rafiki_
Well-Known Member
Wot Trevor said, it is a ground plate. Same on my Azi.
It's a shocker!
- Thread starter Montemar
- Start date
stillwaters
Well-Known Member
And it's also best not to swim in freshwater marinas!
Ok, chances are it won't be a problem, however, electricity leakage particularly into fresh or brackish water has claimed a number of lives, often children's, in freshwater marinas where either the marina and/or moored boats have been leaking sufficient electricity into the water.
In fact, it only takes a relatively small current in freshwater to disable a swimmer enough to lead to drowning, and then a slightly larger current could actually prove instantly fatal. Additionally, touching something like a charged part of a boat or pontoon whilst still in the water can also be as dangerous.
Ironically saltwater, which is more conductive than freshwater, is actually safer, due to its conductivity being nearer to that of the human body, thereby allowing most of the current to pass around a person on its way to ground.
Having been into quite a few older marinas over the years, where electric supply has been quite erratic, I've sometimes wondered why boats aren't always fitted with isolation transformers, which for the sake of a few hundred pounds would prevent much of the leakage which typically happens. Victron, for instance, even claim that up to 80% of the wear of a boat's anodes could be reduced by fitting one, and they are almost essential on metal hulled boats, especially aluminium ones.
Ok, chances are it won't be a problem, however, electricity leakage particularly into fresh or brackish water has claimed a number of lives, often children's, in freshwater marinas where either the marina and/or moored boats have been leaking sufficient electricity into the water.
In fact, it only takes a relatively small current in freshwater to disable a swimmer enough to lead to drowning, and then a slightly larger current could actually prove instantly fatal. Additionally, touching something like a charged part of a boat or pontoon whilst still in the water can also be as dangerous.
Ironically saltwater, which is more conductive than freshwater, is actually safer, due to its conductivity being nearer to that of the human body, thereby allowing most of the current to pass around a person on its way to ground.
Having been into quite a few older marinas over the years, where electric supply has been quite erratic, I've sometimes wondered why boats aren't always fitted with isolation transformers, which for the sake of a few hundred pounds would prevent much of the leakage which typically happens. Victron, for instance, even claim that up to 80% of the wear of a boat's anodes could be reduced by fitting one, and they are almost essential on metal hulled boats, especially aluminium ones.
BartW
Well-Known Member
it seems that your metalwork is not connected with the mains earth,
you can test this with a AC Volt meter,
if you are unsure about how to safely measure 230V voltages, DON’T do this yourselve, asc a friend or the yard,…
go to the mains supply in the yard where you have plugged the lead to the boat,
measure voltage between the two mains pins
and measure again between each 230V and ground pin,
between the mains pins you should measure approx 230V AC
between one pin and earth you should read the same (approx 230V)
between the other pin and earth you should read 0V (or 1...3 volt max)
if the measurements to earth don't show something like this, you have no or a bad earth.
(in some very rare occasion you should read approx 125V on each pin to ground, but that sort of mains network has become really exceptional, I don’t know for sure in UK)
if you do measure the above, (230V and 0V to ground) your earth connection is ok.
measure the same on a mains socket in your boat,
and Or measure again on the power supply lead, where this is connected to the boat plug,
with this method you can find out if or until where the earth pin measures ok,
If boat supply earth is ok,
then measure voltage between one mains pin and your metalwork,
if this is NOT 230V / 0v, your metalwork is not connected to mains supply earth.
the tinkle can be caused by a electric device's housing / earth that touches your metalwork, and that device is not connected to mains earth.
Or
the boat earth is not connected to shore earth.
In 230v devices with switched power supply’s, sometimes there are capacitors between mains and earth, (RF filter) so that you can “feel” the 230V when the unit is not connected to earth.
This is typical for computer power supply’s, it feels unpleasant, but it is not leathal.
