Fault On House Electrics (Rccb Tripping)

Talk Electrician Forum

Help Support Talk Electrician Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

adam1984

Junior Member
Joined
Apr 24, 2012
Messages
27
Reaction score
0
Afternoon all.

I have put this in here rather then the learning zone but please feel free to move it mods.

This is a weird one but I thought i would ask your thoughts to satisfy my own cuisosity and apologies for long post!

Board is a Crabtree with 1no RCCB. The RCCB tripped when the TV was plugged in and socket turned on. RCCB would not instantly re-set but it did after a couple of minute.

The RCCB supplied: Downstairs power, Upstairs Power,  kitchen, Extension, utility/boiler (5mcbs)

So I reset RCCB. Go back to "TV Socket", plug in Martindale socket tester, switch on socket switch and RCCB trips (do this  a couple more times and keeps tripping) The TV socket is on Downstairs power MCB.

Homewoner says that its normally the tumble dryer / kettle / microwave (on the utility MCB) that ususally trips the RCCB but once reset they work again.

Reset RCCB and and all MCB's are in the ON position. Go to utility room and plug Martindale socket tester into socket, switch on and RCCB trips again. I try several different sockets and trips every time however when the boiler is fired up it doe not trip the RCCB.

If I turn off the MCB to the Utility room and try my Martindale socket tester in the kitchen sockets then it trips the RCCB. If i turn off the the Extension and utility / boiler MCB then the "TV Socket" does not trip the RCCB and nieither do the kitchen sockets.

Now the extension is actually a 2 storey extension but when I turn this MCB off it only turns the power off to the downstair extension (granted the upstairs may have been taken off the upstairs power)

I took off every socket face on the affected circuits and wiring all looked fine. I checked all cables where possible (ones clipped direct etc) for signs of damage. I asked the homewoner if they have done any DIY recently. I checked all outside equipment for signs of water ingress or damage and everything I checked looked ok and no signs of damage.

The homeowner has lived in the house for approx 4 years and on the face of it it is really modern and had a massive refurb job done by the previous owners but the current homeowner has said they have had quite a lot of problems with te house and especially with the electrics.

I think that there is a dodgy conection somewhere but I couldnt find it so must be burried in / behind a wall somewhere.The junction boxes I found were wired ok. Anyone shed some light on what they think it may be? Ways in which you would try and trace fault? No insulation resistance test was carried out.

 
Anyone shed some light on what they think it may be? Ways in which you would try and trace fault? No insulation resistance test was carried out.

To be quite blunt and honest...

Without actually doing any RCD tests and Insulation resistance tests you have so far proved very little. 

RCD tripping suggests somewhere on one or more of the circuits that the RCD supplies there is a cumulative leakage greater than 30ma. 

This could be damaged cable, or some foreign object bridging some conductors..

(damp, dead rodent, nail through cable etc..)

Or it could be that the cables are all perfectly OK but there are some appliances with excessive earth leakage...

Or it could be that the RCD is just over sensitive! ??

A martindale socket tester will not prove or diagnose any of these...

Wrong tester for wrong problem..

bit like trying to find why my engines not firing correctly with a tyre pressure gauge...

(wrong tool for that problem!)

You need to go back and do some relevant tests on all of the circuits supplied by the RCD.

and test the RCD..

Guinness

 
Last edited by a moderator:
I would carry them out first. Probably before even taking any accessories off

agreed..  you should be able to do some IR tests @ 230v, L&N combined with ref to E, without damaging any plugged in appliances.

Then investigate further dependent upon what results you get off each circuit...

You may be able to identify a dodgy appliance...

Double check ALL appliances that work with water...

Washing machines / Dishwashers / Central Heating controls / Electric Kettles / Steam Irons / Immersion heaters... etc..

They are all prime suspect for causing intermittent RCD trips if a bit of damp spills out where it shouldn't!

Guinness

 
Last edited by a moderator:
Thank you for your replies. The thing that is puzzling me is that the boiler would not trip the RCD but the utility room sockets do and they are on the same MCB.

Also the kitchen sockets would trip the RCD when the extension and utility room MCB's are on but when I turned off the Extension and Utility room MCB's the kitchen sockets would not trip the RCD.

Also everything was unpluged and the Martindale alone would trp the RCD

 
You can get some very strange effects when there's something in the house with a bit of leakage but not quite enough to trip the RCD on it's own.

Do the proper tests and you will get to the bottom of it.

 
Last edited by a moderator:
Thank you for your replies. The thing that is puzzling me is that the boiler would not trip the RCD but the utility room sockets do and they are on the same MCB.

Also the kitchen sockets would trip the RCD when the extension and utility room MCB's are on but when I turned off the Extension and Utility room MCB's the kitchen sockets would not trip the RCD.

Also everything was unpluged and the Martindale alone would trp the RCD

The point is that so far you have not eliminated anything from the equation...

Too many variables...

Three key suspects:

1/ Cable fault.

2/ RCD fault.

3/ Appliance fault.

It could be any one..

OR

It could be a combination of more than one!!!

The tests you have done so far do not prove or disprove any of the three key suspects!

You have got to go back and do some proper tests to eliminate possibilities from  the problem.

Guinness

 
A martindale,socket tester is,good for "showing some things" but it is NO good for testing

Imuse a Socket and See whistly thing quite a lot....BUT never for testing.

Used it today actually tomfind an MCB

Board at one end of a corridor.....dis board 50 m away at other end.

Whistling stops when MCB is tripped. BUT that is where i stopped with the plug in tester and did safe isolation

'Orses fo courses

 
Thank you for taking the time to reply. My lack of experience meant that I did not continue with the process or trying to find the fault and advised the home owner to seek a experienced Electrician. I will take the very helpful advice given and hopefully have an opportunity in the future to use it.

 
I went to have a look and was not paid for being there. Home owner got my number from a family friend

 
Do you have access to an RCD tester and IR tester, or do you know someone who does. It would be good if you could go back along with someone more experienced and with the correct test equipment to follow the process through. I think you could learn a lot. Where about in the country are you?

Doc H.

 
First thing you need to know is if the RCD is over sensitive ,  you can't trust brand new ones let alone old 'uns .   You say its Craptree ..is it a modern one ?   If it is its probably as good as their MCBs. 
default_tongue%20in%20cheek.png


 
worth considering shared neutral - sounds like the circuits aren't what they should be. So i would be inclined to do as suggested above to check rcd and then if thta doesn't help test the entire house with particular attention to power circuits ie rings not being as they should be!

 
Top