Before the pump driven espresso machines you had lever espresso machines the brewing group water did come directly from the boiler. With the pump driven espresso machines the introduction of the heat exchanger came. In the situation of a espresso machine this means that there is a tube which is located inside the steam/water boiler, but not in direct contact with the water. So the water which flows true the heat exchanger only get’s the heat from the boiler.
You do find this system on most espresso machines. Traditionally every brewing group has it’s own heat exchanger. In most cases this heat exchanger is placed diagonally inside the boiler. Some espresso machines, like Cimbali use a tube which sticks into the boiler and can be removed. Or La Spaziale uses a heat exchanger boiler which is connected to the brewing group.
