Lighting fault

[thomo27]

Hi all

Im working as an apprentice and I was in the process of removing a pendant and putting in a large chandelier

I had 3 sets of cables connected to the pendant , 3 browns to loops , 2 blues to N and a blue sleeved brown in SL.

We didnt have any umbrella fixings to fix the chandelier so I connected all browns to 1 piece of teminal block , the 2 N's to another and the Blue sleeved brown to its own.

The result being that all lights in the next room no longer work.

I will add that when I removed the cables the sleeving fell of the Switched live so I asked my workmate to flick the switch off and on whilst I tested for 240V on the relevant blue ,once identified I then sleeved it.

From experience can you guys give any insight into what might have happened ?

 

[PrenticeBoyofDerry]

Is there still a voltage at the loop?
you may have pulled a cable out when re-fitting

 

[rebuke]

The obvious answer would be you've misidentified the switched live, and hence have broken the neutral to the rest of the circuit (the next room).

I'd suggest you verify you have the correct SL, by isolating the circuit, then doing a continuity test between the blue you believe to be the switched live, and it's associated brown - verify that with the switch closed you have continuity, and with it open you don't, I suspect you'll find you've got the wrong one...

 

[TicklyT]

Your testing proedure looks a little flawed to me - what were you measuring for 240V with reference to?

If you had chosen the switched live as your reference, the neutral loop in would show the same results as the switched live you were looking for.

Testing with respect to earth is flawed if you cannot guarantee earth continuity to the fitting. induced voltages on a disconnected conductor could be anything, and it's not unknown for CPCs to be used as strappers for 2-way switching by those who don't know better.

Testing as rebuke suggests is a better approach:-
1. you're not working live,
2. you are proving continuity through the switch from a known reference point, and
3. Apprentices working on live installations when there are safer alternatives available probably deserve to be meggered

Sit down for five minutes with a piece of paper, draw yourself a diagram of what you can see, write down what you want to know and how you intend to test it, and you will probably see there are several different combinations that will give you the results you observed.

For instance, consider what happens to a disconnected loop out neutral if a light switch has been left on, or there's a bathroom fan with a timer connected to the circuit.

 

[thomo27]

great advice as always thanks guys

'If you had chosen the switched live as your reference, the neutral loop in would show the same results as the switched live you were looking for'

Yeah I feel a bit silly now lol

I also tested by holding a voltage glow stick against the blues and asked another worker on site to flick the switch , when the switch was flicked on/off there was 2 blues that glowed and 1 that glowed on/off at the flick the of the switch , this was the 1 sleeved and connected up.

However I will do a continuity test to identify for sure