Electric current through Hull

[KirstieH]

Hello. I know I am becoming a regular on here and I promise I will start to return the favour as I am learning so much but I just need a little more advice...

 

Yesterday whilst preparing my boat for blacking I noticed a number of pinholes and got myself in a tearful panic thinking they might go right through....I poked a little bit of wire in and found they did not, but was too scared to actually measure them as I had generally had a bad boat day (BBD).

 

HOWEVER.....Whilst down there scraping, I noticed a current in one area of the boat (It was plugged into shore power). I have felt this before on laptops and other electricals...not a shock so much as a dull fizzy buzz (Can't explain)...Is my boat trying to electrocute me? I am trying to love it but I don't think the feeling is mutual!

 

Who should I get to look at her as I don;t want to touch electrics myself (Its the one thing I won't fiddle with)

 

Thank you so much for any advice

 

 

 

 

[Chewbacka]

You should NEVER feel any form of electrical fizz from your boat. Something is seriously wrong.

Unplug shore power until it is fixed.

 

Do you have any small inverters on the boat that are powered up? If so turn that off as well.

 

You then need someone that properly understands boat electrics (240V AC system) to find the problem.

 

Small stray electrical currents will cause corrosion and pitting, but voltages that you can feel, may kill you or others.

 

Sorry I can not tell you what to do to fix it, but there are too many unknowns.

[Tiggs]

There must be no current flowing in your hull - if there is, it is likely that it will destroy it (it may take a few years, but will not last the usual 20-40).

 

If you can feel it, it may be, like you say, similar to laptops with non-earthed switched mode power supplies; although I don't really understand why it would be in only one area.

 

I suggest you get a boat electrics expert to take a look. Sounds like you need to check your earthing arrangements and maybe fit a galvanic isolator or isolation transformer for shore power.

Edited June 29, 2016 by Tiggs

[Loafer]

Agreed. I'd stop that immediately!

[jacko264]

Sorry i am not a electrician but it sounds like a bad earth on something

Please let us know if you find out what it is causing the problem

Graham

[roland elsdon]

Ha...see other post. Galvanic isolator if your boat is on mains. Your electric leak is more worrying than your rust. Can eat a hull. Some people earth boat to mains through charger or inverter, ( inverters use negative return to battery and battery uses negative to engine)

Mains earthed to hull very bad idea.

At least get an rcd but best pull out mains.

Temp solution. Rcd extension lead and battery charger rather than using mains ring.

Never put mains ring in my boats, always use inverter rcd and extension lead

[KirstieH]

Ha...see other post. Galvanic isolator if your boat is on mains. Your electric leak is more worrying than your rust. Can eat a hull. Some people earth boat to mains through charger or inverter, ( inverters use negative return to battery and battery uses negative to engine)

Mains earthed to hull very bad idea.

At least get an rcd but best pull out mains.

Temp solution. Rcd extension lead and battery charger rather than using mains ring.

Never put mains ring in my boats, always use inverter rcd and extension lead

I don't think I get all this so forgive me I do have an inverter (Not pure sine) and battery charger and mains. Would a GI earth the boat? Is something touching the hull which shouldn't? eeekkkkk

[Tony Brooks]

Kirstie, I agree with the rest, stop using a shoreline until this is checked out by someone who catually knows about mains on boats.

.

Ha...see other post. Galvanic isolator if your boat is on mains. Your electric leak is more worrying than your rust. Can eat a hull. Some people earth boat to mains through charger or inverter, ( inverters use negative return to battery and battery uses negative to engine)
Mains earthed to hull very bad idea.
At least get an rcd but best pull out mains.
Temp solution. Rcd extension lead and battery charger rather than using mains ring.
Never put mains ring in my boats, always use inverter rcd and extension lead

 

 

I hope that is just bad wording. If you have any form of mains from any source on a boat there should be a single "earth" to hull bond. Otherwise any RCD may not work and under fault conditions you may kill someone.

 

I hope that you mean that the shoreline "earth" should be "isolated" from the hull bond by an isolation transformer or galvanic isolator.

[Alan de Enfield]

Having read the title - That's a relief - we are moored up in Hull at the moment and I had a moment of Panic.

 

(There are a lot of 'undercurrents' running thru' Hull this week due to the very large Polish Population).

[KirstieH]

Thanks guys.

 

I am not going to sleep on her tonight. Just borrowed a voltage checker and it said it was 1 volt running through...

Having read the title - That's a relief - we are moored up in Hull at the moment and I had a moment of Panic.

 

(There are a lot of 'undercurrents' running thru' Hull this week due to the very large Polish Population).

This is no time for laughs....I could be chargrilled over here!

Sorry 1volt through the hull

[Richard T]

Where is your boat? We can then help you to find a qualified sparky to look at your boat electrics.

[Tiggs]

1V a.c. or d.c.? Have measured both? I don't think you would feel 1V.

 

If 1V is the correct reading, the leakage is probably high resistance so is actually more volts than this until you measure it. This is good since the current capability is low.

 

(and it's not through the hull - volts are "potential difference" equivalent to "pressure" rather than "flow" - amps are "flow")

 

Do you have a connection somewhere that you shouldn't have?

 

Yes. It could be a fault in your wiring or in your equipment.

