I'm also in agreement that the removal of heat from the fuses is not well handled in some plug designs  - to the point I have seen browning and cracking of the plastics around the live on both plugs and sockets, and on one tumble drier the live pin melted the plastics and fused into the socket and actually stayed there when the rest of the plug was finally prized out with vast force. At which point I decided that isolating the circuit was in order to fit a new socket. The neutral pin, presumably carrying the same current was by comparison unscathed.

Plugs on lower wattage or shorter use devices fare much better, and most seem to last more or less for ever.

I think my concern of corrosion would be amplified with a lead assemby stored in a car boot or on a hook in the average garage, as being likely to oxidise faster than the indoor one even without heating from the load or the fuse.


I'm only half joking about the gold alloy plating - it does wonders for the Mil std connectors,  they really can take the current on much smaller stubbier pins (the souriau 38999 series III are especially impressive you do need the tooling or to be able to solder, but after the initial shock at the price, well worth it in a few critical no expense spared  locations..) 

Mike.

13 Amp plugs of old had brass pins and brass terminal screws. Some modern accessories are new being fitted with brass looking terminal screws that are in fact steel, and brass "plated" to look like solid brass. This is confirmed by placing them onto or near to a strong magnet.


I am wondering about possible degradation of the new steel plated screws. What next, steel plug pins with a coating to look like brass?


Z.

Some EV charging leads have thermistors built into the plug, so the manufacturers seem to be aware of the tendency of a BS1363 plug to overheat.

Thoughts on the possibility of moving the fuse out of the plug and a few inches down the cable to reduce the heating of the pins (as a special plug for long duration loads)? Yes that would mean a very short length is only protected from short circuit by an upstream MCB of uncertain value, but there could certainly be mitigations for that, perhaps mechanical protection or oversizing of that section of cable.


Certainly many of us will have encountered a fuseless 13A plug (normally made by inserting the neutral pins from a second plug in place of the live pin) used for welders, etc. and this bodge does seem to run cooler, or at least I've never seen one that was thermally damaged.

Another line of attack might be to design a plug for a non-standard shorter and therefore  less dissipative fuse with the same gauge of fuse wire but less of it.

There are fuse designs where the fuse-link is quite short, but pulled by a spring so the opening distance is maintained. 

In terms of size a possible starting point the BS646 (the 3/4 inch by 1/5 inch dia ones in shaver adaptors, the better lamp dimmers etc) fuses are made up to 5A, and are supposed to be OK plugged into the same socket as the mains plug. The penalty is that official breaking capacity is only 1kA, compared to the 6kA of the BS1362 but in reality failure is not normally an issue Dissipation is up to 0.8w for the 5A ones but quite a bit  less for the lower ratings.

Mike

Being an "old timer" from an industrial background who occasionally used the old 5A and 15A Sockets.  I was told that a 13A Plug is really a 10A Continuously Rated Plug and that 13A should only be used for short durations.

Going on from that, I also believe that Twin 13A Socket Outlets are only rated at 13A total continuous output ( I may be wrong but this also could have implications with 2 cars being charged simultaneously).   

If I was running a 10A plus load for Hours, a 16A BS4343 (Commando) socket would be my socket of choice.


Dave