2 shore power cables on a Fairline why?

[superheat6k]

Can't you actually get 230V only from one phase+neutral, when using one of those red 3ph sockets?
Phase+earth would trip the RCD, afaik.

Providing the single phase is simply one phase (any doesn't matter which) to neutral then the balance of the RCD is satisfied. An RCD works when the current does not balance, e.g. current in both neutral and the phase must balance, so if they do not the current flow must be to somewhere else, i.e. via the protective earth, which will trip the RCD.

 

[MapisM]

Sure- you obvs wouldn’t connect phase to earth.

An RCD works when the current does not balance, e.g. current in both neutral and the phase must balance, so if they do not the current flow must be to somewhere else, i.e. via the protective earth, which will trip the RCD.

'Salright folks, that's exactly my understanding.
My post #33 wasn't meant to "correct" what jfm said - I only asked because I half reminded that the earth is managed in a somewhat different way in the UK compared to continental EU, and I was wondering if such difference was that 230v can actually be pulled from phase+earth, in UK grid.
But I might well be mixing up my memories, mind...

 

[Rocksteadee]

Not convinced I'd like to be supplying another boat with electricity via my Y. What happens if he electrocutes himself from it.

This was supplying my boat from my Y. However I do take your point.
I used to be an industrial spark so know what I am doing but for Fred Bloggs next door is another matter.

 

[Deleted User YDKXO]

I tend to unplug the second cable of neighbouring boats if I need to plug in and there is just one plug per berth. Sometimes people get unaccountably cross. I do prefer marinas with a selection of sockets on each from 16 amp to the full 3 phase.

I used to come across that a lot in Croatia where it is very rare to get more than 16A. If I was parked next to a boat which was using 2 sockets and one of them was allocated to my berth, I would ask the skipper of the boat politely to remove it and if he wasnt on board, I would have no hesitation in removing it myself because it simply isnt fair. I did have one occasion when the other skipper refused point blank to remove his plug from my socket so I complained to the marina and they told him to remove it
FWIW, I also fitted a Victron Multiplus inverter/charger unit which can be programmed to limit the current taken from the shorepower supply to a preset amount and it will automatically top up any additional current demand from the inverter/batteries. Quite useful in marinas with only 16A supplies but obviously you had to be very careful about managing additional power demand over 16A. It was particularly useful when switching on my aircon which tended to consume a start up load a lot higher than 16A and which often blew my shorepower but used to settle at less than 16A when stabilised

 

[superheat6k]

'Salright folks, that's exactly my understanding.
My post #33 wasn't meant to "correct" what jfm said - I only asked because I half reminded that the earth is managed in a somewhat different way in the UK compared to continental EU, and I was wondering if such difference was that 230v can actually be pulled from phase+earth, in UK grid.
But I might well be mixing up my memories, mind...

The 'Grid' as we actually use it as consumers in the UK is actually a myriad small transformers from substations, each supplying a local area, say 1 or 2 streets or perhaps a marina. So the earthing arrangements are actually a fairly simple Earth connection normally a large metal rod buried in the ground by the substation, connected to the Neutral star point at the transformer.

These transformers don't in reality pass anything back to the grid that is likely measurable, so for those of you "micro generating" all you are really doing is passing your "micro generated" power along to some nearby neighbours to help run their fridge, or the TV on standby. The net result is that there will be marginally less draw through the transformer. I expect the power generators regard these micro generations as nonsense, but probably not PC to mention this.

I digress.

So if you do not have an RCD and you like taking (stupid) chances then yes likely a connection between any phase and earth will see you draw a decent 240v supply. Problems start on a very dry day after very dry weather, e.g. like now, when the earth resistance increases, then the current flow to complete the circuit may not always go the normal way. So the return resistance / impendance increases, causing the local voltage drop to fall. Then something closer to you on the Protective Earth line gathers a higher potential due to the overall resistance along the total circuit. At some point this higher potential may reach a lethal level.

Obviously this is all starting to get a bit complicated, so it is simpler better to use the proper Neutral, and allow your Protective Earth to be a Protective Earth, and not a pseudo Neutral.