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

 

[Q.S.]

Hi, It could be a fault on the cables which would show up with an insulation resistance test or it could be a neutral wire connected in the wrong place in the consumer unit. You need a sparks who is used to fault finding to test everything. You talk about having 2 RCDs - they should not be connected from one to another but both direct from the main switch. This way only part of the electrics will turn off not the whole lot. If you can email a photo of the C.U. with the cover off I might be able to help more. [email protected]

 

[Tidy]

Hi,

Thank you for the reply. I think i may have my terminology all mixed up, i am just a mere designer lol

The RCD part is on the left with poorly labelled switches....

There is (from what i can read)

Shower
Cooker
Sockets
Sockets - Garage

 

[robsparky1975]

I would test the shower wiring,get an electrician who has the correct test equiptment,its a traceable fault,it has been known before for spiders and such like to be across terminals on things and thats why tripping occurs occasionaly,could be a simple fix or might take longer,but a good electrician will trace it/test and put your mind at rest.what area do you live,perhaps a forum member may be able to assist.

 

[Tidy]

Could the shower wiring affect the sockets though? I thought (probably incorrectly) that the whole point of an RCD is to only disable the offending circuit?

I am in the midlands... robin hood country lol

 

[Plonker 3]

Could the shower wiring affect the sockets though? I thought (probably incorrectly) that the whole point of an RCD is to only disable the offending circuit?

I am in the midlands... robin hood country lol

Check your PMs

 

[telectrix]

echo rob here. correct test gear is essential to trace this fault. there could be a connection lurking away out of site, or possible water ingress somewhere. post your location, one of us may be close to you.

 

[Spark in a tie]

Hi, do I take it that it's the same RCD unit that's constantly tripping?
If so, it might be an idea to swap with another of the RCD's that you have protecting the other circuits, just to see if there's a fault on the device itself.
I also notice that on your c.u schedule there's no mention of your boiler? It may be a long shot, but if it's supplied by this rogue circuit and you're problem is approximately the same time each morning - and this happens to co-incide with when your boiler fires up your heating - you may have a fault on the pump or internal PCB.
Either way, I'd suggest getting an experienced spark involved who's a confident fault-finder.

 

[Tidy]

Hi Everybody,

Our electrician is coming back next week but if he can't find the fault i will contact those of you who have PM'd me (thank you)

When the electrician came out, he swapped one of the switches with another circuit in case it was faulty. He also said that after many times of tripping some switches become easier to break (ie, less resistance) which he said is not happening with ours.

We tested things with the boiler off, so could it have an affect?

 

[telectrix]

if the fault is N-E as opposed to L-E, then an appliance that is switched off could be the problem unless the socket/FCU that supplies it is double pole. N-E faults sometimes give bizarre reactions from RCDs.

 

[Tidy]

So with all appliances unplugged, it might be as simple as a socket that is not wired up correctly? (forgive me if i have completely mis-understood your post)

 

[telectrix]

if a socket is incorrectly wired, the fault would generally only become apparent when a load was applied.

 

[Tidy]

So would that explain the difficulty in trying to turn the sockets switch back on on the CU?

 

[telectrix]

it's impossible to diagnose on the forum. generally if you have a L-E fault, it will not manifest itself with the breaker turned off. however, these faults are the pig's ear in how they appear. only with a thorough test can this be found if you have eliminated appliances by unplugging.

 

[Tidy]

Thank you, I hope we can get to the bottom of it.

One thing that still worries me, is the buzzing we get from the CU when the shower is on? At our old house this never happened... the only noise from the shower was generally me singing...