But as soon as the unit is connected to earth, the tickle is gone,
the RCD doesn’t trip, because the current is very low. (impedance from these capacitors is very high at 50hz)
I hope you / someone understands
good luck
Seastoke
Well-Known Member
bart whilst that is basic test the only way to test the earth and rcd is with the proper testers
BartW
Well-Known Member
mine has the same, I guess this is the Italian way of doing the grounding in a boat, I believe brits makes are done different.
this is a grounding plate, for making good contact with the water.
from there goes a flat brass strip, over the total length of the boat, and every metal part, seacock, engine, P-bracket, tanks, etc... are connected to this strip.
also mains earth wire is conneced to this strip,
so in case the shore earth is not good, the boat is very well connected with its own grounding plate to the surrounding water.
when the boat is out of the water, there is ofcause no connection, and then the mains lead should keep this grounding connected to earth.
MapisM
Well-Known Member
Memo to self: don't trust JTB suggestions on electricity.
I don't think it's so impossible that the OP would electrocute himself again, after unplugging the boat from the dock.
Truly yours, the LBOK inventor.
Seastoke
Well-Known Member
i might be wrong but you wont get a good earth from the water ,i would be pleased to see the test ,try your meter one on 230 and one in the water i bet you get no reading
MapisM
Well-Known Member
Is there a different one? I'd be curious to hear the logic.
Genuine question, mind - not meant to prove that Italians do it better, before anyone say so...!
superheat6k
Well-Known Member
I assume the responder here is in the US. A subtle difference is that the UK single phase standard voltage is 240v, rather than 230v. Although this 10volts does not seem significant, the mode of power derivation is completely different.
Generally the UK does not use centre tapped earth substation transformers, whereas the US in many places derives 230v from two phases of a 230v 3 phase supply, where the neutral doesn't exist, and the ground / earth is derived from the distribution star (or wye) point. (UK Standard is 415 v phase to phase +- 6%, or to be really pedantic since ~ 1995 400v +10% - 4%)
I think the idea is that you are at a lower potential for electric shock with each leg at 115v to earth, than we are here where each phase is one leg of the 415v system that distributes the power from the local substation. The derived single phase voltage of the nominal 415v 3 phase UK standard supply) is 240v per each phase to earth (calculated as 415 x 1/Sq Rt 3).
Absence of an effective earth or a non grounded at source neutral can result in the neutral line voltage floating to any level between earth (0 volts) potential and almost full mains voltage, which is why earth > neutral bonding at the supply source is so critical. A bad earth on a non direct bonded system could lead to a neutral floating, this in turn could cause tingling where perhaps 50 or 60 volts is the floated voltage being imposed on the boat's bonding circuit.
For this reason as the prior poster suggests, I would start at the shore power supply point to see if this has 0 volts between neutral and earth. But due to the sheer complexity of why 3 and single phase electrical distribution systems are as they are, if you do not understand then get someone who does to make these checks.
If you do not understand you cannot safely decide if what you are measuring is correct or not.
Nigel Calder's excellent Boatowner's Mechanical & Electrical manual accurately describes both US and European / UK systems, and crucially there differences, and does this without delving to far into the theory of AC electrical systems.
BartW
Well-Known Member
there is a misconception that I read before here on the forum,
In European electric installation you can swap neutral and phase in a monephase installation,
there is absolutely NO need to connect Neutral of your boat with neutral of the shore supply, and phase of the boat on phase of shore power.
In my boat neutral and phase are indicated very clear, but I'm sure that on some occasions shore connection might have been swapped (boats neutral to shore phase, boats phase to shore neutral, without any risc for safety, nor tripping fuses nor rcd's.
Moreover do you know that a standard european "shuko" 230V plug can be plugged in two directions .
The Blue CEE connectors have a stadardisation and a small indication of N and L(phase) on the pins, but I'm sure there are leads around that are reversed, and still everything works safe and sound !
I'm not sure in the UK how house systems are made in that respect,
but I'm quite sure that all brit boats can perfectly run on EU electric supply, so not alway's 100% shure which pin is N and which is L.
(no discussion about the GND pin ofcause )
in a victron is a relais that can connect neutral to ground.
in case the victron is floating (generator or invertor operation) the relay will connect boat earth with one phase (defined as neutral from then. )
this works automatic, the victron unit detects this situation.
superheat6k
Well-Known Member
I am not familiar with European standards, but do know the UK IEE standards generally mean that electrocutions are rare. The issue for boaters is that saltwater is thrown into the mix and often with people who like to fiddle, and some who get close to achieving Darwin award status.
