Hi, can anyone explain how a back boiler central heating system works, my son recently moved into a new house, built approx 1985, he says it has a park ray fire with a gas boiler, it has a switch near the boiler that allows him to switch between fire and gas..he tells me that he can can only get hot water in the summer if the switch is set to gas , and the room stat is turned up but with the rads turned off, that sound wrong to me ..any ideas???.