Extra loft light

[rjm2k]

A few years back I boarded my loft and added a light which runs from the ceiling rose in the room below and has its own switch in the loft. Now my loftspace has been increased due to the removal of the main water tank and I'd like to add another light controlled by the same switch further down the loft. I guess the easy way is to connect the new light to the existing loft light, but I know you aren't supposed to take a spur from a spur on a ring main, is this an issue with light circuits? if so, what's the best way of wiring this up?
Thanks

 

[ricicle]

There should be no problem just paralleling up with the existing light as long as you are not fitting something stupid like a 500W t/h fitting and feel competant to do the work.

 

[Space cat]

The "no spur from a spur" rule is to do with cable and breaker sizes. On a ring main you're using two lengths of 2.5 sq mm cable in parallel. These have a current rating of 20 amps each and they're on a 32 amp breaker. In practice, that 32 amps will not divide equally between the two cables but it'll be sufficiently well balanced so as not to overload one of them.

When you put a spur on, you're using a single length of the same cable and so, on the face of it, the breaker is too big. The let-out is that you can't draw more than 13 amps from a single socket or FCU. This is one of those cases where a fuse protects cable that lies upstream. (Another one is your main service fuse which has to protect the cable coming in from the street.) But, if you were to put a second spur onto this spur, you could draw 26 amps; too much for the cable but not enough to trip the breaker.

Lighting circuits are different in that the cable is all at least 1 sq mm. This is adequately protected by a 6 amp breaker so you can 'spur' multiple lights off an existing light with impunity. There is no difference, current-wise, between adding a light in parallel with an existing one and tapping into a rose to add a new light with it's own switch.