Re: Europiccola question

opo wrote:

Proper brew temperature is not boiling point which is needed to push
the water up into the chamber. Once the machine group head warms up
that water is no longer cooled down to brew temp upon pulling down the
lever. If you maintained a proper brew temp after the group head
warmed up there will not be enough pressure to push water up into the
brew head to fill it.

If you set your PID to keep the water hot enough to generate enough
pressure to fill the group head it will be too hot once the group head
gets hot. You have the same problem only good for 2 to 3 shots with
very hot to boiling water and a cooler group head.

If I interpret you correctly, on a Pavoni the boiler
temperature is controlled by the physical properties
of boiling water, not really by anything electrical
which only serves to save energy by not adding heat
to a boiler which is already boiling.

Therefore, if anything, the value of the pressure
gauge on the higher-end Pavoni models is that it
(indirectly) indicates the temperature of the water
supplied by the boiler.

Water temperature is brought down to an acceptable
brewing temperature by the cooling effect of contact
with the grouphead, which is a major point with regard
to plastic vs. brass pistons in these machines, brass
having much higher specific heat. (Which raises the
question, what acceptable piston materials have the
highest specific heat? Without checking Wikipedia,
I'd guess depleted uranium with a conformal coating
FDA-approved for food contact.)

So, if we PID anything on a Pavoni, it should be
either the piston or the whole grouphead. For
example, a temperature sensor and heating element
could be installed in the piston to give it a
controlled temperature for the first shot. Then,
a valve could switch the feed for the grouphead
to a reservoir of cool water to bring it down
below the optimal temperature (the PID and heater
turned off during this phase, of course), and
the PID/heater turned back on to pre-heat the
grouphead to the optimal temperature for the next
shot.

Would this answer all of your objections to the
Pavoni and PIDing thereof?
.

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