Smoke alarm 3rd core, WHY ?

[D Skelton]

however an isolation point is required?

And that isolation point can be the main switch if you like!

The only requirement for 'local isolation' as some like to call it is defined in 132.15.2 which to summarise states that a fixed electrical motor needs a readily accessible and easily operated means of switching off. Well I don't need to tell ya that 'switching off' is not the same as 'isolation'

 

[MDJ]

appreciate this mate, thanks for the info. another grey area considered to some I suspect, it is good to learn something new, cheers.

 

[shagbite]

No it doesn't, what you have posted there is a direct quote from The Electricians Guide To The Building Regulations. This book is as it says... a guide. It is simply a book, written by an individual and is not statutory in any shape or form.

yep, i'll concede to that. even though it's non statutory it's still good advice, but i accept your point.

what i will say is that, whilst you may be correct about the lack of any hard and fast rules regarding isolators, as the installation designer i must make an assessment of the type of equipment that is being installed and who is going to be using it. extractor fans have permanent lives, motors and moving parts; there is every possibility that something could go wrong at a later date which would require a competent person to carry out repairs. it's not beyond the realms of possibility that these repairs might need to be carried out in less than satisfactory light conditions and because of this, i believe it's good practice to provide isolation from a point other than the fuse board.

also, it might be acceptable to use the mcb for isolation in a tn installation, but what about a tt? i'd want both line and neutral disconnected. it's obviously not ideal to isolate the entire installation, so a fan isolator is the perfect solution.

 

[D Skelton]

yep, i'll concede to that. even though it's non statutory it's still good advice, but i accept your point.

what i will say is that, whilst you may be correct about the lack of any hard and fast rules regarding isolators, as the installation designer i must make an assessment of the type of equipment that is being installed and who is going to be using it. extractor fans have permanent lives, motors and moving parts; there is every possibility that something could go wrong at a later date which would require a competent person to carry out repairs. it's not beyond the realms of possibility that these repairs might need to be carried out in less than satisfactory light conditions and because of this, i believe it's good practice to provide isolation from a point other than the fuse board.

also, it might be acceptable to use the mcb for isolation in a tn installation, but what about a tt? i'd want both line and neutral disconnected. it's obviously not ideal to isolate the entire installation, so a fan isolator is the perfect solution.

I absolutely agree, you're right, there are more than enough scenarios where fitting a 3 pole isolator would be the most reasonable thing to do. I have always stated that fitting a 3 pole isolator is often good practice, my only point was that it wasn't a requirement. The whole reason I 'took a stand' so to speak to the myth that 3 pole isolators MUST be fitted was because of the amount of hear say and rubbish floating around in the ether. People talking of building inspectors failing jobs because of the lack of 3 pole isolators, 'sparks' rubbishing other sparks work, people wasting time fitting both fuses AND isolators??? I just wanted to bring some clear, consise and accurate information to the table to clear the matter once and for all.

Personally, when fitting extractors, I rarely fit 3 pole isolators as most fans that I fit require fusing down so 9 times out of ten I fuse down the bathroom light and fan together, thus killing two birds with one stone. What you choose to do is up to you, and as long as it complies with regs, isolator or no isolator, I can assure you I wouldn't be rubbishing your work

 

[dim_bulb]

Love the way the thread started out as smoke question then a slight detour onto bathroom fans and isolation