3A fuse for toilet fan - Again!

[diditmissen]

I want to install a timed fan in existing downstairs toilet (currently no fan at all). It would appear that it is now necessary to feed this via a 3A spur.

I know this could be done by feeding the toilet lighting via a fused spur, but this would kill the lights if there was an overcurrent fault on the fan.

Due to problems accessing the wiring to the pull switch, I really do not want to have to go along the lines of a 2-gang switch to provide a switched live separate to the lighting one.

So, here's the question:

As the fire incidents (as far as I am aware) which prompted the call for fused supplies to fans involved problems with condensation on timer PCBs and hence the permanent live, could I use an unswitched fused spur inline with the permanent live. ie connected via the Live In & Live Out terminals of the spur? I suppose it is possible to connect the Switched live also via its own spur. I know this would certainly work (however messily) but would it be permissible? Do I just do away with the fuse as millions of existing installations have?

 

[Chri5]

If the wiring is from the lighting circuit there is no need to provide a f/spur, the lighting MCB is normally rated at 6a and is considered adequate.

As for a fan isolator, one is required if the room doesn't have natural light. If you have natural light then the lighting circuit can be switched off and day light service / mtce of the fan done with safety (as in, not in the dark).

Isolation switches allow the lighting to remain on while you clean, service or do mtce on a fan, and are convient, even whe the room has day light- but are not an essential other than when the room as no day light.

 

[diditmissen]

I'm not convinced either that a fuse is needed on a fan. Surely if a fault develops which is severe enough to start a fire, then it would trip a 6A MCB, possibly more quickly than it would blow a 3A fuse.

Unfortunately, from reading MANY posts on here, there seems to be a growing concensus that fuses should be used, if only to satisfy manufacturers' recommendations etc.

I would like to be able to use a timed fan (with 3 pole isolator) and have the lights stay on if the fan were to blow the fuse. Okay, I'd rather be in the dark than dead, but is the risk being blown out of proportion a bit?

 

[Chri5]

I would like to be able to use a timed fan (with 3 pole isolator) and have the lights stay on if the fan were to blow the fuse. Okay, I'd rather be in the dark than dead, but is the risk being blown out of proportion a bit?

Maybe I'm reading the above statement wrong, with the 3 pole isolator you would only have the MCB as fuse protection. If the fan goes pop and takes out the MCB all lights on the MCB will be off.

On a 6a lighting circuit with a modest wattage fan, there is no need to provide a f/spur.

 

[Spark123]

If the manufacturer specifies a 3A fuse then you need to install one to comply with BS7671:2008.
One method I started using is to stick the lights on an unswitched 3A fuse spur with the fan and also provide a 3pole isolator.

 

[GaryMo]

If the manufacturer specifies a 3A fuse then you need to install one to comply with BS7671:2008.
One method I started using is to stick the lights on an unswitched 3A fuse spur with the fan and also provide a 3pole isolator.

Ditto.

 

[diditmissen]

I think that's what I'll do. Fuse incoming lighting supply at 3A, take PL, SL & N from ceiling rose (or replace this with JB for a new flush fitted light) then via 3 Pole isolator to fan.

Means I'll lose the light if fan blows fuse, but I can live with that, for simplicity of circuit if nothing else.

Seems like all manufacturers are insisting on 3A fused supplies - at least with all the data sheets I've managed to download.

Thanks for help, much appreciated.

 

[ban-all-sheds]

Replace the light switch with a DP one.

Use one side for the lights, feed the other side from a switched FCU with a 3A fuse. Using a switched one eliminates the need for a 3-pole fan isolator.

 

[diditmissen]

The whole point of this post is that I can't easily replace the light switch due to some rather inventive cable routing. It could be done but I'd rather not have to.

 

[ColJack]

most MI will specify a 3A fuse if it's not wired off the lighting circuit....
read the small print..
if it's off a lighting circuit then the 6A breaker will be fine for it..