Electric Shock - Ouch!

[markc]

Firstly, it was my fault. The other day I needed to wire in a spur to a socket on the boat to power a new TV lift and TV. For reasons known only to the stupid part of my brain I only switched off the breaker for the 220V sockets, but the less stupid part of my brain suggested I test that there was no power with my multi-meter - it read zero on 200v (obviously one probe was in a duff place). I then proceeded to wire in the spur behind the the existing socket. I then got a bit of a poke. Thankfully I lived to tell the tale, but what surprised me was that the RCD on the boat (pic below) didn't trip, nor did the breaker on the quay. Question is, should I be worried and if so, should changing the RCD below be on my list of jobs?

 

[superheat6k]

To provide an answer it would be necessary to understand more about your wiring layout. Could be you bridged live and neutral, in which case the RCD would not see a fault. It would hurt a lot and would leave you feeling quite unpleasant for quite some while.

The only way to ensure complete isolation on a boat's shore power is to unplug the lead at both ends.

 

[jrudge]

As far as I know the test is a genuine test ( it applies the appropriate miliamps ) to make it trigger.

If he neutral and live joined the breaker would trip.

Try it again and see what happens !!

If you turn off that rcd does the socket you are referring to go off - ie is it protecting that circuit ?

 

[MapisM]

If you turn off that rcd does the socket you are referring to go off - ie is it protecting that circuit ?

It definitely should.
I mean, I'm pretty sure that in any OEM Ferretti electrical panel, the RCD is upstream of anything AC onboard.
Can't see why anyone should have messed with that...

 

[BruceK]

Question. Doesn't that unit trip when it sees a 30mA imbalance to neutral or earth? Therefore if he was wiring a spur and bridge a gap to another neutral or earth the trip wouldn't necessarily be triggered? My knowlege of these things is dangerous but that is my understanding of it

 

[jrudge]

https://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=4503

Forum post about something similar. It will trip so it won’t kill you but you still get a jolt !

 

[Lon nan Gruagach]

I suggest that you bridged live and neutral while remaining isolated from any other significant conductor. That would present you as a rather small but valid load to the supply.

If there is a lesson to be learned, it is test the tester (and your application of it). Before performing a no volt test, first check that it shows volts on the energised circuit, before you do whatever you have decided will isolate it.

You might also test your boat's wiring by creating test faults. Ideally something like a 10W light bulb as a live to earth fault. An a direct short neutral to earth will trip provided you have appliances totalling more than 100W in use on that circuit.

 

[jrudge]

I do quite a bit of electric work on the boat. I always unplug the shore supply and don’t rely on turning off switches. I do the same at home. Turn off the lot I had a bad shock about 10 years ago and turning the whole lot off is a simpler way to go !

 

[simonfraser]

Stick an insulated set of thin nosed metal pliers accross the wires you think you have isolated.
Nothing to go wrong in your ‘test’ meter.

 

[markc]

I do quite a bit of electric work on the boat. I always unplug the shore supply and don’t rely on turning off switches. I do the same at home. Turn off the lot I had a bad shock about 10 years ago and turning the whole lot off is a simpler way to go !

Agreed! TBH, that's what I normally do, and will do without fail in future!

What worries me about this is the potential for someone getting a shock from a fault on the boat and the RCD not protecting them.

 

[Lon nan Gruagach]

Stick an insulated set of thin nosed metal pliers accross the wires you think you have isolated.
Nothing to go wrong in your ‘test’ meter.

Not good!
Short circuit currents can hit thousands of amps before breakers have a chance to trip. The resulting explosion of the tips of your pliers can cause significant damage.

 

[BartW]

when you were tweeking the wires, and you most probably made a short with your fingers between live and neutral,
the RCD is NOT supposed to switch off,

and due to the resistance of your body, the current was not big enough to switch off any cirquit breaker...

in any 230V installation, you're supposed never to be in a situation to make a short between live and neutral, (with the body)
the RCD is there to protect that current is flowing through your body from live to earth
in this case on your boat, your body was touching the GRP or the furniture, = isolated from the "earth",


so to me the situation seems "normal"

 

[Portofino]

I do quite a bit of electric work on the boat. I always unplug the shore supply and don’t rely on turning off switches. I do the same at home. Turn off the lot I had a bad shock about 10 years ago and turning the whole lot off is a simpler way to go !

