Yes a PID controls the boiler temp fairly well. No a PID controlling
Silvia's boiler temp does not control the actual shot temp tightly, This
has been tested by many people including myself using accurate measuring
devices including Scace Thermofilter and of course by taste. The problem is
with all passively heated grouphead designs, including Silvia. The solution
to stabilizing Silvia for consistent back to back shot temps is using two
PID's, one controlling the boiler temp and a second controlling a rope
heater for the group. You could also "simulate" a series of a half dozen
shots before EVERY shot from idle to ensure consistent shot temps whether
shot one or shot two (which only increases a couple degrees over shot one in
a series) or shot three (up 4 or 5f already) or shot 6 (up 12f from shot one
and now stablized). Of course you've just nearly drained the tank. Of course
now the cost of Silvia is well above an entry level HX machine and still has
her major steaming limations.
I also didn't mention Silvia's intra-shot lack of stability, dropping a good
7f start of shot to end of shot. Solution to this is adding boiler water
input pre-heating. Read up on Andy S's highly mod'd Silvia and what it took
to get there.
This isn't conjecture. This is talking about many years experience from many
experienced people. There are very good reason the best machines in the
world like La Marzocco and Synesso use saturated group designs, designs more
group temp stabile than E61's, not super light weight groups that cool
rapidly (and inaccurately) between shots.
Kona Kurmudgeon miKe mcKoffee
URL to Rosto mods, FrankenFormer, some recipes etc:http://www.mckoffee.com/Ultimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/From: homeroast-admin
[mailto:homeroast-admin] On Behalf Of Michael Wascher
Sent: Sunday, January 06, 2008 8:16 AM
Subject: Re: Beyond Silvia > RE: +First machine...possibly a used
The PID should control the temperature to a tighter tolerance than
that. However, what is being controlled is the temperature at the
thermocouple (I assume that is on the boiler?). The group is outside the
From what you are describing, the group has enough mass that it is
retaining much of the energy it gets when it is heated. The first thing that
comes to mind is to move the thermocouple to the group but the long loop
delays would probably make this unworkable.
One of the limitations of a PID is that it only controls the heat
into the system. There is no way for the PID to cool down the system.
I think this is a case of what is good for an unPIDed machine (large
group head mass to store heat energy & keep temperatures stable, the entire
system in a steady state) is not good for a PIDed system. Based on this, the
espresso machine I'd choose to PID is one with little mass in the group, low
enough mass that it cools slightly between shots.
Is there anything you can do to make the group cool faster? Remove
mass? Add a heat sink? Stop/slow flow in a loop through the head (does the
unit have a group heated by a water loop?)?
On Jan 5, 2008 11:48 PM, miKe mcKoffee wrote:
The first question is why considering the upgrade? Is it
because often pull
a series of shots and even with a PID while the actual
boiler temp will be
determined by the PID the group temp rises shot to shot up
~12f by the 6th
shot so there's really no shot temp consistency beyond two
shots at most
even with PID? Is it because of waiting to come up to steam
temp? Is it
because of after steaming having to flush like crazy to get
boiler temp back
down to shot temp range? Indeed those where all reasons why
Missy left our
home after 4 years!
FWIW HX surfing is quite different than Silvia surfing and
accurate. And with an Eric's digital thermometer group
adapter it's a
breeze. But still somewhat a PITA compare to DB. While quite
happy with the
Bricoletta, especially it's stellar cup quality capability
(quite on par
with our PID'd Linea at the Kafe) and the Bric's very fast
someday may go DB at home for greater ease of use. But it
won't be Brewtus
or VII. Very interested to see how the coming Viebemme DB
models pan out in
the US later this year.
Kona Konnaisseur miKe mcKoffee
URL to Rosto mods, FrankenFormer, some recipes etc:
Ultimately the quest for Koffee Nirvana is a solitary path.
To know I must
first not know. And in knowing know I know not. Each
found exploring the many divergent foot steps of Those who
have gone before.
Sweet Maria's List - Searchable Archives