It's a shocker!

BartW said:
I don't suspect the rcd, rather a squeezed or soaked wire
Click to expand...
Aargh! Don't mention soaked wires.
That's a small nightmare I used to struggle with at home...
...The laundry in the basement has an external pump to discharge grey waters, and it's connected to the same power line of the washing and drying machines.
Unfortunately, the last bit of cable feeding the pump is permanently soaked, and even after replacing it with a better insulated one, the standard 30mA RCD tripped off frequently.
Eventually, a 300mA RCD with reinforced immunity fixed the problem.
I just hope that SWMBO would withstand the 300mA current while using the washing machine, if the worst comes to the worst... :rolleyes: :p
 
BartW said:
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 :)
Click to expand...

bart i have to disagree yes it might trip but it would be relying on your body as a leakage to trip it ,when this happens the chance of dying is very high ,or why do we bother with the earth wire ,just make everything double insulated ,,anyway the message is the test button tell you an rcd is performing right and having 230 volt between live and neutral does not guarantee there is a good earth ,but hay ho have it tested properly or take the risk
 
I think if i knew the previous owner was an "electrician", i would get a marine electrician to check the boat over. Boats are definitely not the same as houses and most electricians don't understand the need for galvanic protection, lightening protection and a decent earth for safety and how they should be constructed on a boat. I once owned a house that previously belonged to an electrician, it was an electrical nightmare.
 
seastoke said:
bart i have to disagree yes it might trip but it would be relying on your body as a leakage to trip it ,when this happens the chance of dying is very high ,or why do we bother with the earth wire ,just make everything double insulated ,,anyway the message is the test button tell you an rcd is performing right and having 230 volt between live and neutral does not guarantee there is a good earth ,but hay ho have it tested properly or take the risk
Click to expand...

Oh sure with a good earth any installation is much more safer,

but my point is, that a installation is much safer with a RCD than without,
even without a good earth it will trip in cases like:

there is a current leakage in your washing machine and the leak goes through the water supply
there is a leak in the central heating and the leak goes through the pipes
there is a leak in a domestic water boiler, and the current goes through the fixings of the boiler,
or in some situations current goes through the human body,

in all these situations the RCD will trip when the leak current goes over the RCD treshold (standard 30ma or 300ma in europe) and without a good earth,

again,
a RCD does not need a earth connection to work,
with a good earth all these examples will be more safe.
 
superheat6k said:
I thought 30mA was the limit of effective safe operation for an RCD. Isn't 300mA somewhat on the high side ?
Click to expand...

Regulation in B for domestic house installation is 300ma, and a seperate cirquit at 30ma for bathrooms and washing rooms, pools, etc. ( or you can do everything at 30ma)

I've seen similar in other EU country's but don't know the specific regulations.


In my boat I have a Residual Current Meter, (with alarm) permanently installed in my 230v supply systems.
 
kashurst said:
I think if i knew the previous owner was an "electrician", i would get a marine electrician to check the boat over. Boats are definitely not the same as houses and most electricians don't understand the need for galvanic protection, lightening protection and a decent earth for safety and how they should be constructed on a boat. I once owned a house that previously belonged to an electrician, it was an electrical nightmare.
Click to expand...

I agree. Everything except the 230 volt stuff is however straightforward and easy enough to understand. The problem with 230 volt stuff is it can kill you! If wiring and connections are done properly, carefully and take account of the marine environment then there should not be a problem. I suspect my boat may be a bit like your house in that somewhere something has been badly wired up between the input socket to the boat and the RCD on the main fuse panel. I think I know what it is namely a feed to a second RCD before the immersion heater. I bet there is a feeble little pallet box for the spur off covered in condensation! The problem is where is it located? Probably right next to the boarding ladder where I got the tingle!
 
BartW said:
Regulation in B for domestic house installation is 300ma, and a seperate cirquit at 30ma for bathrooms and washing rooms, pools, etc. ( or you can do everything at 30ma)

I've seen similar in other EU country's but don't know the specific regulations.
Click to expand...
B, I'm not sure whether it's a formal rule here in IT or not (btw, I was told that the regulation changed recently, and I've yet to see changes which are not in the direction of higher restrictions...), but common practice is definitely 30mA max in domestic installations, with a strong recommendation of 10mA RCD + dedicated power line for the Jacuzzi (if any).
I've only seen 300mA RCDs used in industrial environments.
Otoh, I just had no other practical solution to fix the issue I mentioned... :o

BartW said:
In my boat I have a Residual Current Meter, (with alarm) permanently installed in my 230v supply systems.
Click to expand...
Niiiice! Can you possibly post a link to the device that you would recommend?
 
superheat6k said:
It could also be lethal. If for instance another numpty had cross wired the supply lead live and neutral, the boats metal work could reach full mains voltage. This would be more than a tingle.
Click to expand...
Here's my story.
Arrived at a new marina a few days ago & found "big" sockets on the 16A hook-ups. Got the adapter (big plug, small socket, connected by short lead) out of the locker and plugged in. All tickety-boo. The adapter came with the boat, never used it before.
On Friday we were doing a job which involved removing instrument panels. We found a coil of cable ending in 3 bare conductors protected only by heat shrink, the cable labelled 220v. And it was live. So we bought a junction box, cut all power (including inverter of course) and terminated the cable properly in the junction box. Powered up again and tested.... the neutral was live and the positive wasn't. Huh? It was only then, for the first time since we arrived, that I noticed that the tiny little reverse polarity warning light was on. Detective work followed and I can think of at least 2 other forumites who are ahead of me at this point.
The adapter was cross-wired, and its 16A "small" socket is not marked correctly for the UK. The boat travelled around quite a bit including Scandinavia in its last ownership. We think the adapter may have been deliberately set up for a location where live and neutral are the other way round. Anyway, it was a genuine LBOK.
Of course I should have tested the adapter before I used it. But I didn't. And there is an example of how the potentially lethal situation can arise. If I'd noticed the reverse polarity light we'd have solved the problem straight away. I will next time, promise.
(My favourite LBOK story is the caravan we bought where the previous owner had provided an additional fixed plug for the incoming hookup lead, at toddler height, "protected" by a plastic flap :disgust:)
 
MapisM said:
Niiiice! Can you possibly post a link to the device that you would recommend?
Click to expand...

the device is a Bender RCMA420-D-2 (display) & W35AB (measurement coil)
http://www.bender.org/documents/RCMA420_datasheet_NAE1042051.pdf

here you can see the display unit, on the top right corner,
(the display's shows 8ma of Residual Curent at that moment)
don't have a picture from the coil

IMG_2865.jpg
 
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