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[diy-wes]

Hi there, bit confused about what's going on with one of the circuits in my flat. For context, the only change I've made to this circuit is moving a socket from a bedroom into the hallway - pretty standard, no new wiring.

Yesterday I went into the kitchen (the second socket in this circuit is in the kitchen) and switched on the kettle; the RCD tripped. I switched it back on and tried the kettle again, and the kettle didn't turn on at all and the RCD didn't even trip. I thought the kettle was buggered but it works on other sockets (apart from the new hallway socket). Other appliances work (a coffee grinder and a small plug in induction hob).

I have a socket tester and it is giving me what looks like an 'earthing' error on both sockets. The new hallway socket is wired up fine, I've tried multiple sockets to make sure the sockets are not faulty. Unfortunately, the kitchen socket is glued into the wall and I can't even get off the socket plate. Before I go about some serious demotion in the kitchen to get this socket out, are there any other recommendations?

Strangely, I've tried the kettle again today which comes on and then cuts out after 2 seconds and the RCD on the fusebox still doesn't trip....(I've tested the RCD using the Test button just to make sure that is ok.

Any advice would be greatly appreciated. It just seems so weird! Like why would this randomly happen? What might be causing this?

Thank you!

[Mr White]

I have a socket tester and it is giving me what looks like an 'earthing' error

You have answered your own question

The new hallway socket is wired up fine

Clearly, it isn't

are there any other recommendations?

Get an electrician in to do the job and test it properly for you, before you kill yourself or worse still, before you kill someone else.

[ericmark]

Test equipment is expensive, and even if you have the ability to test and inspect likely it would not be economical for you to do it DIY.

In the main in the UK we use a ring final system, this allows us to use less copper and was invented at the end of world war 2 to save copper with the post war rebuild.

So we have a cable which can't take the full supply on its own, and we can have a socket that works but can be overloaded due to ring being broken.

Easy enough for an electrician, he will measure the loop impedance, open a socket and test if the ring is intact if so do the work, then measure the loop impedance again, and this measurement will tell him if he has made any error and there is a disconnected wire. But without that meter the only option is to switch off the isolator if one is fitted, and open the consumer unit and disconnect wires to test, often there is no isolator and HSE rules say must be isolated else where, so to do the test he either calls the DNO for a disconnection or brakes the rules and works in a live box. Normally he does the latter, but clearly there is danger involved and it is not some thing you want to do DIY.

[diy-wes]

Thanks for the advice @ericmarc - really helpful. My mate has a multimeter (not an electrician) so we'll give that a go and see if there is a break in the ring. If we can't figure it out then I guess we'll have to bite the bullet and call a sparky in!

[ericmark]

[quote="diy-wes"]My mate has a multimeter (not an electrician) so we'll give that a go and see if there is a break in the ring.[/quote]
Yes the multimeter with a socket removed can identify a break in the ring final, however you do need to know what to test, it is tested with the circuit isolated, but isolated is not the same as switched off.

The problem is to test at a socket you can disturb things when replacing the socket, to test you really need a loop impedance meter and a insulation resistance meter, not just a multimeter.

With isolator off (not the MCB or RCBO but the isolator so either the RCD or whole house isolator) you need to remove a socket on the faulty ring and test.

Between both lines to see if ring final is intact.
Between both neutrals to see if ring final is intact.
Between both earths to see if ring final is intact.
All above should show less than one ohm. The incoming supply likely has an impedance of 0.35 ohm and the total should be less than 1.365625 ohm so looking for less than one ohm which needs a low ohm ohmmeter.

Between line and neutral to see if isolated.
Between line and earth to see if isolated.
Between earth and neutral to see if isolated.
This needs to be tested at 500 volt and should show more than one meg ohm. It needs an insulation tester to test using 500 volt.

The test needs all neon indicators out of circuit, and any USB sockets removed for the line - neutral test, some times we use 250 volt for line - neutral test, and some times we have to use out experience to judge if the readings are really showing a fault, or if due to some thing we can't switch off.

Once the socket is replaced the loop impedance test and the prospective short circuit current test indicates if we have disturbed anything when replacing the socket.

In your case you know there is likely a fault, so once tests are done you should know if fault is in line, neutral or earth, but you don't know which socket or cable has the fault.

So we use experience and decide where the cables likely run, and we split the ring in two and find out which half the fault is in, then split the faulty half in half, and so on. Until socket or cable is identified with fault.

I would as an electrician start with it live, and use the loop impedance tester readings to give me a good idea the route taken by the cable, it may even show where the fault lies, so with the proper test gear the process is so much easier.

The loop impedance to ensure the MCB trips in time must be less than 1.365625 Ω and the PSCC needs to be more than 245 amp for the volt drop to be within limits, (assuming a 32 amp ring final) however we look at the home and judge what is likely, so with a socket right by the CU we are looking at around 0.4 Ω and for a twin ring in a home 3 bedroom house we expect well below 1.36 Ω only with a large house would we expect it to be near the limits.

There should be an insulation certificate or minor works certificate or an electrical installation condition report which says what reading were found in the past, so by comparing today's readings with the readings taken in the past one has a better idea if there is some thing wrong.

A ring final can loose a connection and still work, it will not be working safely, but it still will work, so it is recommended on change of occupant an EICR is done, which will identify any breaks in the ring final plus other faults, and this should be repeated every 10 years. This is to high light problems before damage is done.

With rental property in England it is law the EICR is done every 5 years, the ring final is a good system, but it does need checking every so often to high light faults.

I suspect you have at least 2 faults. And I suspect there is a loose cable, which could cause a fire, so I strongly advice not to DIY to find fault as likely you will only find one of the pair of faults, and there will still be a fire risk.