Thermal stability: Commercial vs Prosumer

[sheygetz]

Dan said in his musings on the Elektra A3 "... even the commercial HXs are noticeably more "civilized" than their less pedigreed [read: prosumer] colleagues."Buyer's Guide to the Elektra A3. Now, I've come across quite a few similar statements in the course of my "research" to the effect that commercial machines are more stable than prosumer ones, but haven't found much by way of substantiating evidence. Is there any?

Anyway, if we hold this to be true I wonder

• 1) Which are the decisive factors?
  2) How could this influence/ help my buying decision?

1) As far as I can see, most prosumer machines discussed - and thus owned - by people on CG, a.c., German Kaffee-Board and here are a pretty homogenous lot: heat-exchangers with a thermosyphon-group (Bezzera's boiler-connected-to-group system forming the most substantial minority). On commercial machines, however, you find all sorts of proprietary systems (This is just "paper" knowledge, please do correct me, if I'm mistaken.). So what could be the unifying element here, providing improved stability? The use of rotary over vibe pumps doesn't do the trick, as Jim Schulman & Ken Fox found http://groups.google.de/group/alt.coffe ... cd65?hl=de. Would it be bigger boilers, longer HX elements - any ideas? Or is it more a question of specific make rather than "pedigree"?

2) Now, while there are quite a few 1-group machines of commercial pedigree around, very few fit the restrictions of regular kitchen setups. Add to that, that some people aren't willing to have a 5+ liter boiler - be it for ecological, sanitary or economic reasons - that leaves you with only a handful of available models. Question is: Do these atypically small commercial models still retain the suggested temp stability advantage. If sheer size (of boiler, tubing, whatever) is the decisive factor, they wouldn't. So I could just as well get a, say, Butterfly instead of a Rancilio S26 (or I'd have to move and get a Classe 8 ).

The funny thing is, that for home machines with their typically intermittent use temp consistency would be much more important than for continuously used commercial models. In a nutshell - do smallish commercial machines put an end to complicated flushing rituals? (I hope I got my point across, sorry it took me so long .)

sheygetz

[another_jim]

I think if you are doing 10 shots in a row at 1 minute intervals, a prosumer machine with a smallish boiler and HX is going to give up the ghost fairly quickly. My Tea starts losing temperature if the shot rhythm gets faster than 1 every 105 seconds or so. At 1 shot per 90 seconds, the differences start getting big after about 7 shots, at 1 shot a minute, the fifth shot is pretty well sink material. If I'm steaming, I have to leave about 2 minutes between shots. This is well beyond my needs, and so no big deal in home use; but for commercial purposes, the machine is underpowered.

In terms of flushing after an idle; the bigger everything is the more complicated it seems to get, since the system has longer memory. My Tea pretty well overheats to its max after 15 minutes (although there's small changes after that). When I was playing with the Ken's Juniors, and had TCs on the groups, I nearly drove myself crazy with trying to stabilize the machine for the first shot. It was different after 15 minutes, 30 minutes, and so on up to several hours.

On older LMs after idle, it's basically impossible to do anything except dump the first two to three shots (or in a store, put them in lattes). The newer ones with preheat and better groupheads, and the Synessos, seem to have solved the problem. But the example shows that a commercial machine could well be a complete dud for home use where the most important factor is that the first shot after idle should be very good with minimal fuss.

In this respect, the prosumer machines do better than smaller home machines and most larger commercial ones.

[HB]

In a nutshell - do smallish commercial machines put an end to complicated flushing rituals?

It's difficult to generalize.

The prosumer / semi-commercial HXs like the Isomac Tea, ECM Giotto, Quick Mill Andreja Premium, and Expobar Lever seem to behave similarly, as I documented in HX Love. The Cimbali Junior and Elektra A3 don't follow the same routine, but I've found them less complicated to manage in the sense that their flushes are shorter and the effects less dramatic, which I attribute in part to the "thermal inertia" Jim alludes to.

My assumption is that the prosumer versus commercial distinction lies in the HX size and the group's thermal mass. For example, the volume of a typical prosumer / semi-commercial HX is only ~110ml, so flushing the usual four to six ounces (~120 to ~180mls) is emptying it completely and then some, explaining quite clearly why some refer to it as "temperature surfing." And just to keep things interesting, the A3 behaves somewhat like an E61 (thermosyphon aggressively heats the grouphead, quick flush to bring it to brew temperature) and somewhat like a Cimbali Junior (flushes are relatively low-volume).

I'll stop here and solicit Ken Nye's opinion on the subject. His favorite espresso machine is the Faema E61 Legend and he also has the Elektra A3 in-house. Not to put you on the spot Ken, but would you briefly describe your temperature management routine for the Legend? And do you think it's "complicated" for low-volume usage?

[malachi]

On older LMs after idle, it's basically impossible to do anything except dump the first two to three shots (or in a store, put them in lattes).

What do you mean by "older" in this case? Are you talking GS and older or are you talking early gen Linea? I've never worked on a GS in a commercial environment, but found that even the first gen Lineas required no more than an initial "warm up" flush.

