My Wife and I just recently moved into one half of a rented duplex that has an old oil boiler for heating and hot water. It seems as though if we set the aquastat high enough to have comfortable hot water (135/140F ish) for a shower, all the radiators begin to heat up whenever the boiler switches on the keep the water warm, and in the morning it takes a very long time to have any hot water if we leave the boiler on overnight (if we turn it on in the morning about 30minutes before our showers we get enough hot water). Originally thinking that the thermostat was the problem, we had it replaced, and it seemed to work, but they had also turned the aquastat back down to 120F and once we turned it back up the radiators seemed to come back on again. Is it the aquastat, or something else with the boiler? Any thoughts?