garden lighting fault, advice please


I hope it's OK to post a request for help on an outside problem, it's on electrics not plants.
We have a garden lighting circuit, looks as though it was professionally installed, but could be at least 20 years old.
It has an earth leakage CB. The CB is tripping out all the time so obviously there is a fault.
Have checked what I can see of the cable and it is two core, red and black. No sign of an earth wire, although the sockets have an earth wire in them, it doesn't seem to connect to the cable, just to the joint box on each post in the garden.
All the sockets are round pin and I was thinking of changing them all for square pin, hoping at the same time to cure the tripping out.
Could the tripping be due to simple condensation in the old sockets, or is there any way to check to see if the cable itself is faulty. ( if its the cable then we will abandon it as it would be a megga job to replace it. )
Any ideas or advice please. Is it normal to have such a circuit without an earth wire?
Thanks in advance
John Fox
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John Fox wrote:

Personally I would have said it's extremely dodgy especially outdoors, not to have an earth connection. Are the posts metal? In which case they could be relying on each post to be earthed by being stuck in the earth. Just how reliable this is I'm not qualified to say.
Condensation could be causing the tripping or the old cable could have broken down somewhere. I would replace the cable with twin and earth if I were you as well as replacing the sockets.
--
MAlc



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Hi. Check the cable again it may be a steel wire armoured which uses the wire sheathing as earth ,if professionally fitted the steel would not be visible as it is clamped by the terminating gland as it enters the junction box and may have a pvc shroud over it. The socket would then have a green earth wire connected to the metal box.
As you say condensation and age could be your problem but if you have no earth then replace the cable.
HTH CJ
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The cable could also be pyro and you would have the same thing.
Adam
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Ah that starts to make some sense!
I can't see the sheathing but there is a change in diameter of the cable on either side of the cable gland and it would also explain the positioning of the earth wire. I'll try to undo one of the glands at the weekend to make sure.
Assuming that the cable is of the armoured type, is there any way to check that the cable itself isn't degrading. Don't want to fork out for a box full of weatherproof sockets only to find out that the cable itself is faulty.
Thanks for the info so far.
John Fox
cj wrote:

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You need to measure the resistance of each wire to earth, i.e. neutral to earth and live to earth (obviously with no mains there). I suspect that you may need a megger to do this properly but a digital multimeter may suffice. WHat you could then do is go round the various sockets disconnecting the live and neutral so you have isolated sections which you can then measure to find which section the fault is in and hopefully which socket rather than which piece of cable.
Malc
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Thanks for the advice, very useful.
John Fox
Most Noble and Honourable the Malcolm of Giggleswick under Table wrote:

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