question

plusaufmasseknalltklasse avatar image
plusaufmasseknalltklasse asked

Multiplus output requires RCD protection

Hi folks,

I have a question regarding RCD-protection for the Victron MultiPlus 12/500/20-16.

External AC detached:

The manual says that it is equipped with a ground relay that connects neutral to ground if no external power supply is attached. And for a mobile installation (mobile home) the case must be grounded to the chassis.

For my understanding this is still a TN system that would require a RCD at the inverter output that could detect leakage current to ground/chassis and trip.

External AC attached:

The system is connected to external ground (again TN system) and the RCD on the input side would be in line with the RCD on the output side. Both RCDs would fulfill their duty but the input side RCD would also protect for inverter failure.


Is this understanding correct? So do I need an RCD on input and output side?

I have seen several setups (with only a single socket as well as several sockets) that do not have an RCD on the inverter output side. I understand this is okay in an isolated (IT) system but due to the ground relay I believe this does not apply here.

Thanks for your comments.


MultiPlus Quattro Inverter ChargerGenerator
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3 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

You don't need a RCD on the input* but you definitely should install one on the output of the MultiPlus.

*unless you also have connected some loads at the input.

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plusaufmasseknalltklasse avatar image
plusaufmasseknalltklasse answered ·

Thank you very much for your fast reply. This already solves my question, but as a follow up:

I thought it is a "standard procedure" to have an RCD at the input (e.g. it if there is none fitted on the mains connection, or the inverter malfunctions?)

And I recently found this circuit diagram that implemented both:

https://www.victronenergy.de/upload/documents/1.6KVA-12V-MultiPlus-230-Volt-system-example-4-PIN-VE-Bus-BMS-Lithium-Orion-Tr.pdf

Is there a difference to my setup? Why should/could I drop the input RCD?

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Máté Őry avatar image Máté Őry commented ·

I have the same question. Just searched for this topic after realizing that the schematic posted in #90788 doesn't have an RCD between the shore connector and the quattro AC input, while most other system schematics do.

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plusaufmasseknalltklasse avatar image plusaufmasseknalltklasse Máté Őry commented ·

I assume by "shore connector" you mean the 5kW generator on the bottom right?

In that case the setup is a little different, since this generator could actually be an isolated (IT) system without ground. In that case an RCD wouldn't work here.

Since details about this generator are omitted this is of course just my guess to "make" this drawing reasonable.

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Vance Mitchell avatar image
Vance Mitchell answered ·

I prefer to have a RCD on both the input and output.

In some countries I believe it is a requirement to have dual pole switching on both the input and output and I find it is just as easy to use an RCBO (combined RCD and breaker) for both.

Note however that I am not a qualified Electrician and would advise that you check with someone qualified where you live.

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