Fusing bathroom timer fans

[goasis]

Hi all, happy Christmas! There was a thread on this subject a while back, not many people said that they actually connect bathroom extractor via a 3A fuse, despite many MI's seemingly asking for it. And certainly it's not something you see often, triple pole isolators yes, sfs's less so. Is it something we mostly just 'overlook'.
And if you were to do it, would you loop power in/out throught a sfs, then drop down to light switch off load side. All bath lights and fan off load side? Do away with TP iso?

 

[Baddegg]

I do it, normally just drop the whole bathroom down to 3 amp through fused spur.....

 

[Yahtzee]

I fuse it through a Click grid 3pole switch and a fuse module or if there is more than 1 light fuse down one of the lights to operate the fan via a fcu.

 

[RED~SIX]

Never fused a fan down. Have fused down shaver sockets in the past from memory but not always.

 

[Timbo]

You still need the 3 pole switch to isolate for maintenance.

 

[Pretty Mouth]

I emailed Manrose about this a couple of months ago, to see if the switched live to the fan needed fusing down as well as the permanent live. Perhaps I didn't word the question very well, as I got an ambiguous reply.

Me:
Hi,
The MF100T instructions require that a 3A fuse is fitted. Does this need to be fitted so that it protects the permanent live, the switched live, or further upstream so that it protects both?
Thanks,
Pretty Mouth

Reply:
Hi Pretty Mouth,
Hope you are well,
The 3A fuse would be fitted early on in the installation on the permanent live,
Hope this helps.

 

[sinewove]

I emailed Manrose about this a couple of months ago, to see if the switched live to the fan needed fusing down as well as the permanent live. Perhaps I didn't word the question very well, as I got an ambiguous reply.

Me:
Hi,
The MF100T instructions require that a 3A fuse is fitted. Does this need to be fitted so that it protects the permanent live, the switched live, or further upstream so that it protects both?
Thanks,
Pretty Mouth

Reply:
Hi Pretty Mouth,
Hope you are well,
The 3A fuse would be fitted early on in the installation on the permanent live,
Hope this helps.

Have started using Greenwood Airvac fans and the ventaxia inline fans which don,t need a 3A fuse as long as cct has a 6A mcb.
Can make life easier.
Regards,S

 

[SparkyChick]

If required, like @Baddegg , I will fuse down the whole of the bathroom to ensure both permanent live and switched live are covered. If the manufacturers instructions state it should be fused (or show it in their wiring diagrams) I would follow this guidance... the regs state quite clearly manufacturers instructions should be taken into account and I'm not sure I have the technical knowledge to argue the case in court should it come down to it.

That being said, I'm moving to fitting fans that don't require it such as the S&P fans but I give the client the option with a brief run down of the costs associated with both approaches. The S&P fans aren't cheap but when you compare it to parts and labour to modify the circuit (assuming you can get to it easily enough to make that job relatively quick) in the short term at least it's far more appealing from a price perspective to use a more expensive fan that doesn't require a fusedown.

 

[goasis]

You still need the 3 pole switch to isolate for maintenance.

Is that correct? Surely a sfs would serve this purpose? Is the idea of a triple pole iso for maintenance from a particular regulation?

 

[DPG]

Is that correct? Surely a sfs would serve this purpose? Is the idea of a triple pole iso for maintenance from a particular regulation?

A triple pole isolator isolates all live conductors - neutral, live, switched live.

 

[sinewove]

Is that correct? Surely a sfs would serve this purpose? Is the idea of a triple pole iso for maintenance from a particular regulation?

If your relying on the 6A mcb to protect the fan you would need a 3 pole fan isolator for the 3 live conductors to the fan.Or could the main switch be classed as the fan isolator?
Regards,S

 

[goasis]

A triple pole isolator isolates all live conductors - neutral, live, switched live.

Sorry, yes I realise this, what I meant was, if you are fusing down the whole bathroom via a 3a sfs, then this would isolate all the conductors.

