Help, Lighting Trouble!!

[carl9254]

Right been on a job today to swap an electric oven, done. but while i was there they said they had some lighting problems.
Last night the fuse got blown to bits when they turned the bathroom light off. (yes its an old re wire able fuse box) so i checked in the ceiling rose and everything looked ok, took each wire out and did a beep test with my meter and one cable beeped between live and neutral, is this my problem?? I am not very experienced at testing and fault finding. I then put every cable back apart from that 1 cable.
So i risked putting the fuse back in and no bang but only part of the lighting circuit works, obviously because this cable is the loop and it was live when i tested it.
Im going back in the morning so any help would be great!!

 

[eddielarge]

Sorry to ask but what is a bleep test. Have u tried an IR test, sorry to ask this but are u an electrician as it's a light and you did a few basic tests. Are u sure its L and Nu tested between and not the sl and live. As this would bleep.

 

[carl9254]

Sorry, its a resistance test but i set it to bleep if the 2 wires are in contact. Its definitely not the switch wires as i found them. But its not a megger i am using, just a multi meter.

 

[eddielarge]

Sorry, its a resistance test but i set it to bleep if the 2 wires are in contact. Its definitely not the switch wires as i found them. But its not a megger i am using, just a multi meter.

Surely u have to test and find out the incoming leg and if the ir is ok then test out going leg to next fitting. And then test switch line. Oh and make sure all lamps are out. This is how I would approach it.

 

[RexT]

Hi carl9254,

It is interesting that the fuse blew when the light was turned off and I am worried that you may harm yourself or others if you pratice the 'find out whats what' with live conductors. Every one has to start somewhere but don't learn by killing yourself or others, it's worth asking before if you are uncertain. Just because it doesn't go bang means its safe.
I agree with the comment by eddielarge, I would start by confirming safe isolation of the circuit (ensure that it is dead to work on) then doing the dead (de-energised) tests confirming the continuity of the live, neutral and circuit protective conductors, then do an insulation resistnace test across the line to neutral, line to cpc, and neutral to cpc. (This should prove if there is a short between the conductors or not). Write down your results and check them to what you should have. It would be a good idea for you to draw a simple diagram of the connections to establish that they are correct. This should help you in the process of finding out what was wrong. Always try to work in a logical sequence and dont get dragged along into assuming things.

Hope this helps,

Best wishes,

Rex

 

[SirKit Breaker]

Have you got 3 twin and earth cables at the pendant?

If you have, and it sounds like it, then you will have 3 red, 3 black and 3 earths, or brown and blue depending on the age of the cable.

You need to find the switch cable, this will be one of the 3. Do this by disconnecting all 3 at the pendant, then with your multimeter touch it on one of the pairs of black and red with the switch turned on, if it beeps then that is the switch. At the pendant connect the remaining 2 cables, red to red, black to black and neutral of the light, Then connect the switch cable red to other reds and black to the live connection at the light (this should be sleeved red). Shove all the earths together and your lights will work.

BEFORE STARTING MAKE SURE THE CIRCUIT IS NOT LIVE.

 

[carl9254]

I actually have 4 cables, someone has obviously got another feed for something. But i have found which is the switch cable and that is fine, the cable i have left out, which i think is the trouble some cable is live when the fuse is back in so it is the feed from another light. They dont have much of a loft but im going to get myself in there tomorrow and see if i can trace where it is coming from. Could it be the fact it is not this cable but when it is put in the ceiling rose and power is too all the other cables it could be one of them?? I am only going off the fact that this cable gave a reading when tested between live and neatral and none of the other cables in the ceiling rose did apart from the switch wire obviously.

 

[eddielarge]

I actually have 4 cables, someone has obviously got another feed for something. But i have found which is the switch cable and that is fine, the cable i have left out, which i think is the trouble some cable is live when the fuse is back in so it is the feed from another light. They dont have much of a loft but im going to get myself in there tomorrow and see if i can trace where it is coming from. Could it be the fact it is not this cable but when it is put in the ceiling rose and power is too all the other cables it could be one of them?? I am only going off the fact that this cable gave a reading when tested between live and neatral and none of the other cables in the ceiling rose did apart from the switch wire obviously.

Sounds like mice or rat in loft.

 

[Phil]

or a squirrel as i found out in mine. messy things they are up in the lofts

 

[GStueyXR]

In a lighting circuit, you will get continuity between line and neutral conductors if there is a bulb in another part of the circuit, and the switch is on. Either remove all bulbs or switch off all lights.

Simples.

 

[RexT]

Hi Carl2954,

I have been thinking and still find it odd that it caused the fuse to blow on a situation where the light was being turned off (ie opening a circuit)
Wiring check at the switch or switches is a good check.
Good luck and I think the advice by the guys here is very good,
Hope you get to the bottom of the trouble,
Best wishes
Rex