oomis: in such a case it would be okay if the water boiler never went to 110 at all during shabbos not just when the water is going in. i heard of someone who rigged his system exactly as you describe.
DY, Berlin, etc: grommo is ussur mdirabunun. many great talmidei chachumim matired electricity use on shabbos and yuntiff. the olam didnt agree (and the tzad hetr was based on faulty science in any event).