Bathroom extractor fans and 3 pole isolation: A source of much controversy

malcolmsanford said:

I was just wondering what type of HEPA filter should be installed on this bathroom fan ........................ I think it goes to show that there are too many people in the building industry with too much time on there hands when we need to worry about moving air about in a bathroom ..................

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I've just done Bpec Ventilation course and see results of condensation and toxic mould quite regularly -by understanding ventilation properly you start to appreciate why "moving air " is essential.

I will never fit a switched fcu for ventilation to prevent people switching their air supply off.

To fit ventilation in new build now requires Bpec training and commissioning to prove it works.

Part F and the domestic ventilation compliance guide are areal good read too !

plugsandsparks said:

Its barking i know, basically you have to intercept the perm live going to the switch and into a FCU, that way you isolate both perm and switched at the same time. Then put the lot through a 3 pole isolater for maintenance.

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But then you have broken the live to the switch if the fuse blows and that negates the discrimination between light and fan which is what the idea of the isolator is, to give discrimination between the fan and light for maintainance purposes.
Hence my issue with the instruction manual. Manrose suggested I speak to an electrician and then ignored further questions.

BrianDB9 said:

I've just done Bpec Ventilation course and see results of condensation and toxic mould quite regularly -by understanding ventilation properly you start to appreciate why "moving air " is essential.

I will never fit a switched fcu for ventilation to prevent people switching their air supply off.

To fit ventilation in new build now requires Bpec training and commissioning to prove it works.

Part F and the domestic ventilation compliance guide are areal good read too !

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From experience in hotels that is what the isolator is for!!!!! When the fan is noisy.....

sbelec said:

But then you have broken the live to the switch if the fuse blows and that negates the discrimination between light and fan which is what the idea of the isolator is, to give discrimination between the fan and light for maintainance purposes.
Hence my issue with the instruction manual. Manrose suggested I speak to an electrician and then ignored further questions.

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Tell me about it, that was straight from Primeline destructions, needless to say i took it into consideration

Engineer54 said:

As far as i'm aware the BS covering these fuses do not recognise any other fuse rating other than 3A and 13A!! Other ratings that are available, do not and should not include the BS 1362 number!! The other point being, that the same BS does not include protection of appliances, only conductors!! So this is one manufactures instructions you don't comply with!! lol!! ​

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I'm not saying you're wrong, but if you're right I really need to get on the phone to niglon! lol

FCU outside bathroom to cover feed to light switch, triple pole isolator next to fan.... if the fan developes a fault and takes the fuse out your house tenant/owner can switch the fan off and then replace the fuse to get the bathroom/toilet light back on, this is isolation to avoid a loss of lighting, given the situe where they couldn't get the light because they could not isolate fan individually then most joe public would run a 230v extension and table lamp into the bathroom not a stuation that wants to be premoted because of poor design.

sbelec said:

The IEE Electricians Guide to the Building Regs states:
"An extractor fan supplied from a lighting circuit for a bathroom without a window should have its own means of isolation, otherwise replacement or maintainence of the fan would have to be carried out in the dark. A fan with an automatic run on should be fitted with a triple pole isolator which must be fitted outside zones".
Whilst I agree with the posts completely, not fitting an isolator in these circumstances where someone was hurt or killed because they hadn't disconnected the supply because it was dark or fell off the ladder in the dark would potentially be liable as they had not carried out the appropriate risk assessment on design. The fact that it is in writing from the IEE would compound the issue.

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The electricians guide to the building regs does what it says on the tin mate, it is nothing but a guide and is fraught with red herrings throughout. I think you need to read through the whole thread as I have given quite a detailed explanation as to how this guide is often misinterpreted for regulation. Fitting a readily accessible means of switching off, or as some numpties like to call it 'local isolation' (which it isn't in any way [and that's an argument for another day]) has got nothing to do with whether or not the room is going to be dark without a window!

sbelec said:

This leads me to my real grrrh, some fan manufacturers require a fuse in circuit and then talk about the lighting circuit switch live and a permanent live for the fan run on. How do you wire up a single pole fuse into 2 live supplies but still leave a situation where the fuse is not in the light part of the circuit?

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You may not need to fuse down two line conductors as the bathroom may not need timer over run with the fan, the bathroom might not even require a fan at all and you can always choose a fan from many manufacturers that don't require it to be fused down. Alternatively, use a fan with an integral switch. Again, read through the whole post/thread again. Another thing to think about is if it is a new build or structural changes have been made and you install an isolator so your customer can just switch off the fan when you're gone, how does your install comply with Part F? Fuse the circuit down however so if you want to turn the fan off you've got no light, the customer won't switch it off. This isn't neccessarily how I would do it every time but it is worth bearing in mind. Each situation is different and should be treated as such, yes there are times where fitting a three pole isolator is going to be the best option but the point I am trying to make is that there is no black and white regulation regarding fans and three pole isolation and those who bang on about how it needs to be installed 100% of the time are just showing their lack of knowledge and lack of experience.

sbelec said:

Something I have mentioned before and today replaced a fan where the electrical company had run the permanent live through the fuse but not the switched supply. I suppose this is the best of both, the switched live is only energising electronics to start the fan and not necessarily supplying the power to drive the fan in almost the same was as low voltage control wiring and contactor energising 3 phase motor supplies.

