Advice on fault-finding a shorepower problem please

[silver-fox]

Today my shorepower on board failed in the marina.

A quick check at the boat end of the shore power cable revealed all was well that far, 220v live with earth and Neutral Zero v.

Once connected to the boat the following readings were obtained:-

All devices switched off. L 229V N 61V E 0V

Under load (water heater or battery charger) L 229V N 229V E 0V.

All testing done at the distribution board on the shorepower feed.

The consumer end of the circuitry splits via 3 trip switches into ring main, water heater, battery charger. I get the same test result whichever option is picked to provide the load. From that I concluded the problem exists between the shorepower socket and the distribution board.

Between the shorepower socket and the distribution board is a single cable with an RCD which does not trip, (neither does the RCD on the Pontoon).

I am assuming I have got some sort of short between L and N, but if so why doesn't it trip the RCD? I have checked the terminal connections for loose wires etc but can find nothing amiss.

Any advice on how best to proceed gratefully received.

 

[VicS]

Bad connection in the neutral somewhere. ??????

Check shore power connectors both ends of the cable ( ring the cable through with a continuity test)

Bad connection in the shorepower supply .... try a different supply

Bad connection on board between the inlet connector and the consumer unit.

But how are you testing .... Digital multimeter ?????? Guaranteed to make a fool of you sooner or later because they take so little current att they will give a normal reading through a bad connection when there is no load

 

[silver-fox]

Vic
Thanks for the suggestions I'll fully test shore supply in the morning.

I swapped out the shore cable, still the same problem.

Appreciate it could be a bad connection but why am I getting such high readings on neutral when you it should be zero?
I have tested across most of the connections both under load and without and can't find any voltage drop.

Yep I am using a fluke digital multimeter and have heeded you moments on this - thanks.

 

[ProDave]

Yes poor connection somewhere on the neutral.

WHERE did you make those voltage measurements? On the input connector? At your consumer unit?

You are getting the high voltage on neutral because it has a very high resitance contact somewhere.

UNPLUG the shore power cable bring the shore end to the boat and do some RESISTANCE checks to follow the neutral connection from your consumer unit to the plug to find out where the problem is.

 

[silver-fox]

Thanks Produce, I'll do that in the morning

 

[VicS]

Vic
Thanks for the suggestions I'll fully test shore supply in the morning.

I swapped out the shore cable, still the same problem.

Appreciate it could be a bad connection but why am I getting such high readings on neutral when you it should be zero?
I have tested across most of the connections both under load and without and can't find any voltage drop.

Yep I am using a fluke digital multimeter and have heeded you moments on this - thanks.

Not the cable then

That leaves the marina installation and your on board installation.

You are getting the 61 volt reading on the neutral with no load ( presumably measured relative to earth) because that's one of the silly readings you can get using a digital multimeter.

You are seeing 229 volts when a load is connected because you are reading the voltage of the live through the load.

Take particular notice of Pro Dave .... He is a professional electrician !

 

[superheat6k]

My money is on a bad connection on the shore power cable !

 

[VicS]

My money is on a bad connection on the shore power cable !

Despite having the same problem after swapping the cable ? Two bad cables ?

 

[david_bagshaw]

Having swapped the shore line, my money would be on a poor shore socket connection in the cabinet.

 

[cegri]

Check the water heater. Disconnect the cable completely and test again.

 

[silver-fox]

Thank you VicS and ProDave for your advice.
I found the problem this morning, it was actually supply side. There were two duff sockets on the Pontoon pillar. The third was good!

What threw me was my meter showing 220v which disappeared when a load was applied.

But you live and learn! Just have to put the boat back together now!!

 

[VicS]

Thank you VicS and ProDave for your advice.
I found the problem this morning, it was actually supply side. There were two duff sockets on the Pontoon pillar. The third was good!

What threw me was my meter showing 220v which disappeared when a load was applied.

But you live and learn! Just have to put the boat back together now!!

Thanks for the feed back

 

[penberth3]

Thank you VicS and ProDave for your advice.
I found the problem this morning, it was actually supply side. There were two duff sockets on the Pontoon pillar. The third was good!

What threw me was my meter showing 220v which disappeared when a load was applied.

But you live and learn! Just have to put the boat back together now!!

For future use I'd recommend a proper socket checker - three neon lights to confirm all Ok at the socket. Not expensive, quick and easy, and safer than poking about with a multi-meter.

 

[ProDave]

Thank you VicS and ProDave for your advice.
I found the problem this morning, it was actually supply side. There were two duff sockets on the Pontoon pillar. The third was good!

What threw me was my meter showing 220v which disappeared when a load was applied.

But you live and learn! Just have to put the boat back together now!!

Have you reported the problem to the marina?

This makes a good case for making a simple short adaptor of a commando plug to a 13A socket, into which one of those 3 light socket testers is plugged. That would allow you to test a shore power socket before you plug your cable into it.

Accepting that those 3 light testers are far from perfect, but they give a general idea.

 

[Ruffles]

No biggy, but.

If the duff sockets were tripped they would be disconnected on L not neutral. That suggests that two sockets have a loose N connection which is a bit of a coincidence. Or have they switched L and N in the pillar?