+1

Esp with the boat I pull the plug always and turn the 3 way switch to off .
There’s seperate a inverter somewhere for the hot water ,so I also make sure that’s off and the telly ,so that’s turned off too .
Obviously theses inverters usually have nowt to do with say replacing a cabin socket , but same principle they are a supply 220 v —- and you never know behind panels etc in you get in a muddle with the wiring ,or the previous owners been in there and not put stuff back correctly.

When a got the boat we had a very good boat sparky ( Sunseeker recommendation) retro fit the Aircon .
I also commissioned a new hob - induction, new cockpit fridge - 24 / 220 v auto switchable ,new charger to an upto date all singing and dancing , point is he also replaced the RCD and generally went over everything-inc the geny out etc - checking it was up to running the Aircon .

For me it was a big step up in sophistication from what we had before systems wise and like Marc I just wanted to know not assume all the electrics were - well in a word safe !

Our RCD on the boat trips occasionally if there too much load put on .Like say in the winter oil heaters ,on then somebody turns the hob on the cook , then the kettle I guess we exceed our 32 A x 220 V from the shore .

Both trip, shore and boat RCD when somebody plugs a wet ended shore power lead in , or hoses down the socket by accident. They just trip the line holder thus far has not felt a jolt .

Interesting thread

 

[Grubble]

Agreed! TBH, that's what I normally do, and will do without fail in future!

What worries me about this is the potential for someone getting a shock from a fault on the boat and the RCD not protecting them.

You should invest in a mains socket tester with an RCD test built in. These are cheap enough on ebay. Plug the tester into your sockets one by one and you can a) check they are wired correctly and b) test the RCD protection on the circuit.

Something like this:-

https://www.ebay.co.uk/itm/Hilka-13A-Mains-LED-Socket-Tester-RCD-Test-230v-UK-Plug/152788433213

You should also invest in a non-contact mains tester - these buzz and light up when near to a live wire. Again cheap insurance that you are not about to kill yourself when doing these kind of jobs and as a bonus are very useful for identifying which circuit/cable is which.

 

[markc]

Grubble - I think a mains socket tester is a good idea, thanks. I always use a non-contact tester when I'm working on electrics at home, and I'm normally super safe... I have no idea what I was thinking on the day in question... I was probably so wrapped up in the range of jobs I had to do, I was running on some sort of daft auto-pilot

I did check afterwards that the circuit was shut off when I manually tripped the RCD, and it was. What had happened is that at some point in the past, this socket had been added to the boat, and instead of hooking it up to the existing ring for the sockets, added it to a new and unmarked breaker on the aux panel.

 

[jrudge]

This happens all the time. It is a shame that they are so difficult to label In an oem fashion - so it remains only known to true person who fitted it

 

[penberth3]

Stick an insulated set of thin nosed metal pliers accross the wires you think you have isolated.
Nothing to go wrong in your ‘test’ meter.

I'd suggest any enthusiastic amateurs ignore that idiotic comment. 230V isn't something to joke about.

 

[TQA]

If it were my boat I would be calling in a professional electrician. I do not mess about with 250 volts.

 

[Seastoke]

when you were tweeking the wires, and you most probably made a short with your fingers between live and neutral,
the RCD is NOT supposed to switch off,

and due to the resistance of your body, the current was not big enough to switch off any cirquit breaker...

in any 230V installation, you're supposed never to be in a situation to make a short between live and neutral, (with the body)
the RCD is there to protect that current is flowing through your body from live to earth
in this case on your boat, your body was touching the GRP or the furniture, = isolated from the "earth",


so to me the situation seems "normal"

if I am correct the unit is an rcbo which detects shorts between live and neutral and is a 40amp type c ,and the rcd side is 30 ma

 

[Seastoke]

you can have a test done on your rcd ,there are 5 tests you can have done