Extractor fan with fused isolator

[JohnW2]

All the instructions say is a double pole fused spur although further in the detail it says an omnipolar switch. It also says the circuit must be protected by a 3A fuse.

Is that in addition to the 3-pole isolator they also require? Per what I recently wrote/intimated, it could be that they are talking about having a double pole 'fused spur' (FCU) in the feed to the light+switch and then, in addition, a 3-pole isolator feeding the fan - hence both L and S/L would then be protected by the fuse.

As EFLI has said, there is no other way (that I can think of) in which one could avoid the risk that the S/L would remain live at the fan even though the fuse protecting the permanent live had blown (even having two fuses would not achieve that).

Kind Regards, John

 

[JohnW2]

Exactly. Is there not a diagram in the instructions similar to Bernard's?

Good question. As I've just written, it sounds as if they may well be asking for an FCU and a 3-pole isolator (i.e. per bernard's diagram) (despite the fact that reqs require neither) - since I can think of no other way of 'covering all bases'.

Kind Regards, John

 

[mjas]

Bernard. Thank you. I wasn't looking to use the isolator to control the light, only to isolate the fan. I can see what your diagram is proposing which would make the fused part of my switch obsolete. I could have bought the £2.50 isolator switch instead.

There is no diagram with the fan.

 

[EFLImpudence]

What model fan is it?

 

[JohnW2]

Bernard. Thank you. I wasn't looking to use the isolator to control the light, only to isolate the fan. I can see what your diagram is proposing which would make the fused part of my switch obsolete. I could have bought the £2.50 isolator switch instead

... but if you wanted to comply with the requirement for a 3A fuse, you would still have to also install an FCU in the feed to light and it's switch.

You could use the fuse in what you've got to do things as per bernard's diagram (as well as using the product to isolate the fan), but that would require a bit of rewiring of the light/switch.

Kind Regards, John

 

[bernardgreen]

 

[JohnD]

....
Does your new fan incorporate a timer?

Are you planning to instal it so it continues running for a period after the light is turned out?

 

[mjas]

Thanks for the advice. The lighting circuit is a bit like spaghetti so it is going to take some sorting out. As per earlier comment, the original fan wasn't even installed with a isolator so I'm hopefully now moving it in the right direction.

It's a Manrose MF100T fan, and, rather foolishly, I've realised I should write to Manrose for some clarification which will hopefully answer where the fuse should sit to meet their requirements.

 

[mjas]

Thanks to everyone for all your feedback and advice.

 

[EFLImpudence]

It's a Manrose MF100T fan, and, rather foolishly, I've realised I should write to Manrose for some clarification which will hopefully answer where the fuse should sit to meet their requirements.

Ask them what they state for European sales where such things are not available.

If they say it is British Wiring Regulations then tell them it is not.

 

[mjas]

They have just sent the following which confirms Bernard's diagrams. EFL... I've asked your question back.

 

[JohnW2]

The lighting circuit is a bit like spaghetti so it is going to take some sorting out. .... I should write to Manrose for some clarification which will hopefully answer where the fuse should sit to meet their requirements.

As for the spaghetti, as bernard's diagrammatic representation of what I recently suggested in prose would only require (finding and!) re-routing ghe connection to the light switch to your isolator+fuse product. If youy did that, it would satisfy whatever 'requirements' the manufacturer might have, since it would afford 3A fuse protection to both the live and switched-live (with a single fuse) and also a 3-pole isolator for the fan.

However, also bear in mind what EFLI is saying - that there is very little (if any) electrical justification for these 'requirements' stated by the manufacturer, and whatever else they are based on, it is not any 'regulations'.

Kind Regards, John

 

[JohnW2]

They have just sent the following which confirms Bernard's diagrams.

Not quite ....

... that diagram appears to include no 3-pole isolator for the fan. Instead, there is just a 2-pole isolator+fuse (presumably a FCU) in the feed to both the light and the fan.

That means that one can only isolate the fan by also isolating the light - which annihilates the nearest to a (not very convincing) argument for having a 3-pole fan isolator - namely that it enables one to isolate the fan (to work on it) without having to lose use of the light!

Provided you can sort out the 'spaghetti', I still think that the method I mentioned (and depicted by bernard) would be your best bet.

Kind Regards, John

 

[bernardgreen]

Being able to fully isolate the fan while still having the light operational does help when the fan has gone wrong and is running continuously ( disturbing sleep ) and light is need to see in the room.

 

[bernardgreen]

which confirms Bernard's diagrams.

As johnW said it doesn't confirm my drawing, you can send them a copy of my diagram mentioning my name as the author of it.