La Marzocco mini Serie Manuel page 22

Steam boiler
pressure gauge
Next it will be necessary to check the expansion valve. As the integrated brew group heats to operating temperature
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the pressure in the integrated brew group will rise. There is an expansion valve behind the drain tray that allows
some water to escape during this process to limit the maximum pressure in the integrated brew group to 12 bar.
Please monitor the integrated brew group pressure gauge during the initial heating process. You should notice the
gauge approach 12 bar and stop. If the pressure gauge does not reach 12 bar or if the pressure gauge rises above
12 bar, then it will be necessary to adjust the expansion valve. Please follow the next step to properly adjust the
expansion valve.
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Integrated brew group
pressure gauge