The flowmeter sends a signal to the microprocessor as the water flows; when the programmed
amount of water is reached, the microprocessor turns off the solenoid valve and pump,
releasing the pressure against the portafilter.
Since the La Marzocco is built to a different principal than other espresso machines, let’s look
at the individual systems that make up the entire machine.
1. BOILERS
There are two stainless steel boilers that work independently to provide steam and hot water
or hot water for brewing espresso.
The rear boiler provides steam pressure and the front boiler provides hot water for brewing
espresso.
The rear boiler operates partially filled and above boiling.
The front boiler operates completely full and just below boiling.
2. GROUPS
The groups are the actual brewing chambers that house the coffee to be brewed.
The La Marzocco uses a hollow stainless steel group welded directly on the stainless steel
boiler.
It is critical to prevent the machine or group from cooling down.
Hot water is constantly circulating in the group any time the machine is hot.
This allows the group to maintain the correct brewing temperatures at all times.
Once the dispense button is depressed, hot water that has been circulating though the group is
released by means of a solenoid valve.
Water flows from the left side of the group (as you are facing it) to the flowmeter (AV models)
or to directly to the solenoid valve (EE models).
The water then travels back into the group on the right side and through a tube before it is
dispersed onto the fresh coffee grounds.
3. GROUP VALVES
Each group has a solenoid valve mounted underneath to allow water to flow through the group.
Group valves are three way valves that allow water to flow in a specific direction and that
direct any back pressure to be discharged into the drain box.
Each valve consists of a housing or body, which contains the valve seat, and a piston, that
travels within a valve stem.
The piston is spring loaded to create a seal when the valve is at rest.
The valve is opened with a coil that creates a magnetic charge and draws the piston away from
the valve seat and is closed with spring pressure.
Summary of Contents for Strada
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