Electrical Advice Needed Pls

[Off]

I have  a Consumer unit from electrium part no: b4471/2 (I cant find a pic of it on the internet, sorry).

It has the main switch which switches on/off the whole board followed by three switches which are for lights in my home and one socket which work perfectly.

Another on/off switch which covers the further 9 separate switches for various household sockets, cooker etc.

If I turn off one particular switch out of the group of three which covers the hall light and  socket - then the main on/off switch which covers the 9 switches WILL stay on.

I can then use anything in the house so long as it holds a charge of no more than a hair drier on a low setting! If I turn the hair drier up to high - then it trips out.  Again, this is on any socket in the house.

Does anyone have any ideas on what the problem is?

Thanks

Off

 

[apprentice87]

Is it only the hair drier that does it or anything?? What if you plug the hair drier in a different socket and try it??

john..

 

[HandySparks]

When was this consumer unit installed? And who installed it?

 

[NozSpark]

It sounds like you have an insulation resistance fault in the circuit that you're turning off (turning off the MCB does not fully isolate the circuit)

The fact that heavy loads also trips the RCD can be a normal event with this kind of fault

You really need to get someone around to throughly test the problem circuit

 

[Andy™]

you have a fault, possibly N-E. without test equipment it will be very hard for you to find

 

[sprocketflup]

Or a faulty hair-drier

 

[apprentice87]

Yep, if any sort of heavy load anywhere in the house trips the rcd, then i think Noz and Andy are exactly right, a N/E fault.. [part of the current flowing in ANY of your circuits partially returns via the earth instead, thus partially bypassing the RCD, and so unbalances it, and so it trips]

john...

 

[ProDave]

I have  a Consumer unit from electrium part no: b4471/2 (I cant find a pic of it on the internet, sorry).

It has the main switch which switches on/off the whole board followed by three switches which are for lights in my home and one socket which work perfectly.

Another on/off switch which covers the further 9 separate switches for various household sockets, cooker etc.

If I turn off one particular switch out of the group of three which covers the hall light and  socket - then the main on/off switch which covers the 9 switches WILL stay on.

I can then use anything in the house so long as it holds a charge of no more than a hair drier on a low setting! If I turn the hair drier up to high - then it trips out.  Again, this is on any socket in the house.

Does anyone have any ideas on what the problem is?

Thanks

Off

The "main on/off switch" that covers these "switches" is an RCD and the "switches" are MCB's

The fact you can't leave this particular one on without it tripping the rcd suggests it has a fault.  It is VERY unusual to have ove circuit covering lights and a socket. So something strange there.

Even when that is turned off the neutral to that circuit is still connected so that can cause an earth leakage and as more load is applied to other circuits will cause the rcd to trip.

You need a qualified electrician to come and fault find the installation which could be very quick or it could take a while to find and correct the fault.

 

[binky]

turning hairdryer to higher setting is probably energising a second heating coil in the hairdryer which is faulty and causing your RCD to trip. You don't get a heavier load than a tumble drier or cooker, if these can operate without trouble, then it is, in my opinion, not your circuits.

 

[Andy™]

most hairdryers are class II

 

[Off]

Is it only the hair drier that does it or anything?? What if you plug the hair drier in a different socket and try it??

john..

Thanks all for your replies.  Much appreciated.

I will do my best to answer the questions clearly.

The hair drier is not faulty.  It works perfectly in the socket that I have left working attached to my house lights MCBs (group of three switches).  All the sockets on the other MCBS (group of 9) will only hold a very small amount of electricity - eg: the timer clock on the cooker, the lights on the washing machine or tumble drier.

When trying to turn these appliances on, then it trips out.  So I experimented to see roughly how much charge it would hold and it is up to the low setting on the hairdrier.  If I turn it to high setting - it trips out. 

The "main on/off switch" that covers these "switches" is an RCD and the "switches" are MCB's

The fact you can't leave this particular one on without it tripping the rcd suggests it has a fault.  It is VERY unusual to have ove circuit covering lights and a socket. So something strange there.

