question

Markus avatar image

Multiplus With Generator And Residual Current Device

Hello,

I have a Multi 48/5000 and a very cheap but good working 2.5KW gasoline generator connected to AC IN.

At final installation tests, I found out that the Residual Current Device does not work, when the generator is running and supplying power, even though I connected a good earth to the generator.

It seems, the generator is not capable of a RCD.

Is it OK to hard wire PE and Neutral on the Multi? Or what is common practice?

Thank you.

Markus


MultiPlus Quattro Inverter ChargerGenerator
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2 Answers
Guy Stewart (Victron Community Manager) avatar image

MEN (Earth to Neutral link) in Victron Systems.


One of the common issues that I see in new installations is issues with the MEN.


There are three possible locations for the MEN link to be created in Victron systems. All are appropriate depending on the systems design and configuration.


The most common MEN location in Australia is the main AC distribution board.


This link requires there to be no MEN in any connected generator and the internal ground relay inside the Multiplus inverter charger to be DISABLED.


In this configuration, the generator needs to be hard wired and permanently connected, which is usually the case in off grid systems.


If you wish for the generator to be able to be disconnected and used safely in mobile applications then the MEN needs to be created inside the generators.


This means removing or never adding the MEN inside the AC distribution box on the stationary system.


This also requires you to ENABLE the ground relay inside the Inverter Charger. So that when the generator is removed, the system then creates a temporary MEN internally.


It is important to be aware that the process of checking and engaging the MEN linking relay inside the inverter charger also introduces some small amount of earth leakage.


This is not normally a problem unless there is another source of earth leaking inside the system and the combined effect can be enough to trigger RCD’s.


It is advisable to remove or correct the other sources of leakage. Common causes of apparent earth leakage can be surge protected power boards.


Another possible configuration is if the system is mobile. Then the MEN is usually created at the AC distribution box of the shore or grid supply.

Again, the ground relay needs to be ENABLED so that when the system is disconnected from the grid, the MEN is dynamically created and the system is safe.


It is normal to hear the ground relay engage and click into place.


This is general information only. Specific safe installation practice is the responsibility of the suitably qualified and licensed installing electrician.


  • Permanent generator - Permanent Installation. MEN created on AC box, internal relay disabled. No MEN in the generator.


  • Mobile generator - Permanent Installation. MEN created in generator, dynamic ground relay enabled.


  • Mobile system. MEN created on grid input AC distribution box, dynamic ground relay enabled inside multiplus.

In all these system types, there should be only one earth stake / grounding rod connected at any one time.

I am not a qualified electrician, and this is not official manufacturers advice from Victron Energy. These are my own personal observations of dozens (maybe hundreds?) of installations and configurations around the world. Incorrect installation can be fatal and is best left to those who are familiar with local requirements for electrical safety.


Regardless of who did the installation, RCD’s or other safety equipment should also be regularly tested.

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Just wanted to say THANK YOU Guy for the superb writeup. Thanks to your excellent explanation, I was able to solve my generator syncing issue (mobile generator, but original installer had not made MEN connection at the generator).


Also, is there any update on the AC wiring guide you mentioned in your Nov 27 comment below? I'm sure it will be extremely helpful when it becomes available.


Hi Jet,

There is an update - of sorts.

Margreet's Book Wiring Unlimited has a section on RCDs:

Wiring-Unlimited-EN.pdf

I did not write this document, so there may even be sections that I would do differently. There are often several ways in these situations, depending on local requirements.

jetx avatar image jetx Guy Stewart (Victron Community Manager) ♦♦ ·

Thanks Guy. Haven't studied this in detail (yet), but looks very well done and very helpful!

  1. G'Day Guy.. are you sure?

    You write
  • Permanent generator - Permanent Installation. MEN created on AC box, internal relay disabled. No MEN in the generator.
  • Mobile generator - Permanent Installation. MEN created in generator, dynamic ground relay enabled.


for me an permanent Installation has men on Genset with RCD and internal enabled and mobil mostly not because of missing earth connection on mobile genset

just my thoughts not a common advise ;)


Hi Peter,

There are many ways to do it and different expectations all over the world.

The preference/expectation/AS3000 wiring standard in Australia is that a permanent Neutral Earth Link is made in the main AC distribution box, and a generators output is hardwired to that (via the Multiplus).

In this configuration, you can't safely use the generator directly without the multi.

There is no use for the internal relay, and another one on the generator will cause problems.


So;

Yes, I am 100% sure & also

No, it is not possible to be certain in the slightest :)))

I solved it in creating MEN on Multis AC OUT and disabling earth relay. RCD works now. I have to put a note on generators connection cable. But as this is a cheap mobile generator from a hardware store. I didn't want to create a MEN on this generator. I had to choose if a problem can occur if you connect this generator somewhere else then, or if another generator, with own MEN is maybe connected at the installation somewhen. I chose second. But I have to mention, this is not an official installation. It's a hobby installation, at own risk.

Generator is on the lower left.

Markus avatar image

Thank you for that awesome answer Guy.

It would be good to have a note on this in the manual.

I forgot to mention, that this is an complete off grid installation.
The Multi and the generator is located in the shed.

Regards,

Markus


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You’re welcome, and thank you for your many helpful answers on the community.


Work is currently underway by a senior Victron Manager on an extremely comprehensive wiring guide, I hope that an early version will be publically available soon.

It’s a fine line for the company to walk providing information about AC wiring. There are many possible configurations, and a little bit of advice can be dangerous if not understood in context, or with appropriate training, or sufficient test equipment.

Markus avatar image Markus ♦♦ Guy Stewart (Victron Community Manager) ♦♦ ·

It's a pleasure to help.

That is good. I do understand this fine line :o(

JohnC avatar image JohnC ♦ Guy Stewart (Victron Community Manager) ♦♦ ·

That would be amazing Guy. I've found electrician's eyes tend to glaze over when you talk MEN switching and earthing on boats especially.

And if I can be pardoned a little fun: https://www.victronenergy.com/blog/2017/11/27/the-trouble-with-generators/

Check out the closeup on this rooster!! Good work too. Cheers..