So, I've been lurking for quite a while, reading up and trying to determine the right machine to buy. Fascinating place you've got here, and it's answered tons of questions for me already, and as it has for many others, bumped my price range up quite a bit from what once seemed absurdly high (Silvia for six hundred whole dollars!?!)

Anyway, a couple machines have caught my eye lately, and they've raised a question that I haven't been able to find any discussion on in the archives. To wit: what's the deal with all those commercial machines with non-saturated, non-E-61 group heads, like the Astoria Argento, Unic Diva, various Rancilios, the La Pavoni Pub V, and so on? Some of these appear to have some kind of a thermosyphon, but others appear not to. They all typically take the form of a honking big boiler with HX, and a fairly small group head bolted more or less to the boiler, along the lines of:

http://www.espressotools.com/category/0 ... grouphead/

While there seems to be varying opinions on just how fanatical the home barista should be about maintaining flat line temps, no one disagrees that temperature stability in the head is a good thing. So what's it like on these guys? How difficult is it to work out a home surf routine on one of these commercial 1 grp monsters?

document wrote:While there seems to be varying opinions on just how fanatical the home barista should be about maintaining flat line temps, no one disagrees that temperature stability in the head is a good thing. So what's it like on these guys? How difficult is it to work out a home surf routine on one of these commercial 1 grp monsters?

If there's one thing I've learned after many in-depth espresso machine evaluations, it's that attempting to predict espresso performance from a spec sheet is utter folly. More than once I went into an evaluation anticipating the outcome based on my understanding of the design, only to be proven wrong. Pressure profiles, preinfusion and the forgiveness factor documents one of my more flagrant bad assumptions (preinfusion = good tolerance of errors in barista technique).

That said, as a general observation, commercial groups are designed to perform their best under load, the very opposite of the conditions in your kitchen. You can "trick" them into behaving as if they've been under load by flushing and waiting techniques. Or you can reduce the difference between full out usage and near idle time usage by twiddling the boiler temperature lower (Ken Fox and others have successfully used this technique in combination with a PID controller). The effectiveness of any of these techniques is very dependent on specific characteristics of a given espresso machine.