Switch wire or live

[Cueball]

Can anyone shed a bit of light on this for me?

I’m installing an SELV extract fan with a timer suitable for use in zone 1 above a shower supplied from a lighting circuit. I’m going through a 3-pole isolator and am intending to also use an fcu to protect the fan with a 3a fuse as per the manufacturers’ instructions. The big question is do I fuse the switch wire or the permanent live? Like I say I intend to go through an fcu after the isolator in order to protect the fan because otherwise I’d only have the 6a lighting mcb for protection. I’m a big believer in best practice and all that but am I guilty of going a bit over the top here and should I knock the extra protection on the head?

So the question is, switch wire or live? Anybody knows the answer it would be greatly appreciated.

Cheers,

Cueball

 

[gizmo]

Neither ! The MCB would operate quicker than the fuse in most circumstances anyway !

 

[andrew692003]

If you are wiring of a lighting circuit make sure its fed from a 6A or 10A supply and that should be enough. You shouldn't have to fuse that down at all.

Cheers

 

[Des 56]

Why dont you just use a switched fused spur with a 3amp fuse for the supply
There would be no need for a 3 pole isolator
The switched fused spur feeding the fan transformer with a permanent live and also feeding a pull cord with a switch return to trigger the fan via the transformer switch live terminal


Fuse protection for the fan has to be for both switched live and permanent live,use the method I have described and both feeds to the transformer will be fused

 

[solo2771]

Live I would have thought

 

[Risteard]

Neither ! The MCB would operate quicker than the fuse in most circumstances anyway !

The Regulations require you to comply with manufacturers' instructions, however.

 

[marksparky]

hi the way i always do it is usin a dual box to bring mains into fused spur 3amp then take a link from load to 3pole isolater

 

[Eggster71]

I'd run the supply to the bathroom lights to the spur, you could even put in an RCD ine if the circuit's not already protected, and from there run to your rose or whatever. 3A should be enough to cope with most of your lighting and that way both line and sw/live are covered.

 

[Cueball]

Folks,

Thought I should clear this one up. According to the manufacturer there's no need at all for seperate fuse protection, as Gizmo said the mcb should operate quicker anyway. With hindsight it stands to reason as the only thing protecting individual lights on the circuit is the breaker. Kinda makes sense.


Many thanks for all the input, cheers for now.

Cueball