RCD Tripping, Nothing in Sockets, no load... what now?

[Tidy]

Hi Everybody,

We just moved into a detached house in last friday, only to find that the RCD keeps tripping for no reason :S I have had an electrician out who checked the RCD and said the box is fine.. and must be the sockets.

We unplugged every item in the house and tried to turn the socket switch back on (on the CU)... it trips the RCD, after 4 or 5 attempts it holds and we have power. (lights etc are not affected).

If we press the test button the RCD main switch does as it should.... and if we turn the socket switch OFF the main RCD will switch on immediately and hold. If we start to plug items back into the sockets sometimes it trips... sometimes it does not... there is no pattern.

I have pulled all the sockets away from the wall to make sure there are no trapped wires and for any interference with the back plates.. all ok, and still trips for no real reason.

The electrician (as above) has tested the CU with some little plugin things and said its fine and working as it should.

The worst time is the morning (between 8 - 10am), there are no washing machines on, no dryers, the combi boiler is off.. so essentially no load at all.

Other notes of interest is the previous owner who i have contacted (because of mail he needs to pick up) asked about the electrics... his words were

"its the shower, if i wanted to use the shower i had to make sure the washing machine, dryer and microwave was off). I had all the sockets tested and my electrican could not find anything wrong with the wiring.

Surely that would affect the shower switch... and not the sockets switch (the shower is not on the sockets - tested that lol).


I am sorry to pick everybodies brains, but i will go through when it has tripped and see if somebody is blatantly obvious?

1) Plug in extension cable with nothing in... Sockets RCD flicked as well as main RCD
2) Plug in hoover into kitchen socket.... main RCD off
3) Walking across the landing towards the shower... main RCD switch off
4) Jumping on the landing floorboards...no change (in case of rogue nail in floor boards lol)
5) Turning TV sockets on (which has an xbox, DVD player, 50" plasma, Wii), sockets rcd off, main switch off
6) 2 minutes into a shower, sockets off, shower off, main rcd off

This morning when i was just about to have a shower and had to reset the main switch, when i managed to finally get all switched to stick there was a buzzing noise coming from the CU - but it only happened when the shower was turned on (electric shower).

I am at a real loss at what to try next, with everything seeming to be checking out i seem to working (web designer) out of fear that my PC will shut down at any time with no warnings etc...

I am no expert but after many nights browsing the web and trying to diagnose the issue, would it be possible to think that it might be an earth problem for the house?

Thank you all again

 

[telectrix]

could be that the shower is overloading it's breaker, but not enough to trip it. a breaker of . say 40A, will stand around 57A for up to an hour before tripping, but may buzz.

 

[mhar]

I mis-diagnosed a grey water pump coming on when the cu was energised. It was the rcd fizzing. The rcd tested fine on the normal tests. Strange thing was it only fizzed when it felt like it and the fizzing did not cause it to trip but it did trip randomly. Took a while (a good while!) to diagnose, all terminations were good, rcd seated correctly etc etc but by replacing what appeared through testing to be a perfectly good rcd, problem solved

 

[Tidy]

So it "could" actually be a faulty RCD?

 

[mhar]

It could be any number of things or a combination of any number of things including a faulty rcd.
The danger here is that in your desire to give your electrician as many clues as possible to what appears to be a simple problem you could get frustrated and careless and touch something you don't want to be touching. By removing socket fronts etc you could introduce another fault (trap a cable for instance) which makes the diagnosis even harder for your electrician.
Anybody who has pm'd you from here is showing a high level of confidence in being able to correct your problem so contacting them would be my next step if your existing electrician gets stumped.

 

[Tidy]

Thank you mharries1, there is no way i would jump into trying anything myself. Changing sockets and basic stuff like that i dont mind having a fiddle, but somebody on the thread asked for a pic of the CU wiring... there is no way im taking the cover off just out of protection for myself.

I wanted to get an insight into what the problem may be, not to advise the electrician that is coming, but to possibly understand what he is trying and if he is stumped offer some of the comments on here as just "another brain" so to speak.

I do appreciate everybodies help, and fingers crossed all will be sorted this time next week. If not i will be back and phoning some of the kind people who have sent me some PM's.

 

[Plonker 3]

If your electrician can't diagnose it, ask him t write down what he has done as they could well help another spark who you get to come round and investigate the fault.

Also no matter how trivial tell anyone who does come round exactly what happens and when.

 

[Tidy]

Absolutely, I think my main concern is an open cheque book situation... which i feel this is heading... But hey, its needs to be safe!

 

[Plonker 3]

Well any decent sparks will keep you informed along the way about cost and how much longer it may take. When I do fault finding if I find nothing in the first couple of hours I will let the customer know and see if they want me to proceed, after all I would like them to know what is happening and not me just walking round there house all day for a bit of cash.

 

[cook1e]

did your electrician disconnect the circuits from the consumer unit and test the cables from there - I recently proved a fault to the garden lighting via a fused spur that fed a pir outside, problem was the customer had put baton lamp holders on a wall and covered them with clay plant pots for the winter - so have a look for fused spurs and work out what they do, pir lights etc may not manifest the fault until they trigger

martin

 

[Octopus]

Hi Everybody,
The electrician (as above) has tested the CU with some little plugin things and said its fine and working as it should.

little plugin things - alarm bells ringing!!!!!!

Difficult to diagnose as others have said but IR testing followed by continuity would be a good start.

How old is the house/wiring?

 

[telectrix]

little plugin things - alarm bells ringing!!!!!!

not from british gas , was he?

 

[OldeSparky]

earth neutral fault

 

[timo1]

My money would be on the RCD, especially if there does not appear to be any ryme or reason to the tripping. Once that was changed then you know you are'nt chasing smoke when you are fault finding..

 

[OldeSparky]

My money would be on the RCD, especially if there does not appear to be any ryme or reason to the tripping. Once that was changed then you know you are'nt chasing smoke when you are fault finding..

should be tested first..

repeating my self ..earth neutral fault

 

[Edd]

Absolutely, I think my main concern is an open cheque book situation... which i feel this is heading... But hey, its needs to be safe!

shame your not in essex,, its fault finding that keeps me going, espesially if others cant sort it.. its like a chalange.. i would spare an hour of my time for free to fault find, just to keep the cogs well oiled..

Ps thats probelly why im always skint,, maybe i need to charge