On 29/09/2018 10:04, The Natural Philosopher wrote:
On 29/09/18 09:29, Scott wrote:
Simplistically, am I right in understanding that a lighting circuit is
linear (not a ring main)?

Yes

All the action takes place on the red (*)
wire.
Yes

In each room there are two drop cables: one to the switch and
one to the light fitting.

Yes ot no depending

The electricity goes from the ceiling to
the switch then back to the light fitting (via the black) then through
the light bulb to the main black wire.Â* The same is repeated in each
room.

No.

Erm, yes! That's the way most loop-in systems are wired. Ideally with
some coloured sleeving over the neutral wires where they are being
re-purposed as switched lives.

In genereal the cable goes from te curcuit to the stich, and then on
again to the next swich and cables are run from te switch to te light
fitting. So the switch has THREE cables entering it.

That is another method ("switch loop in"), but its far less common.

Even if te light fiffing istelf carries the nain circuit it is
coinventional to run TWO cable to the switch so as NOT to have s bcak
wire being swtiched live.

That's even less common (to the point I have never seen it done)

This means only one cable is connected to the consumer unit.

Yes

Â* I
believe a red sheath should be fitted to the black wire at the switch.

Yup

I believe its not done like that in best practice, I never have.

Its is a regs requirement, since you are using a wire for a purpose its
colour would not indicate otherwise. I will agree its frequently missing
however, but it should be there.

In the limit you need to carry live, switched-live and earth to the
switch as you have surmised, but I do not think that normal T & E colors
are used in that case.

You can get a T&E with two red/brown conductors, but its rarely used
since normal colours and over marking is acceptable.



--
Cheers,

John.

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