Electric current through Hull

[KirstieH]

So do I need a Boat / Marine electrician or a normal / house electrician? With they be able to tell if it is a dodgy shore power connection?

 

Apparently the people we purchased it off never used shore power they only used to run the engine for their needs to this is good re hull right?

Edited June 30, 2016 by KirstieH

[alan_fincher]

I put one end of the machine on my knee and the other on the outside of the hull where I had removed the blacking. It is out of the water on blocks and I have unplugged everything taken out shorepower and turned the inverter off.

 

I'm not convinced you are measuring anything useful, and certainly nothing accurately!

 

Note if this is in a boatyard, out of water, I have seen serious issues with power supplies I have plugged into when out for blacking. If you can't rely on their electrics being safe, (and in the case I saw they most certainly were not!), you need to be confident that your boat has the necessary protection on board.

 

Is there any chance the boat is not sitting at the same angle as it would in water. I ask because we had serious issues because we had a boat on an "uphill" slipway, with the 240V power connected to an inlet on the back of the cabin. It was constantly tripping out much of the boatyard. It turned out that the slope of the boat meant that instead of rainwater discharging from the usual gaps in the handrail, it was all running to the back corner, and cascading down into the power connector. When we opened it up, it was both waterlogged and "half fried" inside.

[ditchcrawler]

Hi Guys

 

Thanks so much. Sorry I am teaching all day today so am not near the boat as it is moored 70miles away, adding to my stress.

 

I was prob not using the machine correctly, I just wanted to check that it was real and I wasn't imagining it. A guy lent me the machine but didn't show me how to use it or help me (Not that I expect free help!). As I say I just wanted to see if it read anything. Maybe I was reading me knee!

 

I put one end of the machine on my knee and the other on the outside of the hull where I had removed the blacking. It is out of the water on blocks and I have unplugged everything taken out shorepower and turned the inverter off.

 

It is only the hull everything in the boat was working fine and not giving off any ripples or buzzes. I will not go back on without an expert.

 

I am trying not to wish I hadn't started this and thinking about the long term happiness. I don't mind regular maintainance and fixings but everything is revealing itself at once and I need to remain calm!

 

You guys are great.

You wont feel anything on the boat, It is between the boat and earth that the voltage exists,

[alan_fincher]

So do I need a Boat / Marine electrician or a normal / house electrician? With they be able to tell if it is a dodgy shore power connection?

 

Apparently the people we purchased it off never used shore power they only used to run the engine for their needs to this is good re hull right?

 

A domestic electrician is likely to be useless. You need one experienced in the very different issues that relate to living in a steel box that floats on water, but can be connected to anybody's supply, whether good or bad.

 

Even many people calling themselves marine electricians have proved to be way off the mark, so you really need one by recommendation, not just by plucking a name off the Internet.

 

Where is the boat?

[KirstieH]

Again thank you. I am taking in all advice. I understand my measurements are almost pointless I just wanted to see if was imagining it! I know it holds no value really.

 

OK so the boat is in Medway. - If anyone knows of anyone there! I know it is not inland territory.

 

It is on a flat surface and connected (Not anymore) to a shore power line which is used by another liveaboard on hard standing.

 

Apparently the people we purchased it off never used shore power they only used to run the engine for their needs to this is good re hull right?

 

I really want to sorted ASAP as we have so much to do and need to get to grips with the Pit situation ASAP (I am hoping this is not as bad as It would appear)

Edited June 30, 2016 by KirstieH

[Alan de Enfield]

 

Apparently the people we purchased it off never used shore power they only used to run the engine for their needs to this is good re hull right?

 

 

Unfortunately - not necessarily.

 

If the boat has been in a marina or moored near boats 'hooked-up' to a land-line then the electricity could 'leak' from anywhere and cause pits on any boat, pontoon or metallic structure in the vicinity.

[boathunter]

I saw something interesting today. A boat (not mine) with a 2.5kw inverter. The inverter provided power to the ring main by, wait for it, a 13A plug on the output, plugged into a socket on the ring main. No protection as it bypassed the trips and if you were to pull out the plug it would fry you until the batteries ran down. Oops. The owners had no idea but now they do have stopped using it.

 

I've only had a boat for a few weeks but this kind of dangerous bodgery seems par for the course in boat land. I've been stripping out supposedly professional mains wiring on mine this week, an appalling mish mash of semi-permanently fitted extension leads and so forth, mains cable left under cupboards with bare ends, water leaking onto one such extension lead from a loose pointless extra sink drain pipe tied up behind the hob at half full sink height. All this work had been paid for including the inverter wiring on the other boat.

 

I feel lucky I have at least half a clue, but others don't and have to put their trust in professionals.

Edited June 30, 2016 by boathunter

[ditchcrawler]

I saw something interesting today. A boat (not mine) with a 2.5kw inverter. The inverter provided power to the ring main by, wait for it, a 13A plug on the output, plugged into a socket on the ring main. No protection as it bypassed the trips and if you were to pull out the plug it would fry you until the batteries ran down. Oops. The owners had no idea but now they do have stopped using it.

