Duct extraction fan safety

[pipme]

Hi,

Have tried to find an answer .. but :-

Triple pole isolation for bathroom (inc. shower) extractor fan with timed over-run.
Is there a single unit (will be placed, ceiling, on landing outside bathroom) which provides switching and fuse protection for both switch and permanent live to fan?
If not, how can I fuse protect both the switched and live to the fan?

Thanks.
P.

 

[breezer]

you will not find an "off the shelf" switch that can isolate both shower and fan at the same time

to isolate fan you want one of these

for the shower you want one of these

 

[pipme]

Hi,

Thanks Breezer.

My first posting and I muddy the water, !!

What I meant to say was :- Can I 3 pole isolate the extractor fan and incorporate fusing for live and switched, (just the duct fan unit no other appliance ) ? Or will the units on sale (FCU I believe) only fuse protect the main Live to fan?
Sorry about my confused writing.

Thanks.
P

 

[ban-all-sheds]

The only thing I can think of is a normal isolation switch and then two unswitched FCUs, or (neater) 2 grid-plate fuse modules.

 

[Big_Spark]

pipme, the fan in your bathroom SHOULD be fed from the lighting circuit, so there is no need for it to be fused seperatly.

As for a dual fuse 3 pole device, No, no such thing exists for sale as there is no need for one if circuits are installed in compliance with the Regs.

 

[pipme]

Hi,

Thanks everyone.

Think I see how now ....

Will be using lighting circuit .... dual pole fused unit outside bathroom, from there to bathroom lightswitch usual configuration to light unit. But include live, switched live and neutral to 3 pole isolator then to fan.
Or leave out the 3 pole isolator. I think the dual pole does the trick.

The reason for all this is that I had an extractor fan ( lighting circuit ), this was supplied and fitted as part of a new bathroom several years back ( contractor ), I was a little concerned that the instructions for that fan, found later in loft, called for isolator and 2 amp fusing ... we had neither.
A couple of evenings ago I switch on bathroom light ... fan does not start, light off then on ... fan starts and runs, apparently ok.
Afraid I am a mech engineer not elect, I felt something was not right, you know how it is !!
Main off, fuse in POCKET, strip fan ... bit cruddy .. visual of outer casing shows a brown scorch mark and slight buckling in one corner ... a resistor on circuit board has fried with local discoloration, does not appear immediately recent, no 'burnt' smell. ( fuse in pocket is correct value )
Ok new kit required, DIY I am thinking , instructions again call for 2 amp fuse and isolator.

Cheers.
P.

 

[breezer]

KEEP the tripple pole isolator, it is there so that it isolates the following.

Permanent live to fan

Neutral to fan

SWITCHED LIVE to Fan

its not uncommon for timed fans as you have to "give up" after a few years, personally i do not like them.

 

[pipme]

Thanks all.

Reckon I'll fit the triple too.
I wonder how common it is, for 'timed' extractor fans to give up the ghost ?
I am now very wary of any appliance 'out of sight' especially in the loft and out of my direct control !! I'll be wary when insulating the ducting ... keeping well clear of motor housing.

I would advise anyone with loft extractor.... check the fan and ducting internals regularly ..... you may be surprised at the crud.

PS ! With 1 wife and 2 daughters using the shower, hair washing for half an hour each etc ..... Do I need an extractor fan to clear the culmunus !!

Cheers,
P.

 

[securespark]

You only need one or the other.

If you use a dp FCU, then the feed that currently goes to bathroom light will feed the fcu and the outgoing terminals will feed the light, via the existing switch.

Thus, when you switch off the FCU, the live and switchwire go dead.

Instead, wire a live, switchwire and neutral feed from the ceiling rose or junction box to a triple pole isolator then onto the fan.

 

[pipme]

Thanks SP,

It is a conundrum to a non spark, use DP with fuse or 3P without fuse.

Think I'll opt for DP with integral fuse. Reckon I could (but will not) then use 3P after bathroom switch and before fan. Juist means I could Isolate fan and still have the light on in bathroom I suppose.

I'll be back with a shot at describing what wiring exsists and what I believe it does, 1968 house having single core neutral cabling and twin + earth for live and switched L.

Thanks again.
P.

 

[pipme]

Sorry Securespark I meant thanks SS

I must be boring you all now, so onward !!
Current bathroom wiring.
Bathroom light switch. Supply side.
Two 2core + earth, one 3 core + earth. Cables. All three red lives connected together : three associated earths connected together.
The two, 2core+earth cables are supplying the power from existing lighting circuit and being connected are allowing supply to the next room in the chain. ( the neutral conductors are snipped and unused )
The 3core + earth, load side, has a permanent Live (the 3rd red), a yellow, being the switched live, earth, and snipped unused neutral.

The 3core + earth from pull switch supplies an existing junction box ‘x’ ( round plastic type ) at this box the Neutral single core part of lighting circuit is brought in. In terms of a cable which has been parted then reconnected inside the Junction box.
A 2core + earth cable supplies the bathroom light fitting, from this junction box ‘x’, using switched live, neutral and earth.

A 3 core + earth (N/Req ) supplies the fan. Again from the junction box ‘x’. Live, switched live (yellow), neutral. Earth is connected at junction box, but snipped and not required at fan.

There are about 2 metres separating the cabling to bathroom switch and the neutral connections to the existing junction box ‘x’.

My proposed method :- I will pull the supply to bathroom switch cables, reconnect together in new junction box A.
Pull the neutrals from box ‘x’ and reconnect in a further new junction box B.( 2metres distant from A) From this box take a link neutral to the junction box A.
From Box A take a single 2 core + earth to the 2pole FCU sited on landing, forming it’s supply live neutral and earth.
From the FCU load side, another 2 core + earth to a third junction box C, from here take 2core + earth using live and earth only re-providing supply to bathroom switch, then, also from box C 2core + earth using only neutral, link to original junction box ‘x’.

I hope this can show how a simple looking job, to a non-sparky, can become quite complex, and I wonder how many extractor fans are properly installed ( not that I am saying my ideas above are correct ) Just that a wiring schematic for the fan looks quite simple, the reality is, from what I can see in my loft, quite different.

Am not about to embark on the project without discussion ….. I have described the current situation as well as I can ……. This was the contractors installation about 5 years ago.
Funnily enough the main contractor was a PLUMBER … a sparks did the electrics. I must say all has worked perfectly until now.

Sorry folks.
P.