FCU for Extractor fan

[SparkyChick]

Take a look at the weedy tracks on the PCB for the average fan, there's your fuse, right there!

True, but in designing PCBs I've sometimes been surprised how much little tracks can take before they burn out... well, you have to test these things sometimes

 

[westward10]

Your lights are on the common lighting circuit in any case!

IF you decide to have an FCU, IMO this needs to be in the line feed BEFORE the bathroom light, that way you fuse both the permanent live as well as the switched live.

However, the whole thing is nuts. Lets assume there is a 6A MCB protecting the whole lighting circuit., Now you introduce a BS1361 3A fuse just for the fan and light. HAve a look at the discrimination graphs and tell me which device trips first in the event of
1. Overload (unlikely)
2. High current short circuit.

Boo Murdock got there first…

That'll be a BS1362 fuse

 

[telectrix]

i'm with des. i'm not a fan of triggering the fan with the light ( pun intended, so there ). separate switch for fan every time. in our gaff, it's a 4 way grid outside shower room... shower room lights, fan, foyer light, soffit lights (PIR override).

 

[Taylortwocities]

That'll be a BS1362 fuse

Bloomin' spel chker.

 

[Pat H]

The fan is a humidistat fan and very quiet. So no real issue with it coming on with the light.
An outside switch isn't always the most convenient if you discover a need for sudden ventilation...

 

[Wilko]

[QUOTE="Taylortwocities, post: 1247782, member: 11045]
Lets assume there is a 6A MCB protecting the whole lighting circuit., Now you introduce a BS1361 3A fuse just for the fan and light. HAve a look at the discrimination graphs and tell me which device trips first in the event of
1. Overload (unlikely)
2. High current short circuit.
…[/QUOTE]

Hi - so I did that, and what I found was for a mythical 8A current (1), the 6A mcb will never trip, but the 3A fuse melts somewhere between 0.3s and say a couple of minutes. High current faults are cleared by both (2), and at 30A it's possible the mcb will be quicker, as you say

Being of unsound mind, a while back I did try to create a fault with a timer fan to give this awkward small overload current, but I failed and ate chocolate instead.

 

[SparkyChick]

Hi - so I did that, and what I found was for a mythical 8A current (1), the 6A mcb will never trip, but the 3A fuse melts somewhere between 0.3s and say a couple of minutes. High current faults are cleared by both (2), and at 30A it's possible the mcb will be quicker, as you say

I'm glad you've posted that because I did exactly the same and drew exactly the same conclusions, but didn't want to overstep the mark as a relative newbie

 

[Octopus]

The fan is a humidistat fan and very quiet. So no real issue with it coming on with the light.
An outside switch isn't always the most convenient if you discover a need for sudden ventilation...

I'm assuming that this bathroom has,a toilet.... So what's the point of the humid stat fan.... It can't detect smells!

 

[The Ghost]

The bathroom today for instance has just been refurbished/finished by a builder. Looks good! So I say ah well shame about the finish gotta fit a 3a fuse in the feed. Just Pull up your floorboards and screw up your lovely bathroom and charge you a fortune (I am reassuringly expensive), and you get another ugly switch into the bargain! Ok? lovely. No I don't think I should be playing twisters with the manufacturer! They should fit their own fuse into their own product. It is incomplete if it is not intrinsically safe. I imagine a lot of fan manufacturers after hearing about one of their fans catching fire thought Oh oh its suing time. And they just managed to squeak out of it by blaming the contractor, poor sod. So now instead of making their product safe, we have to cover for their shoddy production methods! Ok rant over.
And anyway the three pole isolator, I often find switched off as most people can't stand the noise so it does have a function after all.

 

[Ib≤In≤Iz]

Interesting discussion. The last bathroom fan I fitted I ran the whole lighting circuit via a SFCU with a 3A fuse. Only because the manufacturer listed this as a requirement in the installation instructions.

 

[Octopus]

Interesting discussion. The last bathroom fan I fitted I ran the whole lighting circuit via a SFCU with a 3A fuse. Only because the manufacturer listed this as a requirement in the installation instructions.

All we need now are 3A mcb's and Rcbo

 

[Andy78]

I do a bit of work fitting fans and LED downlights for a couple of bathroom fitters. Most situations see me adding a RCD SCFU for my bathroom install so the fan fuse pops in there.

 

[Andy78]

All we need now are 3A mcb's and Rcbo

Most decent brands should be able to supply a 3A mcb.

 

[Des 56]

All we need now are 3A mcb's and Rcbo

Well we are half way there Murdoch
3 Amp MK MCB - B Type - https://www.tlc-direct.co.uk/Products/MK5903S.html?ad_position=1o1&source=adwords&ad_id=45425533757&placement=&kw=&network=g&matchtype=&ad_type=pla&product_id=MK5903S&product_partition_id=174055712467&test=finalurl_v2&gclid=COizxZbks9ICFbgW0wod2-UBCA

 

[The Ghost]

I must say, thinking about it, it is nice to have a female sparks in the conversation mix. There should be more! @SparkyChick