On 29/09/2020 19:14, Harry Bloomfield wrote:
John Rumm explained :
While normally placed on their own circuit, sharing with the heating
controls sounds fine as well since they are unlikely to be more than a
couple of amp at most.

3kw immersion heater = 12.5amps !

As a very temporary solution, it will be just acceptable to connect it
via a 13amp plug, into a socket. Your heating control circuit will
likely be only 3 or 5amp amp fused.


you are using 240 V in your I = P/V calculation.

Due to EU hamronisation, system voltage is now closer to 220 V so that
makes I = 13.63A......