HELP!! I'm in the dark! - MCB problem

[wooks]

Please could someone help.

Everytime a bulb blows on the lighting on my ground floor (usually a GU10 50W spotlight), my MCB trips, and all the lights switch off (which as i believe it, is the right thing to happen) - i can usually just reset the MCB, turn the lights back on, which tells me which bulb has gone and i can then replace it.

However, in the last week, i've found that the MCB trips and the downstairs lights just go off!! - But NO bulbs have blown!!

When i try to reset (turn back on) the MCB, it makes a kind of knumb popping sound and doesn't stay in its ON position, in fact it just falls back to OFF.

I have to wait at least 15 mins before i switch it to its ON position and actually have it stay on.

4 days ago when the MCB first tripped, i waited 10 mins or so, reset the MCB and it seemed to be fine.
Then yesterday it tripped again and i did the same thing - again, it seemed fine (all the lights stayed on).
However, today, it has happened 3 times, the tripping is becoming more frequent and as i write this i'm sitting in darkness having not reset the MCB, for fear that it will just trip again!!

Could someone give me some advice as to why this might be happening and what i might be able to do to stop it - could it be a problem with the MCB. I didn't think there would a problem in resetting it.

It has worked fine for the 4 years i've been in the house and there have never been any problems!

Please help if you can - thanks!

 

[plugwash]

While it could possiblly be a fault in the MCB I would tend to suspect that there is something else going on. Most likely an intermittant short somewhere.

Unless you have an insulation resistance tester and know how to use it or you can access and inspect the bulk of the wiring in the circuit in question I would say it's time to call an electrician.

 

[Spark123]

Stop trying to reset the MCB.
It sounds as though is switching off because there is a fault on the circuit somewhere, it could be water in an outside light fitting, cable damage somewhere, bad connection or lamp heat causing melting.
Take a look around to see if it is something obvious like I said above, apart from that leave it off and call a sparky.

 

[wooks]

Plugwash,

Thanks for coming back to me so quickly.
Yup, you're right i have no equipment and no idea how to test, so i will be calling an electrician, however, my concern is that with the weather as it is at the mo (snow still falling), i'm not sure i'll be able to get anyone out.
So i was wondering if there was anything i could do!

Do you know if the MCB should be sticking in the OFF position like that - or more to the point, should i be having any problems in resetting an MCB?

From the other posts i've read on here, they suggest that if an MCB goes off, you should be able to simply turn it ON again - this is what's worrying me! I didn't think MCB's have time limits!

 

[wooks]

Thanks Spark123 - i have left it off for a while now - since around 10pm.

When you say water in an outside light, would this light need to be on in order to trip the MCB!?

The reason i ask is because it has been snowing/sleeting quite heavily here all night and my outside light could have water in it - however, i don't have it on all the time, its essentially a front door light, so only put it on when somene rings.

 

[Spark123]

Possibly, depends how it is wired. Sparks often do their best to avoid having more than is necessary in an outside light as it is often a pain to work all the wires inside them so it is probably yes - you'll need to have the light on, but I wouldn't swear to it!
Any signs of a water leak anywhere else? Could be water dripping into a JB or similar?

 

[wooks]

Thanks mate.
TBH i don't think there is a water leak anywhere as the house seems pretty water tight - but i can't be sure of course.
I'm hoping its the outdoor light - i'll check in the morning before i phone the electrician.

Wish i knew more about this stuff - i'm really worried that if there is a problem with the wiring then the only way to get to the ground floor lighting will be via the floor boards on the first floor!