Can I Borrow Your Grey Matter?

[securespark]

I attended a job today.

A lighting fault.

Customer said she got home during the day (no lights left on) and the fuse had blown for downstairs lights.

The board had two 5A fuses, one intact, feeding the upstairs lights and one blown. The blown one is connected to a sliced-off length of 1 milli that has been shorting.

My inital thoughts were maybe the cable had been sliced through by accident or by a rat. So I looked for the other end, but could not locate it.

This seems unlikely now, so I thought about the other option: that the downstairs and upstairs lighting are linked and the downstairs lighting has gone off because of an open circuit live or neutral.

Several things hint this may not be the case:

Usually, in a one-lighting-circuit house, the downstairs lighting is wired first. In this case, the upstairs is fully functional, so that would imply that if the circuit was wired as one, the feed from the fusebox must have gone to the upstairs first.

Usually, in a one-lighting-circuit house, the strappers are a twin & earth & the feed is connected to the hall switch with the switchwire at the landing switch.
In this case, the link from the landing switch position to the hall switch position carries 3 conductors (albeit twin and earth, not 3 core! )

There is no continuity between the hall ceiling rose cpc and the CU earth bar.
That means all three conductors are open-circuit.

I have been round all connections on the upstairs lighting. There is nothing loose or disconnected.

The blown fuse is labelled downstairs lights.

To my addled mind, the above things make it likely (though by no means certain) that the severed cable I found is the feed to the downstairs lights.

The one thing bothering me is I cannot locate the other end of the severed cable...

Can you offer any thoughts, please?

 

[Spark123]

Look at the closest light and see if you can follow the wires.
Odd that it is severed tho! Maybe someone has been playing and doesn't want to admit it!

 

[comms]

Not spured the down lighting off socket circuit?

I think you gonna have to lift the floor above cu & closest light to the cu, & trace the cable run.

OR maybe It's a set up for one of these TV trader programs (can he find & be honsest about the fault)

 

[Spark123]

Aye - there wasn't an old man who speaks in a fake foreign accent and looks like matt alright in disguise was there?

 

[333rocky333]

If you terminate the cut cable and replace the fuse what happens.

The other lights may be before the cut and it It may have been cut off ages ago and only just shorted.

 

[flameport]

The sliced cable is almost certainly the feed, as for the other end:

- Outside light that someone ripped off the wall, severing the cable in the process.

- Cable was in the wall cavity and something fell down the cavity onto the cable.

- House owner not providing the full story, such as someone tried to replace a light, pulled on the cables, broke them, then put the old light back and pretended nothing was wrong.

- Thieves started to rob the place for copper but gave up after the first cut

 

[securespark]

If you terminate the cut cable and replace the fuse what happens.

The supply is restored, but only to the cut length: It runs from the CU to the hallway under the floor: about 2, 2.5m.

That's the odd thing: I can't find the other end.

Assuming there was one. That may be a disused feed that has blown the fuse ages ago and the downstairs lights are actually wired in with the upstairs.

OR

My hunch is right & there is another end hidden somewhere under the floor.

I'm back tomorrow, so I'll have another good look round then.

 

[big-all]

bell transformer on the lighting circuit!!
havent got a clue if it would matter but mines is connected to the lights and can play up

 

[bernardgreen]

Best Guess

Some one cut the feed from CU to downstairs lights leaving the cut end you found, the other end that fed the downstairs lights was pulled back to somewhere it could be connected to the upstairs lighting circuit. That new connection has now gone open circuit.

 

[mattylad]

Are there little bits of rat (dead) under the floorboards too

 

[securespark]

Look at the closest light and see if you can follow the wires.

Did that. Results below.

Odd that it is severed tho! Maybe someone has been playing and doesn't want to admit it!

My thoughts entirely. But you have to go off what people tell you.

I think you gonna have to lift the floor above cu & closest light to the cu, & trace the cable run.

Did that. Results below.

The sliced cable is almost certainly the feed..

- House owner not providing the full story, such as someone tried to replace a light, pulled on the cables, broke them, then put the old light back and pretended nothing was wrong.

Very close!

Are there little bits of rat (dead) under the floorboards too

No, but I did look, expecting to find something that was once alive & chomping...


Traced the feed from the nearest light, heading down the hall wall next to a door frame...pulled off the architrave to find a severed 1 milli cable behind.

I am certain the householder was not telling me the truth, for whatever reason. The cable was completely severed very cleanly. After lifting the laminate floor to access the hall floor void, it became clear the flooring guys had sliced the bottoms off the door frame to fit the laminate under.
In doing so, they had severed this cable. That was laid before the HH moved in, two weeks ago. So, the lighting cable was severed at least two weeks ago, blowing the 3036 to oblivion & back, yet the lights worked a couple of days prior to my visit?

A modern-day electrical miracle!!

 

[Adam_151]

So what did you do... did the homeowner accept a bit of trunking up the wall to carry a new light feed.... or did you put it back in the door frame

 

[securespark]

On the basis that my repair was temporary, I let the cable out from behind the architrave into an adjacent (accessible) box containing a gas pipe & jointed it with a fresh length back to the CU.

I left extensive paperwork condemning the installation as NTCS & AR.