Extractor fan need 3 amp fuse

[spiderplant0]

I bought two VASF100T timer extractor fans to replace the existing fans in 2 bathrooms. It says the fans need 3 amp fuses to protect them. My current setup has an isolator switch for the the fan and 6 amp fuse for the downstairs lighting in the house's mains fuse box (MCB). I guess the options to protect the fan are...

1) Add extra 3 amp fused spur boxes for each fan. (Don't want to do this as its a lot of hassle cutting into the plasterboard etc.)
2) Replace the existing fan isolator switch with a fused one and re-wire to isolate both the fan and the light.
3) Replace the 6 amp fuse in the fuse box with a 3 amp one (it only supplies 3 rooms). This seems the simplest option (if you can get 3 amp fuses for the fuse box)..

What would you recommend / what is legal?

 

[EFLImpudence]

The fuse is not necessary electrically but some people think it should be fitted because the manufacturer says so because there are such things in the U.K.

 

[jurassic sparkk]

6A fuse will be fine.
Forget the 3a fuse.

 

[Jon c]

If the manufacturer says there should be a 3A fuse it is best to put one in, if you try and claim on the warranty and haven't followed their instructions they will probably refuse. The way to do it is very straightforward, just replace the fan isolator with a fused fan isolator like this:

https://www.cef.co.uk/catalogue/products/4912421-10a-triple-pole-fan-isolator-switch-with-3a-fuse-white

 

[Jackrae]

Fuses in supply lines are there to protect the supply line, NOT the end of line device. Manufacturers warranty terms cannot hide behind whatever fuse or breaker the supply service is.

 

[EFLImpudence]

Another thing:

In the diagrams the fuse is placed before the light fitting. This is definitely not required nor advisable.

https://www.cef.co.uk/catalogue/products/4912421-10a-triple-pole-fan-isolator-switch-with-3a-fuse-white

This item only has a fuse on one of the line conductors so it would also have to be placed before the light fitting (where an ordinary FCU would do) or not be as the manufacturer has demanded in the diagrams.

 

[spiderplant0]

Thanks everyone.
@Jon c, I think you are recommending adjusting the wiring so that both the light and fan are switched (Option 2). If I dont do this, as the fan has 2 live terminals I would need a fuse for each live (I haven't been able to find a dbl fuse isolator).
@Jackrae, are you saying replacing the 6 amp MCB in the main fuse box with a 3 amp one is a bad idea? If a fault occurs in the fan, will the fuse not trip no matter where the fuse is located? EDIT - UPDATE. Or do you mean this is dangerous, as someone in the future may change the 3amp fuse back to a 6amp one, as they will have no idea of the rating of each of the connected devices? That makes sense.

 

[Harry Bloomfield]

I would suggest that even a 1amp fuse might be enough, but in all likelihood, the 6amp MCB, would trip before the fuse would respond. Whilst the 6amp MCB is to protect the house lighting wiring, the 3amp is recommended to protect the likely smaller wiring in the fan itself.

 

[Jon c]

Another thing:

In the diagrams the fuse is placed before the light fitting. This is definitely not required nor advisable.




This item only has a fuse on one of the line conductors so it would also have to be placed before the light fitting (where an ordinary FCU would do) or not be as the manufacturer has demanded in the diagrams.

I'm not understanding why the light would need fusing down, surely the fan has no relation to the light fitting?

EDIT:
I missed a detail on the diagram, the manufacturer essentially wants the Line AND switched Line to the fan to be protected by a 3A fuse, that's not something I've seen in any set of instructions in the past, most are happy with just the permanent Line fused at 3A

 

[Jon c]

Thanks everyone.
@Jon c, I think you are recommending adjusting the wiring so that both the light and fan are switched (Option 2). If I dont do this, as the fan has 2 live terminals I would need a fuse for each live (I haven't been able to find a dbl fuse isolator).
@Jackrae, are you saying replacing the 6 amp MCB in the main fuse box with a 3 amp one is a bad idea? If a fault occurs in the fan, will the fuse not trip no matter where the fuse is located? EDIT - UPDATE. Or do you mean this is dangerous, as someone in the future may change the 3amp fuse back to a 6amp one, as they will have no idea of the rating of each of the connected devices? That makes sense.

Can you access the loop in wiring to the bathroom? Looks like to truly comply with instructions the only options would be to install a 3A FCU at this point so all the bathroom wiring is fused down to 3A, or indeed replace the circuit breaker. Both these options seem overcomplicated, the instructions are certainly unusual!

 

[JohnW2]

If the manufacturer says there should be a 3A fuse it is best to put one in, if you try and claim on the warranty and haven't followed their instructions they will probably refuse.

Some manufacturers try anything in attempts to try to wriggle out of warranty claims (even though, if they thought about it, they may come to realise that it could well cost them less to replace a relatively inexpensive item than to expend a lot of time arguing!), but (as could be pointed out to them) their argument in this case would almost certainly be unsustainable, particularly given that I would imagine that any (I would think incredibly rarer) failures during the warranty period are most likely to be 'mechanical', clearly unrelated to the presence/absence of any fuse.

In any event, as hinted above, how often do extractor fans fail during the warranty period? I personally cannot recall having ever heard of this happening.

Kind Regards, John

 

[JohnW2]

This item only has a fuse on one of the line conductors so it would also have to be placed before the light fitting (where an ordinary FCU would do) or not be as the manufacturer has demanded in the diagrams.

That is true, but if the manufacturer attempted to wriggle out of a warranty claim on the basis of absent fusing of the S/L they would be on even thinner ice, since the S/L is invariably connected to nothing within the fan other than through a very high value resistor.

Kind Regards, John

 

[Harry Bloomfield]

I missed a detail on the diagram, the manufacturer essentially wants the Line AND switched Line to the fan to be protected by a 3A fuse, that's not something I've seen in any set of instructions in the past, most are happy with just the permanent Line fused at 3A

Normally the permanent Line is the one which actually supplies power to the fan, whereas the switched Line is just used for signally purposes - no actually current draw on it.

 

[EFLImpudence]

That is true, but if the manufacturer attempted to wriggle out of a warranty claim on the basis of absent fusing of the S/L they would be on even thinner ice, since the S/L is invariably connected to nothing within the fan other than through a very high value resistor.

Yes, but people cannot say the OP must follow the instructions but do it differently than stated.

 

[Jon c]

Some manufacturers try anything in attempts to try to wriggle out of warranty claims (even though, if they thought about it, they may come to realise that it could well cost them less to replace a relatively inexpensive item than to expend a lot of time arguing!), but (as could be pointed out to them) their argument in this case would almost certainly be unsustainable, particularly given that I would imagine that any (I would think incredibly rarer) failures during the warranty period are most likely to be 'mechanical', clearly unrelated to the presence/absence of any fuse.

In any event, as hinted above, how often do extractor fans fail during the warranty period? I personally cannot recall having ever heard of this happening.

Kind Regards, John

Agreed it probably wouldn't hold up if you argued with them but generally for the cost and difficulty of getting a 3A fuse in for a fan I'll just do it. Funnily enough I had an inline fan fail within a year, the problem was a piece of copper on the motor windings had broken, can only assume it was a manufacturing defect in the wire that eventually broke after being used for a while from thermal cycling.