spuring off existing junction box wired in 1.5mm

[amateurSparky]

Hi
I want to add a new light in the hallway. The cable that I've purchased is 1.0mm twin and earth. The existing lighting circuit is wired in 1.5mm. Can I just use the 1.0mm for the lighting? The elctrician that orginally did the wiring put the downstair + upstairs lights on one mcb.

 

[EFLImpudence]

If a 5A fuse or 6A MCB - Yes, no problem.

Are you asking a question about up and down on the same circuit?

 

[PrenticeBoyofDerry]

It's good practise to keep the conductor sizes on circuits the same CSA.
The question you should be asking yourself is, was there a reason why 1.5mm was used rather 1.0mm.
Things to investigate;
Derating factors of cable (insulation, conduit/trunking, protective device type, cable grouping)
Protective device rating, load demand, Zs values.

 

[amateurSparky]

i think its 1.5 looks alittle too wide to b e 1.0. its just run through the cavity and the ceiling void so no conduit. its a 6a type b 60898. I think just to be sure i put some digital calipers just to be sure. I didnt see any markings. double check to.orrow. thanks for the heads up.

 

[EFLImpudence]

No need.

Just use the 1mm² cable.
Its maximum current carrying capacity is 16A - quite adequate for a 6A breaker.

A lot of electricians just use 1.5 (max. 20A)- It seems to have become fashionable for some reason.