Switching between EHU and leisure batt & inverter for 240V supply

[Ray]

Hi All,

I am looking for a bit of advice if possible. It regards electrics in a 1971 VW Campervan.
I currently (I think this is an accepted pun?) have electrics installed for Electric Hook Up (EHU) to an RCD then to the van sockets. I am about to install a 120Ah AGM leisure battery that will be wired up to an inverter (probably a 1000W pure sine wave inverter; not yet bought).

I would like the inverter to supply the van sockets when the van is not on EHU and to automatically switch between the two (i.e., isolate inverter when EHU connected). It doesn’t seem like there is any good advice on the net about the best way of doing this. So i’ve been head scratching and now have some diagrams of what I think will work.

If somebody more knowledgeable than I (not difficult) could look at the diagrams and advise that would be greatly appreciated.

n.b. between the inverter/EHU and the van sockets on the diagram there is an RCD (not shown). My intention would be to wire into the RCD which will then supply power to the sockets. Also, I would likely install a fuse between the battery and the relay. The battery in the diagrams is the leisure battery.

Many thanks in advance!
Ray

p.s. I know that mentioning a pure sine wave inverter is controversial…. I have my reasons for this choice…. namely that I will be running laptops, also I want to minimise interference for TV, radio etc.

p.p.s. The van is mostly used for camping but will also be used for selling teas and coffees etc in the near future, likely to be at locations where I will not have EHU. I won’t need to boil a kettle but will need to keep a hot water urn hot for approx. 3hrs at a time. The urn I am interested in needs constant 190W to maintain water at boiling temperature.

[Author]

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