st599
Well-Known Member
I remember working in a Van with a hydraulic mast once - there was a warning that if we hit an overhead cable and couldn't identify it as sub 1kV, the SOP was to leap out the back ensuring we landed 11m away.
Earthing 'mains' circuit on my boat
- Thread starter pcatterall
- Start date
I remember working in a Van with a hydraulic mast once - there was a warning that if we hit an overhead cable and couldn't identify it as sub 1kV, the SOP was to leap out the back ensuring we landed 11m away.
PaulRainbow
Well-Known Member
That's true, but the RCD relies on correct wiring installation.
If the boat only has shore power it's reliant on the shoreside installation being correctly grounded, any failure shoreside could mean stray current in the water. Grounding the vessels PE to the water gives a second path to safety that is entirely self contained on the boat. Shoreside installations have to be fitted with ground fault and over current protection (RCD/MCB/RCBO etc), but we still have out own RCD and MCBs onboard, so we don't rely on someone elses installation protecting us and our boats.
It's becoming more and more commonplace for boats to be fitted with inverters and generators. If the vessels PE isn't connected to the water the onboard RCD is unlikely to work and anyone in the water has no protection against electric shock from faulty systems leaking current into the water.
st599
Well-Known Member
What happens if you're in a Marina in say Germany which has centre-tapped earths? (Do they still have those?)
dankilb
Well-Known Member
Thanks Paul - those do look the business:
I’ve only got the Marinco socket, which was being flogged off cheap(ish) so I could probably get back close to what I paid...
You can see why it was cheap, when the 32A plug alone is >£100! But I didn’t know they were prone to melty plug syndrome - assumed for the money they were ‘one of the good ones’!
Cheers, as always
PaulRainbow
Well-Known Member
If the boat is wired correctly, should all work OK.
PaulRainbow
Well-Known Member
Thanks Paul - those do look the business:
I’ve only got the Marinco socket, which was being flogged off cheap(ish) so I could probably get back close to what I paid...
You can see why it was cheap, when the 32A plug alone is >£100! But I didn’t know they were prone to melty plug syndrome - assumed for the money they were ‘one of the good ones’!
Cheers, as always
I've changed a few that haven't looked too healthy. If you do some Googling there's lots that have melted
The ratio one will actually take the blue plastic site style plugs, but they're not waterproof, so you get a good contact, plus the stainless one is nice and shiny
superheat6k
Well-Known Member
That is truly shocking !It might be worth remembering that it's not so important in sea water, as i understand it, but it certainly bears some though for those who boat in fresh water.
I'm also not keen at all on a BSS type scheme, but i am concerned about the 240v systems on a boat. The cheap Chinese inverters and lack of knowledge of DIY installers is a disaster waiting to happen. I have no doubt that we'll be reading about someone dying or being seriously harmed by such installations anything soon.
I see some shocking 240v wiring on an all too regular basis, this picture is from a fairly modern mobo, circa £200K in value that my client had just purchased. The client wanted to be sure that everything was 100% correct, so in addition to fitting a new nav suite, my remit was to check everything and fix anything that was less than 100% correct, a very sensible man. There was a double socket, spurred of off the fridge ! Someone had added two more sockets, all spurred off of a galley socket, using a mix of any old cable they had lying around.
You can see why i jump up and down a bit in some of the AC/Inverter threads when people start arguing that the Earths don't need connecting
View attachment 109554
jdc
Well-Known Member
I end up confused about what I should actually do to my actual boat. The neutral is NOT bonded to earth on the boat, but the cases of equipment are bonded to the anodes, prop-shaft and SSB ground-plane, which are NOT connected to the incoming earth of the mains lead. All equipment is double insulated.
Post 10 seems to imply that Neutral and Earth must be connected at the boat. But that's not what I have. What I have is a TT system - which is after-all exactly what is normal for sheds etc where they have lots of exposed metal parts. (It's also what I have for my electric car charge point, although the relevance of this is unclear but a boat has some points in common, including much stored DC energy and inverters and battery chargers, but usually lower Voltages than an EV's propulsion battery).
So, making it as robust as possible, what, if anything, should I change?
To help it's perhaps worth listing some of the common situations which one finds oneself in:
(1a) A UK marina, afloat. The Earth and Neutral are bonded together upstream of the boat, possibly in a (3-phase) TN-S system.
