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Exposed 24VDC in a Bathroom

Harry Heathfield
Hello IET Forum,


I'm hoping someone can point me in the direction of a suitable standard that refers to exposed 24VDC conductors not being appropriate in a bathroom. My client would like to use the two metal hinges of a bathroom cabinet mirror as the +/- conductors; I'm not comfortable with them connecting any electricity through metal hinges, let alone in a bathroom! I've consulted with BS7671:2018; it says up to 30VDC is appropriate for the zone, but that doesn't mean exposed, of course! My client wants me to provide unquestionable evidence as to why they can't do it, but I'm struggling to find anything that isn't open to interpretation. Can anyone help?


The best I can find so far is from IEC 60364-4-41, Annex A.1 “Live parts shall be completely covered with insulation which can only be removed by destruction”.


Kind Regards, Harry
  • 0
    BS7671 only seems to require basic insulation if the cabinet is within zones 0/1/2.


    However, if it's possible for someone to get a noticeable tingle just by touching the hinges when wet, even if perfectly harmless, then common sense dictates not to do that. At best, any new owners will waste money reporting a "fault" to electricians, and at worst it desensitises people to taking such tingles seriously in a bathroom.
  • 0
    If you've got 3xpised metal hinges in a bathroom  then there's a real risk of excessive leakage current due to  dampness from bathing and showering  this will eventually lead to at least a partial short circuit all in all its a very bad idea I don't think the system would last more than 6 months
  • 0
    broadgage:

    Even if not actually prohibited I would consider it poor practice to have 24 volts DC fully exposed to touch in a wet location such as bathroom.

    I would consider that 24 volts DC should be at least somewhat enclosed or protected against touch, though not to the same standards expected for mains equipment.

    A non shuttered socket outlet for 24 volts DC, fine.

    A within reach lamp holder for 24 volts DC fine.


    A "tension wire" lighting system at 24 volts DC not good practice. Nor a similar voltage on exposed door hinges.


    I perceive some risk of poor contact, and the user fiddling with it with wet hands.


    The comparison with lights on lorries is relevant, only one pole of the supply is EASY to touch being connected to the body of the vehicle. The other ole of the supply is much less easy to touch being present on recessed lamp holder contacts and the like.


    It is prohibited, BUT only in Zones 0, 1 and 2, see Regulation 701.414.4.5 of BS 7671

    701.414.4.5 Requirements for SELV and PELV circuits

    Where SELV or PELV is used, whatever the nominal voltage, basic protection for equipment in zones 0, 1 and 2 shall be provided by:

    (i) basic insulation complying with Regulation 416.1, or

    (ii) barriers or enclosures complying with Regulation 416.2.


    If the bathroom cabinet is not in Zone 1 or Zone 2 (effectively more than 0.6 m away from the bath or shower) then there is no requirement for basic protection.

     


  • 0
    gkenyon:
    broadgage:

    Even if not actually prohibited I would consider it poor practice to have 24 volts DC fully exposed to touch in a wet location such as bathroom.

    I would consider that 24 volts DC should be at least somewhat enclosed or protected against touch, though not to the same standards expected for mains equipment.

    A non shuttered socket outlet for 24 volts DC, fine.

    A within reach lamp holder for 24 volts DC fine.


    A "tension wire" lighting system at 24 volts DC not good practice. Nor a similar voltage on exposed door hinges.


    I perceive some risk of poor contact, and the user fiddling with it with wet hands.


    The comparison with lights on lorries is relevant, only one pole of the supply is EASY to touch being connected to the body of the vehicle. The other ole of the supply is much less easy to touch being present on recessed lamp holder contacts and the like.


    It is prohibited, BUT only in Zones 0, 1 and 2, see Regulation 701.414.4.5 of BS 7671

    701.414.4.5 Requirements for SELV and PELV circuits

    Where SELV or PELV is used, whatever the nominal voltage, basic protection for equipment in zones 0, 1 and 2 shall be provided by:

    (i) basic insulation complying with Regulation 416.1, or

    (ii) barriers or enclosures complying with Regulation 416.2.


    If the bathroom cabinet is not in Zone 1 or Zone 2 (effectively more than 0.6 m away from the bath or shower) then there is no requirement for basic protection.

     






    Thank you all for taking your time to read my post and provide comments; it's appreciated. 


    Graham, your quote above is enough for me to go on. I checked with my copy of BS7671:2018, and I'm pleased to read 701.414.4.5 (for others reference, page 241), as the cabinet is intended to be installed in Zone 1, according to the customer. Considering the mirror cabinet will be installed in a bathroom, I feel I can negate the need for other standards and quote section 701. Any electrician who comes to install the mirror should be checking BS7671; hopefully, they'd see 701.414.4.5, leading to a refusal to install the cabinet in a bathroom. Thank you, Graham; I should have looked at section 701 before asking this question!


    Kind Regards, Harry


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