conservatory lighting

[hairyjon]

Hi Folks! I want to put some lights in my NEW conservatory. They are from B&Q Lambo model with 4 50W halogen GU10 lamps in each unit. There are 4 units.There is a supply close by but it is not a ring, only a spur to a shed that supplies lighting and 1 twin13A socket. It has its own circuit breaker in the split load consumer unit. How can I do this with regard to the new regs? Any info would be appreciated. Being a newcomer to this site I have now read some of the advice given by Ban All Sheds and JohnD and quedelec. It's nice to know that our enquiries are taken seriosly. Please would one of you explain to someone who has a little understanding of mains electrics explain the difference between a ring and a radial supply? thanks Jon

 

[comms]

Final ring circuit = the circuit cable from circuit breaker in consumer unit goes from socket to sockets & cable returns back to the same circuit breaker in the consumer unit, normaly 2.5mm cable 32amp mcb.

Radial circuit = circuit cable from circuit breaker in consumer unit goes from socket to socket & terminates at the last socket (does not return to cu), 2.5mm cable with 16amp or 20amp mcb or 4mm cable 32 amp mcb.

From the cable thats supplying the shed, fit a fused spur from this fused spur take 1.5mm t/e cable for the light circuit, use a 5amp fuse in the fused spur.
As for regulations your extending an existing circuit, so it's not notifiable work but a minor works cert & required testing need to be done.

 

[hairyjon]

Thanks Comms for your advice. I thought this would be the case with my lights. Would I have to use a circuit similar to that of a ceiling rose for switching purposes? With regard to the difference between radial and ring circuits wouldn't a ring be more efficient in carrying the load?

 

[comms]

For the lighting take the 1.5mm t/e (phase, neutral & earth) from the fused spur straight to the light switch, this will mean you can use the space in the back box as a junction box (so make sure it's a deep back box). Take phase to common of switch, neutral in to chock block same with the earth. Now run 1.5mm t/e from switch L1, neutral & earth to light fittings.

As for ringmain over radial it depends, if you use 4mm t/e for a radial theres no difference as both will have a protective device of 32 amp. But if you were to use 2.5mm for a radial you would be restricted to a maximum of 20 amp.

What is the rating of the mcb/fuse of the shed radial circuit 16 / 20 / 32 ?

 

[hairyjon]

Hi Comms
Thanks again! The shed radial has a 32A MCB in the CU. All that is run of it at the mo is a 4ft. flourescent and there is 1 13A twin socket which is not used very often and when it is it's only for light power tools. This radial was installed before I moved in 18 years ago. My house is an ex-council house an Airey prefab built in the late 1940's. The CU was replaced about 10 tears ago and is a Crabtree Starbreaker split load 6+6 way unit. Hope this helps. Regards, Hairyjon.

 

[hairyjon]

I'm back again! Have just realised that I've got about 200m of 1.0mm T&E (don't know where it came from!) and no 1.5!!!! As these lights are the only things that will be on the circuit can I use it or do I need to go shopping again! I calculate the current at 3.4A for all 4 light units. Also can I use a switched FCU instead of having a seperate light switch?

More regards, Hairyjon

 

[comms]

1.0mm will be fine.
Yes you can use a switched fcu as the light switch.

 

[hairyjon]

Thanks again Comms! The FCU even has a neon indicator so I can tell when the lights are on!!!!! Is there a quick divorce facility on this website 'cos my missus says that I'm gonna need one if I don't put a dust sheet down before I start drilling 'oles! Apologies for the amount of info contained in my last msg. The reason will become clear as time goes on- watch out for my next question it's a biggy. Regards, Hairyjon.