La Marzocco linea mini Mode D'emploi page 26

It is possible to regulate the pressure of the steam boiler by
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pressure switch.
Rotate the screwdriver clockwise to increase the pressure, vice
versa to decrease.
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The temperature of the brewing water is measured at the most
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critical point in the integrated brew group where temperature
fluctuation is the greatest.
This parameter is set at the factory at a preset nominal temperature.
The temperature of the water exiting the integrated brew group
is held constant by means of the mass of the group casting.
Even though the temperature of the water may vary slightly, the
temperature of the water exiting the group is constant.
To properly calibrate the temperature of any espresso machine it is
important to measure the temperature of the water exiting the group
by means of an external temperature measuring device.