Faulty shore power cable

[blackrose]

Came back to the boat today after a few days away. Batteries at 100% and inverter running the mains fridge. I wanted to run the washing machine and the sun wasn't really out so I switched over to shore power and found I had a polarity light out on my consumer unit and mains power was intermittent. I couldn't work out what was wrong initially but then changed the shore power cable and the problem was solved. I'll check all the cable connections in the blue 16a plugs over the weekend, but just to check that I haven't got faulty cable (2.5mm2 arctic blue) what test can I do with my multimeter? Just a continuity test on both ends of the L, N, E wires in turn? Is there some insulation test I can do?

Edited February 10, 2023 by blackrose

[rusty69]

You will need a megger to do an insulation test. The fault likely falls in the plug/socket unless there is obvious physical damage to the cable. 

Edited February 10, 2023 by rusty69

[Tony Brooks]

1 minute ago, blackrose said:

Came back to the boat today after a few days away. Batteries at 100% and inverter running the mains fridge. I wanted to run the washing machine and the sun wasn't really out so I switched over to shore power and found I had a polarity light out on my consumer unit and mains power was intermittent. I couldn't work out what was wrong initially but then changed the shore power cable and the problem was solved. I'll check all the cable connections in the blue 16a plugs over the weekend, but just to check that I haven't got faulty cable (2.5mm2 arctic blue) what test can I do with my multimeter? Just a continuity test on both ends of the L, N, E wires in turn? Is there some insulation test I can do?

Insulation test. As the multimeter will only put 9V into the wires a problem the 240V finds is unlikely to show up unless it is a dead short. If you have a Megger/insulation tester then ste to 500V and test between L&E, L&N, N&E. All should give a similar and very high resistance. Probably high K owns or M ohms.

[blackrose]

Ok thanks. Probably one of the terminals worked itself loose.

[GUMPY]

If you don't have the proper test gear the easiest thing to do with a suspect cable, apart from binning it, is to cut the plug and socket off and remake both ends. This should eliminate any bad connections which is the usual cause 

Edited February 10, 2023 by Loddon

[blackrose]

Yes, will do.

[GUMPY]

What often happens is that one of the inner cores breaks under the cable clamp. This makes the cable intermittent under load but if you test it with a multimeter it will appear fine. Seen it hundreds if times at work.

[jonathanA]

More likely you'll find plug/socket full of water, rusty/corroded terminals and conductors ... cleaning everything up and a remaking the connections should sort it . 

 

 

Agree with loddon cable break close to either end is also a possibility. I See it loads of times on just about any portable appliance problem within 6 inches of the plug or where cable enters...

Edited February 10, 2023 by jonathanA
Eta cable break