I beg to differ, a ring main of 2.5 twin and earth is good for well over 3 kw. the recommended MCB size for a 2.5 ring main is 32A. A 2.5 radial circuit can be fused at 16A. Your average dish washer or washing machine can pull well over 2.5kW. This info is from the IEE Regs 18th edition.
Although this factually true Pete, but in all fairness your dish washer or washing machine etc is not really a compatible comparison really ?.
It is only pulling a high "pulse" demand when the heater element is calling for heat, from the timer control in the appliance.
On a one hour cycle, this maybe only be 15 - 20 minutes use of heavy demand to heat the water, but in the rest of the cycle, it is demanding a much lower demand than that.
The "Granny" is pulling a constant load of 2 Kw's over a MUCH MUCH longer time, if your SOC is very low.
This is why heat can be felt at a plug top when this high load is constantly passing through the small pins that secure the 13 Amp fuse, over a long period of time.
Long exposure to a high demand will and has caused brown burn stains and has been witnessed at the live conductor pin, at both the plug and the socket outlet.
This risk can be reduced by the use of higher quality electrical equipment, of course.
The weakest part of the set up is here, the conductor points in the three pin plug.
This condition is clearly been evidenced when pulling 2 Kw's.
But then increasing the demand to 3 Kw's surely must increase the risk of damage to the electrics or even a chance of fire ?.
A domestic emersion heater rated at around 3Kw's is very likely to be supplied by a 2.5mm cross sectional cable and yes it works absolutely fine.
But, here it will be wired on its very own dedicated circuit and will be terminated with the higher and correctly rated switching accessories.
Same cable size, same load demand, but totally different application format.
I have used a "Granny" cable for about seven months before having my dedicated wall box installed about 6 years ago.
The "Granny" has now been retired for only very occasional use or purely as a back up.
Only speaking for myself here Pete, but I would never wish to run a "wish list" charger ratted at 3.0 Kw's through my domestic outlets ( all MK branded ) over a long period of time, on a daily or even a weekly basis to be honest Pete.
I like to charge our car on the cheaper "Off - Peak" tariff that we have.
I have no issues or fears doing this while I am sleeping.
Using the supplied 2Kw supplied "Granny" ......... Errrrr - I am also okay with this ( ish ).
But the though of increasing that demand to 3 Kw's via three pin plug ( over night ) ???????.
Some folks are even using plug in timers also, hopefully rated at the correct load scale.
Our electric oven pulls roughly about 3 Kw's via a 30 amp dedicated circuit on a 6.0mm cross sectional cable.
3.0 Kw's on a three pin plug ????.
Not for me thanks !.
Here is a video that explains it better than I can !.
It's a great video, but if you fast forward too 4mins 30 seconds, it covers the concerns surrounding constant use of a standard Granny unit on a domestic application.
