Inverter, RCD & 230v Relay Switching earth safety questions

[chamzamzoo]

Hello all,

 

I have spent some delving through such classic threads as:

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/RCD-Circuit-breaker-and-Inverter-/30196/

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Inverters/27409/

&

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Inverter-Advice/37699/

 

and am much wiser from doing so.

 

I have some residual questions however, I'm hoping our combined wisdoms will conquer..

 

I am putting together a small camper in a VW T5. I specced up the electrics a few months ago when I didn't really know what I was doing, but knew roughly what we'd want it to do. I've learned a lot since then and loved it, but I'm not quite sure how best to proceed with the 230v side of things.

 

I've got:

Victron 12/375w Inverter & remote switch, AC / DC are isolated and has separate chassis ground terminal (inverter neutral output is NOT bonded to earth in this model, although it does recommend it if local regulations say so: https://www.victronenergy.com/upload/documents/Manual-Phoenix-Inverter-250VA-1200VA-EN_NL_FR_DE_ES.pdf)

EHU & Consumer unit with RCD and 1 x 6 amp double pole MCB and 1 x 10 amp double pole MCB.

230v auto switching relay (live and neutral)

two 3 pin sockets

two x 110ah AGM batteries in parallel

The setup is currently installed as follows (although not complete and potentially could be changed..). If this setup is safe though I would like to keep it as it has high ease of usability.

Inverter & EHU (via consumer unit) wired to 230v auto relay, in turn wired to the two sockets. EHU will override the inverter.

The earths for the sockets and inverter output cable are collected & screw terminated together inside the box the 230v switcher is in, this is then connected to the VW chassis via two bus bar links (one in the consumer unit, then another, then to the VW chassis mounting point- all 4mm2 cable or artic flex)

the inverter is connected directly to the battery positive (50amp fuse) and negative terminal, which also happens to be connected to the VW chassis ground

the separate inverter ground is connected to the battery negative terminal and in effect the VW chassis ground also.

 

Questions...

 

Using the 230v auto switcher and bonding all my earths together has confused me a bit, what's the safest way to proceed?

 

1) Bond the Inverter neutral output to earth and install an RCD between the inverter and the 230v auto switcher? If so what's the best way to bond the neutral and earth?

 

2) (means dismantling half of it) Keep the inverter and EHU powering separate sockets (although they will still end up sharing chassis earth). RCD on the inverter output socket. Would this still require bonding the Inverter neutral to earth for the RCD to function though? again, what's the best method?

 

This is what the manufacturers manual says:

 

This is a Safety Class I product (supplied with a protective grounding terminal). The chassis must be grounded. A grounding point is located on the outside of the product.

 

The AC output is isolated from the DC input and the chassis. Local regulations may require a true neutral. In this case one of the AC output wires must be connected to the chassis, and the chassis must be connected to a reliable ground. Please note that a true neutral is needed to ensure correct operation of an earth leakage circuit breaker.

 

I think they mean the inverter chassis here.

This is pretty clear, but what's throwing me is the earth wiring for the inverter and EHU, does that need to be kept separate on a relay too?

 

They talk about triple pole relays here: http://www.motorhomefacts.com/forum-printtopic-1-14307-10-0-asc-viewresult-1.html

 

Sorry for the huge first post, I wanted to give as much information at once to save to-and-fro. Hope someone has some input :)