 

I've only had a boat for a few weeks but this kind of dangerous bodgery seems par for the course in boat land. I've been stripping out supposedly professional mains wiring on mine this week, an appalling mish mash of semi-permanently fitted extension leads and so forth, mains cable left under cupboards with bare ends, water leaking onto one such extension lead from a loose pointless extra sink drain pipe tied up behind the hob at half full sink height. All this work had been paid for including the inverter wiring on the other boat.

 

I feel lucky I have at least half a clue, but others don't and have to put their trust in professionals.

When I was an apprentice there were 4 common types of sockets found in houses. D&S that took a round pin fused plug. the fuse was one leg of the plug, a 3 pin 5 amp and its big brother a 15 Amp three pin, then of course the one we use today the 13 A square pin plug. This meant that working in peoples houses tradesmen needed a variety of adaptor leads. The local Gas depot were issuing there men a set of short leads with a 13A plug on one end and with one of the others on the other end. They then had an extension lead with a 13A rubber socket on each end to use their tools from.

Unbelievable but true.

[boathunter]

When I was an apprentice there were 4 common types of sockets found in houses. D&S that took a round pin fused plug. the fuse was one leg of the plug, a 3 pin 5 amp and its big brother a 15 Amp three pin, then of course the one we use today the 13 A square pin plug. This meant that working in peoples houses tradesmen needed a variety of adaptor leads. The local Gas depot were issuing there men a set of short leads with a 13A plug on one end and with one of the others on the other end. They then had an extension lead with a 13A rubber socket on each end to use their tools from.

Unbelievable but true.

It's sort of slightly alright if you're aware? Chap didn't believe me as we were just chatting and I happened to notice. Then he pulled the plug to show me I must be mistaken and got a belt.

[markgregoryuk2000]

Once disconnected a shore line (at the boat end) only to find I was hold a blue circular plug rather than a socket.

 

Quickly sent the owner off to disconnect from the Bollard while I held onto the plug.

 

I know, should always disconnect bollard end first, so there's no chance of dropping a live socket in the water.

[Paul C]

Once disconnected a shore line (at the boat end) only to find I was hold a blue circular plug rather than a socket.

 

Quickly sent the owner off to disconnect from the Bollard while I held onto the plug.

 

I know, should always disconnect bollard end first, so there's no chance of dropping a live socket in the water.

 

Shouldn't be an issue unless you lick the socket.

[roland elsdon]

Sorry meant multiple mains earthed to hull bad idea, poor eyesight and iPhone. Have seen boat wired in past with hull used as earth return from individual sockets rather than single earth bonding. God knows why. On the same boat the 12v negative was also on the hull from all fittings with a single positive wire.

Didn't buy it. Hair stood on end.

[WotEver]

 

Unfortunately - not necessarily.

 

If the boat has been in a marina or moored near boats 'hooked-up' to a land-line then the electricity could 'leak' from anywhere and cause pits on any boat, pontoon or metallic structure in the vicinity.

Not if it's not connected to shore power it couldn't. There's no circuit. It's just a lump of steel floating on the water.

 

Tony

[BruceinSanity]

Hair stood on end.

Isn't this exactly what we are worrying will happen to the OP?

 

Joking aside, I absolutely agree with all the previous posts. Don't connect the shoreline again until the boat has been checked over by a competent marine sparks.

[MtB]

So do I need a Boat / Marine electrician or a normal / house electrician? With they be able to tell if it is a dodgy shore power connection?

 

Apparently the people we purchased it off never used shore power they only used to run the engine for their needs to this is good re hull right?

 

 

KirstieH, thanks for the photo.

 

The most critically important thing is missing from the photo. WHERE have you touched the ends of the two leads to get that reading of 0.12V DC?

[Bill]

Not if it's not connected to shore power it couldn't. There's no circuit. It's just a lump of steel floating on the water.

 

Tony

 

If its moored up against an earthed metal structure it can become part of the circuit, does not need its own shore power earth connection. Rare I admit but not impossible.

[Alan de Enfield]

 

If its moored up against an earthed metal structure it can become part of the circuit, does not need its own shore power earth connection. Rare I admit but not impossible.

 

That is what I was alluding to - It was the explanation put forward (for a non-connected boat) for pitting on a boat in a marina we used a while ago.

[ditchcrawler]

 

If its moored up against an earthed metal structure it can become part of the circuit, does not need its own shore power earth connection. Rare I admit but not impossible.

Like this maybe, seen today on the Coventry Canal, one each end.

[Alan de Enfield]

Just as we do when refuelling aircraft - crocodile clip to earth.

[ditchcrawler]

Just as we do when refuelling aircraft - crocodile clip to earth.

These ones weren't on a wind out cable reel. been there got the tee shirt

[Tony Brooks]

Just as we do when refuelling aircraft - crocodile clip to earth.

 

Yes, but that is to prevent static causing a spark. In this case its about trying to equalise the voltage in hull and water/ground.

 

It may help if you have a shoreline and no GI/IT but if no shoreline is in use it is more likely to allow the hull to form a cell with the ground and corrode itself. Much better leave the hull totally isolated from the soii.