Dual Boiler 1 Heater

This machines are also called "Heat Exchanger" machines: The coffee boiler has no separate heater but gets heated up by the surrounding steam boiler. But, there is a separate coffee boiler with around 300 ccm and a fresh cold water injection which is better than the coffee boilers from so called dual boiler machines, they have a too big coffee boiler and no fresh oxygen rich water injection system. Advantage, fresh, oxygen rich water for the extraction Disadvantage, control of extraction temperature thorugh adjustment of steam boiler temperature with a Geisinger thermometer on the brewing group.