Extractor fan need 3 amp fuse

[Jon c]

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.

My thoughts also, which is why I was surprised to see the instructions want the SL fused at 3A too!

 

[EFLImpudence]

Agreed it probably wouldn't hold up if you argued with them

Argue with them then.

but generally for the cost and difficulty of getting a 3A fuse in for a fan I'll just do it.

Bigger fool you.

 

[JohnW2]

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

Agreed - but my point was that if one chose to 'argue' (ultimately, at least theoretically, 'in a Court'), one's case would be even stronger (electrically) if the only 'issue' were failure to fuse the S/L.

Kind Regards, John

 

[Jon c]

Bigger fool you.

Why? Would you also not follow the instructions for, say, a smart light switch, which might be required to have 6A fuse protection, and just stick it on a 32A circuit? Why not follow the instructions when they are perfectly sensible, and not hard to achieve. Granted there are examples of instructions out there particularly for ovens and hobs that are plain wrong for instance talking about 16A FCUs and the like, but that is a different situation

 

[JohnW2]

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.

That's obviously your choice/decision (as it would be for anyone else), but I would personally not be inclined to 'advise' others to install an (electrically) unnecessary) fuse just to reduce the risk of arguments about a warranty claim - something which is extremely unlikely to ever happen, anyway.

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.

Fair enough, but that comes into the category I mentioned of faults which a manufacturer could not successfully argue had resulted from absence of a fuse

Kind Regards, John

 

[Harry Bloomfield]

Why? Would you also not follow the instructions for, say, a smart light switch, which might be required to have 6A fuse protection, and just stick it on a 32A circuit? Why not follow the instructions when they are perfectly sensible, and not hard to achieve. Granted there are examples of instructions out there particularly for ovens and hobs that are plain wrong for instance talking about 16A FCUs and the like, but that is a different situation

IMHO, if manufacturers demand a fuse, then such a fuse should be included within the unit itself. When ever I have designed any equipment, I design in suitable fuses to protect it.

 

[JohnW2]

Why not follow the instructions when they are perfectly sensible, ...

What is 'perfectly sensible' about requiring a 3A fuse to be installed in series with (almost always) a 6A MCB ?

In the event of a fault within the product, it's pretty likely that the MCB would operate before the fuse, anyway - and, in any even, neither MNCB nor fuse would have to do anything until after something nasty (very probably 'irrecoverable') had already happened within the fan.

Kind Regards, John

 

[JohnW2]

IMHO, if manufacturers demand a fuse, then such a fuse should be included within the unit itself.

Some people ('blindly') take that view. I personally prefer to think for myself.

Kind Regards, John

 

[Harry Bloomfield]

What is 'perfectly sensible' about requiring a 3A fuse to be installed in series with (almost always) a 6A MCB.

Perhaps because - the manufacturer cannot be aware of the rating of the fuse for the circuit.

 

[Jon c]

What is 'perfectly sensible' about requiring a 3A fuse to be installed in series with (almost always) a 6A MCB ?

In the event of a fault within the product, it's pretty likely that the MCB would operate before the fuse, anyway - and, in any even, neither MNCB nor fuse would have to do anything until after something nasty (very probably 'irrecoverable') had already happened within the fan.

Kind Regards, John

I will agree that electrically, a 3A fuse is likely to be of no use. But the regs do say “The installation of electrical equipment shall take into account manufacturers’ instructions”. So quite simply where practical and reasonable, I will follow them, if there is no reason not to.

Tin hat on, in the OPs situation, I would just use a fused fan isolator, which would only have a 3A fuse on the permanent Line. Reasons being, in all the fan instructions I've seen (including other vent axia fans!) there has never before been a requirement to fuse the SL, and it may not be reasonably practical to fuse down the entire bathroom lighting circuit

 

[JohnW2]

Perhaps because - the manufacturer cannot be aware of the rating of the fuse for the circuit.

OK - but even though they should provide any over-current protection internally if they believe their product needs us, why could they not specify the maximum 'acceptable' overload protection of the circuit (e.g. "6A maximum"). As their instructions are written, they would still require a 3A downstream fuse even if the circuit had, hypothetically, 2A upstream protection (and, yes, 2A MCBs do exist - which clearly would make no sense.

Don'f forget that it would take something like 5-10A 22A (at least 50 times the normal running current of such a fan) to ever blow a 3A BS1362 fuse (even if current were sustained continuously).

Kind Regards, John
Edit: Error corrected (I was thinking of 13A fuses - apologies!)

 

[EFLImpudence]

I will agree that electrically, a 3A fuse is likely to be of no use. But the regs do say “The installation of electrical equipment shall take into account manufacturers’ instructions”.

Take into account and decide the fuse is not required.

So quite simply where practical and reasonable, I will follow them, if there is no reason not to.

There is a reason. It is not needed.

Tin hat on, in the OPs situation, I would just use a fused fan isolator, which would only have a 3A fuse on the permanent Line.

So now you are telling him NOT to do as the manufacturer has stated.

Reasons being, in all the fan instructions I've seen (including other vent axia fans!) there has never before been a requirement to fuse the SL,

I would dispute that.

and it may not be reasonably practical to fuse down the entire bathroom lighting circuit

Of course it isn't.
Are you now saying the manufacturer's instructions are wrong?

 

[JohnW2]

I will agree that electrically, a 3A fuse is likely to be of no use. But the regs do say “The installation of electrical equipment shall take into account manufacturers’ instructions”.

Indeed - but, fortunately, they relatively recently changed the wording to what you quite ("... take into account..."). Previously that had been a 'requirement' to comply with MI's (even if they were 'wrong' or daft).

So quite simply where practical and reasonable, I will follow them, if there is no reason not to.

As I've said, that's your choice/decision - but it's rather different to be 'advising' others to do the same.

Tin hat on, in the OPs situation, I would just use a fused fan isolator, which would only have a 3A fuse on the permanent Line. Reasons being, in all the fan instructions I've seen (including other vent axia fans!) there has never before been a requirement to fuse the SL, and it may not be reasonably practical to fuse down the entire bathroom lighting circuit

I would have thought that would, for you, be the 'worst of all worlds' - you will have installed an 'unnecessary' fuse, yet still not fully complied with the MIs, hence leaving you open to arguments about any warranty claims.

Kind Regards, John

 

[Jon c]

Perhaps because - the manufacturer cannot be aware of the rating of the fuse for the circuit.

Indeed, however if that were the rationale, it seems to me more sensible to simply require a 6A mcb rather than a 3A fuse, which I agree can be a faff at times. We have a similar issue with ovens, they often want a 16A fuse/MCB, this isn't a standard oven/hob circuit in the UK. The general concensus around this seems to be to connect it to a 32A breaker anyway, on account of being a fixed load, so overload is impossible. And we all know the difficulty in finding MCBs for older boards, do we really require a new board/sub board for a replacement oven?!

 

[ericmark]

Most the fans I have looked at the windings are thinner than a 3 amp fuse, so if stalling the fan would blow a fuse, then a 3 amp would not help, the winding would go first.

So when supplied from a 6 amp lighting circuit there is no real point fitting a second fuse.

There are fan isolators with fuses built in, but seems a little pointless.

As to fuse protecting only the cable that is true for portable appliances, but for built in equipment the manufacturer can stipulate semi-connector fuses if he wants.

However unless the manufacturer is changing a faulty unit how would they know? Fan fails you return it, asked if 3 amp fuse fitted you answer yes even if not fitted, how would they know otherwise?