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Nope, nothing at all like control wiring, for a start the switched line alone will power the fan, take the permanent line out at the fan and you'll just lose your over run.

Accept what you say, but any action in court where guides (building regs are law) and BS7671 (also a guide) are not taken into account you lose - unless you have very good documented evidence that what you have fitted is better. It comes down to the phrase complying with BS7671 and the guides are "likely" to show consideration to the Electricity at Work acts and Health and Safety Acts including risk assessment.
Used to be involved in design, construction and installation of plants and even 20 years ago I was challenged by HSE to show the assessment I had carried out was in line with the manufacturers recommendations and BS7671 and where it was not clear in either document that it was "the best solution" having assessed various options. My daughter who is a legally trained housing officer looks to written standard evidence of compliance to regs through best paractice guides so if I left out the isolator and somebody said it should have one then I would have to show that custom suggested it could be omitted and the guide would be accepted.
My Elecsa membership requires me to have available the appropriate guides and I have been asked to show compliance.

So all I say is ignore guides including BS7671 at your peril and an example of that is the guy in prison who did not fit cables in zones and who through not testing properly a young lady was killed. The fact that testing could have been carried out before the nail went through the cable was ignored. (the actual incident was pre 17th edition and rcd's were not required on immersian heater cables buried in the wall).

sbelec said:

Accept what you say, but any action in court where guides (building regs are law) and BS7671 (also a guide) are not taken into account you lose

So all I say is ignore guides including BS7671 at your peril

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BS7671 is not a guide, it is a non statutory set of regulations and classing that and other guides as one and the same is ridiculous. If you like guides so much why don't you have a read of David Cockburns guides!

D Skelton said:

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I'm not saying you're wrong, but if you're right I really need to get on the phone to niglon! lol

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Unless things have changed in the not too distant past, perhaps you should!! lol!!
I've also only ever seen time/current curves for 3A and 13A fuses!! Perhaps things have changed on the fuse current rating side of things, but not as far as 1362 fuses being designed for appliance protection!!

If an appliance NEEDS protection, then the manufacturer should be supplying/incorporating a suitable means of protection. Not rely on the installer to provide it within the building wiring installation!!

Engineer54 said:

If an appliance NEEDS protection, then the manufacturer should be supplying/incorporating a suitable means of protection. Not rely on the installer to provide it within the building wiring installation!!

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Agreed!

D Skelton said:

BS7671 is not a guide, it is a non statutory set of regulations and classing that and other guides as one and the same is ridiculous. If you like guides so much why don't you have a read of David Cockburns guides!

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Non statutory means simply that, it is not on the statute books as law, you cannot be prosecuted under it however you can be prosecuted under HSE Acts which are law who may quote BSI and IEE literature as safe, standard technical parctice.
Just like you cannot assume that complying with BS7671 will make you immune to prosecution, HSE quote from BS7671 states that "compliance with BS7671 is LIKELY to comply with the relevant statutory instruments". It does not say guaranteed.....

Following on from this, publications and guidance from the IEE on BS7671 could similarly be quoted simply because they are deemed as an authoritive voice. As an expert witness anyone with the "technical experience" could be called to Court and give testimony either in support of non-statutory documents or to disprove its content as poor based on their own research. Very difficult when up against major documents but not impossible, if you have the money.

As a footnote one of the documents Elecsa demand at their annual assessment is the On-Site guide! As well as BS7671, Part P and the Memorandum on Electricity at Work Regs.

Ok mate, whatever. There is no telling you coz no matter what anyone says you will still believe you're right. Still... You are wrong.

I maintain my point. There is a vast difference between a set of non-statutory regulations and a guide. You can't be prosecuted under EAWR for not following the on site guide can you!? A guide by it's very nature is a simpler way of explaining something more complex, a means of giving basic instruction (OED definition). It will guide you through those complexities with much easier to understand language. Well what is BS7671 guiding you through?

Again, if guides are the be all and end all then give one of David Cockburn's guides a read then come back and tell me that you're still right.

The HSE will not quote just 'any' IEE literature when prosecuting, they will use BS7671, that is all, because if you have followed BS7671 then you will have by definition followed the guidance to BS7671. If you follow the much watered down guidance however, then you may not have complied with BS7671.

Another thing worth pointing out is the fact that there are people within the highest circles at the IEE who still haven't got a foggyest what they are talking about when it comes to electrical installation so claiming that all of their literature is bomb proof is a load of rubbish in my opinion. Even BS7671 is full of mistakes and uneducated doctrine.

D Skelton said:

It would seem that whenever the topic of bathroom extractor fans comes up, triple pole isolation has always been a rather debated subject. There are those of you who talk about not having to fit an isolator if there's a window and there are those of you who say that an isolator should always be fitted. Well, I'm writing this today to see if I can help clear up this subject once and for all.

