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Discuss Bathroom extractor fans and 3 pole isolation: A source of much controversy in the Electrical Wiring, Theories and Regulations area at ElectrciansForums.co.uk.

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  1. D Skelton
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    D Skelton Fidei Defensor Trusted Advisor

    Location:
    Canada
    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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    Last edited: Jun 24, 2011
  2. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Agree totally with your post.
    However I would suggest that not only is it applicable to extractor fans, but would apply to any item of equipment.
     
  3. nickblake
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    nickblake Trusted Advisor

    Nice one thats a great post , im going to have to read it again its friday im tiard and have had a few san meigels lol , having my fingers almost chopped of by a bathroom fan being switched on i now try and install inline fans in lofts with an isolator/fuse next to it so it can be locally isolated nice post
     
  4. TPES
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    TPES Regular EF Member

    Good post, agree with what is said..

    Is it not required that all live conductors are isolated, including the neutral? Hence the reason for a 3 pole fan isolator, the MCB, SFCU or standard pull cord switch will isolate the line conductor, but could there not still potentially be voltage on the neutral?
     
  5. D Skelton
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    D Skelton Fidei Defensor Trusted Advisor

    Location:
    Canada
    Reg 537.1.2. In a TN-S or TN-C-S system the neutral conductor need not be isolated or switched where it can be regarded as being reliably connected to Earth by a suitably low impedance. For supplies which are provided in accordance with the Electrical Safety, Quality and Continuity Regulations 2002, the supply neutral conductor (PEN or N) is considered to be connected to Earth by a suitably low impedance.

    Edit: Remember, reg 132.15.2 only requires a means of switching off, not isolation. Isolation in accordance with any other regulation, whether on a TT system or a TN-S or TN-C-S can be provided by the main switch.
     
    Last edited: Jun 24, 2011
  6. TPES
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    TPES Regular EF Member

    Have you swallowed a regs book? Your good.... I'm envious of your regs knowledge.
     
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  7. D Skelton
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    D Skelton Fidei Defensor Trusted Advisor

    Location:
    Canada
    No swallowing involved at all, I just gently caress it now and then :D
     
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  8. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Before or after you go to bed?
     
  9. D Skelton
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    D Skelton Fidei Defensor Trusted Advisor

    Location:
    Canada
    Doing it anywhere other than in bed would just be rude! I'm old fashioned like that
     
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  10. Kevin
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    Kevin Guest

    Out of interest, is the conversion of a standard bathroom to a disabled adaption 'wet room' considered a structural change, and therefore fall under the remit of Part F?
     
  11. D Skelton
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    D Skelton Fidei Defensor Trusted Advisor

    Location:
    Canada
    My personal thoughts are no as you are only changing the layout of a specific room, not making structural changes of any kind. Ripping out an old shower to create space for a whole wetroom for example I wouldn't define as a structural alteration however taking out a dividing wall I would. I guess it's down to your interpretation of the words 'structural change' or 'structural alteration' Advice from a structural engineer may steer you in the right direction also.
     
  12. malcolmsanford
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    malcolmsanford Trusted Advisor

    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 ..................
     
  13. sparkdog
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    sparkdog sparkdog Electrician's Arms

    Location:
    Sunny Sussex
    Business Name:
    C MacRae Electrical
    That's useful info.I recently had a builder and sparky's mate going on about building control wanting a 3 pole isolator fitted and I pointed out there was no requirement in the regs for that.
     
  14. nickblake
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    nickblake Trusted Advisor

    Be careful doing that you'll end up with a load of on site guides running around
     
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  15. Electro-tech
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    Electro-tech Regular EF Member

    So an extractor fan supplied from a lighting circuit for a bathroom without a window, should have it own means of isolation,for maintenance in the dark.
     
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