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.
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:
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.
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).
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?
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.
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.
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