Whilst the machine is idle, the brewing water just circulates around the group head
and heat exchanger
(slide 3), if the machine has been sat quite a time, then its a good idea to carry out a quick flush before making the coffee.
When you select a beverage, the group head solenoid opens and the pump
starts running to increase the pressure up to 9 bar (slide 4), the operation will continue until you either stop the flow, or the flow meter
and control circuit reach the preprogrammed level setting.
At the end of the brewing cycle, the machine then stops the pump
and closes the group head
solenoid which stops flow to the portafilter, as the solenoid valve closes the built up pressure in the group head is then allowed out via the exhaust port on the valve (slide 5).