immersion heater wiring - need to be cleared up please!!

[stevehayes]

sorry but i need to clear something up for piece of mind!!

an immersion heater has its own radial circuit from the cinsumer unit, usually rated at 16amps (mcb) - twin and earth runs from this to a double pole-switched socket near the heater? correct? in my socket i have a cartridge fuse, rated at 13amps. in a book i have been reading it says the twin and earth should run to a 21amp double pole switch!!! well mine is only 13amp!! and from this point a 21amp heat-proof flex is run to the immersion heater. well i have a 2.5 mm flex from the socket to the heater, but IF this is 21amp (as standard) then how comes it doesn't blow as my socket is rated at just 13amps!!! i am a bit confused!! probably just being silly though but would like some help!!...??

 

[Steve]

a 3kw heater draws, for arguements sake, 13 amps.

where they got 21 amps from is beyond me. I've never heard of a 21 amp rated circuit.

And 2.5mm² copper can carry about 26 amps optimum.

 

[stevehayes]

thanks Steve. so basically the book was wrong!! a 13 amp fuse is correct in the socket? also, i know a 2.5mm flex is the correct size to use for an immersion heater (so this too being written as 21amp) is incorrect!!

 

[Steve]

Its not a socket. (I hope). It should be a fused connection unit if theres a fuse. 13 amps it correct. And the feed for this should be a 16 amp MCB.