I can think of a couple of ways to overload a socket using only legit UK stuff.
The most insiduous is to use a double socket. Afaict double sockets are NOT required to be tested for the full 26A that someone could pull through two plugs.
I would agree that poor quality plugs and sockets often can't take the continuous load of 13A. A kettle may be 13A but only for 4 minutes and I have noted since the introduction of safety plugs with the plastic finger guards there has been an increase of failures. However unless the plug is down rated you can still plug in a 3Kw electric fire and that is the max load. As to two 3Kw items into a double socket I have noted the standard is:-
"BS1363-2:1995 requires for double socket outlets that both socket outlets have loads applied via test plugs, 1 test plug having a load of 14 amps whilst the other has a load of 6 amps, making a total load of 20 amps on the cable supplying the double socket outlet. The double socket outlet is then subjected to this loading for a minimum continuous period of 4 hours or longer until stability is reached with a maximum duration of 8 hours (stability being taken as less than 1 degC rise within 1 h). The test is passed if neither the terminals / terminations, nor the accessible external surface, increase in temperature by more than 52 degC."
Also from MK
"All MK socket-outlets are manufactured to comply with BS1363 part 2: 1995 and are rated at 13A per unit. Double socket-outlets have been manufactured and tested to exceed this rating by margin that allows electrical safety and reduces the risk of heat and mechanical damage to components due to overloading. It should be noted that BS1363 part 2: 1995 does not allow double sockets to operate at twice the permissible maximum loading and it should be remembered that double socket-outlets are not manufactured to be able to withstand a 26A load for sustained periods of time.
Research by ourselves and third party organisations has shown that all MK double sockets can safely withstand a continuous load of 19.5A for an indefinite period. Increasing the load slightly will begin to cause heat and mechanical stresses on the components in a relatively short period. Testing showed that a load of 22.3A was sufficient to cause heat stress that would cause a browning of the faceplates and sufficient heat to cause insulation damage to cable cores. A load of 24A for 43 hours was sufficient to cause significant heat damage to the material in which the socket-outlet was situated and within 75 hours sufficient to cause significant damage that would lead to the very real potential of fire.
MK recommend that users of their sockets consult professional design Engineers when designing installations to avoid the possibility of heat and mechanical stress to components and installations caused by overloading of MK socket-outlets."
Taken from similar debate on IET web site
Yet go to MK web site and down load PDF and it states:-
"Current rating: 13A per socket outlet
(except 3 gang which is 13 amp in total)" Which I assume means you can draw full 26A on a double socket? There is a limit on ambient temperature "(not to exceed an average of more than 25°C in any 24
hour period)" so may be first was from some old catalogue?
Personally if not 26A then there should either be some overload device to stop one reaching 26A or at least it should be marked on front of socket.
The second is to use a socket doubler (or worse two of them one in each side of a double socket). Unlike most other adaptors socket doublers are not required to be fused.
Old socket doublers often did have one socket direct and two sockets fused but to comply with BS 1363 all outlets must be fused and although I have found adaptors and doublers without the fuse these have not been marked as BS 1363.
The weight of plugs fitted into socket doublers is the main problem and it can mean the plastic safety part of the pins gets compressed and allows the unit to push the spring grips upwards and lose connection with the lower part of the pin. I had though as a result these had been withdraw in favour of the multi-adaptor where a standard fused plug is connected by a short length of cable to a 2 to 10 way array of sockets. However last visit to Poundland I noted old type on sale again. I did not check to see if BS 1363 marked.
However to warn the public not to use the old type square adaptors is far comment but nearly every office one goes into has a multi-adaptor to run computer, printer, monitor etc. And with such a low current draw there is no real danger and if we feel multi-socket extensions are dangerous then maybe the government should follow New Zealand and abandon Part P so people can fit extra sockets rather than use these multi-socket extensions?
