Its a tricky one!

[neil12345]

Hi all,

hope you are well, DIY'er after some thoughts if possible. After a period of very heavy and prolonged rain my electricity trips, when I turn off the switch for the power to the shed (pic attached) I can put the electricity back on.

Sometimes I can then immediately put the shed switch back on and all is well, sometimes I need to leave it a few hours before it will go back on without tripping. When it is at a stage where it won't switch on without tripping I've turned off sockets, lights etc in shed and it still trips when shed power is switched on.

That would make me think the the issue is with the armored cable that's mainly buried under soil, however what I don't understand is that if water is getting into the cable and causing a trip why would it all be OK again, sometimes immediately, sometimes after a few hours as the ground, let alone the cable, won't dry out in that time?

Any thoughts as to what could be causing it or any further steps to diagnose?

Thanks all, any input hugely appreciated.

 

[littlespark]

First thought is water ingress into the equipment in the shed.

Is it a substantial brick built outhouse, or just a shed?
Domestic style white plastic fittings are not really suitable for in a shed.

With the power off, completely, to the shed…. Remove the face screws and look behind any switches and sockets. See if there’s water.

 

[PS Electrics]

Hi all,

hope you are well, DIY'er after some thoughts if possible. After a period of very heavy and prolonged rain my electricity trips, when I turn off the switch for the power to the shed (pic attached) I can put the electricity back on.

Sometimes I can then immediately put the shed switch back on and all is well, sometimes I need to leave it a few hours before it will go back on without tripping. When it is at a stage where it won't switch on without tripping I've turned off sockets, lights etc in shed and it still trips when shed power is switched on.

You are only switching off the Live so if it is a N to CPC leak it will still trip.

That would make me think the the issue is with the armored cable that's mainly buried under soil, however what I don't understand is that if water is getting into the cable and causing a trip why would it all be OK again, sometimes immediately, sometimes after a few hours as the ground, let alone the cable, won't dry out in that time?

How is the armoured terminated? do you have an external box to that wall? As littlespark said check for water leakage at all junction boxes and accessories and fittings before suspecting the armoured cable itself. Check anything external first as that is the most likely.

And obviously follow safe isolation procedures.

Any thoughts as to what could be causing it or any further steps to diagnose?

Thanks all, any input hugely appreciated.

 

[Taylortwocities]

You are only switching off the Live so if it is a N to CPC leak it will still trip.

The switch in the picture above is a double pole switched fuse (FCU) so switching that off isolates both L&N which points the problem at something after that FCU.
Its a reasonably easy job to track this down. You can start randonly opening up any junction boxes in the circuit chain, or make a logical approach:- break the circuit chain in the middle and narrow the location down.

That would make me think the the issue is with the armored cable that's mainly buried under soil, however what I don't understand is that if water is getting into the cable and causing a trip

Very unlikely that armoured cable would suddenly start letting water in - unless you have been doing some serious digging in the garden! It is even more unlikely that water in a cable would dry out after an hour or two. Water has got into something, most likely an external junction, light fitting, etc

 

[OnlQQker]

In most cases after heavy rain, I've found it to be an outside light causing the problem.
This could be a pir light outside of the shed, or garden lights coming from the shed etc.

 

[PS Electrics]

The switch in the picture above is a double pole switched fuse (FCU) so switching that off isolates both L&N which points the problem at something after that FCU.
Its a reasonably easy job to track this down. You can start randonly opening up any junction boxes in the circuit chain, or make a logical approach:- break the circuit chain in the middle and narrow the location down.

I wasn't referring to the switch in the picture I was referring to this "I've turned off sockets, lights etc in shed and it still trips"