I think reversed neutral / live shore power leads, many of which are home made, are very common, as are occasionally found reversed shore power sockets, and on a properly insulated system are not a problem, but if there is a false neutral somewhere aboard the boat (earth > neutral connection), combined with a poor earth connection then the situation can easily become dangerous.
In such a situation the bonding circuit could end up directly connected to the live connection. Even this only becomes a problem when a person makes a connection between the live bonding circuit and true earth.
This is also why functioning RCDs are so crucial.
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BartW
Well-Known Member
I'm in Belgium, but I'm talking about all Europe,
most of the networks are 230/400V (3 phase with neutral, 230V between neutral and phase, 400V between 2 phases)
they used to be 220/380V and many people still name these voltages.
there are only a few regions left that have the older 3 x 220V network, (neutral is not available or not used in these networks)
the regions that I know of that still have that are the " Leuven" region in Belgium and Toulon region (iirc) in France .
BartW
Well-Known Member
again another misconception, (excuse me for the comment, because you probably meant this ok ! ;-) )
an RCD can perfectly work without a good earth.
example:
take your washing machine at home,
lets assume the earth connection in the socket is not connected
there is a problem in the machine and there is a connection from the phase to the frame.
the rcd will not trip,
if you touch the washing machine while you are standing on the wet floor,
a small current will flow through your body, and the rcd will trip !
ofcause when the earth is good, the rcd might trip sooner,
but rememer that any RCD doesn't need a earth to work.
the RCD test button works without any earth wire connected to the unit.
tbh I know very little about washing machines, but its only about the principle
BartW
Well-Known Member
agree,
but such a fault is extremely unlikely, because this can simply not work (if there is any rcd somewhere in the chain, which is fairly sure nowaday's )
BartW
Well-Known Member
Is there a different one? I'd be curious to hear the logic.
Genuine question, mind - not meant to prove that Italians do it better, before anyone say so...!
some time ago there was a thread, I believe from Portofino, with a question about that brass strip along the bottom of his boat,
and iirc some posters had quite some question marks about that,
(or is this immagination or a dream ? )
I was unable to answer at that moment, but would be interested to learn if this is done differently in other (non IT) boats
Portofino
Well-Known Member
A
There's two -look like copper quite thick like the ones you see running down a church to conduct lightening .
Iirc they conect to anodes bolts through the hull on the transome -- I think ?
Plus the inside of that metal plate between the engines deep in the bilge .
I think they also run fwds up the fwds E room bulkhead in a black box --with more conduit coming out .
Prob those green /yellow wire gathered up .?
Next time I,am on the boat I,ll take some pics .
There are various green /yellow wires connected to internal metal work -but then they run neatly into conduit --so can,t see where they end up .
So I think you are right Bart ,your explanation makes sence --- some sort of GND plate .
Or one is for the GND plate and the other possible anode related ?
Used a Italian boat electrician base in SoF ( sunseeker reccomended ) in 2015 to install Aircon ,galley hob , 80 A Dolphin charger and new 220/24 switchable cockpit fridge .btw -tested every thing through .
I,ll be honest --- it's all a mystery to me this boat 220 v stuff but interesting .
Yes that's right --never really got to the bottom of it .
There's two -look like copper quite thick like the ones you see running down a church to conduct lightening .
Iirc they conect to anodes bolts through the hull on the transome -- I think ?
Plus the inside of that metal plate between the engines deep in the bilge .
I think they also run fwds up the fwds E room bulkhead in a black box --with more conduit coming out .
Prob those green /yellow wire gathered up .?
Next time I,am on the boat I,ll take some pics .
There are various green /yellow wires connected to internal metal work -but then they run neatly into conduit --so can,t see where they end up .
So I think you are right Bart ,your explanation makes sence --- some sort of GND plate .
Or one is for the GND plate and the other possible anode related ?
Used a Italian boat electrician base in SoF ( sunseeker reccomended ) in 2015 to install Aircon ,galley hob , 80 A Dolphin charger and new 220/24 switchable cockpit fridge .btw -tested every thing through .
I,ll be honest --- it's all a mystery to me this boat 220 v stuff but interesting .
