Never mess with 240V

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mariadz

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Please no comments along the lines of “no place for 240V on a boat”....please! Or USB chargers :) I know.

I had recently fixed the windlass remote and flushed with my success decided to swap a couple of 240V sockets. I have done this loads of time before so shouldn’t be an issue and a five minute job, at least until the flash bang as I realised that the power was back on! It presented an interesting symptom.

https://mariadz.com/2018/04/30/replacing-sockets/
 
I used the type that has a light on each switch for all the double sockets so I can double check whether each socket is live or not. I also unplug the lead from the boat before doing anything but a dead light check is also a comfort.
 
I usually find that very little voltage reaches my boat when I pull the mains cord from its plug-in attachment.
I'm reading Darwin at the moment.
 
It is good of the OP to admit what he has done here. A classic reminder that electricity is safe until you forget that it is dangerous. Doing anything with 240v systems on a boat other than plugging something in - remove the shore power connection first and ideally keep the lead and its plug in your sight as you work.
 
easy done. especially if the wife turns on the power again to have a cup of tea... i keep a tester screwdriver handy, and tape the breaker off now. or do it when she is out(!)
 
I don't see why anyone would bother with testing with a meter or those fancy socket testers just to see if the systems live.

Just unplug the shore power, you wouldn't change a jigsaw blade with it plugged in. (or at least I hope you wouldn't) For the extra 1 minute it takes to do its worth it ten times over.
 
Ceirwan said:
I don't see why anyone would bother with testing with a meter or those fancy socket testers just to see if the systems live.

Just unplug the shore power,...
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That might be OK when you know you've only got one feed, and you're absolutely sure you've disconnected the right one. Otherwise, "never assume", and check anyway.
 
When in the 70's ( please correct me as this is from long memory ) Mike McmUllen was fitting out his trimaran ' Three Cheers 'for the OSTAR at Plymouth his wife Lizzie ( also v experienced sailor ) dropped a 240 volt drill in - no C/B's in those days - electrocuted.

Mike and Three Cheers started and went a long way on the northern route I believe then never heard of again - eventually a long time later bits of the boat washed up.

They said Mr McMullen was very strong mentally and he must have been run down by a ship or something, but she was the love of his life, if I had been in that situation I might well have been past caring much what happened re weather etc...
 
We would also need to switch the inverter off. To be fair we have indicator lights on the panel for the shore power. My usual technique is if a panel or electrical wires are open then the power is off. The key lesson learned for me is not get distracted or half finish a job. If you do, redo your checks as if starting the job.
 
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Ceirwan said:
I don't see why anyone would bother with testing with a meter or those fancy socket testers just to see if the systems live.

Just unplug the shore power, you wouldn't change a jigsaw blade with it plugged in. (or at least I hope you wouldn't) For the extra 1 minute it takes to do its worth it ten times over.
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Always check with a meter.... It is a requirement for all qualified electricians to do so if working on any exposed high voltage conductors.

The only time I didn't I had serious shock off a cable that I had disconnected at both ends....
Induced voltage. On many marinas your shore power could well run alongside someone else's for some distance. Just saying your advice to unplug is not a safe working practice for a professional so why be a dead amateur.
 
Make sure you disconnect yourself then check and check again. When I asked SWMBO to disconnect the shorepower, not only did I get a shock but the neighbours were annoyed that their power had gone!
 
Checking sockets with a meter is a little fiddly on UK sockets, as they have a shield over the contacts which is moved out of the way by the earth prong on a plug. It can easily be moved with e.g. a screwdriver, but you'll need a third hand... My meter (Brymen BM257s) actually includes non-contact voltage detection, but I would still measure after removing the cover.
 
TSB240 said:
Always check with a meter.... It is a requirement for all qualified electricians to do so if working on any exposed high voltage conductors.

The only time I didn't I had serious shock off a cable that I had disconnected at both ends....
Induced voltage. On many marinas your shore power could well run alongside someone else's for some distance. Just saying your advice to unplug is not a safe working practice for a professional so why be a dead amateur.
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Well in answer to the induction point, which as well as being incredibly unlikely is simply to unplug it at the boat end, this even saves you from walking down the pontoon. I'm sure its good practice to test it as well.

People can do what they want, but I'd say its common sense to pull the plug out of the shore power and turn off the inverter when working on 240v in a damp salty environment.
 
superheat6k said:
It is good of the OP to admit what he has done here. A classic reminder that electricity is safe until you forget that it is dangerous. Doing anything with 240v systems on a boat other than plugging something in - remove the shore power connection first and ideally keep the lead and its plug in your sight as you work.
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:encouragement:

During my mid teens, I pulled the electric lawnmower cable too hard and yanked the wires out of the socket. Fetching a screwdriver and turning the power off I returned to kneel on the damp grass to make the repair. The wire needed stripping, so I used my teeth as usual. This was before the advent of RCDs. I hadn't disconnected the mains!

I believe I was saved because the action of stripping with teeth is to pull the wire out of your mouth and the rather sever jolt I received sped the disconnect. I was on my own and fortunately didn't loose consciousness.

I immediately resolved to always have the "pointed end" of an extension cable (which is what a boat's shore power cable is) in sight when working on the other end. That was 45 years ago and I still follow my rule.

A couple of years ago I discovered that an old friend uses my story during the induction of all of his new engineers.

John
 
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