Best pick heat exchanger coffee machines

An espresso machine with the heat exchanger system is a machine with two water circulation systems. Since the boiler is not completely filled with water, steam may by drawn after the machine is fully heated. A heat exchanger is built into this boiler. When making coffee, fresh water from the tank is used which is pumped into the heat exchanger, heated there to the optimal brewing temperature and then directed to the brew group and portafilter. Thus, fresh water is always used to brew espresso. Brewing temperate is not as stable as with a dual boiler system with PID.