Bathroom fan fuse question

[pirate]

This house was destroyed completely yesterday. My pal who is the next door neighbour told me the fire was caused by a bathroom fan...the same pal I fitted a new bathroom extractor fan for a few weeks ago.
He seemed slightly concerned...
Do all MI's require a 3A fuse these days? If not, would you fit one anyway?

 

[littlespark]

I am starting to.
Just rewired an upstairs flat. (Guy downstairs bought it and is knocking into one big house)
He doesn’t know what fans he wants or needs in the bathroom, as they both have opening windows. I’m sure building control will put him right,
But in the meanwhile I’ve fused each bathroom seperately.... l & n feed down to switch, then 3 core up to the attic to an accessible WAGO box, then onto existing light fitting.
If it turns out he wants a run on fan, got a live, sw and neutral in place.... if he wants fan on seperate switch, I just need to change the switch outside the door to a 2 gang, and run 2 sw up the 3 core.
So whether it says in MI to put a fuse in or not, There’s one there.

I’ve never actually seen a fan catch fire....Even through overheating. normally something else catches first.... net curtains or whatever.

a house caught fire near where my parents live. Was in the attic, and was traced to a plumber who had been soldering pipes earlier in the day. Hadn’t noticed the ceiling joist smouldering when he left.

 

[Dustydazzler]

I personally rarely fit a 3a fuse , generally just feed the fan from the bathroom light circuit.
I have on occasion fitted a swi fuse in the loft with a 3a fuse but only if the loft is easily accessible to change the fuse if needs be...

 

[buzzlightyear]

This house was destroyed completely yesterday. My pal who is the next door neighbour told me the fire was caused by a bathroom fan...the same pal I fitted a new bathroom extractor fan for a few weeks ago.
He seemed slightly concerned...
Do all MI's require a 3A fuse these days? If not, would you fit one anyway?

Did your pal ask for can of petrol to go with the fans he put in. Lol.

 

[Andy78]

That's fairly quick for an official verdict of a fire investigation. How has the fan been held as culprit ?

No not all manufacturers ask for a fuse to be fitted.

I fitted one last week that asked for a 3A fuse on the diagram for the standard version, but none at all on the diagram for the timed version. Further on in the literature it said the fan had an integral thermal overload cutout to protect it from such an event.

I've come across plenty of burned out fan motors in the past but never one that has thermally damaged any of the very thin plastic cases they live inside.

 

[Midwest]

Ditto. I take into account manufactures instructions, and install a 3A fuse if so required. But I've come across knackered fans, filled with detritus which has burnt them out, not blown or tripped any fuse, with no fire damage.

I'd rest easy, there'll be another cause.

 

[littlespark]

Possibly caused by a plumber professing to be an electrician....

Shhh... I didnt say that!

 

[ChrisElectrical88]

Yeah I do fit one with every fan.

 

[LewisM]

a house caught fire near where my parents live. Was in the attic, and was traced to a plumber who had been soldering pipes earlier in the day. Hadn’t noticed the ceiling joist smouldering when he left.

Are you over Luton way?, Same thing happened here a few years ago from him leaving to the fire was 12 hours.

 

[littlespark]

Are you over Luton way?, Same thing happened here a few years ago from him leaving to the fire was 12 hours.

Nah. We’re in Scotland.

 

[richy3333]

Always fit a triple pole switch with fuse. Many MI ask for it. I spoke specifically to Manrose technical because I was asked to EICR a house where the owner was suing the builder and they said their instructions have asked for a fuse for decades. The 3 bathroom fans involved in the case all required fusing down

 

[Ian1981]

What will a 3 amp fuse do that a 6amp mcb won’t?

 

[pc1966]

What is the likely stall current of one of these motors? I doubt it is more than 0.1A.

In any case, what will a 3A fuse do to prevent a fire? It could take up to 1 minute at 9A to blow, that is 2kW X 60s = 124kJ of heat to dump somewhere. Oh maybe if blowing hard it could keep itself cool?

 

[Pretty Mouth]

What will a 3 amp fuse do that a 6amp mcb won’t?

It will break the circuit at lower overload currents:

 

[Ian1981]

It will break the circuit at lower overload currents:View attachment 59361View attachment 59362

I don’t expect any overload current on what is essentially a fixed load.
The point of it stalling is valid I guess

 

[Pretty Mouth]

I don’t expect any overload current on what is essentially a fixed load.
The point of it stalling is valid I guess

Must be, I can't think of any other reason for it. It'd be interesting to do an experiment to see how much current these fans pull when stalled.

 

[pirate]

Many thanks to all of you for your responses to my query. Based on only hearsay evidence, i will try to ascertain the exact cause...rumours abound in such cases. If my bathroom fans went on fire (2 of them, installed by a "bathroom Fitter" with no isolator, no fuse etc) there is nothing combustible in the bathrooms themselves, so only a fire caused by overheated cables elsewhere could cause such devastation.
anyway, I'll update if I can, but thank you again for your replies.

 

[littlespark]

It gets difficult...
Fan has stopped spinning and still buzzed, but customer doesn’t do anything about getting it fixed.... or even isolated.
6 months down the line, fire!
Investigation shows fan overheated. “Which wouldn’t have happened if there was a fuse”

I’m sure the motor could heat up over time, not enough to pop a fuse, and still ignite any dust that had settled on the non spinning blades.

 

[Ian1981]

6 months like that, now a 3 amp fuse makes sense haha