What is the purpose of 2 shore power cables.

[st599]

The voltage has been 230 v since 2009 it says on the label. Oh ye.

It hasn't. UK is 240, EU is 220, so the label says 230 +/- 10

 

[starfire]

The voltage has been 230 v since 2009 it says on the label. Oh ye.

Used to be 240V plus or minus 6%, now 230V plus 10%, minus 6%.
So nominally 230V, but actually 240V

 

[Elessar]

Used to be 240V plus or minus 6%, now 230V plus 10%, minus 6%.
So nominally 230V, but actually 240V

Makes no difference!
Still

 

[Seastoke]

It hasn't. UK is 240, EU is 220, so the label says 230 +/- 10

Show me a label that says any plus or minus ,no forget it I have to work to BS7671 AM2 , some work to Google .

 

[jakew009]

As said above, the marina supply is made up from a 3 phase supply. Each single phase socket phase is made up from one of the 3 phases and a neutral. Also, as explained above, the voltage between each phase is 415 volts (which hurts if you get it wrong). The voltage between any phase and neutral is 240 volts. Any red sockets will have all three of the phases and a neutral inside the plug/socket. Blue sockets/plugs contain a single phase and a neutral. Marinas will wire blue sockets on different phases (so that all three phases are balanced). So, two blue sockets MIGHT be wired to different phases thus having the potential (excuse the pun) of 415 volts between them.

So having two cables connecting connecting to your boat might introduce two separate phases onto the boat.
Boat builders often split the boats services in order to keep this risk to a minimum.

In my case (like most boats) the Air Conditioning system is run from one cable and the rest of the boat from the other cable.
Also, in my case, I know that the electric pile that we plug into has all its blue connectors on different phases so my boat DOES have the potential danger of 415 volts on the boat.
But it isn't a problem as long as you know not to mix the supplies - which is difficult to do anyway.

That's also the reason 'widow maker' cables (ie. 2x 16A plugs that combine to make a 32A supply socket) are so dangerous.

Ignoring the fact that you have live pins exposed if only one leg is plugged in, if you end up connecting each leg to a different phase, the moment you plug the second plug in it will likely grenade in your hand

I thought that they generally kept all the sockets on the same post on the same phase for exactly that reason but I'm not a marina sparky.

 

[Elessar]

That's also the reason 'widow maker' cables (ie. 2x 16A plugs that combine to make a 32A supply socket) are so dangerous.

Ignoring the fact that you have live pins exposed if only one leg is plugged in, if you end up connecting each leg to a different phase, the moment you plug the second plug in it will likely grenade in your hand

I thought that they generally kept all the sockets on the same post on the same phase for exactly that reason but I'm not a marina sparky.

A 2x 16A to make a 32A is a potentially lethal device that should never exist.

But what will happen if you plug it into 2 different phases?

A “hand grenade” as you suggest? No, it will trip an MCB at worst.

Why all this 3 phase scaremongering?

But you are 100% right about a 2x16A to 32A being dangerous.

But 32A to 2x16A is fine (though you should probably have 16A fuses in the plugs to be sure)

 

[jakew009]

A 2x 16A to make a 32A is a potentially lethal device that should never exist.

But what will happen if you plug it into 2 different phases?

A “hand grenade” as you suggest? No, it will trip an MCB at worst.

Why all this 3 phase scaremongering?

But you are 100% right about a 2x16A to 32A being dangerous.

But 32A to 2x16A is fine (though you should probably have 16A fuses in the plugs to be sure)

I've never tested it but I bet you would get a pretty exciting bang as you plug the ceeform in, hence my 'grenade' scaremongering The fault current that would flow would be massive. I imagine the RCD would trip before the MCB assuming it works.

If you've ever cut through a live bit of twin and earth with a pair of snips you'll know what a bang it can make as the blade edge disappears. With 415V it's just twice as big a bang.

