rules of thumbs for lighting circuits

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TTbangbang

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Evening ladies and gents,

I remember reading a post where someone had said they wouldn't put more than ?8 light fittings on a circuit. What rule of thumbs do you have for lighting circuits and why? And that question goes to no.2! :D

I've been designing lighting circuits and worked out that 1800W (18 lights) can be carried by under 35m of 1.0/1.0mmsq with a 10A breaker. I then idly opened an old Collins wiring book and it said any more than 1200W means splitting the circuit... :eek:

(and what happens with fittings with multiple pendant lights? Three chandeliers in one room with 5 lights each take you over 1500W...)

Thanks for any enlightment Pray

 

Admin1

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TT, You need to Slow Down with all your reading.

Oh, Speaking of which - I'm off to College. :_|

 

maccarooni

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Hello TT

On lighting circuits we always treat each lamp as potential 100 watts. This was ok when they were all normal pendant drops as you could put a 100w lamp in them. However with a wide variety of fittings is this still neccessary. ? Probably not, as if you have put in a room 8 GU10 fittings. the max would be 400w, unless you changed each drop to pendant, then it COULD go up to 800w, buy only a twit would do that. but take the 8 d/lights out and put in a couple of say chandaliers with six or eight lampholders on each, then it could go up to say 40/60w candle lamp timestimes 8 x 60w on each x 2 chandaliers 480 + 480 = 960. So even when its written on the fitting ( do not exceed say 40w people still go larger ). Its no a definitive answer but hope fully shows some of the problems that can occur. We tend to limit lighting circuits to 6A when possible and from a load point of view, go no more than a kW. Just in case the customer upgrades at a later date.

Macca

 
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Evening ladies and gents,I remember reading a post where someone had said they wouldn't put more than ?8 light fittings on a circuit. What rule of thumbs do you have for lighting circuits and why? And that question goes to no.2! :D

I've been designing lighting circuits and worked out that 1800W (18 lights) can be carried by under 35m of 1.0/1.0mmsq with a 10A breaker. I then idly opened an old Collins wiring book and it said any more than 1200W means splitting the circuit... :eek:

(and what happens with fittings with multiple pendant lights? Three chandeliers in one room with 5 lights each take you over 1500W...)

Thanks for any enlightment Pray
although your current carrying capacity, (clipped direct with no thermal insulation or grouping or other correction factors), may be ok......

Don't think you will satisfy max permissible volt-drop. 3% on lighting circuits =6.9v max.

1.0mm = 44mv/A/m

Allow general 66% total load for diversity.. so 1800watt becomes 1200watts

so 1200watts @ 230v = 5.22a and

Voltdrop = (44 x 5.22 x 35m)/1000 = 8.03volts? Too high

stick it on 1.5mm 29mv/A/m drops to 5.29volts sneaks in ok! :D

OR say max load is call it 1300watts?

with Diversity approx 870watts = 3.78amps

So with our 1.0mm Volt drop now = (44 x 3.78 x 35)/1000 = 5.82volts :)

So either.. Drop your loading OR increase cable CSA! ;)

Remember the acceptable volt drops have changed with 17th..

old used to be 4% on all circuits... Lights now only 3%!! :eek: :|

Appendix 6 OSG covers these bits! :D

 

Admin1

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Excellent explaination and example as per usual, Sir.

Pick any prize off of the TOP Shelf. Even Welshy's Twix. :eek:

 

cheggers

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Im old school I was always taught no more than 14 lighting points

 

TTbangbang

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Thank you for the responses :D

Really appreciate the time-servers giving their experience. Noobies like me only know (ah-hem!) the theory.

I had selected the circuit using the final circuits in Section 7 of the OSG thinking that the VD had already been worked out, doh. Lesson learnt.

 
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Excellent explaination and example as per usual, Sir. Pick any prize off of the TOP Shelf. Even Welshy's Twix. :eek:
Blimey! :eek:

your in a good mood!! :D

givin out Twix's! you must have had some good news today m8?

or has Mrs Admin forgiven you for the "ECU" !!!! :eek: :O:O problems! ; \

so you can sleep back in the house again not the Workshop/Shed? :^O :^O:^O:^O

Guiness DrinkGuiness Drink

 
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Thank you for the responses :D Really appreciate the time-servers giving their experience. Noobies like me only know (ah-hem!) the theory.

I had selected the circuit using the final circuits in Section 7 of the OSG thinking that the VD had already been worked out, doh. Lesson learnt.
Better to learn here....

Than just after you have finished pullin the cable in to the 18 light points! :) :D :D:^O:^O

 

Admin1

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Blimey! :eek: your in a good mood!! :D

As always, Mate. :D

givin out Twix's! you must have had some good news today m8?

Not at the point of typing this out - But I have now. :D :p (Will update the "Recovery" Thread.

or has Mrs Admin forgiven you for the "ECU" !!!! :eek: :O:O problems! ; \

She forgave me on day 1 - My 'Puppy Dog' eyes did the trick.

so you can sleep back in the house again not the Workshop/Shed? :^O :^O:^O:^O

:D

Guiness DrinkGuiness Drink
Don't mind if I do Mate - Thank you. Guiness DrinkGuiness Drink

 

avinalarf

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Thank you for the responses :D Really appreciate the time-servers giving their experience. Noobies like me only know (ah-hem!) the theory.
Fully agree TT, even though I've done a fair bit of practical work myself, I've learned so much just by reading some of these threads - they've made a lot of sense of what I've been learning from the books!

Keep up the good work!

 

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