Is it just about the nuances? Does the TB do what the discrete boiler does, but with less control over the variables? Is that it? Is there more to it?

The thermoblock for steaming will not give as much steam power as a true boiler. It could be a reasonable compromise, as it seems to be on the Quickmill Silvano.

A thermoblock is basically a heating element with no storage space (no "boiler"). The metal gets hot and water is passed through it. Because of the short duration the water is present in the thermoblock the amount of heat energy transferred is not very controllable. They work OK for steam, like dropping water on a hot, dry griddle ("SSSsssss"), but for espresso brewing it is inconsistent at best.

The assumption I was making is that the TB is used for steam only, as in the Silvano.

the QuickMill Silvano has a thermoblock for steam and also has a separate steam bank pump so it can steam and pull a shot simultaneously. Here is some food for thought on the use of a thermoblock for steaming.

Is the single boiler double use, HX or double boiler system better than a thermoblock only machine like a Krups or a cheap DeLonghi (some DeLonghi models are SBDU's)? Sure it is. The steam thermoblock in the Silvano has it's basic operations in common with a Krups thermoblock since both heat water - I have seen both up close - the Krups (XP4000, XP4030, 964, 969) system is different in appearance than the one found in the Silvano - in the photo below on the left courtesy of Chris Coffee you will find a large circle of gray metal below the red word "bracket" - this is the steam thermoblock - it is found behind the brass boiler inside the machine. On the right is the group assembly of the Krups. The Krups thermoblock is the part sitting above the polished metal group.



Most home use machines with a thermoblock will look similar but the Krups is nicer in build than some cheaper models I have dissected. These are required to hold a larger volume of water than the steam only thermoblock because this part functions as the entire boiler for the machine. Since the pump must still deliver 9 bar of water pressure, the cooler water from the tank will negatively affect water temperature stability while pulling the shot - hence the bad rap thermoblocks earn for brewing espresso. Make this block larger and the stability improves - ask it to flash boil only a small amount of water at a time for steaming and the design works very well.

Sorry I wasn't clear. What I'm comparing is the DB system vs a system like the Silvano where the TB is used for steam only, while the boiler is used for shots.

sweaner wrote:The thermoblock for steaming will not give as much steam power as a true boiler. It could be a reasonable compromise, as it seems to be on the Quickmill Silvano.

Couldn't the TB be improved to the point of being comparable to the boiler, perhaps by adding more wattage? Or is the TB for steam simply a fundamentally flawed concept?

My first experience was with a Francis Francis x8 capsule machine that was effectively a very low-end sbdu with weak thermoblock steaming. One of the many reasons I moved up was that I couldn't make decent microfoam.

After a year on my upgraded setup, I happened to dig out the X8 a few times and to my surprise was able to make good microfoam on it, albeit slowly. (ok for macchiato or short cap though definitely not for big drinks). The problem was the combination of low-end equipment and my lack of experience.

My guess would be that it should be possible to engineer a good thermoblock steamer if it has enough wattage. IIRC the Silvano was changed midstream from about 700w to 1200w, both way more than I had. I guess it comes down to cost vs. speed and startup delay.

This (excellent) site reviewed beginner equipment some years ago, and now has a high end equipment orientation. So it's hard to find expert evaluations of the newer entry machines using thermoblock steaming and PID brewing, such as the Crossland and the Silvano. Not having owned one I can only guess that this configuration might have a lot of potential.

...it's hard to find expert evaluations of the newer entry machines using thermoblock steaming and PID brewing, such as the Crossland and the Silvano. Not having owned one I can only guess that this configuration might have a lot of potential.

My musings exactly. Is the steam boiler so superior to an adequately powered TB?

When was the last time you saw a thermoblock spit out a super strong steady continuous blast of dry steam with enough force to quickly stretch your milk before it overheats.

With the power limitations of single phase 110 VAC in a big boiler US prosumer home machine maybe the question should be would an adequately powered boiler produce enough steam to get significantly better performance than a thermoblock.

From what I have seen with thermoblocks on internet videos and personal experience with a Briel Appollo (maybe the appollo is not a good expamle of a good steam thermoblock) yes a steam boiler is better. Can a thermoblock be made that has equal steam pressure as a high wattage steam boiler, maybe, would it be cost efficient and practical enough to favor over a steam boiler, I don't know. The thermoblock on my old briel did burn out a couple of times.

My Brewtus is a little anemic but adequate and steady in the steaming department while my Silvia (Old Version) was the strongest blaster I have owned while there was still steam in it's little boiler. My Sama Export is somewhere in between. Regardless some of the Silvano steaming videos are quite impressive for what it is and most likely good enough in a lot of cases.