Lighting circuit calculation help

[bathcity]

Hi everybody,

I've been asked at college- when installing additional lights to a house, whether it is necessary to install a seperate circuit when the existing lighting circuit already contains 10 lighting outlets. I know as a rule of thumb it's 10 lighting outlets per circuit, but what calculations do I use to determine this?

Thanks in advance.

 

[KFH]

The OSG diversity calc recommends a mimimum of 100W per lampholder or the connected load. 100 X 10 = 1,000 W = 4.3A. With the increased use of CFLs and LEDs the recomendation may one day change but there are stil lots of 5 X 40W light fittings being sold.

 

[manda]

I think it is possible to have 11 or 13 lighting outlets, depending on the rating of the protective device used, i.e 5A fuse =11 outlets, 6A MCB = 13 outlets but, as you already mentioned, best practice would be 10. I may be wrong, but that's how I understand it.