Wiring New Lights

[DanDanT]

This is probably a really simple question - but I'm doubting myself...

I'm building new bookshelves / a tv cabinet thingy in my front room alcoves, and want to install lights in the top shelf. I'm not going to bury the last run of cable in the wall, but instead in a groove I'll cut in the back of one of the pieces of wood. Therefore I want to use flex instead of t & e cable. It'll come from a junction box in the subfloor, with regular t & e to the switch, previous junction box etc.

I bought 0.5mm2 three-core flex, which is rated up to 3A. But the breaker in the consumer unit is obviously 6A. Presumably I need to fuse it down to 3A with a FCU (or use a thicker 6A flex)??? The reason I'm doubting my logic here is after the t& e terminates in a normal ceiling rose, flex decends to the bulb... how can this be? :s

Also, I've been using Screwfix's 5A four terminal junction box without really thinking... should I be using a >6A as the breaker is 6A??? I'm getting myself confused.... help! Why are lighting circuit breakers 6A when you fuse down to 3A if you spur off the ring main??? Why are 5A junction boxes so common?

 

[ad13]

the flex for a light pendant holder only carrys 1x100watt lamp which is 0.41amps, so this is adequate for the load, as for the lights in the alcove why dont you switch the light with a fused spur and rate the fuse at 3amp?

 

[ban-all-sheds]

Why are 5A junction boxes so common?

Because rewirable fuses for lighting are (and therefore before MCBs all lighting circuits were) 5A, and the manufacturers have never bothered to re-rate their products.

 

[DanDanT]

So is it commonplace to use 5A junction boxes on a 6A circuit? Prusumably there is some tolerance there?

 

[securespark]

the flex for a light pendant holder only carrys 1x100watt lamp

and it is also 0.75mm², not 0.5mm².