About 3-way Solenoid Valve Operation
I took the brewhead 3-way solenoid valve off, and surprisingly I found
the spring around that solenoid nucleus is a lot softer than I would
expect. I know the pressure from brewing boiler could get about 12 bars
when water expands, so how could this spring hold that much pressure? It
is kind of stupid to ask, but I just really don't understand it. I also
noticed there is another harder spring that holds the viton seal of
solenoid nucleus, but it seems it has nothing to do with the functioning
of solenoid valve.
When the solenoid valve is active (during extraction), the coil

pushes the
piston to the closed position using electromagnetic force. This force
takes the place of the stiff spring you are referring to and resists the
extraction pressure. When de-energized, the magnetic force is removed
and the light spring returns the piston to the Water Pump Control Valve open position and lets
the water flow out. This is a "normally open" (NO) type solenoid. A
boiler fill type solenoid will work in reverse, opening when energized
(well you can use NO, but that would degrade its service life and the
programming for the controller is different, so dont just swap them).

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2011-08-26

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