Lighting circuit problem

[doc39]

My downstairs lighting circuit tripped after I installed a new light fitting. I took it down and examined all wiring which looked fine. I reset the MCB and it tripped again without the light fitting installed just connector block. Now when I reset the MCB it appears on (not tripping) but there is no power to the circuit or the rest of the downstairs lights. Has the wiring being permanently damaged or is the MCB faulty? That is besides the fault which was there after the fitting was installed.

 

[fireman22]

how many cables have you got at the light

 

[doc39]

3 cables. Al are 2 core and earth. Coloured red and black except the switched main with the red tape attached.

 

[TheGaffersSon]

How have you wired them in the block, and have you checked your connections?

 

[Spark123]

How have you connected them? How many bits of block have you got?

 

[doc39]

All are wired in a block. 3 earths together with sheathing. 2 blacks together, 3 reds together and switched live on its own. Does n't seem to be any problem with connector block.

 

[fireman22]

can you pull cables out of the ceiling screw may have damaged cable

 

[Spark123]

Can you verify the switched live cable is the switch cable with a multimeter?

 

[doc39]

No but it was the original switched live. It worked with old fitting and still has red tape around it!

 

[fireman22]

sounds like screw damage which has "blown" the breaker. try to pull some slack out of the ceiling

 

[Spark123]

Long shot that it could have been mixed up, the other option of a damaged cable is also feasable, without any type of test equipment you are going to struggle.

 

[doc39]

I had considered fitting screw may have damaged cable. Looked under floorboards above and could not see any problem. Still does not explain why MCB now in on postion with no power in any downstairs circuits.

 

[fireman22]

if you can seee the cable in the area where screw could have touched then it may be the case that the red tape was wrongly marked? maybe? are you sure black with red tape was going to the live of the fittting? if this is all you have done and you haven't damaged any cable cant see what it could be other than maybe you have pulled cable out of a junction or nearby light, which is shorting?

 

[Spark123]

An MCB is a mechanical device, if the mechanism is broken it may look like it has reset but hasn't. It could be just disturbing the wires has shown up an underlying fault. Without any test equipment it will be almost impossible to find the problem.

 

[doc39]

I think screw damage may still be most likely and i can pull all 3 cables completely out from above to examine them. But why does MCB appear on when nothing is now live?