If the timer is closed i would assume your are looking for hot water during the timer 'on' periods ? Why would you also want to inhibit the thermostat operation during the timer 'on' period ? I'm lost !!!!!! :confused: and in cold water !
DS
I have seen a fcu fed off the load side of a shower switch supplying an extract fan. The wiring between the switch and fcu was 1.5mm. As ELF has said, as long as the circuit is designed properly.
DS