The advice and statements by some contributors to this forum must be treated with caution. There are no experts, we are all learning. I hope the following dissertation, clears the confusion which has arisen on what is a fairly important topic.
The current rating for the twin socket, is greater than that of the single socket and is largely due to the increased thermal heat dissipation, in the case of the twin socket. The rating of any electrical carrying conductor whether a cable, copper bar etc., obviously depends on the rate at which the heat is transferred to the surroundings. There is an increased surface area and thermal mass in the case of the twin socket, this is variable and depends upon the manufacturers’ design. The total thermal current rating for 2 plugs in the same twin socket, is above 13A for both; but not double (26A), it is about 19A (see the article below), but the specific manufacturer must be consulted for recommendations.
Fortunately, for most situations, this is not something to worry about, diversity would be applicable, where two appliances are plugged into the same twin socket outlet, i.e. it would be very unusual to have two appliances, each continuously pulling 13A).
The following article is 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.
Striving for perfection in an imperfect world.
