I have a heating system using a 300litre heat store tank. It is connected to solar as well as oil and a solid fuel stove. A coil provides mains pressure hot water. Oil & solid fuel flow pipes go in near the top of tank. Central heating flow pipe goes in near centre of tank. All 3 return pipes go out at the same level which is about 1/3 from the bottom of the tank.
Oil work ok
My problem is with solid fuel
When I light a fire and water starts to warm up it is putting the return water through the radiator return pipe instead of the stove return pipe. This return pipe is connected to the cold feed pipe and hot water is then blowing back into the header tank and overflowing to the outside. I have overcome this resonably by fitting an assistor pump to the solid fuel return pipe. This is fitted by forming a by pass loop on the pipe with the pump in the loop so as the pipework is still open to allow gravity system to work. The problem with this system is that I need a thermostat to bring pump on at the right time and also turn off when the stove goes cold. Getting the pump to turn on is ok but turning off is a problem as thermostat keeps the pump going after the stove has gone out and ends up cooling the water in the heat store tank. If oil comes on before pump turns off then water also keeps pumping around stove making stove a very inefficient radiator.