On an aside, Personally I think this idea of the fan and lights being on the same switch is a bit daft as well, i dont need the fan to come on every time I have a wee or brush my teeth. Equally I don't need the lights on everytime I have a shower or create some other need for extraction.... (sprouts anyone?!)

 

[DPG]

Sorry, yes I realise this, what I meant was, if you are fusing down the whole bathroom via a 3a sfs, then this would isolate all the conductors.

On an aside, Personally I think this idea of the fan and lights being on the same switch is a bit daft as well, i dont need the fan to come on every time I have a wee or brush my teeth. Equally I don't need the lights on everytime I have a shower or create some other need for extraction.... (sprouts anyone?!)

Absolutely - more often than not you either need the light or the fan, but not both.

 

[Timbo]

If your relying on the 6A mcb to protect the fan you would need a 3 pole fan isolator for the 3 live conductors to the fan.Or could the main switch be classed as the fan isolator?
Regards,S

If you switch off the fused spur you switch off the lights as well. Not too clever if you are carrying out maintenance.

 

[goasis]

If you switch off the fused spur you switch off the lights as well. Not too clever if you are carrying out maintenance.

Yeah i kinda get that, but it's not the strongest case, how often are we "doing maintenance " on bathroom fans, at night time, without access to a site light or similar?
Don't get me wrong, I'm not disagreeing with you, just was wondering how others approach it and why, and how many switches and isolators do we end up with outside the bathroom? Could end up looking like a display at the wholesalers.... fan iso, sfs, spur for shave point, light switch, towel rail etc etc!!

 

[telectrix]

just find the round brown lighting JB in the attic with L,N and S/L inside and the cpc.s twisted over the box. 3 croc clips and away you go.

 

[brianmoooore]

No isolator other than the s/fused spur is required if it is located adjacent too the fan or immediately outside of the bathroom door.
A job I did in my own house yesterday was to change the wall mounted bathroom fan (building works have made it no longer on an outside wall) for an inline fan in the loft. Original (sole) isolator is a s/fused spur immediately outside the bathroom, but now I have added a TP isolator next to the fan in the loft. Also serves as a junction between the fan's flex and the fixed 3&E.
I think I've posted on here before about a fire in a new build near me which the rumours said was caused by the omission of the 3A fusing required by the instructions.

 

[radiohead]

I think I've posted on here before about a fire in a new build near me which the rumours said was caused by the omission of the 3A fusing required by the instructions.

It wasn't caused by the omission of a 3a fuse, because a current far exceeding 3a could flow for a long time on a seized fan motor, sufficient time to cause the motor to seriously overheat before the 3a fuse blew.
I recall the case and the manufacturer of the fan used the omission of the 3a fuse by the contractor as a get out of liability, despite the fact that a 3a fuse almost certainly would not have changed anything.
One problem with fusing fans is in replacement of existing fans where a fuse has not been installed. Rearranging the wiring to fuse the whole bathroom via an FCU is overkill where an existing fan has failed, I normally replace the standard 3 pole switch, if fitted, with a clik 3 pole/fuse combination which fits a single plate, and just fuse the perm live. The fan runs on the perm live, NOT the sw live, so IMO that is sufficient to meet manufacturers requirements. Alternatively use a fan which does not require fusing, Vent Axia is one example.
Of course on new work it is a simple matter to arrange for all line conductors to be fused with an FCU feed to the bathroom.

 

[brianmoooore]

It wasn't caused by the omission of a 3a fuse, because a current far exceeding 3a could flow for a long time on a seized fan motor, sufficient time to cause the motor to seriously overheat before the 3a fuse blew.
I recall the case and the manufacturer of the fan used the omission of the 3a fuse by the contractor as a get out of liability, despite the fact that a 3a fuse almost certainly would not have changed anything.

Very possibly, but having successfully absolved themselves from liability, no doubt the contractor got the blame, which he could have avoided if he had fitted the fan to the manufacturer's instructions.
The switched live usually connects straight to a fairly high value resistor in these fans, so there's arguably no possibility of overload on this supply, and S/C protection would be taken care of by the 6A MCB in the CU.