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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)?


F
  • 0

    gkenyon:






    So "it would be reasonable to interpret" is in my opinion an assumption at best.


     




     




    Which is the point I was making.. ie WITHOUT FURTHER INFORMATION it is quite likely that the data sheet could be interpreted that way. Hence adding to the confusion, as I said.


    I do hope you didn't assume I was disagreeing with anything you said ?

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    -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)




    Glad not to be alone on this one, but equally well they have not specified 2 x 13 A.


    I maintain that a twin socket is rated at 14 A + 6 A. That is not necessarily the same as, for example, 10 A + 10 A. It may be more or less onerous.

  • 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




    That different room bit is a new one to me! Where does that come from then? 

  • 0

    perspicacious:
    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




    Reply>>>>>>>>>>>>>>>>>

    14th Edition Reg. A.31.


    "Each socket-outlet of a twin or multiple socket-outlet shall be counted as one socket-outlet for purposes of Reg. A.30 and Table A.3M." A.40 refers to socket outlets, so 2 single sockets are 2, and one twin socket outlet is 2 sockets also.


    Z.

  • 0

    -2400-:




    gkenyon:






    So "it would be reasonable to interpret" is in my opinion an assumption at best.


     




     




    Which is the point I was making.. ie WITHOUT FURTHER INFORMATION it is quite likely that the data sheet could be interpreted that way. Hence adding to the confusion, as I said.


    I do hope you didn't assume I was disagreeing with anything you said ?


     




    There are some truths that need to be considered though, as people are saying:


    (a) Most double socket-outlets would be unlikely to experience 2 x full 13 A loads.


    (b) Most users would be unlikely to know or care that the double socket-outlet was only rated 13 A total.


    (c) An electrician fitting a double socket-outlet can clearly see the marked rating, so they should not install double socket-outlets where two heavy current-using appliances might be plugged into the same double socket-outlet - specifically, I'm talking about laundry, dishwashing, and cooking appliances like ovens that might be used for extended periods, supplied with a plug, rated around or over 2 kW.

  • 0

    Chris Pearson:




    -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)




    Glad not to be alone on this one, but equally well they have not specified 2 x 13 A.


    I maintain that a twin socket is rated at 14 A + 6 A. That is not necessarily the same as, for example, 10 A + 10 A. It may be more or less onerous.


     




    The standard does not say that. It says:


    • The double socket-outlet is stress tested with 14 A + 6 A loads connected.

    • The manufacturer marks the rating on the accessory


    In the case of a double socket-outlet, the rating is clearly marked (on the rear) with, usually, 13 A these days.

  • 0
    We've definitely been round these discussions previously in the (older) Forum


  • 0



    gkenyon:




    Chris Pearson:

    Glad not to be alone on this one, but equally well they have not specified 2 x 13 A.


    I maintain that a twin socket is rated at 14 A + 6 A. That is not necessarily the same as, for example, 10 A + 10 A. It may be more or less onerous.




    The standard does not say that. It says:


    • The double socket-outlet is stress tested with 14 A + 6 A loads connected.

    • The manufacturer marks the rating on the accessory


    In the case of a double socket-outlet, the rating is clearly marked (on the rear) with, usually, 13 A these days.


    So what do we mean by the word, "rating" which is in the subject heading?


    If MK states that it's twin sockets may supply a combined current of 19.5 A continuously, why are they not rated at 19.5 A? If such ratings were applied, purchasers might choose to buy the sockets with a higher rating so competition might drive up the quality.


    If a multiple socket-outlet may safely supply only 13 A, why are they not required to have a 13 A BS 1362 fuse in them?


    The 1984 version of the standard is the same as the current one as regards labelling. Unfortunately, the original 1947 standard is not downloadable from the BS site.


    I am tempted to put a clamp meter on the circuit when both washing machine and tumble drier are running.

  • 0

    Chris Pearson:


    So what do we mean by the word, "rating" which is in the subject heading?

    In this case, surely we are talking about the "Rating of the double socket-outlet". It would make no sense for the marked rating of "13 A" to mean "2 x 13 A", especially given the tests in the standard.


    If MK states that it's twin sockets may supply a combined current of 19.5 A continuously, why are they not rated at 19.5 A? If such ratings were applied, purchasers might choose to buy the sockets with a higher rating so competition might drive up the quality.


    I don't know, perhaps some are ... just the Logic Plus ones I have are rated 13 A, as are most double socket-outlets I see. Which ones are you talking about, and what is the rating marked on the back in accordance with the standard? It makes no sense for the socket-outlet to be rated less than the manufacturer states it's rated for?


    However, it's still not "26 A" or "2 x 13 A" is it?



    If a multiple socket-outlet may safely supply only 13 A, why are they not required to have a 13 A BS 1362 fuse in them?


    This has already been explained in another post. It's no different than an unfused double adaptor being used with a single socket-outlet.


    The 1984 version of the standard is the same as the current one as regards labelling. Unfortunately, the original 1947 standard is not downloadable from the BS site.


    Agreed


    I am tempted to put a clamp meter on the circuit when both washing machine and tumble drier are running.



    I can tell you what you will see for domestic machines, which is as follows:



    On high heat, the tumble dryer will use about 1-2 A when only the motor is running, and 11-12 A when both parts of the element is switched on. Depending on the weather (temperature and humidity), and how damp the clothes are, the highest current is drawn between 40 and 80 % of the time.


    The washing machine (washer only - not washer-dryer) is roughly similar - slightly more motor current on spin - but only draws its full power of approximately 11 A when heating. On a boil wash in winter, time to get to temperature can be a considerable time. However, on most cycles in use, I'd guess the heater on a modern machine is on for about 10 minutes at most.


    A dishwasher heater is on for longer - especially where the machine has a drying cycle at the end also.


    So, in a domestic situation, you will get about 24 A for periods of 10-30 minutes at a shot, probably meaning many double socket-outlets would deteriorate in a couple of years at most, dependent on usage - greater risks in winter.



    Commercial / industrial usage is a very different kettle of fish.





     



     

  • 0
    Yes commercial and industrial are totally different things.


    I was having a nice Indian meal with a friend recently. The service was excellent and the food wonderful. Towards the end of the meal the restaurant become fuller with diners. A waiter came over and apologised as he had to get behind my seated dining companion to access a cupboard door. He opened the door and reset a M.C.B. Evidently a new piece of kitchen equipment had caused yet another overload. An overloaded ring no doubt. The consumer units were at the very front of the restaurant and the kitchen at the very back, so a sparks will have an interesting job in running a new cable.


    Z.

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