Earth leakage

[Trevethan]

The power keeps popping at the pontoon sometimes straightaway, sometimes after 10 to 30 minutes or so.

I've more or less isolated the cause as the battery charger.

A chap at Sterling said that it was unlikely that the charger was the fault, but suggested the cause might be earth leakage, especially since the weather is a bit damp.

We share a power stanchion with someone else and the problem has pretty much developed since she hooked up... however the trip still goes even when we are on our own so I guess its a coincindence.

The questions are -- Is what the Sterling chap says reasonable?
How do I trace the leakage -- multimetre set to measure amps and bridge live and earth and neutral and earth?

What else might be the problem?

I have checked each breaker in the 240v consumer unit and the wiring appears fine.

The voltage live earth is 232, ditto to neutral.

The batteries are 2 x 200 amp semi traction. about 2 years old and sow about 13 volts when charged. They could probably do with a top up though as the electrolyte level looks a little low.

But would that cause problems?

Any other suggestions?


Cheers,

Nick

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[Robin]

We had a similar problem after a period of heavy rain which I eventually traced to the 'waterproof' socket the shore cable plugged into. Although the wiring looked OK and I trimmed it back and remade the connections the trip still went. I had previously tried another shore lead and tried turning everything 220v on board off, including the charger and all the 220v switches/RCD trips so the culprit had to be on board either in the wiring from the socket or in the socket itself. I tried dismantling the socket and cleaning every part in case there was a leak path somewhere, but it didn't work. I then fitted a new socket and hey presto problem solved.

Can you borrow another lead to try? If that works you know the problem is in your lead (probably in one of the connectors), if it doesn't then look at the on-board part of the system and starting from the socket outside that gets wet.

Whatever you do be very careful with 220v AC, around water especially, disconnect the cable every time at the marina end before taking anything apart

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by Robin on 09/02/2004 11:01 (server time).</FONT></P>

 

[Trevethan]

I have some spare cable, I'll knock up a new lead... but that doesn't explain why the battery chargers causes it to fail and a 500 wat panel heater doesn't... of course the 500 watt panel cable isn't earthed -- maybe something to do with it?

Sterling suggested removing the earth from the plug for the charger and trying it then (making sure I don't touch the charger as it would give me a 110 volt shock)



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[Budgie]

After similar experiences I would also look very carefully at the shore power lead and connections at the boat. We found that water was getting into plug at the boat end of the power lead.

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[AndrewB]

Like others, when I've had a problem its nearly always turned out to be in the shore cable or terminals, but occasionally in the marina unit, specially if someone has fitted a low-rated fuse.

A normal trickle charger operates at very low current so rarely causes problems - don't know about the Stirling unit though. If you are quite sure though that you have isolated the problem to the charger, then the next step is to test it for a short with a multimeter as you describe. Popping after a while does suggest this is not an out-and-out short, though. Damp is one possibility. Is the unit heating up? Sometimes a tiny short in, e.g. a transformer, can heat and allow more power through.

Your batteries are unlikely to be the problem. A short there should simply cause the charger to cut out.

Are you earthed through the hull, or only back to the shore line?

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[Trevethan]

240V is only earthed via shore cable following consensus of the forum!

As an update, SWMBO just called saying power popped off again, this time with just the TV running... grrrr...

Maybe the cable is the culprit

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[catmandoo]

sounds like a load problem or intermittant earth leakage fault some where

you dont say whether ELCB or main breaker tripping.

is polarity correct on both boats ?

What load has you new neighbour added to the common supply? Are you both at same polarity ?

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[Trevethan]

I'll sugggest she check her polarity. The pontoon breaker has just one switch I think so I don't think its possible to tell whether its earth leakage or over current -
- but then it only really started last night went about 15 times... and I wasn't in the mood to check the pontoon supply to deeply -- especuially as it was very cold and windy last night!

I should have bought a polarity tester at Maplins earlier... bugger.. will try and get one on way back to boat.

I don't think we can be overloading as it will pop with all the CBs off exception of the battery charger circuit (separate circuit and CB just for charger)

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[Trevethan]

Thanks for all the posts. I made up a new shoore cable last night and that seems to have helped. The power did trrip when I turn on the battery charger the first time, but next time it was fine. Power along the whiole pontoon went aq couple of times during the night (usually when one of the boats further along turns on a tumble dryer(!) but when the pontoon master switch was thrown everything came back as per normal.

I suspect that girlie opposite's shore cable is the main cause as she shorts everyone, but us least, which means we have smnallest leakage. didn't bother with metring earth losses last night too cold and dark by teh time cable was made.

I will remake out old cable and suggest she try that to see if the problem lessens.

Tried half the afternoon to find a polarity tester -- nowt in Maplins, the woman in Robert Dyas tried to sell me a multi voltage DC adaptor and everyone else looked at me blankly.

