Loft lighting

[Mini1961]

Hi all whats the best way to wire loft lights, want to have a switch on wall under the loft ladder, at the moment i have not put any cables in for them so what ever you think the best method is, i,e, from lighting circuit or ring, + what is the most lights i can install if i were to say come off a fcu @ 6 amp,

Thanks

Mini1961

 

[Chri5]

In the loft you will have access to the 1st floor lighting, this sounds like it must be the 6a circuit that you mention in your post.

6a x 230v = 1380w

Add up all your 1st floor lamp loads (on the assumption that there all on at once), take that figure from the 1380w circuit design capacity and that tells you what you can have in watt terms in the loft fed from the 1st floor lighting circuit.

Depending on the wiring style in your house you will have junction boxes in the loft for the 1st floor lights or cables wired to ceiling roses, which are wire termination points for the switch, the live in, the lamp and the live out.

The rest of the termination detail can be found by reading the lighting section in the DIYnot Wiki.

 

[Taylortwocities]

In domestic lighting design we apply what is called diversity. This assumes that not all the lights will be on at the same time. By doing this we can have a larger total load than the fuse would appear to support.

In dom lighting the factor allowed is 66% so your 1380W rises to around 2000W. This assumes its all normal filament lamps, there's more tricks to play if there are fluorescent or energy saving lamps.

 

[Mini1961]

In domestic lighting design we apply what is called diversity. This assumes that not all the lights will be on at the same time. By doing this we can have a larger total load than the fuse would appear to support.

In dom lighting the factor allowed is 66% so your 1380W rises to around 2000W. This assumes its all normal filament lamps, there's more tricks to play if there are fluorescent or energy saving lamps.

Thanks for your replys guys, so if i am right in thinking i can just come off a ceiling rose as i am using loop in out fittings up to my loft fittings (use the loop in out) then down to a switch, i had worked out that my lighting ring 1200 watt load using 100 watt lamps on the circuit what you are saying is that i can add to this if i wanted to put up three low energy bulk head fitting @ 22watts this would be ok,

Thanks

Mini1961

 

[Chri5]

With kids our lighting circuits ground, first or second (loft) are frequently 'all' on



Hence why diversity wasn't considered, since a CFL 21w uses 21w then there's absolutely no issue with over loads.

I tend not to calculate for diversity on lights since it's rare that any single floor will ever get anywhere near the 10 amp rating- 46 GU10 50w isn't very normal

 

[plugwash]

In domestic lighting design we apply what is called diversity. This assumes that not all the lights will be on at the same time.

Which is IMO a rather stupid assumption in most domestic lighting setups. Especially the more basic ones where each room has only one light.