The reason that the circuit breaker or RCD is tripping is that there is a fault on the circuit. Most likely its heat damage caused by too high a wattage lamps being fitted in the light fittings, which has burnt/melted the wiring.

The only way to diagnose/trace this fault is to carry out an insulation resistance test, using a test instrument, and as such its not a DIY job unless you happen to have the correct equipment available to you.

Therefore its best to post up a job and get a registered electrician to identify and repair the fault.

If you haven't had any new lights added to the circuit recently then you most likely have a short somewhere (where a live cable is in contact with a neutral or earth cable either permanently or intermittently). This can be caused by many things, a loose connection (badly fitted connections can come loose with time) in a light fitting or junction box, leak from upstairs, rodent chewing through wire, nail through a cable etc.

If it is a fault on a light fitting you might be able to narrow it down by switching off all of the lights at the switches then switching the breaker back on. If the breaker doesn't trip straight away then go round and switch on each light one at a time and see if this trips the switch. If it does it is most likely a loose connection in or a faulty light fitting wired from the particular switch that tripped it. You will need to get someone to check that light fitting for you for loose connections or signs of burning. If the breaker trips with all the switches off it is probably a fault on the internal wiring somewhere and you will definitely need to call an electrician to trace it and rectify it.

I would recommend calling an electrician anyway as if you have break in a neutral wire somewhere this can cause arcing which can be extremely dangerous and is one of the main causes of electrical house fires. If you leave the breaker switched off this will eliminate any danger until you can have it checked out by a professional.

Almost certainly you have got a problem with the wiring, if you asked me to do it, it would probably take four hours or so to locate the fault, at which point I would be able to tell you how long it would take to fix. It appears from the question you are disabled, so get an able bodied friend to disconnect and turn off as much as possible to try and point to the area of the fault. So not good news really.

Tripping lights have a wide spectrum of faults, it could be a damaged/worn fitting, poorly installed lights sometime ago (latent defect), water ingress from upstairs to downstairs, water ingress of outside lights, loose connections, even vermin chewing cables is a possibility, faulty lighting transformers, there could be insulation breakdown on the cables or even other miscellaneous options such as pond pumps & lighting connected to outside lights which I have seen before!

Hi, going by what you have written the downstairs light circuit has a fault and trips out the circuit breaker (MCB) even if lights are not turned on. If this is the case then the fault cannot be easily isolated without the help of a suitable skilled and qualified person (usually electrician). Test, measurement and isolation of sections of the circuit is needed in order to locate the area or device or cable section that contains the fault.

you need an insulation resistance check done on the lighting circuit to see if there is a fault, or indeed it could be a faulty miniture circuit breaker, either way it requires some expert to help you, hope this helps, regards Jon

Hi Harold, best bet is to get an registered electrician out to carry out some fault finding as the problem could be anything from faulty wiring, faulty switch or even a faulty fuse/MCB/RCD, ring a few up and ask about call out fees etc but please get a registered/qualified electrician, post something on this site and see who is closest to pop out. Is the house owned or rented? if its rented call the landlord or housing office to get them to sort.
good luck Mark @ DTL