This is called up in the instructions for installing a digitally controlled non-electric shower. The water controlling box runs off
12v dc from a separate psu connected to the mains.The actual requirement of "a separate, permanent connected supply must be taken from the consumer unit to the appliance", would suggest that that this supply is to be a radial from it's own MCB. This is nonsense surely and looks suspiciously like someone has just copied the instruction set for a mains driven electric shower.
I've advised using an fcu from the nearby ring circuit, but is this likely to run into problems with people like insurance companies as the manufacturer's instructions have been ignored ?
Rob