Light Switch Project (need advice please)

zorgan · 28 Jan 2010

Hi everyone,

I had a light in my spare room fail on me a few months ago, after taking off the light switch to measure the voltage i was getting all sorts of strange readings, sometimes i would get a reading sometimes it would be wrong etc

I found out that there was a breakage in the cable which lead back to the meter, there was no way i could repair this as i stay in a flat and the ceiling is solid concrete with limited access, the cabling is also tied at certain areas and apart from that some beams there too, would had been quite a big job.

So i decided to break off the existing cabling and replace from the light switch to a socket on the same wall around 3 meters to the right of the lightswitch.

I have so far noticed an old spur there which i believe is on the same circuit breaker as the sockets around the house. (see pic right hand side)

the socket had 2x cable going into it

the spur has 240v supply constant also

as you can see by the pic i took a feed from one of the cables, ran it along behind the skirting, really not sure what to do next though, as i have only an inch or so depth before i hit pretty hard bricks.

The issue i have at the moment is joining these cables, stepping down the ampage so it`s safer. can anyone advise what i should do next?

really need some help, i have a photo here showing the stage i am at.

as you can see the main problem i`m going to have is fitting more cable in there and fitting connector blocks in there?

ONE OPTION could be this?

Swap the spur so its on the left then feed both cables into this? or is this wrong as the other cable (one sticking out is probably going to another socket in the room?)

Then with the right hand side one put a socket only?

Not sure how to do this so everything is above board....

Oh another thing, the meter we have it has no RCD fitted (i dont think)

The main house earth goes to a communal earth i suspect, all i need to know really is the correct configuration, if it means having to chisel more wall away for space to putting more cabling in i can probably just do this.

In the pic below ALL 3 cables are LIVE when tested (left middle and right)
all have an independent feed i think.

big-all · 28 Jan 2010

heeelllooo and welcome zorgan

may i respectfully suggest you stop what your doing as you are not only thinking about connecting a lighting circuit to a ring main you are also involving an old storage circuit

please study some basic circuit diagrams in the wiki to see the dangers and problems you will cause by your lack off understanding

ban-all-sheds · 28 Jan 2010

zorgan said:
I had a light in my spare room fail on me a few months ago, after taking off the light switch to measure the voltage i was getting all sorts of strange readings, sometimes i would get a reading sometimes it would be wrong etc

Voltage between what and what?

Measured with what?

I found out that there was a breakage in the cable which lead back to the meter,

How did you find that?

How and where did it get broken?

there was no way i could repair this as i stay in a flat and the ceiling is solid concrete with limited access, the cabling is also tied at certain areas and apart from that some beams there too, would had been quite a big job.

Does this damaged cable supply anything else? Would replacing it be a bigger job than dealing with the after effects of a fire?

So i decided to break off the existing cabling and replace from the light switch to a socket on the same wall around 3 meters to the right of the lightswitch.

What existing cable(s) run to the light switch? If just one twin & earth cable (probably) then that would be just a switch cable, no neutral, so how would a live from another circuit help you?

Or if the lighting loop runs through the switches, how are you going to keep that intact and separate for the rest of the lighting circuit whilst somehow supplying this one light from another circuit?

Please look at this and see how lighting circuits are wired: //www.diynot.com/wiki/electrics:lighting

I have so far noticed an old spur there which i believe is on the same circuit breaker as the sockets around the house. (see pic right hand side)

You "believe"? What did you turn off to make it safe to work on?

The issue i have at the moment is joining these cables, stepping down the ampage so it`s safer. can anyone advise what i should do next?

You should stop everything you are doing, or planning to do, and probably call an electrician.

You must not leave the socket ring circuit broken.

You must not run cables behind a skirting board.

You must not bury choc-block connectors.

You must not leave choc-block connectors unenclosed.

You must not use choc-block not rated for 30A.

You must not have unsleeved earths.

And what you want to do won't work anyway - taking L/N/E from another circuit to a light switch won't allow you to get the light working, or if it does it won't be safe.

In the pic below ALL 3 cables are LIVE when tested (left middle and right)

Tested with what?

all have an independent feed i think.

an old spur there which i believe is on the same circuit breaker as the sockets around the house.

Well which is it?

zorgan · 28 Jan 2010

Voltage between what and what?

Voltage measured 40Volts if i remember correctly, it then went dead after a while, nothing......this was behind the light switch

Measured with what?

Measured using a multimeter set to AC Measurement

___________________________________________________

How did you find that?

I managed to discover that there must had been something wrong with the cable from the 1st rose in the hallway to the spare room where i was getting inconsistent values measuring on the meter and no light at all from the light in the room (sorry i never meant to say from the meter as all other lighting in the house works just fine)

How and where did it get broken?

I do not know how it got broken, but i believe the location it got broken was within the ceiling heading back toward the primary rose which feeds the rest of the lighting circuit in the flat.

___________________________________________________________

Does this damaged cable supply anything else? Would replacing it be a bigger job than dealing with the after effects of a fire?

I have disconnected the live cable from the primary rose in the hallway so it is not live and does not feed anything else either

____________________________________________________________

You "believe"? What did you turn off to make it safe to work on?

I removed a single 30A circuit breaker then tested with my meter both the socket and the spur which resulted dead afterward.

____________________________________________________________

Tested with what?

My Voltage Meter

____________________________________________________________

all have an independent feed i think.

what i mean to say, each cable is on the 30A Breaker as all are dead when removed, but each cable the left middle and right are live when tested with the breaker in. so i have 3 individual live cables.

