Loft Light Installation - Circuit Cable Hunting

[Tozzy]

Hi,

I need some advice please. I plan on installing a simple light fitting in my loft space which will use a "pull cord light switch". I do have some basic wiring experience and plenty of reference books with one of them dating back to the early 70s!!! Also, I'm very thorough, so I'm confident I can do this work to a high standard as long as I take my time.

It's more practical and cost effective to 'cut' into the circuit than extend it from the last ceiling rose isn't it? The problem is, I need to make sure I'm cutting into the main circuit cable and not a light switch cable so is there an easy way of finding out? I was going to find a cable which is nearest to the spot where the light will be fixed then determine whether it's the circuit cable or light switch cable so I was going to disconnect every light switch cable from every ceiling rose on the upstairs floor and then check if the cable (previously chosen earlier) is still live, that would indicate that it's the circuit cable and not a light switch cable; but I don't know if this is how it is done or not and I want to do it the right way or maybe there is an easier way.

BTW, the lighting installation is loop-in and there's 6 ceiling roses on the upstairs floor.

This will be my first proper wiring DIY project

Hope I'm on the right track so far?

*Waits for someone to say that you can't do this and you can't do that *

 

[PrenticeBoyofDerry]

I need some advice please. I plan on installing a simple light fitting in my loft space which will use a "pull cord light switch". I do have some basic wiring experience and plenty of reference books with one of them dating back to the early 70s!!! Also, I'm very thorough, so I'm confident I can do this work to a high standard as long as I take my time.

Does this include the correct inspection/test methods to confirm that your work is compliant and safe and the documenting of this?

It's more practical and cost effective to 'cut' into the circuit than extend it from the last ceiling rose isn't it?

Is it? Why would you come to that conclusion?

The problem is, I need to make sure I'm cutting into the main circuit cable and not a light switch cable

So maybe it is mare practical and effective to extend from a know source?

so is there an easy way of finding out?

There is a way but not something I consider safe, you would need to identify cables and use non-contact voltage stick/pen, to ID permanent live cables against the switch cable, but this is not an instrument would over trust.

I was going to find a cable which is nearest to the spot where the light will be fixed then determine whether it's the circuit cable or light switch cable so I was going to disconnect every light switch cable from every ceiling rose on the upstairs floor and then check if the cable (previously chosen earlier) is still live, that would indicate that it's the circuit cable and not a light switch cable; but I don't know if this is how it is done or not and I want to do it the right way or maybe there is an easier way.

By the time you have figured that out it could have been more practical and time effective to extend from ceiling rose

BTW, the lighting installation is loop-in and there's 6 ceiling roses on the upstairs floor.

So should be simple to loop in at rose then.

This will be my first proper wiring DIY project

Well make yourself aware of installation techniques and regulations that relate to the present day, not a book that date backs 40 years.
There is plenty of info in Wiki //www.diynot.com/wiki/Electrics:index

*Waits for someone to say that you can't do this and you can't do that *

It's not that you cannot do it, just do some research in to the current regulations. And that you do it safely.
As you say your first proper wiring DIY project, so do some research!

 

[EFLImpudence]

It's more practical and cost effective to 'cut' into the circuit than extend it from the last ceiling rose isn't it?

You don't have to use the last rose.
You can use any of them.

 

[Tozzy]

Hi PrenticeBoyOfPerry,

It'll be easier to quote back so you know what I'm replying to.

Does this include the correct inspection/test methods to confirm that your work is compliant and safe and the documenting of this?

It doesn't include this no, but my motto is: As long as the bulb lights up, it's working no matter what way it's done . Ok, seriously, if an inspection is necessary, I can get the work inspected or if this is something that I can do, then i can learn how to do it. Everyone I know has never bothered though (probably because it involved money ).

It's more practical and cost effective to 'cut' into the circuit than extend it from the last ceiling rose isn't it?

Is it? Why would you come to that conclusion?

For the simple reason that the last ceiling rose might be miles away from where I'm placing my light fitting and it could be a long cable run as opposed to mounting the light close to the nearest circuit cable . Also, I believe the long cable run could contribute to a bit of volt drop as opposed to a shorter run.

The problem is, I need to make sure I'm cutting into the main circuit cable and not a light switch cable

So maybe it is mare practical and effective to extend from a know source?

Of course, whether it be from an existing rose or directly from the circuit cable and I won't be going ahead with anything until I'm 100% certain of the source. I've already spent hours planning this and I'll spend as long as it takes.

so is there an easy way of finding out?