Edited June 29, 2016 by Tiggs

[Greylady2]

Our Boosted Aerial Cable was touching the rear sliding hatch on the coaxial connections, I got a fuzzy zapping from that few times, could it be a chaffed boosted aerial cable touching your hull.

 

 

I am no sparky and new to boating.

Edited June 29, 2016 by Greylady2

[alan_fincher]

In my view there is quite a bit of bad advice in this thread, (or if not actually bad, certainly easily open to misinterpretation).

 

Whilst fitting a galvanic isolator or isolation transformer is of course good practice, it is still fully acceptable not to have one, and you should not be experiencing what you are. Masking the problem, rather than solving it, is not a good idea. You need to FIX the problem, and neither are a fix.

 

Despite how some posts read, there should be a direct bond to your hull of the earth wire of the 240 volt supply coming in, so either there isn't, or the earth on the supply coming in is not actually at zero volts.

 

When you are measuring the 1 volt, if you have one probe of your multimeter on the hull, where are you connecting the other probe to, please?

 

As has been asked, are you measuring 1 volt DC, or 1 volt AC? I'm surprised you can feel either, if it is genuinely only that.

 

Don't take chances with this!

Edited June 30, 2016 by alan_fincher

[Arf]

I strongly recommend getting a good marine electrician in to check the systems and make any repairs needed.

 

I would also measure the depth of any pitting and check this against the small print of your insurance if you can. I understand that there is a risk it could be invalidated by deep pits. Remedial work might be needed to the hull.

 

Sorry if this is alarming, but this could be vital to prevent more serious heartaches later.

[KirstieH]

Hi all

 

OK so didn't stay on the boat last night.

 

Will check pitt depth but absolutely gutted if it was not picked up by the survey as I paid for and waited for the most recommended surveyor I could find. Whilst I understand it is random hull checking I just can't believe they were missed everyone. Are pitts supposed to be like pin holes/ needle holes?

 

I wll get an electrician in to test everything. How can I ensure they look at the right things? It seems that experts only seem to look for the exact thing you ask so I want to be sure how to phrase it so he / she checks everything. I almost need someone to "Teach" me what to look for. I am eading and learning but there is so much t know, but I will get there...or literally die trying!

[Chewbacka]

Tell him your symptoms, if not sure tell him so.

For example you feel a tingling when using certain electronic devices. Is it all or just some? Are they running on shore power or inverter when you get the tingling?

When you experienced the hull tingling was the boat connected to shore power?

These points will help him/her to narrow down the problem to shore power or inverter.

 

As to the pitting, have you spoken to your surveyor? it is not reasonable that he missed it he should have insurance for you to claim against.

But pitting can be difficult to find if it is not very deep or it is in a small area which was not checked when he did a thickness check, but it sounds like fairly deep.

[alan_fincher]

Asking again.

 

When you measured 1 volt, what were EACH of your meter probes attached to?

 

1 volt AC or 1 volt DC?

[MtB]

Asking again.

 

When you measured 1 volt, what were EACH of your meter probes attached to?

 

1 volt AC or 1 volt DC?

 

 

These are two questions I'd like to see an answer to, too, please.

 

This sounds like a serious problem to me. Forget the pitting for now, concentrate on this electrical fault.

 

Please can you confirm you've unplugged the shore line and turned the inverter OFF.

 

ANY tingling or feeling of electricity indicates a serious fault and needs tracing and fixing. Don't treat this casually.

[markgregoryuk2000]

I thought the whole idea of the isolation transformer or galvanic isolator was so the shore line earth was not connected to the boat as sometimes the shoreline earth is poor and will send current through the boat.

 

The ONE critical Item is that the boat is being blacked so is out of the water, in this case the boat should be connected to the shore line earth as it cannot earth through the water.

 

ETA

 

Had a problem with tingling off of copper pipes at old house so added a new earth spike there to fix it.

Edited June 30, 2016 by markgregoryuk2000

[Paul C]

What's most worrying is that neither the on-board RCD tripped, nor the RCD in the bollard. It might be because its too low a current and that you're particularly sensitive to electricity - but unlikely. As with others, worth getting properly checked. And on a technical note, it appears that the earth bond IS there, but the RCD isn't!

[Tony Brooks]

I thought the whole idea of the isolation transformer or galvanic isolator was so the shore line earth was not connected to the boat as sometimes the shoreline earth is poor and will send current through the boat.

 

The ONE critical Item is that the boat is being blacked so is out of the water, in this case the boat should be connected to the shore line earth as it cannot earth through the water.

 

ETA

 

Had a problem with tingling off of copper pipes at old house so added a new earth spike there to fix it.

 

Those were my thoughts, voltage on the shoreside earth cable but can't be sure. That could also cause the pitting with the boat in the water if no GI or IT is in use. Thinking about it if one can get a tingle the voltage is probably high enough to make the diodes in a GI conduct.

[markgregoryuk2000]

The RCD looks for differences in current between the live and neutral (due to leakage to earth), if the fault is not on the boat IE voltage coming from the shore line earth then the RCD will not trip. Unfortunately leakage to an unearthed boat shell would also not trip an RCD until some one provided that earth.

[ditchcrawler]

Yon need an electrician who works on mains electricity to sort this out, its not a 12 volt system problem. Get the shore line unplugged until it can be sorted. The problem may not even be on your boat but could be on the shore supply bollard, you shore lead or the boat.

[KirstieH]

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.