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Wylex 100A dp isolators in plastic enclosures.

hertzal123
Just wondered  why these are not classed as "similar switchgear" to consumer units etc which are supposed to be in

non flammable enclosures in domestics.

                                          Regards,Hz
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    Simon Barker:

    Because one switch on its own isn't "switchgear", whether or not it's "similar" to a CU.  Put two of them together in the same box, and that's another matter.




    Not sure I agree with that definition.


    And in the spirit of the relevant Regulation, it's a "technicality" at best.

  • 0

    AJJewsbury:




    I think that a double pole switch does meet the definition of switchgear as defined in Part 2



    I hope you're wrong - otherwise we'll start to need metal clad rotary isolators and FCUs. Where's the "auxiliary" switching equipment when you only have a single switch disconnector in a box?

     

    but think about what the regulation is intended to do



    Distract attention away from CU manufacturers making plastic cases that weren't quite as self-exitinguishing as the standards required?


      - Andy.

     




    I'm sure there are metal enclosure versions of "REC" switches out there.

  • 0
    When the DNO installs the isolator, they don't have to comply with BS 7671.


    When it becomes the consumers afterwards, and is inspected against BS 7671, the game changes ...
  • 0
    "Distract attention away from CU manufacturers making plastic cases that weren't quite as self-exitinguishing as the standards required?


      - Andy. "


    Wow I loved that comment!


    Signed by the of Tunnel Terminal Activists  (Double screw division)
  • 0

    I'm sure there are metal enclosure versions of "REC" switches out there.



    But ones that can offer shock protection by means of double or reinforced insulation? I'm thinking of TT supplies and TN ones where Ze isn't necessarily below 0.38Ω (e.g. traditional TN-S in the generic case).


    Then there's the whole issue of relying on the DNO's fuse for ADS. BS 7671 seems strangely silent on the issue (there's no equivalent of 434.3(iv) or 433.3.1(iii) in section 411). It does say we can use the DNO's fuse for protecting conductors under fault conditions - where the DNO gives their agreement - but some DNOs are declining to give that agreement these days, instead recommending that customers use BS 7671's rules to allow the omission of fault protection (<3m and installed to reduce the risks of faults and fire to a minimum). Presumably they don't want to he held responsible if network changes alter Ze or they change their protective device. Even the 0.35Ω figure for PME supplies isn't guaranteed - but just a figure the DNOs aim to meet most of the time.


    So in the context of not even really being able to rely on the DNO's fuse to protect property from faults, how sensible is it to rely on it to protect life? even on TN-C-S systems?


      - Andy.
  • 0
    Well, if the isolator is going to be "given over" to the customer, what is the point of providing it anyway - especially if it could be argued not to comply with BS 7671 requirements for fire safety (and all a lawyer needs is an argument like this ...).


    At the end of the day, the argument about the DNO device not protecting the "tails" is what it is ... I'd guess their stance is also a result of the "consumer unit fires" issue also. Basically, in every case where the metal-cased REC isolator is not considered suitable, neither is a metal-clad consumer unit that doesn't provide double insulation or equivalent for the busbars (and upstream devices) feeding the protective devices that provide shock protection.



    In cases where a metal-cased isolator is not considered acceptable, but is desired, the only option that remains, if you really need a separate isolator, is to put the plastic REC isolator in a metal box, with suitable fire-rated stuffing glands for the tails ... no different to the requirement for the main CU itself.


  • 0
    Are there not other products in Wylex's range now, that are more suited to this application in dwellings, that might well help with the insulation issue, and the "can't rely on the DNO fuse" issue?


    (Although, noted they are not in the same price bracket.)
  • 0

    At the end of the day, the argument about the DNO device not protecting the "tails" is what it is ... I'd guess their stance is also a result of the "consumer unit fires" issue also. Basically, in every case where the metal-cased REC isolator is not considered suitable, neither is a metal-clad consumer unit that doesn't provide double insulation or equivalent for the busbars (and upstream devices) feeding the protective devices that provide shock protection.



    Absolutely - but at least BS 7671 is reasonably clear on that - at least for the obvious TT situation. (531.3.5.3.2.201)


      - Andy.
  • 0

    531.3.5.3.2.201

    For Class I enclosures in TT systems where RCD protection is used on outgoing circuits, double or reinforced insulation of all live conductors (incoming cables, extension terminals, etc.) on the supply side of the incoming device, e.g. main switch, shall be used. Insulated and non-metallic sheathed cables are deemed to meet the requirements of double or reinforced insulation.

    NOTE: Consideration should be given to the manufacturer's internal live interconnecting cable links on the supply side of an RCD being double insulated, having reinforced insulation or equivalent mechanical protection.



    To me the 'NOTE' is not strong enough. You may consider it if you like but it rather leaves the door open to misinterpretation . To have insulated and sheathed meter tails into to a DIN rail main switch, but then some bare bus bar to take live feed from the switch to a row of RCBOs, or in the CU of at least one well known brand what looks like very thick enameled wire to the RCDs  appears to be acceptable,  so in one case nothing and in the other only varnish insulating a pre RCD live, and I rather think it should not be.


    I'd be far happier if it said "double or reinforced insulation  is required for all wiring not protected by an RCD or RCBO"

    It does not.
  • 0

    mapj1:




    531.3.5.3.2.201

    For Class I enclosures in TT systems where RCD protection is used on outgoing circuits, double or reinforced insulation of all live conductors (incoming cables, extension terminals, etc.) on the supply side of the incoming device, e.g. main switch, shall be used. Insulated and non-metallic sheathed cables are deemed to meet the requirements of double or reinforced insulation.

    NOTE: Consideration should be given to the manufacturer's internal live interconnecting cable links on the supply side of an RCD being double insulated, having reinforced insulation or equivalent mechanical protection.



    To me the 'NOTE' is not strong enough. You may consider it if you like but it rather leaves the door open to misinterpretation . To have insulated and sheathed meter tails into to a DIN rail main switch, but then some bare bus bar to take live feed from the switch to a row of RCBOs, or in the CU of at least one well known brand what looks like very thick enameled wire to the RCDs  appears to be acceptable,  so in one case nothing and in the other only varnish insulating a pre RCD live, and I rather think it should not be.


    I'd be far happier if it said "double or reinforced insulation  is required for all wiring not protected by an RCD or RCBO"

    It does not.


    There is an easy solution: put a 100 mA type S RCD in the REC2 enclosure instead of the normal switch.

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