Lighting circuit/ wiring not come across before

[Spark Of Light]

Alright ladies n gents,

First post warning lol
Anyway, even though am not qualified, i have read a lot on domestic installations/ circuits etc. But just recently, i have begun to install two new lighting points in a relatives bungalow, me actually expecting it to be junction box wiring system.
having laid all my cable runs/ switch cables/ first fixes etc. I then investigated the original wiring, only to find something i have not either read or seen(in my own installations):

Three single core red (sheathed)cables plus earthing to switch.
1 red to switch Common
2 red to L1 of the one way switch

Following the cables up into the loft, one of the red singles goes onto the next switch point (if this makes any sense?)

From what i've just been reading on here, it does sound like this is what you guys call Switch loop wiring?
But like i said, i have not come accross this before, and so am looking for guidance if poss. I can get pics up, but will take a few days.

Many thanks, iam currently in a position with my cables and switch/lighting points in place, but until i can clarify just what this wiring system is, iam not going any further.
Cheers
Lee

 

[johnny_t]

Don't really know what you'd call it, but it sound like the switch is kind-of the wrong way up, using L1 as the Common and Common as L1 (assuming of course that the next switch in the circuit does not rely on this one being on before it works). Doesn't really matter on a one-way switch anyway.

Your extra red (which I believe is permanent live) then goes to the next switch in the circuit, and then this switched live (from the other side of that switch) goes up to a light fitting. Hopefully that light fitting also receives a single neutral from the light that your first switch was feeding (they can get them from elsewhere, but you have the danger of getting a 'borrowed neutral' which is bad.

Don't know how it stands from a regs viewpoint - Is there an additional sheath (such as grey) beyond the red insulation ?

 

[JohnD]

Three single core red (sheathed)cables plus earthing to switch.
1 red to switch Common
2 red to L1 of the one way switch

Just to check:

You say there are three red cores (plus an earth) going to the switch. You have told us that one goes to COM and one to L1. Where does the third one go?

 

[johnny_t]

If I read it right, the last line of that should read '2 reds.....'

 

[JohnD]

Oh, is that what it meant?

1 I was thinking
2 It was an ordered list
3 Like this

 

[dingbat]

Spark, it was a very common method when wiring in singles in conduit. The lives are looped via the switches, the neutrals via the lights. May older properties use the same method with PVC/PVC insulated singles

So, at every switch you will see two permanent lives in one terminal and a switched live out to the light from the other terminal. And at every light you will find two neutrals, along with the switched live.

When you say you have an earth, is this contained in the same sheath as the red live conductor? If so, this is fine so long as the insulation resistance values are up to snuff. (You do know how to test Ze, Zs, IR, etc? )

To extend the circuit you need to pick up a neutral - ideally from the last light on the original circuit and a permanent live... which is where you may hit snags. If it was me I'd use single black to pick up the neutral and single red & Earth to pick up the permanent live and earth via a junction box in the loft and take these two cables to the first new lighting position, then use standard three-plate (ceiling rose) method for the rest.

 

[Spark Of Light]

Geez, thanks guys for the fast responce wasnt expecting anything back so soon....

to clarify

singles(and single and earth) have been run down to the switch
these are sheathed in grey sheathing
1 of the red singles goes to Common
2 (the others) reds go to L1

I have followed one of the cables into the loft onto the next lighting 1 way switch.

HTH, and thanks again
Lee

So dingbat, to wire in two more lighting points(seperate ones) am i going to have to take a live from a switch, and a neutral from a ceiling rose? onto my newly installed siwtch('s) and ceiling rose('s), and an earth feed to.

 

[dingbat]

Read this and it will all fall into place:

http://www.diynot.com/forums/viewtopic.php?t=7553

There are many ways to wire a lighting circuit and pretty much all of them are covered in that thread. If you spend a bit of time there you should understand how yours is wired and be able to tackle it. As long as the new lights are not in the bathroom or kitchen the work doesn't need notifying.

But do be sure to test everything before you start modifying. And if you don't know how to test I would question your ability to do the job. Best of luck and happy reading.

 

[Spark Of Light]

Read this and it will all fall into place:

http://www.diynot.com/forums/viewtopic.php?t=7553

There are many ways to wire a lighting circuit and pretty much all of them are covered in that thread. If you spend a bit of time there you should understand how yours is wired and be able to tackle it. As long as the new lights are not in the bathroom or kitchen the work doesn't need notifying.

But do be sure to test everything before you start modifying. And if you don't know how to test I would question your ability to do the job. Best of luck and happy reading.

Hi yes, i did have a quick read through that article, and thats the reason why i picked upon the fact that the system could be using the switch as the loop, and not the usual(or more common) ceiling rose as the loop. The lights are not in bathroom or kitchen! Is using a junction box to tap into the permanent live loop wires from switches an allowed practice, or should i be taking it direct from the end in the line switch (even though this would mean more work obviously)
Thanks again

 

[plugwash]

using junction boxes is fine as long as they are accesible.