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Variable Thermosyphon Restrictor Valve
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Everman
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Everman
Joined: 25 Nov 2004
Posts: 1,050
Location: Coffee Land
Expertise: I love coffee

Espresso: Valentina Levetta, Elektra...
Grinder: Mazzer Mini
Roaster: Hottop
Posted Mon Nov 27, 2006, 8:19pm
Subject: Variable Thermosyphon Restrictor Valve
 

I've been doing some reading about how the E61 group works and how certain things effect group temperatures. An interesting thing is that it seems you can do a few different things to effect the group temperature.
  1. You can of course adjust boiler pressure. One drawback is that lower pressure will yield a bit less steaming capability. But there are two other options related to the thermosyphon:
  2. Length of thermosyphon tube from boiler to grouphead. The longer the tube the lower the water temp hitting the group when the thermosyphon is active.
  3. Thermosyphon restrictor:  Seems to be usually made of plastic, sits inside the tube to restrict water flow, effectively lowering water temp.

The third option here is most interesting to me because it's easily adjustable. What I'm wondering is how difficult is it to install one of these? I don't have an e61 machine yet, but this is what happens when you decide to upgrade... :)

It just seems to me that instead of messing with boiler pressure, you can simply use a variable restrictor valve. Then you could enjoy powerful steaming with a high boiler pressure, and a cooler idle temp via the valve (and maybe a longer tube).

Reference links:
Click Here (groups.google.com)
Click Here (groups.google.com)
"Michael Teahan's latest discussion of the E61 group"

actual picture of the valve here: Click Here (www.home-barista.com)

Is this a good idea or am I crazy?
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Luca
Senior Member
Luca
Joined: 27 Jan 2004
Posts: 2,658
Location: Melbourne, Australia

Espresso: H: Maver W: FB-80
Grinder: H: Super Jolly W: Brasilia...
Vac Pot: Hario TCA-2
Roaster: Sample Roaster at Work
Posted Tue Nov 28, 2006, 3:18am
Subject: Re: Variable Thermosyphon Restrictor Valve
 

Yep, I asked our tech about them and he thought that they are good under constant commercial use, but if you have sporadic use they slip ... or something.  I don't know too much about these things, that's why I asked him ;P

The restrictor is made of teflon on the machines that I have seen.

I'm yet to grasp why you wouldn't just put in the narrowest restrictor that you could find and control the temperature via pstat.  All that the restrictor/tube lengthening does is to make the group run colder relative to the boiler ... right?

More reading to be done, I guess ...

Cheers,

Luca

 
General ramblings about coffee: http://www.pourquality.blogspot.com/

Reviews of Australian coffee: http://www.coffeereviewaustralia.com/
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Eric_Svendson
Senior Member
Eric_Svendson
Joined: 19 Dec 2001
Posts: 88
Location: Silver Spring, Md., USA
Expertise: I love coffee

Espresso: Anita, Modified Silvia
Grinder: Mazzer Mini E
Vac Pot: Cona
Drip: Melitta 2-cup
Roaster: Heat Gun/Dog Bowl (just...
Posted Wed Dec 13, 2006, 5:47pm
Subject: Re: Variable Thermosyphon Restrictor Valve
 

This is strange - I have been thinking about the same thing, therefore it is an unusually brilliant idea.  But we can admit that Faema thought of it first and used (uses it?) it on their E61 Legend.

http://www.home-barista.com/forums/viewtopic.php?t=831

The Faema adjustable valve is also referenced in this post:

http://coffeed.com/viewtopic.php?t=78

It SEEMS as though you can only buy the valve as part of the hx outlet line assembly.

I'm sorry that I didn't check your reference posts prior to responding but I do remember the "plastic disk" restrictor as having a hole of 2.0 mm.  Personally, I was thinking of simply substituting a Swagelok needle valve that could "control" the flow similar to the 2.0 mm orifice +/- say 0.5 mm.

Eric S.
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Eric_Svendson
Senior Member
Eric_Svendson
Joined: 19 Dec 2001
Posts: 88
Location: Silver Spring, Md., USA
Expertise: I love coffee

Espresso: Anita, Modified Silvia
Grinder: Mazzer Mini E
Vac Pot: Cona
Drip: Melitta 2-cup
Roaster: Heat Gun/Dog Bowl (just...
Posted Wed Dec 13, 2006, 7:37pm
Subject: Re: Variable Thermosyphon Restrictor Valve
 

More thoughts on this now because it looks as though you and I have done the same initial research.

Hi Luca - you can't/shouldn't put a restrictor much smaller than 2.0 mm in there because if you start approaching the size of typical gicleurs (say 0.8 mm) you will effect brew pressure.  A 2.0 mm orifice will most definitely not affect brew pressure in any measurable sense.

A real question in my mind is why some machines (and I don't know which ones) have a fixed thermosyphon orifice (plastic disk) and others apparently(?) do not.  It surely can't be cost.  At first glance the Faema valve appears to be an elegant solution to, at least, reduce the time & water associated with the cooling flush ritual.  I can visualize a cafe adjusting it one way for the morning rush and another way for the afternoon slowdown or whatever.

Eric S.
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