As I understand it.
A “normal” dhw tank heats from a coil at the bottom, as cold water sinks to the bottom when 75% of the hot water has been used, there is still some hot water at the top. As the tank reheats, the remaining hot water at the top is not disturbed, so can be used while the tank reheats.
A “tank in tank” heats by the water in the outer tank being pumped var the boiler. The takes the coldest water from the bottom of the outer tank at say 10c, heats it to say 30c and puts it into the top of the outer tank. So would this not reduce the temperature of the remaining hot water at the top of the inner tank to 30c until part way through the heating process?
If so how can hot water be used while the tank is being reheated?
A “normal” dhw tank heats from a coil at the bottom, as cold water sinks to the bottom when 75% of the hot water has been used, there is still some hot water at the top. As the tank reheats, the remaining hot water at the top is not disturbed, so can be used while the tank reheats.
A “tank in tank” heats by the water in the outer tank being pumped var the boiler. The takes the coldest water from the bottom of the outer tank at say 10c, heats it to say 30c and puts it into the top of the outer tank. So would this not reduce the temperature of the remaining hot water at the top of the inner tank to 30c until part way through the heating process?
If so how can hot water be used while the tank is being reheated?