Finally there is not a single male 240 volt water proof (ish) connector to be had in London -- luckily I had a spare on the boat. Both the swindelries were out of stock -- actually Arthur Beale (quite good place actually.. olde worlde chandlery but not twee like Nauticalia)) doesn't do that sort thing and Ocean Leisure, who claim to be a chandlery are more interested in flogging you clothes and scuba gear than anything uselful for a boat.

Are there any others in town, cos Southend is a bloofdy long haul just for a plug!

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[catmandoo]

I got a tester with just a 13 amp plug on end . I plug it into the various sockets on board.and it tests polarity and has a knob to turn in steps to check tripping current eg 15 25 35 milli amp etc

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[halcyon]

Probable that there is a insulation breakdown in the charger, that is allowing a small current to flow to earth, AC or DC. This means that you have an inbalance between in and out on the mains, thus tripping the RCD.

This can be very bad, it is possible that you could be leaking up the earth cable to the pontoon, or you could be leaking throught your stern gear or skin fitting. This occures due to a earth path through the water to ground then to the marina's earth spike, then down the pontoon power cable and socket to your boat. Sounds totally silly, but a long time ago when mains on boats was still new, we lost a two props on a 45 foot cruiser in about two weeks, fault was a little leakage in the battery charger.

I would get the charger checked out if you half suspect this is the fault, at least then you know it's not if it checks out ok, but you could do a lot of damage if it is.


Brian

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[claudio]

<font color=red>How do I trace the leakage -- multimetre set to measure amps and bridge live and earth and neutral and earth?</font color=red>

Please don't set your multimeter to AMPS. If you measure between live and earth on the amps setting, you will short out the supply and blow your meter up and possibly injure yourself!

To measure leakage, UNPLUG your lead from shore power, switch your meter to OHMS range, leave all equipment switched on and meaure between live and earth terminals on your shore power lead.





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[petery]

... I had the same problem

Absolutely, precisely the same thing happens to my boat with it's 40A Sterling Charger and a 1000w fan heater.

I found the earth pin on the charger plug was getting extremely hot. No problem when the fan heater only was on. I don't have an AC ammeter to measure the current flow through the shore earth.

I assume the problem arises from the connection of the shore earth to the boats 12v earth and the external anodes - but I could be wrong.

I carefully disconnected the earth wire to the Sterling - it sparked! The supply did not trip when I left the earth wire of the Sterling disconnected for an experimental period.

Heaven knows what the corrosion on the anodes and prop will be when I lift the boat out.

I have bought a galvanic isolator and assume this will fix the problem.

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[VicS]

Re: ... I had the same problem

The earth pin was getting extremely hot.... THE EARTH PIN WAS GETTING EXTREMELY HOT !!!!!!!! You've got a big problem there somewhere. I suggest disconnect from the mains and get it sorted before you reconnect. The earth leakage protection can't be working either and your system is seriously dangerous.

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[petery]

Re: ... I had the same problem

.. rest assured that's exactly what I did and I won't reconnect until I fit the galvanic isolator.

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[VicS]

Re: ... I had the same problem

While I'm not saying don't fit a galvanic isolator I don't think it's the answer to this problem. You must have a serious fault some where and for some reason the RCD, earth leakge circuit breaker, or whatever you prefer to call them, has not tripped. So you must find the fault and establish why the thing hasn't tripped.

A galvanic isolator is designed to prevent currents with a small driving voltage from passing but to allow current from higher voltage faults to pass. It sounds as though you are returning current through the earth connection rather than the neutral and that the earth pin is making poor contact in the socket or the connection in the plug or the socket is poor.

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[petery]

Re: ... I had the same problem

Thanks for your advice. I agree it's serious - you don't expect any current in the earth pin, let alone enough to make it hot enough to scorch the plastic of the plug.

I have asked the Boatyard to check it's wiring to the pontoon socket.

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[halcyon]

Re: ... I had the same problem

One thing to remember is that uptil the late 1980's ELCB's and later RCD's were not fitted to production boats as standard. The fears we have now with leakage and shocks were not concidered, as it was thought that the marina supply ELCB / RCD would provide protection.
So on older boats you may just have a isolater switch, CHECK .

Brian

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[VicS]

Re: ... I had the same problem

In this case the RCD on the marina supply should have tripped.

I can't see a fault on the shore supply causing the symptons described. I would begin by checking the wiring of the shore lead looking for possible reversal of neutral and earth connections and then work progressively into the onboard installation.

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[MainlySteam]

Re: ... I had the same problem

I absolutely agree Vic, I cannot see any likely fault on the marina's side that would cause the symptoms described.

If I was Peter I would be in a panic, before there is an unfortunate accident, to have the boat checked (professionally as he does not appear to have the experience to do so), not the boatyard's supply, as the boat (including the shore cable in that) is almost certainly where the problem is.

John

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