In line fuses and extractor fans

[opps]

Hi.

I am about to replace an extractor fan. It has a switched live, live and neutral but no fused spur.

It was fitted incorrectly.

Outside the bathroom there is a 3 gang light switch.

Initially, the far left rocker switch powered the ceiling lights. The next switch controlled the fan BUT only when the lights were on (the 3rd rocker controls a wall light and can be ignored).

Having locked at the wiring in the ceiling I have now discovered that someone attached the fan's "permanent" live to the ceiling light's switched live.

I have re-wired the connections in the ceiling, the "permanent" live and switched live are now correct. The fan now operates independently of the ceiling lights. The middle switch turns the fan on and off but it acts as a controller rather than an full isolating point. The permanent live which has no isolation point allows the timer over-run.

I know that that there should be a 3 pole switch outside the bathroom and a 3amp fused spur, but there isn't and if I am being totally honest, there won't be one for the foreseeable future. The fan is only accessible from a step ladder.

Given the above, I would be happier if it had overload protection. I am considering using two in line fuse holders.

http://uk.farnell.com/bulgin/fx285/...crid|78108293829|&CAWELAID=120173390000291244

I guess that the most sensible place to fit them will be in the fan (assuming sufficient clearance/space).

I completely appreciate that my suggested set up is far from ideal (read:legal) but I would rather improve the set up, even if it still falls short of the requirements.

Being realistic the other option would be to ignore everything and leave it as it is.

</ducksForCover>

 

[Iggifer]

You're very unlikely to actually NEED a fuse for the fan. The MIs may well say you need a 3amp fuse but I wouldn't lose any sleep over it.

A 3-pole isolator is more desirable, but again, don't lose sleep over it in the meantime. There are plenty of fans out there without 3-Pole isolators. Local isolation is great, but if the fan needs changing, it'll have to be done in the daytime until there is an isolator!

 

[EFLImpudence]

I have now discovered that someone attached the fan's "permanent" live to the ceiling light's switched live.

Perhaps that was how they wanted it to work

I have re-wired the connections in the ceiling, the "permanent" live and switched live are now correct.

That is how you want it to work.

I guess that the most sensible place to fit them will be in the fan (assuming sufficient clearance/space).

That is where the manufacturer's instructions state they should be fitted when used for 240V

I completely appreciate that my suggested set up is far from ideal (read:legal) but I would rather improve the set up, even if it still falls short of the requirements.

No such thing as legal or illegal.

Being realistic the other option would be to ignore everything and leave it as it is.

It would.

 

[Taylortwocities]

Fitting those fuses "in line" would be more dangerous than not having them. In any case, how would you engineer it?
The cables would need to be "split out" inside an enclosure of some sort, and that would mean the cables would need some sort of strain relief on them.

As mentioned elsewhere, the 3amp FCU is pointless on a standard lighting circuit that is protected by a 6amp MCB in the consumer unit. The trip characteristic of a 6amp BSEN60898 Type B MCB shows that it would trip a long time before a 3A BS1361 fuse would pop!

My guess is that makers really only intend the FCU to be used in the cases where the fan is powered from a circuit with a high current limit (a ring final circuit with a 32amp MCB, for example).

 

[Iggifer]

Fitting those fuses "in line" would be more dangerous than not having them. In any case, how would you engineer it?
The cables would need to be "split out" inside an enclosure of some sort, and that would mean the cables would need some sort of strain relief on them

He wanted to put the inline fuse holder in the fan enclosure itself. If you're gonna go to that much trouble, may as well make it a 500mA 20mm glass fuse. There might be some discrimination then, but still, pointless.

 

[opps]

I have now discovered that someone attached the fan's "permanent" live to the ceiling light's switched live.

Perhaps that was how they wanted it to work

I have re-wired the connections in the ceiling, the "permanent" live and switched live are now correct.

That is how you want it to work.

I guess that the most sensible place to fit them will be in the fan (assuming sufficient clearance/space).

That is where the manufacturer's instructions state they should be fitted when used for 240V

I completely appreciate that my suggested set up is far from ideal (read:legal) but I would rather improve the set up, even if it still falls short of the requirements.

No such thing as legal or illegal.

Being realistic the other option would be to ignore everything and leave it as it is.

It would.

I have very little confidence in the competence of the person that previously worked in the bathroom. The 3rd rocker on the light switch controls the bathroom wall light. They used the (unused) earth from the fan as a neutral for the wall lights. Later, when the consumer unit was replaced, using the wall light would have caused the RCD to trip, the light fitting had been left with a dead bulb on purpose. I have already managed to run a new neutral down to the wall light fitting from the ceiling lights- that works fine now and no longer trips the RCD.

It seems illogical that that they would have wanted the fan to turn on with the lights but to not have the timer over run given that they had wired in what was supposed to be a permanent live (but in reality was not). If they wanted it to run only when the lights are turned on, wouldn't they have just run a switched live and branched it to the permanent live and switched live connections in the fan?

For the record I am replacing the Xpelair timer over tun fan with a similar Xpelair fan that has a humidistat plus over run. On sunny days I want to make sure that showering causes the fan to activate regardless of whether rhe lights are on or not. if someone wants to make smells go away they can use the switch.

I genuinely don't understand your comment about the location of the fuse. Sorry, I am not trying to be obtuse. The instructions provided with many fans state that they should be protected by 3 amp fuses. I have never seen a fan that has inbuilt fuse protection. I had assumed that the manufacturer's insistence that there is a 3 amp fuse made it a legal requirement. That said, I take on board the comment from Taylortwocities about a 6amp MCB tripping faster than a wired 3 amp fuse and the manufacturers considering the fact that someone might wire the fan in from the 32 amp ring main.

If you, and the others are suggesting that I do not need to worry about the fuses then I will quite happily follow your advice.

cheers

Opps

 

[winston1]

I would be happier if it had overload protection.

It has. The MCB in your consumer unit. Fused connection units are not used or needed on lighting circuits.

 

[sparkwright]

More than 99% of homes do not have a fused spur or in-line fuses serving the fan fed by a lighting circuit.

However, if you do want a fused spur, the easiest method is to wire it so the fused spur serves the bathroom light as well.

This way the fuse will serve both the perm live and the switched live.

Any other method is going to be complicated and bloody confusing for the next man.

 

[sparkwright]

Unless you fit a proper fused spur unit (or similar) any other method of fusing is likely to be incorrect or a waste of time.

 

[EFLImpudence]

http://www.farnell.com/datasheets/308332.pdf

 

[stillp]

I am considering using two in line fuse holders.

http://uk.farnell.com/bulgin/fx285/...crid|78108293829|&CAWELAID=120173390000291244

Those fuseholders are for various reasons not suitable for use on a domestic mains circuit.

 

[ban-all-sheds]

On sunny days I want to make sure that showering causes the fan to activate regardless of whether rhe lights are on or not.

Use operation of the shower as the trigger for the fan.

This can be done whatever sort of shower you have. What sort is it?

I had assumed that the manufacturer's insistence that there is a 3 amp fuse made it a legal requirement.

Fortunately not, given the number of ignorant buffoons there appear to be working for manufacturers writing instructions.

 

[kai]

The only snag, is where the lights are fed off a TEN amp breaker, not a six amp one, as in the case of many modern buildings.

 

[Iggifer]

The only snag, is where the lights are fed off a TEN amp breaker, not a six amp one, as in the case of many modern buildings.

You could say the same about pendants on a 10a breaker

 

[RF Lighting]

If you use click mini grid accessories, you can fit a three pole isolator and a BS1363 fuse holder on a normal one gang plate.