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Grid switch ratings enquiry

Farmboy
Had an interesting chat with a tech dept this afternoon after coming across some grid switches in a domestic kitchen.


Four grid switches (sharing a common backbox) are each fed via their own 16A cb's, and each feeds 1G sockets (for a cooker hood, fridge freezer, etc). Ignoring the cable sizes (the focus being on the grid switches), given the 13A plug fuses limits the loads in each cct, would you have the current rating of the grid switches equal to or higher than the 16A cb's (e.g. 20A), or lower (but equal to or higher than the socket rating e.g. 13A/14A)?


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  • 0
    The dreaded old I squared R causing Wattage heating again no doubt if the plug pins and socket contacts have any resistance between them.


    Z.
  • 0

    Chris Pearson:




    AJJewsbury:




    Am I reading this differently from everyone else? If a 'multiple socket outlet' is a combination of two or more socket outlets and the rated current of all socket-outlets shall be 13A, surely this means a multiple socket outlet with two socket outlets must be rated at 13A + 13A, or 26A for the unit. Or is this wrong?



    ... e.g. you could take the full 13A from either the left hand outlet, or the right hand one, but not necessarily both together ...

    It would be absurd if one could take the full 13 A from one side of a twin socket and nothing from the other - there would be no point in having a twin socket.

     




    That's not how diversity works?


    No-one would make the same statement about a 4-way (or 6-way or 10-way) "extension" with a 13 A plug, now, would they?

  • 0

    gkenyon:

    No-one would make the same statement about a 4-way (or 6-way or 10-way) "extension" with a 13 A plug, now, would they?




    That's completely different - the total output is limited by the fuse in the plug, and possibly another one in the sockets.


    MK make a triple 13 A fixed socket, but they are collectively fused in the same way by a BS 1362 fuse. Their literature specifies a rating of 13 A for singles and doubles, but 13 A total for triples. It does not say 13 A total for doubles.

  • 0

    That's completely different - the total output is limited by the fuse in the plug, and possibly another one in the sockets.



    It's the same from the user point of view - in terms of what the can safely plug in. (OK the failure mode is slightly different if they get it wrong...)


    The vast majority of appliances draw much less than 13A (it's rare to find a CE marked portable appliance these days that draws more than 10A - as some continental plugs/sockets are limited to 10A) and those than can draw the full 13A usually don't do so for long, so the 13A total limitation probably isn't as restrictive as it might first appear.


    The theory seems to be that a double socket is equivalent to a single socket plus an unfused 2-way adaptor.

    MK make a triple 13 A fixed socket, but they are collectively fused in the same way by a BS 1362 fuse. Their literature specifies a rating of 13 A for singles and doubles, but 13 A total for triples. It does not say 13 A total for doubles.



    MK are renowned for their dual sockets having a overall rating higher than BS 1363's minimum requirements. I don't think we can infer from their statement that the same applies to all other manufacturers.


       - Andy.
  • 0

    Chris Pearson:




    gkenyon:

    No-one would make the same statement about a 4-way (or 6-way or 10-way) "extension" with a 13 A plug, now, would they?




    That's completely different - the total output is limited by the fuse in the plug, and possibly another one in the sockets.


    MK make a triple 13 A fixed socket, but they are collectively fused in the same way by a BS 1362 fuse. Their literature specifies a rating of 13 A for singles and doubles, but 13 A total for triples. It does not say 13 A total for doubles.


     




    The MK Logic Plus double socket-outlets I have here, are rated "13 A" in just the same way as the other double socket-outlet I posted earlier. That is, 13 A total.


    The rating does not say "2 x 13 A" or "2 no. 13 A", it is marked with the total rating in the same way as the single socket-outlet.


    As Andy says, it's about "reasonable chance of an overload".

  • 0
    To add to the chance of confusion, the MK technical data for Logic Plus range states:


    Current rating

    13A

    (3 Gang Switchsocket 13A total)


    which without any further information, it would be reasonable to interpret as though the 2 gang was 2 x 13A, otherwise they might have written

    (2 Gang and 3 Gang are 13A total)

  • Former Community Member
    0 Former Community Member
    Historically when spurring off a ring final circuit, were you only allowed one double or if in different rooms, a single in each of those?


    Regards


    BOD
  • 0

    perspicacious:

    Historically when spurring off a ring final circuit, were you only allowed one double or if in different rooms, a single in each of those?


    Regards


    BOD




    Historically such as in the 15th edition of 1987 a non fused spur could only supply one single or one twin (double) socket outlet from a ring. 


    EDIT. P.S. The number of non fused spurs was limited to not be greater in number than the total number of sockets and items of stationary equipment on the ring.  The number of fused spurs was unlimited.


    Z.

  • 0

    -2400-:

    To add to the chance of confusion, the MK technical data for Logic Plus range states:


    Current rating

    13A

    (3 Gang Switchsocket 13A total)


    which without any further information, it would be reasonable to interpret as though the 2 gang was 2 x 13A, otherwise they might have written

    (2 Gang and 3 Gang are 13A total)

     






    BS 1363-2 requires the manufacturer to mark the rating of the accessory on it ... and this has been done.


    So "it would be reasonable to interpret" is in my opinion an assumption at best. I'm sure I needn't complete the popular engineering saying that begins "Assumption is the mother of all ..."

    I believe it's been clearly demonstrated that the "stress" test in BS 1363-2 isn't even carried out at 26 A (2 x 13 A)


    The data is clearly telling you quite simply that, despite the fact there are three outlets, this still means the whole unit is only rated at 13 A - but it does NOT in any way say that the rating of the double socket-outlet is rated for anything other than its stated rating.

  • Former Community Member
    0 Former Community Member
    Historically such as in the 15th edition of 1987 a non fused spur could only supply one single or one twin (double) socket outlet from a ring.


    My history goes back further as A.40 in the 14th (1966 through to 1976) states: "Not more than two socket-outlets, or one twin socket-outlet, or one stationary appliance, shall be fed from each non-fused spur."


    Whilst the wording of the 13th 114 (B) (ii) is similar, it doesn't define socket-outlets as being single or twin though


    Regards


    BOD
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