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New Light Fitting and now Circuit Breaker Broken

Postby Llian » Tue Jun 26, 2018 7:32 pm

i've just tried installing a new light fitting and assumed it would be straight forward, just match the correct colours into the white box etc but I managed to break the Micro Circuit Breaker when I turned it on.

Following a quick trip to screwfix for a new MCB I've tried again. there are 3 red cables entwined, 2 blacks entwined, one black on its own and one green. The first time which damaged the MCB I'd put all the black in together so the 2nd time I only used the two entwined blacks, not the third. this time the lights seemed to work fine. untill i realised I couldn't turn them off at the light switch.

I then tried opening the light switch and disconecting the live cable and the light still came on... a bit concerning. I reconnected the live cable and for some reason the light didn't turn on this time despite the only change to the curcuit was "completing" the curcuit by reverting that previous change.

I am now not able to get the light to turn on. Although I will say since replacing the broken MCB after the initial failure, the rest of the lights have worked downstairs each time with no problems it's only that one light.

I don't know if it's something to do with the switch, the light itself or the wiring, It previously wasn't connected to the earth but I'm unsure about trying it without connecting to what I think is the earth when I know something is wrong somewhere.

I'm assuming the earth is the earth because it has a inch or so of the green insualtion on it although like i said not used on the previous light fitting and goes bare again after that inch as it goes into the larger cable which both the live and neutral come from in the ceiling.

Any thoughts on what is going on? My DIY skills were non existant at the start of the year so it's a steep learning curve since getting my own place.
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Simply Build It

Postby chriscba » Wed Jun 27, 2018 9:59 am

The single black wire should have had a red sleeve or red tap on it, this is the switch wire(live)
The two blacks together are the neutral loop in & out. you must have had a dead short when you put these blacks together & a load bang.
The three reds are the live loop & switch feed.
In the switch, the black wire should have red sleeve or tape.

if all this correct & the light does not work, check the connections are tight & there is no broken cables.

Frankly speaking, you should never of attempted this, you could have killed yourself, leave it to the sparks next time.
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