 

[PaulRainbow]

I've never tested it but I bet you would get a pretty exciting bang as you plug the ceeform in, hence my 'grenade' scaremongering The fault current that would flow would be massive. I imagine the RCD would trip before the MCB assuming it works.

If you've ever cut through a live bit of twin and earth with a pair of snips you'll know what a bang it can make as the blade edge disappears. With 415V it's just twice as big a bang.

See post #47.

If you connected two phases it would be 2 x 220v, but they wouldn't add up to 440v. All you do is to create a dead short on each phase, hard to say if the RCB or MCB would trip first, although a lot of marinas are using RCBOs these days.

 

[jakew009]

See post #47.

If you connected two phases it would be 2 x 220v, but they wouldn't add up to 440v.

I don't understand that comment at all. In UK phase to phase voltage is 415V.

 

[Elessar]

I've never tested it but I bet you would get a pretty exciting bang as you plug the ceeform in, hence my 'grenade' scaremongering The fault current that would flow would be massive. I imagine the RCD would trip before the MCB assuming it works.

If you've ever cut through a live bit of twin and earth with a pair of snips you'll know what a bang it can make as the blade edge disappears. With 415V it's just twice as big a bang.

It’s the sort of thing I’d like to test

 

[PaulRainbow]

I don't understand that comment at all. In UK phase to phase voltage is 415V.

Only if correctly connected. Joining them together with the cable you described is trying to join two different phases in parallel.

 

[jakew009]

Only if correctly connected. Joining them together with the cable you described is trying to join two different phases in parallel.

Define ‘correctly connected’?

 

[jakew009]

It’s the sort of thing I’d like to test

Yeah me too. But knowing my luck I’d take out the fuse in the cutout

 

[Seastoke]

Yeah me too. But knowing my luck I’d take out the fuse in the cutout

Remember the earth in a marina is a TT system, and not from the transformer neutral.

 

[Seastoke]

Jake, the two 16 amp plug scenario cannot really happen in a marina as the post on the pontoon must be from the same phase.

 

[rogerthebodger]

My mooring electrical outlet has 4 blue 16 amp outlets and I have checked the phases on each 16 amp outlet and have confirmed they are all from the same phase so in my case so the only issue with 2 16 amp plugs and a 32 A socket would be if one plug plugged in and the second left out the second plug pins could be live and not protected

 

[Elessar]

My mooring electrical outlet has 4 blue 16 amp outlets and I have checked the phases on each 16 amp outlet and have confirmed they are all from the same phase so in my case so the only issue with 2 16 amp plugs and a 32 A socket would be if one plug plugged in and the second left out the second plug pins could be live and not protected

The phases are not the issue . The danger, which is foreseeable, is as you unplug the cable the first plug you take out will have live pins.

Dangerous, potentially lethal and such a cable should never be made.

You describe this as “the only issue”.

It’s not.

It someone is working in the distribution box and has isolated one of the circuits feeding one of your dangerous connectors it will remain live.

 

[st599]

It also depends on where you are. With double pole switches and breakers in common use, when we test installations in the EU, it's quite common to have a phase neutral inversion.

 

[Portofino]

So it’s a bad idea to have twin 16 A leads on a boat when one 32 A will work safer ?

Doesn’t answer why they ( builders ) instal said method = twin 16 s when a 32 will do without the risks talked about ^ ?

Mines on a 15 M berth @ 32 A with one heavy 32 A shore power lead fwiw . The berths we get put in are generally 32 s .If not I carry adapters , or the marina send a sparky with a bag load after I surrender my passport as collateral in the Med .Eg they plonk us in a 24 M @ 64 A pedestal

14/15 M seems the cross over from 16 to 32 A .There’s always gonna be slight overlap boat size wise anyhow .
It how it’s dealt with by builders .

 

[PaulRainbow]

So it’s a bad idea to have twin 16 A leads on a boat when one 32 A will work safer ?

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.