Standard diverter valves appear to work off 230v, but as we've got an inverter plus a land line when moored, we don't think that this would be a problem although, obviously, a 12v circuit would be a much better idea. The slight disadvantage of the idea is that only one of the two circuits could be open at a time - the present arrangement allows both, but I thnk that we could live with this as we only heat the radiators very occasionally when moored, preferring the stove when longer periods of warmth are required.
True
No, motorised valves are either one or both.