay. Once I disabled this function the GFI has never tripped. This might be a more US issue since our GFI trips faster than the Europeans.
It’s odd that it works for you just by disabling the pe/n relay. Good for you though. The n/pe bond is isolated from the ac input, as the line and neutral relays are open on the input side until the incoming power is qualified, synchronized, and then connected AFTER the n/pe bonding relay is opened. The incoming ac should never see the internal n/pe bond.
I have seen this GFCI problem on multiple customer rv’s (I own and manage an rv service center in the US) and the only success I have seen is by lifting the ground from the shore connection. I would NOT however recommend this as a solution.
My GFCI only trips after 30-60 seconds. Its definitely not an instantaneous trip. I was able to get the GFCI to stay online for about 8 hours by following someone’s protocol above which involved sequencing the power up of the MP-II. But alas, it eventually tripped.
I also would not recommend lifting the ground. There is a mild leakage current on the skin of my RV that makes me uneasy. For the life of me, I cannot figure out why. I’m assuming the MP is leaking current to ground.