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MapisM
Well-Known Member
Yup. 'Dunno whether it's true also internationally, but green+yellow is definitely the color code for GND cables, in IT. :encouragement:
Montemar
Well-Known Member
Thank you to all for the very informative replies.
I measured the voltage between the fold down boarding ladder and wet ground getting 70 VAC. This was with the 'fridge, charger, thermostat for engine room frost protection, chargers for torches, a couple of 13A sockets and dehumidifier only connected. The 12 VDC system was switched off. After switching off the RCD I measured 50 VAC.
As the replies indicate that this was potentially ( !! ) a serious problem I thought a systematic approach was needed. Armed with a multimeter and an electronics degree I checked the 16A to 32A adaptor then then 16/16A mains lead for shorting. I checked the boarding ladder to earth pin on the mains input socket and also to other metalwork and wet ground and got many megohms. The ladder appears to be fixed to the bathing platform and nothing else. I then checked the 16A mains socket on the boat and found the earth lead had broken at the pin. This was a solid conductor unlike the live and neutral leads which were stranded.
After strip down and repair the fault was completely fixed.
I had never detected this at the pontoon though though it is possible that the recent use of the socket caused the problem. A multistranded earth lead would have prevented this.
I am now left wondering where the 70 volts came from considering what was operating and that the boarding ladder was not connected to other metalwork. Even more concerning is the 50 volts with the RCD tripped off! Current flow through a layer of moisture inside the boat?
The next job will be to fit a new RCD and visually check the cable between the input socket and RCD for damage. Earthing the boarding ladders could be a good idea.
Ironically the boat's previous owner was an electrician!
I measured the voltage between the fold down boarding ladder and wet ground getting 70 VAC. This was with the 'fridge, charger, thermostat for engine room frost protection, chargers for torches, a couple of 13A sockets and dehumidifier only connected. The 12 VDC system was switched off. After switching off the RCD I measured 50 VAC.
As the replies indicate that this was potentially ( !! ) a serious problem I thought a systematic approach was needed. Armed with a multimeter and an electronics degree I checked the 16A to 32A adaptor then then 16/16A mains lead for shorting. I checked the boarding ladder to earth pin on the mains input socket and also to other metalwork and wet ground and got many megohms. The ladder appears to be fixed to the bathing platform and nothing else. I then checked the 16A mains socket on the boat and found the earth lead had broken at the pin. This was a solid conductor unlike the live and neutral leads which were stranded.
After strip down and repair the fault was completely fixed.
I had never detected this at the pontoon though though it is possible that the recent use of the socket caused the problem. A multistranded earth lead would have prevented this.
I am now left wondering where the 70 volts came from considering what was operating and that the boarding ladder was not connected to other metalwork. Even more concerning is the 50 volts with the RCD tripped off! Current flow through a layer of moisture inside the boat?
The next job will be to fit a new RCD and visually check the cable between the input socket and RCD for damage. Earthing the boarding ladders could be a good idea.
Ironically the boat's previous owner was an electrician!
superheat6k
Well-Known Member
Excellent that you have identified the primary reason for the voltage, but even with the Earth link broken why was there 70vac present ?
I am not sure this is the RCD, this simply measures a balanced current on each line and trips if it detects an imbalance >30mA. If the current on one line is different to the other then there must be a current leakage and hence disconnection is required.
I would suspect this was simply the neutral floating, have you checked for any continuity between earth pin and neutral pin with everything switched on (shore power unplugged). It would be better to do this check with a megger set to 500volts. If there is any continuity < 5 Megohms, and likely way below this, then unplug your devices one at a time to find the culprit. I would also do this on the user side of the RCD with the RCD disconnected.
Also have you suffered any excessive zinc wastage or other underwater corrosion issues ?
If the answer to my last question is no, then my money is on the engine room heaters.
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BartW
Well-Known Member
before grounding that ladder, you could try to find where that 50v with rcd off, is coming from,
as you say, find the route of the wires from the boat mains socket to the RCD,
with the rcd switched off, non of the 230V boat systems can be the cause (or am I missing something here?)
or try to disconnecting that boat supply in steps...and look what is happening with that 50V (if you understand what I mean)
as sh6k say's I don't suspect the rcd,
rather a squeezed or soaked wire
