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. The same is repeated in each
room.

No.

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.

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.



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

Yes

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


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

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.


(*) Although I refer to red and black, I appreciate these may be
brown and blue. I have ignored the earth but I assume every earth
should be connected to every other earth at every opportunity.



--
Theres a mighty big difference between good, sound reasons and reasons
that sound good.

Burton Hillis (William Vaughn, American columnist)