Lighting tripping

[Southview]

Hi, Can someone point me in the right direction, I am having a kitchen ceiling plastered and whilst preparing for this I am fitting 3 mains halogens, on preparing the lighting today I switched the lightings circuit off via the consumer unit lighting fuse, I then disconnected the rose and then replaced the wiring into a junction box, the wires from the existing light were red/earth + black/earth the light is operated by two switches. I then connected two 1.5mm cables from the junction box one to feed a single halogen and the other to feed two halogens (linked from light to light), as the ceiling will be plastered I fitted normal pendants for now until job is done, anyway back to problem new wires were connected black to black, red to red and green to green, first pendant fitted and bulb put in, on doing the second pendant the wire was still continous but hanging down from the ceiling I then cut this wire in half, this is where my problem started the consumer unit tripped on the ON / OFF switch ? the wire was not live ? I switched power back on and wired the next pendant and the power tripped again but would not reset, I removed the first bulb and it then reset I then wired the next pendant and fitted three 100w bulbs and restored the power back to the lighting circuit, lights tried and all worked okay, carried on with jobs in the kitchen 3-4 hrs later tidying up lights went out, mcb had tripped in consumer unit all other mcbs were still in, reset mcb and lights back on again, what do I need to check to see what is causing lights to trip, ultimately will be fitting 3 50w halogens.

 

[BR]

The main breaker, is it an rcd/mcb combo unit (does it have a test button) although lights are not supposed to be connected via an rcd, it is possible that yours are. When you cut the de-energised (dead) cable you short the neutral / earth together causing the rcd to trip. There are many other possibilities but this is the first one to come to mind. If this is the cause of the trouble then your rcd is just doing its job and you needn’t worry. It is still advisable to check all junction boxes connections, visual inspection of cable etc. if this is possible.

 

[breezer]

a suggestion, what did you do with the earth cable (bare copper) it sounds like this is touching something, you should make sure it has green / yellow sleeving

 

[BR]

but with the single pole breaker tripped, it shouldn’t make any difference what the earth is touching unless an rcd is fitted. I suppose the earth could be contacting with a live from another circuit, but highly unlikely would you not say?

 

[breezer]

i agree, but just suppose the earth is not insulated and does touch the live

just had a thought

suppose its not at the lights the fault is, say for the sake of argument the poster fitted a jb, to connect the lights to, may be in there, crushed wire perhaps?

 

[Southview]

The earthing has sleeves fitted when I connected them into the JB I was careful when I pushed the wires into the JB but I will check again as I think this might be the most plausible answer as I have not had any trouble previously with the wiring saying that "touch wood" I have had no problems today when the ceiling was plastered with the electrics tripping, excuse my lack of knowledge regarding RCD / MCB I would not no the difference but my consumer unit does have a test button, neighbour suggested I check the earthing cable ? to make sure it is connected correctly as I have had speedfit piping fitted for new washer / sink etc.

Thanks for replies, I will be fitting the halogens shortly when plasterer has finished so I will double check the JB.