Even when that is turned off the neutral to that circuit is still connected so that can cause an earth leakage and as more load is applied to other circuits will cause the rcd to trip.

You need a qualified electrician to come and fault find the installation which could be very quick or it could take a while to find and correct the fault.

Agreed.  But it is practical and I am very thankful for it.  Unfortunately though it never was able to hold my dyson hoover ad whilst it will let me use the washing machine from an extention, it will not let me use the tumble drier as it is too much for it.

When was this consumer unit installed? And who installed it?

It sounds like you have an insulation resistance fault in the circuit that you're turning off (turning off the MCB does not fully isolate the circuit)

The fact that heavy loads also trips the RCD can be a normal event with this kind of fault

You really need to get someone around to throughly test the problem circuit

Thanks NozSpark,

I will look up some info on that.   It would be better if turning of the mcbs did fully isolate the circuit - but that explains something to me.

Yep, if any sort of heavy load anywhere in the house trips the rcd, then i think Noz and Andy are exactly right, a N/E fault.. [part of the current flowing in ANY of your circuits partially returns via the earth instead, thus partially bypassing the RCD, and so unbalances it, and so it trips]

john...

Thanks very much for explaining N/E fault.  Why would part of the current flowing return via earth instead???

Apologies.  Problems posting. 

 

[roys]

A breakdown in the insulation, can happen when say the wire is pressed up against a casing screw(presuming it is not double insulated) which is earthed, the insulation gets damaged and starts to snap, crackle and pop in the words of a morning breakfast cereal.

 

[Off]

How is this fixed, pls?

Hi Roys,

Sorry dreadful problems posting.  It is logging me out each time too.  Seems ok if I do not hit quote or multiquote.

In your example, I guess some insulation tape does the trick.

 

[roys]

As per prodaves post #8, needs checked by someone who knows what they are doing with some test equipment.

Of course you might get lucky and it might just be a faulty hair dryer for example but we are clutching at straws as it is difficult to tell over the internet.

 

[ProDave]

What rating is the mcb that feeds this socket (and lights)  It will say something like B6 or some other number on it somewhere.

Yes you need someone in to do some tests.  Quite possibly if a socket has been connected to a lighting circuit, then the cable may have overheated due to overload and a section of cable may be damaged.

But all we can do is speculate, none of us are there so inspect and test it properly.

 

[Off]

NS B06-C   Done by a qualified electrician.  Don't think this is the problem at all because it is all working fine, as usual, this circuit.

Problem is somewhere in the other circuit of 9 breakers.

 

[kerching]

Are you saying that this NSB 06 is feeding power and lighting?

I have read this three times and i am getting a bit confused,,sorry

 

[Off]

Yes.  But just a lightweight socket.

 

[apprentice87]

That is why it trips when you connect up a tumble drier then.. [being 6A]

Right... You have got a short, neutral to earth, yes?? Now, this can be any circuit you like, not neccessarily the one that is faulty. All the neutrals are connected together in the "neutral block" in the CU.

Now, at the substation that feeds your house, neutral is connected to earth.

So, current can flow back to the transformer neutral either down the neutral, or down the earth.

An RCD compares how much current went down the "live" [yes you lot, i know!] to what "comes back" along the neutral. If there is more than a slight difference, it trips. This is how it tries to prevent you being killed; You stick your finger in a socket, and more flows down the "live" than comes back down the neutral, as the "missing" current is flowing through you... Result.. it trips..

Now you have a neutral earth fault and as you can now see, even if the MCB that feeds the circuit with the fault is off, the neutral is still connected to all the other neutrals, so a large enough load on ANY of the other circuits served by that RCD will cause it to trip...

You need to find the neutral fault. You have NO WAY of doing this unless; 1, you know what you are doing. and 2, you have the correct test equipment. This equipment will cost you about 10 times what an electrician would charge to tell you the problem...

Locating the faulty circuit will be easy, finding the actual fault may not.. Assuming that the wiring is not ancient, it has either been tinkered with by a pillock... or has sustained physical damage...

john...

 

[Andy™]

wonder if someone has wired the socket in a cable only capable of 6a and the sockets been used at 13a and melted the cable...