Lighting circuit not working

[asifboda]

Hi

Any help appreciated before I have to call an electrician and hand over me money...

Porch light blew the other day and the MCB tripped (this is as per the wife's retelling, I wasn't there at the time...). Wife reset the MCB but the circuit wouldn't (and still won't) work. The circuit has all the main lights for the front of the house (living room, our bedroom, hallway etc.) so we're keen to get them back on!

I swapped the MCB for the circuit with a spare MCB just in case there was some problem there (though I don't know for sure the other MCB is OK) but the circuit is still out. There are basically four pendants and two sets of LV halogens on the circuit. Each set of halogens seems to wired as a star.

Any ideas as to what I should check next? What's the most methodical way to isolate the fault? The circuit and all lights on it have been fine until the porch light blew and the wiring in the house generally is in good order.

Cheers

Asif

 

[flameport]

Any ideas as to what I should check next?

The porch light?

If already done, remove the lamps from the other fittings. Possible one has failed as a short across the supply.
Other than that, remove the transformers for the halogen lights.

 

[ericmark]

I would switch off all lights in case it was not the porch light that caused the problem. Remove bulbs if you don't know if on or off.
Try switching a know good MCB and compare the action with lights MCB if they don't feel the same likely you still have a short. On some makes of MCB lever will go to "on" position even though mechanism has tripped you can normally feel when this has happened.

 

[2face]

if you have the skills to swap the mcb try a basic continuity test on the circuit for a dead short,other than that its just a case of find the fault.

 

[Spark123]

I take it the first light from the CU isn't working but the MCB is resetting? If so this is the place to start - firstly isolate the supply. Check all the wires for the lighting circuit are nice and tight in the CU (tight enough so they don't come out but not overtight as to snap the copper! Check the neutrals as well as the lives, also good idea to check the earths too but this shouldn't cause the fault). Then to the first light on the circuit and check all the wires are nice and tight there too.

 

[asifboda]

Thanks guys. I did try a continuity test off the switch for the light that blew (I figured doing it at the switch was OK since I should be making the circuit) but that actually didn't indicate there was a circuit, so I guess I will take the lights / transformers off and recheck the roses etc. Not sure which is the first light off the CU though, any way of working this out?

Cheers

 

[Spark123]

If the CU is in the hallway then I'd start there, if it is in the living rm start with that one.
Start by checking the wires in the CU first tho.

 

[asifboda]

Well I took off all the halogens / transformers etc. and checked all the connections but couldn't see anything, although I did notice that when I attached one low wattage bulb to the circuit and switched it on I got a regular flashing, not very bright.

Got the electrician around, he says that the problem is "there is no neutral" which I think means there is a loose connection / break in the neutral wire somewhere. He said that live and earth were fine, but neutral voltage was only around 12V and fluctuating. I think the first set of lights off the CU are the halogens in the hallway but will have to do more peering into dingy corners to know this for sure.

There are some junction boxes in the ceiling somewhere where the halogen daisy chains were taken off the circuit etc. Finding the break will be tricky though and will involve having to take floorboards up, possibly carpets too, which I'm not looking forward to...

The electrician suggested an alternative, which was to take the neutral from another circuit and link it to the circuit with the problem. Not sure if this is a good idea, sounds a bit "dodgy"...?

Anyway, thanks for the assistance, will update once I have found the problem.

 

[Spark123]

It is a bad idea to borrow a neutral from another circuit. Better to fix it properly.

 

[ban-all-sheds]

The electrician suggested an alternative, which was to take the neutral from another circuit and link it to the circuit with the problem.

Define "electrician"....

 

[asifboda]

yes thought is sounded like a bad idea to jump the neutral.

electrician - someone who cost me £80 for the hour. although he was subcontracted by the company i called (his van had some other name on it, though he was wearing the company jumper...), which i had checked was niceic etc. etc. but won't be calling them again...

asif