1. was going to the socket
2. was also going to the socket
3. is going to the spur

zorgan · 28 Jan 2010

You must not leave the socket ring circuit broken.

understood,

You must not run cables behind a skirting board.

I shall raise the carpet and take up the floorboards instead and feed the cable this way then if need be.

You must not bury choc-block connectors.

okay i understand, what do you suggest?

You must not leave choc-block connectors unenclosed.

okay i understand, what do you suggest?

You must not use choc-block not rated for 30A.

understood.

You must not have unsleeved earths.

this is work in progress, i have earth sleeve here which i shall use if need be.

And what you want to do won't work anyway - taking L/N/E from another circuit to a light switch won't allow you to get the light working, or if it does it won't be safe.

even if i put a separate spur with a more suitable rated fuse?

ban-all-sheds · 28 Jan 2010

zorgan said:
Voltage between what and what?

Voltage measured 40Volts if i remember correctly, it then went dead after a while, nothing......this was behind the light switch

No - not "what voltage?" - "voltage between what and what?"

i.e. between which two points did you measure?

I do not know how it got broken, but i believe the location it got broken was within the ceiling heading back toward the primary rose which feeds the rest of the lighting circuit in the flat.

So you've not actually found a damaged cable?

1. was going to the socket
2. was also going to the socket

Ans they must still do so - you must not leave them disconnected, it's very dangerous.

Please call an electrician.

Oh, and BTW:

ban-all-sheds · 28 Jan 2010

zorgan said:
You must not bury choc-block connectors.

Click to expand...

okay i understand, what do you suggest?

If you use anything with screw connections it must remain accessible for inspection.

You must not leave choc-block connectors unenclosed.

Click to expand...

okay i understand, what do you suggest?

A junction box.

this is work in progress, i have earth sleeve here which i shall use if need be.

WIP should at all times be properly done.

even if i put a separate spur with a more suitable rated fuse?

No, because the issue is one of interconnecting different circuits.

Please get an electrician.

Oh, and BTW:

zorgan · 28 Jan 2010

ok ban-all-sheds

Probably a good idea i do, just so i have a rough idea how much this is going to gost to repair, what do you recon? just so i have a rough idea.

I also know what he is going to say, run another cable from the hallway rose (which believe me is going to be pretty messy and i`ll probably have to do a lot of decorating afterward)

this is going to cost an absolute fortune :/

this is why i would rather seek the correct advise from here and do it myself.

ban-all-sheds · 28 Jan 2010

zorgan said:
I also know what he is going to say, run another cable from the hallway rose (which believe me is going to be pretty messy and i`ll probably have to do a lot of decorating afterward)

There's no other way to get the light working again that doesn't involve even more work.

zorgan said:
this is why i would rather seek the correct advise from here and do it myself.

zorgan · 28 Jan 2010

okay that's a lot of books to read

oh and the light is already working, i have just lost all the sockets in the room at the moment that's all

ban-all-sheds · 28 Jan 2010

zorgan said:
okay that's a lot of books to read

There's a lot to learn.

oh and the light is already working,

Safely?

You've removed the cables from behind the skirting board and run them in acceptable zones?

You've replaced the choc-block with something more suitable and located it properly?

You've added an FCU?

You've rewired the lighting circuit so that there's no interconnection between it and the socket circuit?

You've carried out tests to prove continuity of the cpc, and the ring final conductors?

You've checked the insulation resistance of the modified circuit?

You've checked polarity and the earth fault loop impedance at each point of use?

Just because it works that doesn't mean it's safe.

i have just lost all the sockets in the room at the moment that's all

No, that's not "all" - have you turned a ring into two radials, each inadequately protected and a fire risk?

big-all said:
may i respectfully suggest you stop what your doing as you are not only thinking about connecting a lighting circuit to a ring main you are also involving an old storage circuit

ban-all-sheds said:
You should stop everything you are doing, or planning to do, and probably call an electrician.

ban-all-sheds said:
Please call an electrician.

ban-all-sheds said:
Please get an electrician.

zorgan · 28 Jan 2010

Hooking the socket back the way it was

using the fused spur to the right instead with a 5 amp fuse

this should be safe enough. if anything goes wrong the fuse will go anyway.

if anything shorts between the spur and the light

i will use a junction box and hook it together under the floor boards to repair the socket ring on the left.

I am going to run the cable under the wall/floorboards.

cheers.

ended up working it out myself, this is all i was wanting to do in the first place really.

i doubt very much there will be a fire mate. the old lighting cable is totally disconnected.

Guitarguy · 28 Jan 2010

Providing the earth loop impedance is low enough at that point of supply, which you don't have the equipment to test it with anyway.

DCC · 28 Jan 2010

zorgan said:
as i stay in a flat

Zorgan are you the owner of this flat or are you making someone elses electrics unsafe?

Get an electrician - even if there was a fault with the original cable you'd be surprised how resourceful electricians are at replacing cable without destroying a property.

EdwardCurrent · 28 Jan 2010

zorgan said:
Hooking the socket back the way it was

using the fused spur to the right instead with a 5 amp fuse

this should be safe enough. if anything goes wrong the fuse will go anyway.

if anything shorts between the spur and the light

i will use a junction box and hook it together under the floor boards to repair the socket ring on the left.

I am going to run the cable under the wall/floorboards.

cheers.

ended up working it out myself, this is all i was wanting to do in the first place really.

i doubt very much there will be a fire mate. the old lighting cable is totally disconnected.

You must know that it makes sense to call an electrician to get this sorted properly, or at least to test the circuit.
Regards
Ed.

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Light Switch Project (need advice please)

EdwardCurrent

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