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International plugs and sockets

Chris Pearson
As we leave the EU, with all its standardization, I am bound to wonder why plugs and sockets have not been subject to this process. It isn't even that we have our funny square pins and the rest have round ones. Type C (2 pin) is common, but earthed plugs are mostly type E or F. IEC site.


Oh well, too late now!
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    gkenyon:

    (b) The reason it leads to a clunky design is that the plug has a fuse, which gets warm in use, and the heat needs to be dealt with (end of physics lesson).




     

    And a BS1362 fuse can be very reluctant to blow when overloaded.  If anyone is wondering what happens if you plug two kettles full of cold water into the same 4-way extension lead, the answer is that you get two kettles full of boiling water.  (It wasn't me doing it, I hasten to add!)
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    gkenyon:

    (c) We can't do away with the fuse whilst we still retain ring final circuits.




    Why not put it in the socket (outlet)?

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    That's a possibility, but:


    (a) there might be a knock-on effect on the size of the standard socket-outlet in the same way, even if it's only the minimum depth of a backbox


    and


    (b) It would require ALL existing unfused socket-outlets supplied by 32 A protective devices to be replaced.
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    AJJewsbury:

    Are you going to change the symbol "I" for current as well - after all that's another French invention (by Monsieur André-Marie Ampère) - perhaps to the more obvious (to Anglo Saxons) "C"? (Although you might then have to come up  with something different for all those correction factors...)




    Oui, mais n'est-ce pas « l'intensité de courant » ?

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    Why not put it in the socket (outlet)?




     



    I think that was considered in the early (pre BS 1363) days - but the conclusion was that a blown fuse should move with the faulty appliance rather than stay at the (innocent) socket. That way when something doesn't work and gets plugged into another socket to decide whether it's the socket or the appliance that's at fault, you don't end up with multiple dead sockets that are then useless for perfectly serviceable appliances (until someone get a screwdriver out and replaces the fuses), and the same fault isn't inflicted on the supply multiple times.


    Perhaps less of an issue if the socket incorporates a readily resettable circuit breaker than a fuse.

     



    And a BS1362 fuse can be very reluctant to blow when overloaded.


    As are most overload protective devices - a 16A or 20A MCB (of the rest of the world's practice) probably wouldn't be any better.

     

    (c) We can't do away with the fuse whilst we still retain ring final circuits.



    Minor detail - but it's not so much the ring as our preference for 30/32A circuits - there's exactly the same issue with a 32A radial.


       - Andy.
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    Andy,


    Re the 32 A circuit, yes, agreed - in part. The original move was to the ring final circuit, and this drove the requirement for a fuse (previous to that, was the existence of, generally, 5 and 15 A circuits).


    We are now in the situation where the existence of the fuse in the plug permits the 32 A final circuit for standard domestic and similar socket outlet circuits.
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    Simon Barker:


    And a BS1362 fuse can be very reluctant to blow when overloaded. 


    Any fuse will be very reluctant to blow when overloaded - fuses are not overload protection, they are short circuit protection. From a 13A fuse protection you should be able to draw 20A for a significant duration (BS 1362 possibly indefinitely but certainly >3 hours). Generally overload protection is to protect the equipment, short circuit protection is to protect the electrical installation - somewhat simplified and I am sure you can think of many caveats and exceptions but in principle, that sums it up.

    Alasdair

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    Alasdair Anderson:




    Simon Barker:


    And a BS1362 fuse can be very reluctant to blow when overloaded. 


    Any fuse will be very reluctant to blow when overloaded - fuses are not overload protection, they are short circuit protection. From a 13A fuse protection you should be able to draw 20A for a significant duration (BS 1362 possibly indefinitely but certainly >3 hours). Generally overload protection is to protect the equipment, short circuit protection is to protect the electrical installation - somewhat simplified and I am sure you can think of many caveats and exceptions but in principle, that sums it up.

    Alasdair


     




    The bit about overload protection being for equipment is not true.


    Regulation Group 433.1 permits fuses to be used for protection against overload current; further, the requirements discuss selection of cable current carrying capacity in relation to the rating (and type) of the overload current protective device. Miniature circuit breakers are little different when operating in the thermal region.


    In terms of the role of BS 1362 fuse vs the connected appliance, the fuse is to protect the appliance lead, and not the appliance.


    If we are talking about protection against thermal effects during overload, it's possible to size the cable so the overload current protective device always protects the cable. The adiabatic criterion is only valid for faults of short duration, and the non-adiabatic method can be used - although if you follow Regulation Group 433.1 in relation to Iz this is not necessary.


    Using the non-adiabatic approach (long duration faults), it's possible to demonstrate that a 13 A fuse will protect a 6 A flexible cable against fault current and overload current regardless of the length.

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    "Why not put it in the socket (outlet)?" Because the normal reason for a fuse to blow is a fault in the appliance so you take the faulty appliance together with the blown fuse to someone who can fix it.
  • 0

    Harry Macdonald:

    "Why not put it in the socket (outlet)?" Because the normal reason for a fuse to blow is a fault in the appliance so you take the faulty appliance together with the blown fuse to someone who can fix it.




    OK, so when our European neighbour's MCB trips, what then?


    Isn't a fused BS 1363 plug simply a way of complying with 433.2.1?

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