There is a way but not something I consider safe, you would need to identify cables and use non-contact voltage stick/pen, to ID permanent live cables against the switch cable, but this is not an instrument would over trust.

That's the method i was thinking. I've read this about the voltage stick pen about 100 times this week lol. Everyone seems to say the same thing. I've actually just bought myself one. I always make sure I test it and test it and test it again.

I was going to find a cable which is nearest to the spot where the light will be fixed then determine whether it's the circuit cable or light switch cable so I was going to disconnect every light switch cable from every ceiling rose on the upstairs floor and then check if the cable (previously chosen earlier) is still live, that would indicate that it's the circuit cable and not a light switch cable; but I don't know if this is how it is done or not and I want to do it the right way or maybe there is an easier way.

By the time you have figured that out it could have been more practical and time effective to extend from ceiling rose

yeah, it would be a lot easier. i was going to have the light directly above the hatch and I noticed there was a cable right there providing if it was the correct one and thought, it would only need to be a metre run and won't involve lifting loft thermal insulation up etc to snap a new cable run in place if it were to be spurred, but finding the cable would be a bit of a pain to cut in as I said, I'd have to disconnect all the light switches to find this out.

Maybe I should have a proper good look in the loft first to see what I'm up against.

Thanks for the link. I'll definitely be doing more research on this.

 

[sparkwright]

It's best to avoid junction boxes (nowadays).

As PBoD suggests, get a supply from a convenient loop in ceiling rose. Check it does have a permanent supply in it, your post suggests it does.

Doesn't have to be an end of circuit rose.

From the rose, run a 1.0 or 1.5 mm2 twin and earth cable to the switch, then from the switch to the light.

At the switch, join the earths to the earth terminal. Join the two neutrals to a separate 5 amp connector block. Put one live to one side of the switch, the other live to the other side.

Be sure to use earth sleeving on the bare earths. You said you want a good job, so take care with the cable clipping and make sure it's nice and neat, and make sure the wires at the accessories aren't too short or too long.

 

[Tozzy]

So it's basically like how double pole cooker switch would be wired?

Join the two neutrals to a separate 5 amp connector block.

This is the part that confuses me because I'm thinking you mean the little connecting blocks used in small lamps etc, but you mean the terminals inside the corded pull switch right?? If so,then I think I know exactly what I'm doing now and will likely use your method, but I'll need to reread and think about it in the moring when i feel refreshed

You said you want a good job, so take care with the cable clipping and make sure it's nice and neat, and make sure the wires at the accessories aren't too short or too long.

This is the part that takes me hours because I like to get things perfect otherwise i don't feel like I've done a good job.

 

[EFLImpudence]

Your post has been changed but you know what you wrote.


No,
The ceiling rose is the ceiling rose and junction boxes are junction boxes.
What was meant was don't use junction boxes unless absolutely necessary.

The CPCs(earthwires) must be connected to each other at every point otherwise if it is needed somewhere it won't actually be connected to earth.

The connector for the neutrals goes inside the switch.
You could avoid the need for a connector by carefully removing the sheath and only cutting the live conductor to connect to each side of the switch unless it is a double pole switch and/or the CPC is needed for a metal switch.


Your posts are presumed to be humorous but they do convey a rather too cavalier attitude.

 

[Tozzy]

You could avoid the need for a connector by carefully removing the sheath and only cutting the live conductor to connect to each side of the switch unless it is a double pole switch and/or the CPC is needed for a metal switch

Not really sure what you mean by this, so I'll go with the connecting block method.

Your posts are presumed to be humorous but they do convey a rather too cavalier attitude.

Sorry, it's just the way I talk on most forums, but I'll tone it down, particularly on this forum section. I can assure you though, I take the safety of myself and others seriously so there's no worries there.

I still want to make 100% certain that what I'm doing will be correct so here's a little diagram of the setup:

Untitled

• Tozzy
• 8 Mar 2014
• 1

Is this correct? If so, looks pretty straight forward.

From the rose, I'll likely run 1.5 mm2 twin and earth cable as there is insulation in the loft.

 

[EFLImpudence]

Not really sure what you mean by this, so I'll go with the connecting block method.

Ok.

Sorry, it's just the way I talk on most forums,

That's alright.

I still want to make 100% certain that what I'm doing will be correct so here's a little diagram of the setup:

Untitled

• Tozzy
• 8 Mar 2014
• 1

Is this correct? If so, looks pretty straight forward.

Yep, that's all there is to it.

From the rose, I'll likely run 1.5 mm2 twin and earth cable as there is insulation in the loft.

1mm² would be plenty.