I found that the Mia required far more water to be flushed through the group after the first shot or two than commercial HX machines I've worked on. With the commercial machines, I saw a similar initial "cool down" flush, but then when pulling consecutive shots it seemed far more stable.

[Ken Nye]

In my opinion, commercial HX machines are much easier to manage than prosumer sized machines. Large boilers and HXs are more stable and require far less surfing than their smaller cousins.

My Faema E61 is fairly easy to manage after any idle time. The initial flush will bring temps down quickly, the following shot's temps will display a little more fluctuation than I care for, but after that the temps will remain stable and consistent until the machine is left idle again. The group will require a very brief flush (1-2 seconds) in between shots when used consistently. I rarely end up with more than one sink shot after idle time.

The A3 requires a bit more care after idle time. The initial flush seems to bring temps down just as quickly as the E61, but the the first two shots exhibit less stability. Perhaps this is due to the smaller boiler and HX requiring some time to stabilize. By shot three I can achieve the kind of stable temps that I am used to with the Faema. I am still fairly new to this machine, but as I use it more I am becoming more accustomed to its behavior and I seem to be able to get stable temps a bit sooner (not always).

I also spent about one year pulling shots with a Salvatore Famosa E61 (2ltr. boiler). It was harder to achieve stability with this smaller machine. It was very sensitive to initial flush times. Too little and the shot would overheat during the beginning of the extraction, too much and the temps would drop below the target temp, probably due to the HX needing to refill and heat up. It took me a bit of time to get a feel for this machine. Once I got used to its pace (too much idle time and you would have to carefully bring temps back down, not enough idle time and the machine would not get the recovery time that it required), I could usually achieve stable extractions by the second or third shot.

I will end by saying that I find big HX machines easier to use, but with a bit of practice smaller machines will get great results without too much waste (sink shots). Unfortunately for home baristas, the first couple of shots will almost always end up in the sink. Actually, this is not such a bad thing, since I think that it is a pretty good idea to season the group and PF before pulling shots.

[another_jim]

What do you mean by "older" in this case?

I mean the old Lineas/FB70s without the brew water preheat. The group is cold, and if the brewboiler is adjusted to say 95C, the first shots will be at 92 to 93. This was logged by Barry and several other people a couple of years back.

The problem is the water debit is so monstrous on these machines that flushing water to heat the group crashes the brew boiler by a few degrees. The water flows so fast, each ounce has little effect on the group. Schomer's manual from the period advised keeping the spent puck in from the last shot and flushing through that. Otherwise it took two dumped shots to get the group hot after an idle. The machines were "unflushable" in a regular way.

[malachi]

That's odd. I've worked on those machines for years and didn't experience that. It might just have been due to the combination of garbage shots to season the clean group, a steady volume of business and a methodology that consisted of a quick flush both on removing the portafilter and right before reinserting it.

[sheygetz (original poster)]

Thanks for your responses - I've read them with great interest and some confusion
I guess I've caused this myself when I used the phrases "Thermal stability" and "temp consistency" too vaguely. I was only thinking of the in-between-shots-stability, not even considering the during-shot-stability ( I guess that was too black-belt for me). So, there's actually two criteria. To put this differently:

• *How much does any given machine overheat with, say, 30 to 60 minutes between shots?
  *How much of a temperature loss occurs while the shot's being pulled?

(Is that about right, guys?)

To sum up the discussion so far: Jim says his Tea overheats a lot, but predictably so, while the Juniors he tried bandied about rather uncontrollably. So he would prefer the prosumer machine for typical home use. Dan otoh found specifically the Junior to need shorter flushes and be "less complicated". He assumes that sheer thermal mass is the key, a notion seconded by Ken. (Though AFAIK the Junior only has 2.5l boiler volume and is rather smallish. At least on paper that's not far from a Pulser or Butterfly, isn't it.)

So, it seems to me the jury's still out, right. If mass should be the key, then "small commercial models" (viz. Brasilia Portofino, Carimali Uno, Gaggia TS/TD) don't have much going for them wrt temp consistency.

sheygetz

[HB]

He assumes that sheer thermal mass is the key, a notion seconded by Ken.

That's one key metric I noted along with HX size, but I don't believe specific operational conclusions ("less complicated") will come from generalities ("big boilers mean more stability"). In other words, I feel confident comparing two particular espresso machines side-by-side. Attempting to extrapolate the characteristics of machines I know to those for which I've only seen the specifications of seems foolish.

The crux of this dilemma is that neither commercial nor prosumer espresso machines are designed with the principle goal of producing an ideal shot from idle. Steve will love this comment: If that were my aim, I'd go with a simple lever machine, as that is their purpose in life. Fifteen minutes from an ice cold machine to walking out the door having finished two double espressos is considered slow by his standards.

[malachi]

• *How much does any given machine overheat with, say, 30 to 60 minutes between shots?
  *How much of a temperature loss occurs while the shot's being pulled?

(Is that about right, guys?)

actually, not all machines "overheat" during idle times.

i guess i would say you're looking at:
What is the range of brew temp (above and/or below brew temp as well as the total swing)
What is the range of in-brew temp