What is the purpose of 2 shore power cables.

No, perfectly safe to have two 16a inlets on a boat, provided both are for independent systems.

The dangerous ones being talked about are cables that have 2 x 16a inlets to a single 32a outlet.
But marinas only have one outlet per berth. So knowing this why do builders do it ….double inlet ?
Still waiting for a logical , workable in every day use and safe (if you like ? ) answer as to why ?
 
But marinas only have one outlet per berth. So knowing this why do builders do it ….double inlet ?
Still waiting for a logical , workable in every day use and safe (if you like ? ) answer as to why ?
A lot of UK marinas don’t have 32A outlets.
2x 16A to a 32A is dangerous as discussed.
Where there is a 32A outlet, 32A to 2x16A is fine.
So 2x 16A inlets works everywhere. With a long extension you can usually find 2. If you can’t then 1 allows all the domestics just no aircon. Pop on the genny when you need it.
 
This is all getting totally out of hand.
Two cables to your boat is perfectly safe if the boat is a professionally built boat - in other words the supplies are properly split (AC on one lead - everything else on the other lead).
For those areas where two sockets aren't available, you could use a splitter (one plug into two sockets).
Any overload is protected by the shore supply RCD.
 
Any overload is protected by the shore supply RCD.
By the shore supply breaker (aka OCPD), actually.
Sometimes bundled in a single component that does both functions, but the RCD as such is not affected by load, as long as there's no current dispersion.
[/pedantic mode]... :p
 
I have seen it done in the UK with 2 13 amp plug tops , it wS on a hot tub one did the heating element and one did lights and pump totally separate and totally safe off a 32amp ring circuit might need a type c breaker.
 
Other that waiting for the bang, how would you check if there were two (or three) phases on your pontoon box. The phase split could be done between different boxes on the pontoon.
I’m assuming a 2 to 1 blue plug and socket.
I remember buying (on @Hurricane recommendation) a very useful testing plug but I don’t think that can recognise a particular phase, just polarity and other stuff I assume.
 
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""how would you check if there were two (or three) phases on your pontoon box.""

Single and multi phase plugs and sockets are different and will not fit into each other.
 
""how would you check if there were two (or three) phases on your pontoon box.""

Single and multi phase plugs and sockets are different and will not fit into each other.
The issue is not fitting a single phase plug in to a three phase socket or vice versa, it's what happens if the single phase sockets on the pedestal are on different phases.
 
Other that waiting for the bang, how would you check if there were two (or three) phases on your pontoon box. The phase split could be done between different boxes on the pontoon.
I’m assuming a 2 to 1 blue plug and socket.
I remember buying (on @Hurricane recommendation) a very useful testing plug but I don’t think that can recognise a particular phase, just polarity and other stuff I assume.

If you meter them out, the voltage of two lives on the same phase will be zero, whereas the voltage between two different phases will be 415 ish.

If you get 230 ish you have an inverted neutral somewhere

But it's a dreadful idea in the first place
 
The electrical regulations state all 230 volt sockets ie blue on the same pedestal must be the same phase , all red are 3Phase , but very rare in uk mainly for super yachts or commercial fleet. There will be no boats with two plugs that are connected on board. It’s just a what if idea, and if some dick did this they would pay the price.
 
Being a total nerd I couldn't help but looking at how the superyachts in Monaco were plugged in yesterday (much to my gf's annoyance)

You know you've made it when your boat requires 660A powerlocks to light it up

In this photo you can see three phase and earth powerlocks being fed into a converter box which is changing it into 2 x 125A three phase and earth ceeform style sockets.

Presumably the boat has two totally separate systems internally for situations when the biggest socket it can find is 125A.

Note how there is no neutral, so they must have big transformers on board to drop it down to 230V / 110V for domestic style appliances.



But then you look across at your neighbour and realise he's made it even bigger time than you, as his boat requires these monsters. Anyone know what sort of connectors they are?


 
Being a total nerd I couldn't help but looking at how the superyachts in Monaco were plugged in yesterday (much to my gf's annoyance)

You know you've made it when your boat requires 660A powerlocks to light it up

In this photo you can see three phase and earth powerlocks being fed into a converter box which is changing it into 2 x 125A three phase and earth ceeform style sockets.

Presumably the boat has two totally separate systems internally for situations when the biggest socket it can find is 125A.

Note how there is no neutral, so they must have big transformers on board to drop it down to 230V / 110V for domestic style appliances.



But then you look across at your neighbour and realise he's made it even bigger time than you, as his boat requires these monsters. Anyone know what sort of connectors they are?


Is the electricity included in the berthing fee...or is it metered separately ?
There certainly comes a point where access to the boat is compromised by these cables and chargers
 
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