Finding the source of an electrical fault

[jdmorrisn]

Hi all,

First I will explain my fuse box - it has a main switch to turn everything off and two rows of fuses, the 2nd row has also a breaker switch at the end which can turn off only the 2nd row without affecting the 1st row.

Now everything has been fine, no changes to electrical installations, no additions and then one day, plug in the vacuum and it trips out the 2nd row breaker switch (not sure of correct terminology) for the 2nd row of fuses in the fuse box. Everytime the vacuum is plugged in/switched on (in any socket) it trips out. What makes it more tricky is that now also the outside path light switch I have noticed does the same, switch it on, the breaker trips out.

Now does this mean the fault is somewhere connected with the bottom row of fuses (sockets/switches etc) only or can be anywhere in the house? The outside light is on the 1st row for example.

I hoped to try a method of find and seek by elimination but when I turned off all but the sockets and this breaker and plug in the vacuum the breaker still went off. Surely if nothing else is on, only the breaker and socket fuse then it must be something with the sockets?

Or could it be that outside in the path lights there is a connection problem (perhaps water in one of the lights?) - would this affect this breaker even if the fuse for these lights were switched off?

Before I start undoing every socket, switch and appliance I thought I would see if anyone had other ideas?

Thanks.

 

[breezer]

picture?

 

[JohnD]

picture?

Couldn't agree more
http://www.diynot.com/forums/viewtopic.php?t=129539

Of your consumer unit/"fusebox"

I am particularly interested to know if the thing that is tripping out has a "Test" button on it (I don't know what that is in Estonian).

If it trips when you plug in the Vac it is probably the Vac that is causing it.

I have a feeling that either you have an earth fault on one or both the appliances you mention, or you might have a combination of small earth leakages on the various circuits, which reaches the tripping point when you plug in the Vac.

Please confirm that they used to work OK and you have not fitted new plugs or anything and caused the fault. Check for easy things like dampness or damaged flex,

 

[jdmorrisn]

Hi Guys,

forgive my slow replies, hope you will bear with me, I only get chance to read these comments in the day then do something at night.

Picture I will try to do and upload tonight.

I discover it can't be the Vac since I woke up this morning and noticed by a socket timer that it had tripped out at 1am and I was asleep by then.

At the time this started to happen I hadn't changed anything, no plugs, sockets etc. Everything worked fine.

Where before it tripped out when only plugging an appliance into a socket (vac or hairdryer etc) or switching on the path light switch, now it trips out on its own accord.

The thing tripping out I think does have a test button on it, but I will clarify with a picture.

How do I find these earth leakages if this is the problem?

 

[JohnD]

earth leakages are difficult to find

start by unplugging everything, especially watery appliances (kettle, immersion heater, boiler, pump, shower, hot-tub, washing machine, dishwasher, fishtank) and anything with a heating element (cooker, toaster, immersion heater again) as they are particularly prone to earth leakages

Turn off all the MCBs as it might be a live-to-earth fault (if it is a neutral-to-earth fault this will not help)

With a bit of luck unplugging everything (or using a DP switch for fixed appliances like the cooker) will stop the tripping happening. If so, you can reconnect them one at a time and see when the fault returns.

However, I think you might have a mouse gnawing on the cables.

Or a water leak making some electrical part wet (this is common on outdoor lighting, central heating pumps, boilers, washing machines, fountains, dishwashers, light fittings under the bathroom or a leaky roof) and anything in a cellar.

And it could still be the vac. If your RCD is tripping at 30mA leakage, and there is a background leakage of 20mA, and the vac has a leakage of 10mA, then the vac, added to the background, reaches the tripping current. If the background leakage varies during the day, or with the weather, sometimes it will reach 30mA on its own.

 

[jdmorrisn]

here is a picture of the consumer unit - yes this breaker has a test button on it.

I will try these ideas tonight.

[GALLERY=media, 3795][/GALLERY]

[/img]

 

[JohnD]

it appears to be a 3-phase installation. I can't make out the links but quite likely you have a different phase on the different rows. It looks like the top row is unused so only two phases are loaded

The cable colours are a bit mixed.

3-phase is more dangerous especially for DIY-ing. You will get more than a bit of a jolt if you get a shock between phases it might finish you off.

I would be reluctant to make suggestions without working out how it is all connected.

 

[jdmorrisn]

One quick question, please explain or point me to an explanation on the 3 phase?

Apart from this, in the brass terminals in the top of the unit - what you see is all the earth wires and the neutrals for the 2nd row of fuses .

the 1st row only consists of the main isolation switch and another set of neutral terminals for the 3rd row of fuses (this 2nd row of neutral terminals then has one link wire to the neutral terminals in the brass terminal at the top to link them all together; nothing else is wired here.

the 3rd row consists of another row of fuses with a separate 'RCD'? - although why an RCD on one row and not the other, unless it is because there are more amps on this row?

And that's it.

The colours are fairly understandable in that in Estonia they use cabling that has light brown/blue for switches, dark brown(almost black)/dark blue for sockets/floor heating etc and then 5 core is the same for sauna/cooker etc.

The only way I can think which is quickest to find this fault is to switch off the main isolation switch and disconnect the relevant earth, neutral and live wires for each fuse from their respective terminals one by one, in effect removing it from the circuit. And then checking for the fault? If it trips, replace the wires, disconnect the next fuse E,N,L wires and so on - unless of cause there is more than one fault. Surely this should isolate the problem if it is one fault - what do you think?