How a Silvia Works
All wiring
Off
On, heating up
On, at temp
Brewing espresso
Steam, heating up
Steam, at temp
Pumping hot water
Overheated
Modification for PID
Dual Setpoint PID
Advanced Dual Setpoint PID

Coffee Cup
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Brewing Espresso

With the brew switch in the "on" position, the pump as well as the 3-way valve are activated. The water can now flow past the 3-way valve to the brewhead. Water is pumped through the brewhead. Note that the circuit that powers the pump and 3-way valve is independent from the heating circuit. The heating element is still free to turn on or off as controlled by the brew thermostat while the brewing process proceeds. For more details on how the 3-way valve works, see my article 3-Way Valve Hows and Whys.