(1b) A UK marina, ashore. The Earth and Neutral are bonded together upstream of the boat, possibly in a (3-phase) TN-S system.
(2) A marina in Spain where the neutral and live are often inverted with respect to earth. God knows what system is used ('system' is too grand a word here...)
(3) A foreign marina where the supply is 127V 3-phase so one gets 220V between two phases. It's symmetrical about earth.
(4) My 230V generator. It has neutral connected to earth at the generator (so 'up-stream' of the selector switch).
For 1a, if I connect neutral to earth at the boat, the marina's RCD often trips out.
For 1b, if I connect neutral to earth at the boat, the marina's supply doesn't trip, but I fear there may be a few Volts between the prop-shaft and the local ground.
For 2 I simply change the polarity with the switch (the boat has a swap polarity change-over switch and a warning neon between neutral and earth)
For 3, which is what one routinely sees in 'American' places like Brazil, or the Caribbean, connecting neutral to earth would be dubious, and anyway it trips my RCD.
Situation 4 is pretty normal I think!
At present I have decided to leave it as a TT system, which is contrary to what I understood from post 10, but I am v. willing to learn!
Post 10 seems to imply that Neutral and Earth must be connected at the boat. But that's not what I have. What I have is a TT system - which is after-all exactly what is normal for sheds etc where they have lots of exposed metal parts. (It's also what I have for my electric car charge point, although the relevance of this is unclear but a boat has some points in common, including much stored DC energy and inverters and battery chargers, but usually lower Voltages than an EV's propulsion battery).
So, making it as robust as possible, what, if anything, should I change?
To help it's perhaps worth listing some of the common situations which one finds oneself in:
(1a) A UK marina, afloat. The Earth and Neutral are bonded together upstream of the boat, possibly in a (3-phase) TN-S system.
(1b) A UK marina, ashore. The Earth and Neutral are bonded together upstream of the boat, possibly in a (3-phase) TN-S system.
(2) A marina in Spain where the neutral and live are often inverted with respect to earth. God knows what system is used ('system' is too grand a word here...)
(3) A foreign marina where the supply is 127V 3-phase so one gets 220V between two phases. It's symmetrical about earth.
(4) My 230V generator. It has neutral connected to earth at the generator (so 'up-stream' of the selector switch).
For 1a, if I connect neutral to earth at the boat, the marina's RCD often trips out.
For 1b, if I connect neutral to earth at the boat, the marina's supply doesn't trip, but I fear there may be a few Volts between the prop-shaft and the local ground.
For 2 I simply change the polarity with the switch (the boat has a swap polarity change-over switch and a warning neon between neutral and earth)
For 3, which is what one routinely sees in 'American' places like Brazil, or the Caribbean, connecting neutral to earth would be dubious, and anyway it trips my RCD.
Situation 4 is pretty normal I think!
At present I have decided to leave it as a TT system, which is contrary to what I understood from post 10, but I am v. willing to learn!
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PaulRainbow
Well-Known Member
Post #10 certainly does not suggest bonding shore power on the boat. The only mentions of bonding neutral and Earth are in the Section "Inverters and Generators", which states
"The neutral and Earth must be bonded at source "
Shore power neutral and Earth should absolutely not be bonded on the boat.
But that's not what I have. What I have is a TT system - which is after-all exactly what is normal for sheds etc where they have lots of exposed metal parts. (It's also what I have for my electric car charge point, although the relevance of this is unclear but a boat has some points in common, including much stored DC energy and inverters and battery chargers, but usually lower Voltages than an EV's propulsion battery).
All of these situations are covered with the standard installation i described for shore power, with the addition of a polarity warning device (buzzer or lamp), as required by current regs.
That's correct and how i described it in post #10
Neutral and Earth are only bonded at source, you must not bond twice.
That's OK
That's centre tapped. Standard wiring as previously described will be OK
You have misunderstood post #10, sounds like you have mixed up ignored the various headings.
Please, stop bonding neutral and Earth on the boat, they should only be bonded at source, as you generator is.
PaulRainbow
Well-Known Member
jdc
Well-Known Member
Many thanks for your detailed response. For the avoidance of doubt I don't bond neutral and earth at the boat! It seems that I must have misunderstood / misread what you meant in your post #10. But that's not an attack on you!
PS: I think the confusion arose because the heading 'Fixed Installations' is not indented or numbered to make clear that it's within / subsidiary to the 'Inverters and Generators' section.
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