Help with a problem with a lighting circuit

[schmeagle]

Hi all members of DIYnot.com.

I have a question on a lighting circuit and radial/ring etc and could really use some help with it if you could be so kind?

I have designed a circuit feeding 5 ceiling roses splitting the circuit down to 5 lighting circuits, 2 of which is one way circuits, one is two way with intermediate switching and 2 is two way switching. All this I put on one CB but now with doing a cable calc it seems to not comply. I have now changed the design to feeding the ceiling roses separately but some of the circuits are still too long to comply with the volt drop etc. I am measuring the length of cable from the CCU to the rose, down to the switch, across the strappers and back up to the light furthest away from the switch.
If the volt drop is too great to comply can I run in a 2.5 T&E for the lighting circuit? Any advice on this will be great as I can’t find anything in the BS7671 to say I can’t do this but I have never heard of a circuit for lighting using any thing bigger than 1.5mm etc.

Also if u had 3 rooms and a hallway but the total floor area was over 100m (squared) would you run in 3, A2 radials etc to each room as 100m(squared) seems really small for a house/circuit etc. even my house is bigger than 10m x 10m but still got 1 upstairs ring and 1 down stairs ring?

Thanks for any reply in advance as I am struggling with the planning of this project and really appreciate any help given, I want to get good marks etc (college project).
Thanks again.
T.

 

[riveralt]

I have designed a circuit feeding 5 ceiling roses splitting the circuit down to 5 lighting circuits, 2 of which is one way circuits, one is two way with intermediate switching and 2 is two way switching. All this I put on one CB but now with doing a cable calc it seems to not comply. I have now changed the design to feeding the ceiling roses separately but some of the circuits are still too long to comply with the volt drop etc. I am measuring the length of cable from the CCU to the rose, down to the switch, across the strappers and back up to the light furthest away from the switch.

Five circuits thats interesting - could you put up the figures that you have used to get voltage drop and also could you put up the design drawings for these circuits - it would us help you.

Also if u had 3 rooms and a hallway but the total floor area was over 100m (squared) would you run in 3, A2 radials etc to each room as 100m(squared) seems really small for a house/circuit etc. even my house is bigger than 10m x 10m but still got 1 upstairs ring and 1 down stairs ring?

Show us you design figures and drawings please.

 

[Taylortwocities]

Aye, post up the figures.
I've never known a domestic lighting circuit that didn't comply with vd.

How does EFLI look? Is it on a 6A breaker?

 

[Chri5]

I have designed a circuit feeding 5 ceiling roses splitting the circuit down to 5 lighting circuits

Do you not mean that you have 1 x lighting circuit with 5 x lighting positions ?

Something like

CB----> rose 1---> rose 2----> rose 3----> rose 4 and then rose 5.

Off each rose you have switches, 2 single switches, 2 two way and 1 three way (with intermediate).

Is that correct ?

 

[flameport]

A lighting circuit could be constructed using cable of any size.
However for a circuit with only 5 ceiling roses, it would have to be massively long before any issues over volt drop etc. would be encountered.

The nonsense about 100 square metres is straight out of the 'electrics by numbers' book, and therefore should be ignored.
The length of the circuit and the loads it is to supply are far more relevant.

100m² might seem very small to you, but the fact is there are millions of houses in this country which are smaller than that.
3 rooms and a hallway with an area over 100m² is also rather unlikely, unless you happen to live in Crendle Court.

 

[ELZ4742]

i agree flamo... if this is for a new build, 80% has to conform to low energy fittings reducing the eventual wattage even further.

 

[Taylortwocities]

i agree flamo... if this is for a new build, 80% has to conform to low energy fittings reducing the eventual wattage even further.

Umm 75%

 

[schmeagle]

working on the fig's and pic's now for the lighting.

The floor area for the kitchen and dinning room is 8m by 14.5m
Thus the floor area of just those two rooms I belive to be (8x14.5) 116meters (squared)? or am i thinking wrong on this?

Thanks again pep's

 

[riveralt]

working on the fig's and pic's now for the lighting.

The floor area for the kitchen and dinning room is 8m by 14.5m
Thus the floor area of just those two rooms I belive to be (8x14.5) 116meters (squared)? or am i thinking wrong on this?

Thanks again pep's

Yes not all the cabling has to go around the outside edge of a room.

Use the figures from OSG page 43 onwards.

