I'm extending a lighting circuit to add a couple of wall lights on the
1st floor. I've got the cables laid from the loft down to the back
boxes for the switches and outlets for the lights, and now I need to
connect the new circuit to the existing lighting circuit.

Is it acceptable to spur off the existing lighting circuit at the most
convenient point, or are there rules to follow when deciding where to
spur from?

Most of the diagrams that explain how to add a lighting circuit show
it coming from the last junction box / ceiling rose in the circuit. I
don't know where the end of my lighting circuit is, and sods law would
ensure that it's a long way away from where I want it. I don't want
to be drilling or notching joists if I can avoid it.

My plan is to cut a permanent live cable close to where the new lights
will be and install a junction box at that point to connect the spur.
I'm not sure of the exact topology of the wiring in the loft, but I'm
hoping it doesn't matter.

On 24/03/2020 18:23, Caecilius wrote:
I'm extending a lighting circuit to add a couple of wall lights on the
1st floor. I've got the cables laid from the loft down to the back
boxes for the switches and outlets for the lights, and now I need to
connect the new circuit to the existing lighting circuit.

Is it acceptable to spur off the existing lighting circuit at the most
convenient point, or are there rules to follow when deciding where to
spur from?

Yup, although the circuit type is called a "radial" - you should not
take the term too literally. It doe snot all need to be a single chain,
and its perfectly acceptable to have branches as and where required.

Most of the diagrams that explain how to add a lighting circuit show
it coming from the last junction box / ceiling rose in the circuit. I
don't know where the end of my lighting circuit is, and sods law would
ensure that it's a long way away from where I want it. I don't want
to be drilling or notching joists if I can avoid it.

When wiring a new circuit that is often the easiest way to do it, and
also keeps the number of cables entering each JB / rose etc down.
However for extending, go with what ever works best for you.


--
Cheers,

John.

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I just branched off the most convenient point in the circuit but as I was replacing the total lighting circuit at the time the junction box ended up as part of the daisy chain. I did however fit a FCU in the loft just to be able to isolate the wall lights from the rest. We only switch the wall lights on/off using switches on the fittings so no wall switch.

Richard

On Tue, 24 Mar 2020 18:54:28 +0000, John Rumm
wrote:

On 24/03/2020 18:23, Caecilius wrote:
I'm extending a lighting circuit to add a couple of wall lights on the
1st floor. I've got the cables laid from the loft down to the back
boxes for the switches and outlets for the lights, and now I need to
connect the new circuit to the existing lighting circuit.

Is it acceptable to spur off the existing lighting circuit at the most
convenient point, or are there rules to follow when deciding where to
spur from?

Yup, although the circuit type is called a "radial" - you should not
take the term too literally. It doe snot all need to be a single chain,
and its perfectly acceptable to have branches as and where required.

Most of the diagrams that explain how to add a lighting circuit show
it coming from the last junction box / ceiling rose in the circuit. I
don't know where the end of my lighting circuit is, and sods law would
ensure that it's a long way away from where I want it. I don't want
to be drilling or notching joists if I can avoid it.

When wiring a new circuit that is often the easiest way to do it, and
also keeps the number of cables entering each JB / rose etc down.
However for extending, go with what ever works best for you.

Thanks. It's useful to get confirmation, as real-world experience
often differs from the neat and tidy diagrams.