Bathroom fan again???

[Dawnsdad]

I have looked at hundreds of threads in this and other forums but can not seem to find a definitive answer.
I am about to fit an in-line fan with timer in bathroom, I have done this many times before so know the general Idea,(about 30years ago) but now the MI's are stating an FCU with 3amp fuse is fitted, this will be in addition to the triple pole fan isolator.
So where does this actually go, I have seen many diagrams showing only live or switched live passing through the FCU which appears to defeat the object or breaking into the wiring prior to the bathroom lights, which puts all the remaining lights through the FCU,
So other than changing the wiring circuit so the bathroom lights are not on the ring but are effectively a spur off the ring could someone give any Ideas , Diagrams advice etc..

Many thanks in advance

DD

 

[Space cat]

So, if the instructions are to be believed, your fan has to be on a 3 amp fuse, not the 5 amp fuse or 6 amp breaker that protects the existing lighting circuit. That's really inconvenient.

To be of any use whatsoever, the FCU must go upstream of any fan connections and so, since a timer fan connects to both sides of the light switch and neutral, you'll have to break into the lighting circuit before the switch. This won't be a trivial exercise if you have further lighting circuits fed from the bathroom light fitting. Have you had a look to see what's there already?

 

[EFLImpudence]

.
This can be done using Double Pole switches (not two-gang switches).

DP ceiling pull switches can be obtained if you have one.

Untitled

• EFLImpudence
• 5 Oct 2011
• 1

Depending on the positioning of the items the wiring can be rearranged to the same effect but you will have to obtain a Neutral from the ceiling rose as it is unlikely there will be one at the switch.

The fuse is not required for electrical reasons but regulations state that manufacturers instructions should be taken into account.

With this arrangement the triple pole isolator is not actually necessary as the DP FCU will isolate all live conductors to the fan.

Edit - added blue sleeving

 

[Dawnsdad]

Hi again,
thanks for replies and sorry for delay in responding (I have been away)
went in loft today and went burrowing under 10" of new horrible insulation, found that the lights are fed by a single neutral from a JB and single red and earth to switch and then to light fitting. ( no permanent live at light fitting) so I will take a twin and earth from JB to light fitting via a FCU and then rewire the switch as normal then the fan from the light fitting. removing old live and neutral cables in the process
does that all make sense?

 

[EFLImpudence]

Yes, that's fine.

 

[Space cat]

does that all make sense?

Yes! It would also appear that the three pole switch is not required since the switched FCU completely isolates the light, the switch and all the fan connections, unless of course you want to have the light on while you work on the fan ---

 

[securespark]

Which might be a bon idee!