 

[flameport]

8x14.5 is indeed 116m², however that would be two very large rooms.

Is this a real property, or just something the college made up?
Do you have a floor plan, or what are the sizes of the individual rooms?

Another thing - if those sizes are correct, a ceiling rose as the lighting in those rooms will be useless.

 

[ban-all-sheds]

I have designed a circuit feeding 5 ceiling roses splitting the circuit down to 5 lighting circuits, 2 of which is one way circuits, one is two way with intermediate switching and 2 is two way switching. All this I put on one CB

Then you don't have 5 circuits, do you.

I am measuring the length of cable from the CCU to the rose, down to the switch, across the strappers and back up to the light furthest away from the switch.

And what is that length?

Also if u had 3 rooms.....

The word is "you", not "u".

Please try to learn the difference between SMS messages and other types of communication, and write accordingly.

If you're in college and hoping to get an apprenticeship you should take note of this view from someone currently looking for an apprentice:

why does the education system fail so many kids who would be good in a hands on job if they could read and write too.

You didn't write "u" because you genuinely have problems with English, you did it out of slapdash laziness, and that is not an image you want to be portraying to examiners and potential employers.

 

[ELZ4742]

i agree flamo... if this is for a new build, 80% has to conform to low energy fittings reducing the eventual wattage even further.

Umm 75%

Umm ok.

 

[schmeagle]

I have designed a circuit feeding 5 ceiling roses splitting the circuit down to 5 lighting circuits, 2 of which is one way circuits, one is two way with intermediate switching and 2 is two way switching. All this I put on one CB

Then you don't have 5 circuits, do you.

I am measuring the length of cable from the CCU to the rose, down to the switch, across the strappers and back up to the light furthest away from the switch.

And what is that length?

Also if u had 3 rooms.....

The word is "you", not "u".
Please try to learn the difference between SMS messages and other types of communication, and write accordingly.

If you're in college and hoping to get an apprenticeship you should take note of this view from someone currently looking for an apprentice:

why does the education system fail so many kids who would be good in a hands on job if they could read and write too.

You didn't write "u" because you genuinely have problems with English, you did it out of slapdash laziness, and that is not an image you want to be portraying to examiners and potential employers.

I do suffer with dyslexia and so far I have done really well in my learning. I have always been practically minded and not ever got on with education and learning due to people trying to judge what they did not know about me, I am now 30 (not a kid) and getting the help that I should have got in school but they just said I was a lazy person/learner and did not pick up on my disability. I am also the same with numbers too and swap numbers round all the time, but thanks for your evaluation and I shall bare that in mind that sms writing/text upsets you. Guess you know me better than anyone does so shall let u be the judge of me like all the rest have done in the past.
You are correct though as the proper term would be “YOU” and not “U” I do apologize.

Yes I guess your correct on the circuit only being one circuit as it comes from one circuit breaker, although it not just feeding one little circuit (I believe).
I was going to go to one room(dinning room)/rose, feeding the two way and intermediate switches that controls the dinning room lighting:- two wall lamps rated at a 100W each and ten GU10 recess lamps rated at 50W each spot.
From the feed/rose that comes down to the switch, I was going to spur from that and split the supply to go to the lounge where from another junction box/rose has been installed, there I was going to run down to the two way switching and up to lights etc, two 100W pendants and two 100W wall lights. Once again then splitting the supply to different roses controlling the hall lights:- two way switching with six GU10 recess lamps.
Outside front lights:- one way switching, two 100W coach lamps.
Out side back lights:- one way switching, two 100W coach lamps controlled by a PIR setting.

I am sure even though it on one CB that the hall lighting would be on a seperate circuit than the lounge/dinning room lighting etc. The only reason I am splitting the feed is to just get the power directly to the switches? Please tell me if you know something different?

Thanks.

 

[schmeagle]

8x14.5 is indeed 116m², however that would be two very large rooms.

Is this a real property, or just something the college made up?
Do you have a floor plan, or what are the sizes of the individual rooms?

Another thing - if those sizes are correct, a ceiling rose as the lighting in those rooms will be useless.

Yes I think you are correct to be honest. I have changed the scale of my drawings now so that they are now half the size. thanks for picking that up, I did not realise they was quite so big.

 

[vv2806]

Well, I am sorry to hear you have dyslexia but it is not the reason for writing "u", isn't it? Are you studying to become an electrician?