Trying to find live feed

[Likelyhuff]

I’ve recently moved into house and had an electrician out to install some new lights and shaver point in an en-suite. Problem is that the house is 100 years old and has wiring all over the place (3 floors and 4 different consumer units). He was unable to find a live feed in the existing en-suite spotlights (only power in that room) and so we’ve been pulling up the chipboard on the floor above (a converted loft) to see if we can locate the junction boxes where the live feed is coming into (but no luck so far)

I’ve managed to track down a building regs certificate from 2016 which relates to the loft conversion and a separate certificate for a circuit alteration. My question is - is there any way to track down the full details or plans of what happened to the wiring in the 2016 conversion and help figure out where the cables lie without pulling up the entire floor?

 

[littlespark]

No. There isn’t normally wiring diagrams with electrical work.
Final positions of sockets, lights and switches may be marked up on a plan, but the routes taken will be up to the electrician at the time.


There are 3 ways to do lights.

Loop in at switch, where you have live and neutral at the switch, and a switched live and neutral taken up to the light.

Loop in at light, where the supplies are taken to each light, and a live and switched live taken down to switch

Central joint box. Where a cable from every light, and every switch is taken back to one point.


A lot of installations can be a combination of all 3 methods where additions and alterations have taken place.

 

[Likelyhuff]

No. There isn’t normally wiring diagrams with electrical work.
Final positions of sockets, lights and switches may be marked up on a plan, but the routes taken will be up to the electrician at the time.


There are 3 ways to do lights.

Loop in at switch, where you have live and neutral at the switch, and a switched live and neutral taken up to the light.

Loop in at light, where the supplies are taken to each light, and a live and switched live taken down to switch

Central joint box. Where a cable from every light, and every switch is taken back to one point.


A lot of installations can be a combination of all 3 methods where additions and alterations have taken place.

Thanks I suspected this would be the case. Unfortunately he can't find a live in either the switch or any of the spotlights. Would any documentation exist for the lcoation of a junction box (we suspect the live feed is coming up from the porch on the ground floor)?

 

[MJPD29]

Thanks I suspected this would be the case. Unfortunately he can't find a live in either the switch or any of the spotlights. Would any documentation exist for the lcoation of a junction box (we suspect the live feed is coming up from the porch on the ground floor)?

There will be a permanent live at the switch, it’s not possible for the lights to work if there isn’t. A neutral will be available at the lights.

 

[James]

There is always a live feed in the light switch.

only caveat is when there are 2 switches or more operating the same light fitting, the live feed could be in any one of the switches, not necessarily in all of them.

edit, just been beaten to the post by @MJPD29

 

[Likelyhuff]

There will be a permanent live at the switch, it’s not possible for the lights to work if there isn’t. A neutral will be available at the lights.

He's tested it and there isn't. That's what is so strange.

 

[James]

Might be time for a second opinion.

 

[Pretty Mouth]

He's tested it and there isn't. That's what is so strange.

The only way this is possible is if the switch is switching the neutral (which is a wiring fault).

 

[westward10]

How are they testing for this live?

 

[newfutile]

If the lights are working there has to be a live and neutral or maybe an earth and a wiring fault, they simply cant work otherwise .

 

[westward10]

As already stated there must be a permanent live at the switch but they say this is not the case. Reasons, as already suggested by @Pretty Mouth the neutral is being switched and not the line or, it is being tested incorrectly maybe from live to earth when the earth has no continuity to indicate it is live.

 

[davesparks]

As already stated there must be a permanent live at the switch but they say this is not the case. Reasons, as already suggested by @Pretty Mouth the neutral is being switched and not the line or, it is being tested incorrectly maybe from live to earth when the earth has no continuity to indicate it is live.

Or its just a confusion of terminology.

If I was looking for a feed in a lighting circuit I would be looking for somewhere to connect to both permanent L and N.

 

[davesparks]

There will be a permanent live at the switch, it’s not possible for the lights to work if there isn’t. A neutral will be available at the lights.

Yes but you wouldn't be running a permanent live from a switch and seperate cable for a neutral from a light point to feed additional lights and other points.

They are obviously looking for a place where they can pick up a L and N connection.

 

[Pretty Mouth]

In my local area, pre- 90's lighting circuits were often wired with sheathed singles, so the only place you would find both a permanent line and neutral in the same place would be at the CU. For alterations and additions, I usually have to take the L and N from different points, as @MJPD29 mentioned (usually by wagoing into the cables in the ceiling void).

 

[MJPD29]

He's tested it and there isn't. That's what is so strange.

Time for a change in staff because that’s not possible unless as above it is switching the neutral instead which would need rectified. The light switch has to switch the permanent live to the switched live, that is the basic concept of wiring lighting.

 

[MJPD29]

Yes but you wouldn't be running a permanent live from a switch and seperate cable for a neutral from a light point to feed additional lights and other points.

They are obviously looking for a place where they can pick up a L and N connection.

That shouldn’t be an issue. Many outdoor floodlights have a switched live single pvc/pvc from the switch and neutral/earth pvc/pvc from the closest light on the same circuit, which is perfectly acceptable.

 

[littlespark]

I think the problem is, there’s no power at the switch…. So they’re looking for where it comes from.