Lighting circuits max demand and diversity

[Scott F]

Hi all currently wiring in a new build large property .downstairs lighting has 3 ciruits one circuit feeds 18 lights now (dont know the exact demand of fittings but its a cat/ class a house low emissions etc so he is going to use low wattage lamps)]4 of the lights are outside back and front 2 each],one is sub main cupboard 2 for hall 3 are wall lights for lounge. 2 in centre of lounge,1 in bedroom and 4 wall lights in open plan area.Now if you assume 100 watts per lamp 100 x 18 =1800 /230=7.8 amps.Was going to use 6 A mcb common sense and diversity allowed one is not likly to use all at once if i apply 66% should be ok .Or would it be better to install 10 amp mcb cicuit lengths allowing.Also bearing in mind 100w lamps are unlikly to be used .Any thoughts welcome

 

[Spudnik]

Hi Scott,

To save me typing have a look at Page 96 OSG.

Cheers

 

[Guest123]

Hey.

If the circuit is wired in 1.5mm then why not put 10A MCB on it.

If not then 6A will be fine as you say allowing for diversity it falls below 6A anyway.

Cheers

 

[Scott F]

Yeah thanks for replies guys lenny i think i will stick it on 6a .Jason read osg before posting min 100w to be assumed for lighting but if you have read the above .as designer we are allowed to let common sense prevail just wasn't sure .Pre match nerves and a little self doubt creep in every now and then hence the post cheers

 

[Spudnik]

Got to be honest, if cable allows, i would use a 10A MCB.

Cant see it being a prob.

 

[Scott F]

Will go back and measure lengths .With 10 amp you have 38 mts less to play with(column 4 pg 45 osg) that would be my only concern and yes i know this is the sort of thing one should do before .Usual excuses stress pressure get the job done.etc etc blah blah blah cheers Scott