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Plastic switch in external meter box

aligarjon
Can i fit a plastic switch fuse such as an 800kmf in the external meter box or does it have to be metal.   I am not interested in the dno view, they always seem to be happy with our switch gear in there around here so long as we leave them enough room.



Gary
  • 0
    What is the essential difference between a switchfuse and a 1-way consumer unit?



    A few.


    One is called a consumer unit as it is done to a standard where it is intended for use by ordinary persons, but it's also the application; is that the only consumers equipment?


    DBOs [ consumer units] to BSEN 61439-3 are limited to 63 amp per way; note your example is 45 amp, also it is pre 61439-3, but I get the gist. KMFs and switch fuses can have HRC up to 80 amp /100 amp respectively. The KMF/switchfuse devices usually serve a full blown consumer unit to BSEN 61439-3, in that instance it is clear the consumer unit is the thing intended for use by an ordinary person.


    Those are the essential differences, but there are other things beyond BS7671 and the clumsy wording of 421.1.201,

    like the Building regs and particular requirements for dwellings.

    421.1.201  is only “what shall comply with 61439-3”. Firstly it is "consumer units". In my opinion the "similar switchgear" was to cover the potential use of TPN DBs for a 3 phase domestic or converted to single phase for lots of ways; it becomes a DBO when used in a domestic, most are now 61439-3 anyhow, but when the reg was published, some TPN distribution boards were not manufactured as DBOs. The Consumer Unit is specifically intended for use by ordinary persons, a DBO. Also the similar bit is for self assembled consumer units where you purchase an enclosure separately and the devices separately. I will go with a consumer unit like enclosure with a main switch with one or more ways/MCB’s that you can re-arrange yourself to not escape being 61439-3. But we have to be careful what we attribute “similar switchgear” to. It could lead to a bit of a conflict with notification requirements for building regs.

    Replacing a 800KMF with a new one is not notifiable works because it is not a consumer unit.

  • 0
    Chris Pearson:

    OK, I have a white plastic box on the wall of my house; or in fact, two of them. One has the DNO's and supplier's tackle and the other has a switch-fuse. I reckon that both are my boxes on my land. My land! So where is the legal basis for the DNO "owning" one of them?


    The boxes belong to you.  If a door falls of a box, it's up to you to replace it at your expense.  But if you expect them to supply you with gas or electricity, then you need to provide a box that is acceptable to them.


  • 0
    An independent stand-alone isolator, or alternatively an isolating switch/fuse or isolating fuse/switch is not "similar switchgear"

    I agree that a simple isolator or a single RCD in an enclosure doesn't constitute similar switchgear since neither meet the definition of a distribution board. I'm having difficulty however putting a switchfuse in the same category according to BS 7671's definitions.


    What is the essential difference between a switchfuse and a 1-way consumer unit?
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       - Andy.
  • Former Community Member
    0 Former Community Member
    I reckon that both are my boxes on my land. My land! So where is the legal basis for the DNO "owning" one of them?


    On that logic, you own the DNO service cable, cut-out and meter Chris!


    Regards


    BOD


  • 0
    UKPN:


    Ascertaining whether a plastic isolator/sw/fuse is allowable under the "wiring regulations" would be futile anyway because that question has been thrown around for years and no one from the "institution has stuck their head above the parapet and given a definitive answer. 

    Regards, UKPN.


    That's not true, the words are in BS 7671 itself.

    Consumer unit is defined in the standard. It's an assembly with a main switch and protective devices for the control and distribution of electrical energy.


    An independent stand-alone isolator, or alternatively an isolating switch/fuse or isolating fuse/switch is not "similar switchgear" ... otherwise we couldn't fit standard shower isolators or cooker control units in domestic premises. It could also be argued that an enclosure containing a single RCD, say for a shower, is not "similar switchgear" as it does not include for "distribution", it's a dedicated device (similar, the SRCD).



    However, in full agreement with you, UKPN, on the position regarding fitting an isolator and loosening meter tails ... bring back 2-screw type terminals, or lugs, for larger CSA cable.


  • 0
    OK, I have a white plastic box on the wall of my house; or in fact, two of them. One has the DNO's and supplier's tackle and the other has a switch-fuse. I reckon that both are my boxes on my land. My land! So where is the legal basis for the DNO "owning" one of them?
  • 0
    " The OP wants to install this secondary overcurrent protective device in the DNO meter box enclosure for reasons only known to the OP. "

    Lol....It's either a very large meter box or a very small tail extention.

    Regards
  • 0
    " you cannot fit the lid, as some of the wires come out the front via what should be the gap between body and lid... "

    Oh come on..its been set up for the photo. Not even  a 5 day trainee clown would produce artwork as elaborate as that.

    Regards....
  • Former Community Member
    0 Former Community Member
    Your best course is to request a suppliers isolator via the customer. The suppliers meter operator will attend, fit, and you being there at the same time can reconnect the tails.


    I didn't read the OP as seeking to install an isolator, there could be one there already. My reading is that the OP wants to use "meter tails" greater than 3 m in length, hence the need for a secondary overcurrent protective device as use of the DNO cut-out fuse is not permitted for meter tails exceeding 3 m.


    The OP wants to install this secondary overcurrent protective device in the DNO meter box enclosure for reasons only known to the OP.


    It is past my bedtime so may have been typing utter $£%* so, as usual different viewpoints may follow!


    Regards


    BED
  • 0
    "I am not interested in the DNO view"

    You should be, because without a competency certificate signed by a DNO you are not able to work live on their equipment.

    An unauthorised "isolator" is not covered by the suppliers insurance.

    The fitting of an unauthorised "isolator" will loosen the meter tails irrespective of a withdrawn fuse so the meter terminals will have to be checked afterwards. This of course requires seals to be broken and replaced, again only persons with a competency certificate are able to do this.

    Your best course is to request a suppliers isolator via the customer. The suppliers meter operator will attend, fit, and you being there at the same time can reconnect the tails.

    Ascertaining whether a plastic isolator/sw/fuse is allowable under the "wiring regulations" would be futile anyway because that question has been thrown around for years and no one from the "institution has stuck their head above the parapet and given a definitive answer. 

    Regards, UKPN.

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