Posted By Rod McGovern

I have recently been questioned as to why adaptors that plug into electrical sockets are particularly hazardous. Is it only when they are overloaded? If so, if the chance of overload is assessed as low, does the fuse/trip at the main switchboard not give adequate protection?
In some situations these adaptors seem to be a safer alternative to a 4 way adaptor connected by a cable.
Any comments?
Rod

Posted By Kelvin George
Rod

With your mains electrical socket circuits, if done corectly will be a "Ring main" setup - many years ago it would have been star format (each socket directly connected to your consumer box. This provides each socket with 2 directions of electrical supply.

The benefit of this is that the complete circuit can safely carry 13A of current and the wires can disapate the heat throughout the whole of its' length more efficiently because there is more surface area for this heat to be disapated. It is the disapation of heat which is the important fact because if not done efficiently then the insulation will melt and a short circuit can occur increasing the risk of fire.

If however you then put more than one load on a socket you then introduce a localised area of increased load and with it comes the increase in heat caused by the flow of electricity. Now this is not in itself dangerous but is by definition more hazardous.

If you use a simple mutli plug tthen as Jane stated you increase the mechanical stress upon the socket and increase the risk of mechanically damaging the socket.

Ideally you would only ever have one load per socket, however in the real world this is not necessarily practical. So the safest method of implementing more than one load per socket is to produce a spur from the ring main. To do this easily and safely is to use a multi socket that plugs into the ring main with a plug on a lead. You are then in the position where you can once again have one load per socket - even though you now have a spur with 4 - 6 sockets on it. The advantage of these mutli sockets is that the extra sockets are fused (they usually come with 13A fuse that can be replaced) and that allows you to replace the 13A fuse with a smaller one sufficient for the equipment you wish to plug in at that point.

This situation then gives you localised protection to your ring main by limiting the current you can draw from that individual socket from the ring main. Try and draw too much and the fuse in the mutli socket will "blow".

Hope this helps

Cheers Kelvin

Posted By Paul Cook
Multiway adaptor plugs sold by reputable shops in the uk should comply with BS1363 and as such will be fitted with a cartridge fuse complying with BS1361 having a maximum rating not exceding 13 Amps.

Generally speaking, under normal operating conditions this fuse will prevent a current exceding 13 Amps being from being drawn from the socket outlet into which it is connected.

13a Socket outlets are capable of supplying a maximum of 13a per outlet, this could be one appliance such as a 3KW Washing machine or three appliances such as 3 x 1KW toasters plugged into a type of adaptor or extension lead.
So long as the extension lead or adaptor plugged into the socket outlet is protected by a fuse not exceeding 13 Amps and the protective device (Fuse wire/cartridge fuse/circuit breaker)in the distribution board that controls the circuit does not exceed the current rating of the cable supplying the circuit, overheating and dammage should not occur.

30 or 40 years ago when 15 Amp round pin plugs were in general use, adaptors and plugtops were not usually fused.

With the absence of central heating in most properties this lead to massive overloading, particularly in the winter months, this combined with poor circuit protection (fuse wire etc) and cables manufactured from cotton or thick rubber, was what caused overheating and caused fires to start.