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rsicade avatar image
rsicade asked

Victron MultiPlus II trips GFCI

I installed a Victron MultiPlus II 12/3000/120-50 2x120V in my trailer to charge 400AH of LiFePO3 batteries. When I plug everything in and try to charge the GFCI circuit faults. I've tried 3 different GFCI circuits.

  • With the MultiPlus off, there is no ground fault and I have AC power from the same GFCI outlets.
  • As soon as I turn on the MultiPlus, the power light blinks, steadies, then I hear a relay click as it tries to charge. GFCI faults immediately
  • The input current matches the outlet, it is not blowing the breaker on the curcuit.
  • It happens with all AC output from the inverter off (downstream breakers).
  • I configured the Inverter's ground relay to 'off', made no difference.
  • It works normally from a non-GFCI outlet, and from my Honda EU2000i generator.

I can't find enough information from Victron to understand what the ground relay checkbox does from an elecrical standpoint to know if unchecking it should have made a difference. Not sure whether to return this unit as defective and get another one or if I will have the same problem. My dealer says they don't know enough to even have a conversation with victron about this and, in their experience, victron won't talk to customers. Anyone have any insight into this issue?

Multiplus-II
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ngknick avatar image ngknick commented ·

Did you ever figure out a solution? I have the same setup with generator and transfer switch. From researching it appears the ground relay of the multiplus is the culprit, but I also want to rule out the transfer switch...

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bradgarrison avatar image
bradgarrison answered ·

FIXED!!!


Last year, I installed a Victron Multiplus II, Cerbo GX, and Smart Solar in our 2020 Grand Design 2800BH. While this setup worked flawlessly during boondocking, I encountered an issue when connected to shore power: the GFCI outlet would trip after about a minute. Initially, I suspected the problem was related to the Victron system, as the camper did not trip the GFCI before this installation.

I first verified the wiring multiple times, updated the firmware, and read through numerous posts from others who had experienced similar issues. A few weeks ago, I decided to test the setup further. I used an extension cord with the ground wire cut off and plugged the camper into the GFCI outlet. This prevented the GFCI from tripping, which suggested a grounding issue.

Next, I used a volt-ohm meter to check the resistance between the camper’s steel frame (where the Victron Multiplus was grounded) and the aluminum frame (where the WFCO distribution panel was grounded). I discovered resistance between these frames, indicating a grounding problem. It was a small amount of resistance but enough to trip the GFCI.

The issue stemmed from the change in grounding configuration after the Victron installation. Originally, the 50-amp input connected directly to the WFCO panel, which was connected to the aluminum frame. Also, all the camper circuits are grounded back to the WFCO panel. With the new setup, the input went directly to the Victron, which connected to the steel frame. This altered the camper’s grounding and introduced resistance between the steel and aluminum frames.

To resolve the issue, I installed a ground wire connecting the steel frame near the Victron to the aluminum frame near the WFCO panel. This adjustment eliminated the resistance, and the GFCI issue was resolved.

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derrick thomas avatar image
derrick thomas answered ·

This is a known issue with the 120v MP2 units unfortunately. The ground relay has no effect on the issue, but it does need to be enabled for mobile installations.

There have been a few people mention success with GFCI outlets by using a dogbone adapter with the ground prong clipped. Not ideal or suggested, but it might get you by in a pinch.

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Alistair Warburton avatar image Alistair Warburton commented ·
Absolutely not true in the UK, and likely Europe... Sorry Derrick

There are plenty of folk reading this stuff who simply wouldn't know that things differ around the globe, and sadly a probably couple who will read this and take exception at 'GLOBE'.

Respectfully, general advice on subjects that differ from place to place needs to be qualified as regional, which is why I am not commenting on US REGS.

I would be interested to know what the US REGS are though.
Grounded mobile installations, really?
Would a GFCI be mandatory in that case?
How are fast trip times for sockets handled, an MCB isn't going to work, at least not quickly, not enough fault current potential. We call that Prospective Fault Current in the UK.

I am sure you can google the rest of the acronyms.

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rsicade avatar image rsicade commented ·
That is consistent with what I have read. It appears it is a difference in GFCI thresholds vs european equivalents. Annoying that I bought this in the US for US use and it it going to have problems with newer electrical installations. Was going to put one of these in my boat next year but my marina is replacing the electrical with the newer ELCI breakers, this thing has no chance of working with shorepower with ELCI's. Since I posted the dealer was going to send the unit to the regional repair facility to have it bench tested but after discussing with the Victron regional manager decided the unit isn't faulty. Waiting for their response, they delayed by asking for a wiring diagram. Only way to ensure this will work with GFCI's and ELCI's would be to install an isolation transformer. Not likely to clip the ground to make it work. Thanks for the confirmation.
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Alistair Warburton avatar image
Alistair Warburton answered ·

from... 9. Configuration (victronenergy.com)

Ground relay (see appendix B)

With this relay, the neutral conductor of the AC output is grounded to the chassis when the back feed safety relays are open. This ensures the correct operation of earth leakage circuit breakers in the output. If required an external ground relay can be connected (for a split-phase system with a separate autotransformer). See appendix A.

(I assume that this means is the AC input relays being open)

This whole topic confuses me, 120 0 120 / 240 who cares... If your electrical installation is TNS/TNCS/TNC and you have removed the grid connection with a two pole switch and added another source of power, be that a generator or an inverter then you MUST create a new N-PE bond to ensure there is a low impedance pat that will allow MCB's fuses to operate.

That is what the ground relay is doing, well mostly, chassis was a poor choice IMHO but it is what it is and workable at least. Weather a fuse or MCB has ca cat in hells chance of ever tripping fast enough with such a limited PSC seldom ever gets mentioned. In practice the only way to ensure a fast trip during an earth fault is by protecting everything with an RCD, either separately or using an RCBO.

For TT systems, there is no N-PE bond, in fact the floating neutral is a regular annoyance, causing RCD's to trip when badly designed, lets say Easton derived, equipment creates a path between N and PE.

Additionally, in the UK at least, probably all of Europe, mobile hookups get their own section on earthing.

In essence all mobile installations must be treated as a standalone TT system and have a dedicated earth electrode only for that for that single connection and proximal to it.

Even when the system supplying the mobile connection is itself TT, the site system PE is NOT coupled to the mobile unit.

SO... Unless your standards differ for some reason...

The ground relay is not needed on a TT system and 'could' cause an MCB/GFCI to trip.
Moreover enabling it would mean your system was not compliant, even if it still worked.

For any system...

Everything must be earthed, all earths must be bonded back to the same earth electrode, or grid of electrodes.

If we were talking about a fixed installation, that is not TT, the ground relay would need to be closed when the grid was disconnected to create a N-PE link to replace the one that just disconnected.

Disclaimer... I an NOT an expert on the REGS in the UK and have even less knowledge of REGS elsewhere but I do know what is in play, technically.
You need to check this stuff just to be safe, never mind compliant.

Victron's routes are marine, a whole other ball of wax when talking shore power and boats. I don't know so I am not going to comment on details, but I wouldn't be at all surprised ground connection switching, galvanic isolation and even IT systems made it into that conversation.

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derrick thomas avatar image derrick thomas commented ·
Yes, the regs are different on this side of the pond. North American mobile installations do require the neutral earth bonding. Here, that is handled by the source. Mobile generators are bonded at the generator, shore power is bonded at the service entrance, and the internal relay of the inverter handles bonding when inverting without an external source.
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