There is a common misconception that if a bathroom has a window, then an isolator does not need to be fitted as mechanical maintainence can take place whilst the work area is suitably lit with daylight. Unfortunately, this is not the case at all. Generally speaking (there are exceptions), an extractor fan does not need to be fitted in a bathroom containing an opening window at all providing it can be demonstrated that Part F (ventilation) of the building regs has been complied with. This is to do with the air change rate within the bathroom and has nothing at all to do with mechanical maintainence only being allowed when lit. The amount of lighting that should be provided whilst working is down to the Health And Safety at Work Act not BS 7671. There is also a common misconception that a 3 pole isolator switch must be installed to allow for the fan to be isolated, this is also not the case, points of which I will explain in detail later on.

I have also seen a lot of debate regarding which type of extractor fan has to be fitted. Whether it has to be a timer fan with overrun, humidity controlled or simply one that operates off of the switched live alone. This again is a topic that is down to Part F of the building regs, not any electrical regs that I know of. Whatever the air change rate that specific bathroom needs to conform to Part F, then a fan that is fitted must be able to provide it, regardless of the type of fan. This means it may have to be a timer fan with overrun, it also means it may not need to be, it all depends.

Another point worth noting is that Part F only applies to new builds and refurbishments. A rewire is not a refurbishment as no structural changes have been made to the property. This means that there is no requirement to fit an extraction fan during a rewire alone. A rewire during a loft conversion however would be classed as a refurbishment, this means an extractor fan would need to be fitted and it would need to comply with Part F. Finally, if a bathroom that isn't already fitted with an extractor fan complies with Part F, a new fan installation in that bathroom need not apply to Part F. This means that in this scenario, selection of the type of fan is free for the customer or installer to choose.

Now I come to a couple of regs, first of which is all of those covered by 537.3.1. Essentially, electrically powered equipment shall be provided with a means of switching off where mechanical maintainence may involve a risk of injury. I feel the need to stress that use of an MCB and/or main switch and/or RCD is a perfectly acceptable means of switching off a bathroom extractor fan for mechanical maintainence. Nowhere does it state in BS 7671 that switching off for mechanical maintainence must be provided locally.

Another regulation I will draw your attention to is 132.15.2 which states that 'Every fixed electric motor shall be provided with an efficient means of switching off, readily accessible, easily operated and so placed as to prevent danger'. This is a regulation often pointed to by people who are in the 'Always fit 3 pole isolation club'. Here, 'means of switching off' does not neccesarily mean isolation. An extractor fan that runs off the switched live alone could reasonably be expected to conform with this regulation by use of the light switch alone, thus not needing a 3 pole isolation switch . A bathroom timer fan with overrun that runs off a light that is fused down to 1A via a switched fused connection unit as per manufacturers instructions, could also reasonably be expected to conform with this regulation by use of the SFCU alone, thus not needing a 3 pole isolation switch. A third example I could give you is of an extractor fan with an integral switch, this would not need 3 pole isolation either. Ultimately, depending on your own interpretation of the words 'readily accessible', it could be argued that a bathroom extractor fan could be efficiently switched off with the applicable circuit's MCB depending on the placement and accessibility of the consumer unit.

Now of course, all manufacturers instructions for electrical equipment must be followed to comply with BS 7671 but taking into account all the above highlighted points, what I have demonstrated is that the debate surrounding extractor fans in bathrooms is never black or white. Although it may still be considered best practice, there is no requirement in BS 7671 to fit 3 pole isolation for extractor fans, however, they must be able to be switched off, and there must be some method of isolation for the purpose of mechanical maintainence.

I hope this clears up any future debate or confusion regarding bathroom extractor fans.

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"Now I come to a couple of regs, first of which is all of those covered by 537.3.1. Essentially, electrically powered equipment shall be provided with a means of switching off where mechanical maintainence may involve a risk of injury. I feel the need to stress that use of an MCB and/or main switch and/or RCD is a perfectly acceptable means of switching off a bathroom extractor fan for mechanical maintainence. Nowhere does it state in BS 7671 that switching off for mechanical maintainence must be provided locally."

Just to disagree with you on a few points, have you forgotton that the original intention of the fan isolator switch was to disconnect all the poles (except CPC where used of course) the main concept is to be able to isolate the fan for maintenance. That's difficult to do if the MCB is used to control the circuit if it's dedicated, if it's for the lighting circuit then the regs say that no installation should be installed as to be a nuisance and switching the lighting MCB off in the dark is dangerous and impractical as the Neutral is still connected, isn't it? Also, any thought to the maximum amperage required by the fans. Most suppliers require a 3 amp fuse so that means a dedicated FCU as well. Anyone ever been called out because of a stalled fan?. Dispite what the regs say you must be sensible and provide a system that is well designed and in the interests of the customer, why do a second rate job. Install a FCU and an isolater, many fan companies will not credit a fan if it's burnt out. And while on the subject of fans has anyone had a problem with the Steeple range of fans, especially the humidistat controlled ones?

Read more: http://www.electriciansforums.net/e...on-source-much-controversy.html#ixzz2MZI9Yl5W

On a TN system disconnecting the line conductor only is a perfectly acceptable means of isolation. With regards to fuses, I thought I was pretty clear in my OP.

Read the last paragraph and then disagree with me again