Options for low voltage protection RCD/RVD

[bobakers]

Hi all
I’m setting up a Victron inverter in a composite truck body and looking at options for the LV circuit protection. My understanding is that when connected to the grid, through a correctly wired GPO and lead, the RCDs within the vehicle will work correctly. The issue arises when connecting to a generator without MEN or an incorrectly wired supply.

The MultiPlus is provided with a ground relay that automatically connects the Neutral output to the earth (chassis) if no external AC supply is available. If an external AC supply is provided, the ground relay will open before the input safety relay closes. This ensures the correct operation of an earth leakage circuit breaker that is connected to the output. In a mobile installation (for example, with a shore current plug), interrupting the shore connection will simultaneously disconnect the grounding connection. In that case, the casing must be connected to the chassis of the vehicle. (Extract from Victron MultiPlus manual).

I see my options as follows:

LV Protection Options 2.png

Or do I need just the one RVD as the RCDs will work correctly with the Victron MEN relay, ie

LV Protection Options 2.png

Appreciate your thoughts from those that have experience setting up a MultiPlus with RVDs.

Thanks
Bob

[BruceS]

Bob I'll leave some comments to Terry as I know he is familiar with them.
Some time ago I considered installing one but first I had the local (SA) electrical authority carefully and thoroughly inspect the 'concept' of these RVD's. (via website & email to the RVDsafe owner/designer)
He actually had never heard of them in SA. He took the 'project' to the head office & the resulting answer was "not needed, waste of money, please yourself what you spend your money on".
When I reported these facts on the Caravaners Forum I got a week's holiday for being argumentitive.
I'm not saying they don't work. I have never said that.
If they really are a God's Send, then I really question why every State hasn't adopted them as mandatory ???
It wasn't that long ago that even RCDs weren't mandatory?

[bobakers]

hi Bruce
Thanks for the feedback.
Im not sure they are required when everything is operating correctly but more so when there is either an issue with the incoming supply (ie genset with no MEN, reverse polarity at van park) or operating off an invertor hardwired into the van with multiple outlets and no MEN relay.
If my thoughts above are wrong am happy to be educated.

Thanks
Bob

[bobakers]

hi admins
Just realised this would be better suited to the 240v forum not low voltage . Please move if you see fit.
Thanks
Bob

[BruceS]

I never noticed that either Bob.
I'll have a go at moving it.
I thought Terry would have popped in by now but he has been a bit busy with eye Dr's & doing a large house install.

Topic moved

[supersparky]

..............................
If they really are a God's Send, then I really question why every State hasn't adopted them as mandatory ???
It wasn't that long ago that even RCDs weren't mandatory?

Bruce, They really do work. They have been used in the mining industry for a long while now. Oz is just a bit slow at adapting to change.
As you may be aware AS3001 is currently under review with a release date of ...soon.
RCD /RVD's are one area that is expected to change, so my sources report.

Bob, I haven't yet tested an RVD on a Victron yet, but I have on a few other makes. If you install an RCD and it functions correctly then you can sleep easy. I can't read your drawings properly because I am using my phone,but I can't see a difference in dwg 1 + 2 , and if I am reading it correctly the third dwg offers no RVD protection after the inverter.

[bobakers]

Hi David
The first sketch has a RVD EMR on the input to the Multiplus and a RVD EI on the AC 1 out of the MultiPLus.

My logic for this is that the RVD EMR protects against incorrect polarity when I connect at a caravan park and provides protection when I plug the genset (no MEN) into the truck AC in. The RVD EI provides protection on AC1 when in inverter mode.

My logic for the second sketch is that the MultiPlus provides for a MEN link when there is no AC in from either a genset or caravan park so the RCDs should work correctly so no requirement for the RCD EI on the MultiPlus output of AC1. (AC2 on the MultiPlus is not available when in inverter mode). A RVD EMR is still fitted for AC input to the truck prior to the MultiPlus to provide the same protection in the above paragraph.

Regards
Bob

[T1 Terry]

I still can't see vey well as far as reading goes, so if I completely misinterpreted what was posted then please redirect me as to the part I misread.
First off, the RVD does work no matter what power source is used, an MEN supply, a floating generator, a floating inverter or an inverter with a grounding relay. The down side, they aren't cheap.
The problem with just how the grounding relay is operated can be a problem.
If it is powered by a circuit that looks for any link between the neutral and earth cables before the inverter and switches in if it sees no link but remains open if a link is sensed, then all is good as long as the relay actually switches and the contacts actually create the earth/neutral link ....... electronics and relays being what they are you can never be sure unless you have one of those circuit testers plugged in at all times to verify you have an MEN system.
If it is powered by the external supply voltage, this means there would be no MEN link when the external supply was from a floating output generator, there for the RCD in the vehicle would not function as safety switches. The other problem is with the power supply from an MEN supply failing yet the supply is still plugged in. The MEN link would still be there, just no supply through the active and neutral cables. As soon as the earth neutral relay closed because there was no supply sensed, the shore power RCD would sense a second connection between the earth and neutral cable and determine this to be a fault and trip the shore power RCD as soon as the supply was again available. In other words, you would still be running on inverter/battery power because the shore power RCD had tripped therefore the inverter would not sense a supply on the 240vac input side.

T1 Terry