The Strega may be an HX, but it's also a lever.

While most HX groups do well with a flush, consider that the old dipper-tube style levers like mine run boiler water at 1.2 bar directly to the group. Flushing only heats the group more - no cooling flush here! You'd think that starting hot would be a problem, but the declining temp curve seems to do well regardless.

@Ian - after all, you really didn't READ into my post. I guess you had only reply to the charts without really reading what I'm talking about. I am not talking about the declining temperature profile which you said "so special" about lever machine. I am saying: if you cool the machine with flushing, your brew temperature would be starting at different temperature substantially shot after shot. The declining profile is an inherent thing that's built-in with Strega and I'm not discussing or commenting about that.

@John.B, Jim and others - Totally agree with you about different "original factory setting" among individual machines. My machine, at original setting, also get me too hot the brew temperature if no flushing was done. That's why I'm suggesting to tune down the pstat and tailor measure the tuning to fit your machine. After that, brew without doing any cooling flush. You would get brew temperature starting from pretty much the same every shot. With cooling flush, you'll never know what temperature you're actually start brewing since the cooling water that had gone through the head is inconsistent and the time you start brewing is inconsistent.

The Strega is a different lever machine than the traditional ones. There's an additional temperature controlled heater installed by factory to heat up the brew head. The factory must know that there's some design needs in it to justify such additional cost. I read the Strega's manual and the factory had never mention any need for such cooling flush, but I wonder if other lever machine manufacturers would state such even if cooling is necessary.

The Strega, like the BZ07 & BZ10, has two cartridge heating elements arranged in a parallel circuit. For the 220-240 VAC customers, the resistance of each element is ~ 1044 ohms and thus the resistance of the circuit is 522 ohms and the total power is ~ 101.3 watts. For us here in the USA, the resistance of the circuit (my circuit) is 116.95 ohms and thus the total power is ~103.5 watts at 110 vac. The power calculations vary greatly depending upon your deviation from "standard" voltage but the 95 C button thermostat makes that not relevant.

A typical variance in BZ07 grouphead temperature is 5-6 degrees F and 3.5 degrees C based on the action of the 95C button thermostat (same as Strega).

I'll edit this with Strega warm up and variances tomorrow.

Nice job, Peter.

good thread...just wanted to say some of us like discussing such things and appreciate when people do such tests

I haven't measured temps on mine but I do find the shots to be more consistent when I don't do cooling flushes.

sekihk wrote:@John.B, Jim and others - Totally agree with you about different "original factory setting" among individual machines. My machine, at original setting, also get me too hot the brew temperature if no flushing was done.

Which still doesn't answer my question. What was your machine set to originally & if you changed it for "no flush" operation where is set now?

My boiler started when pressure gauge readings dropped to 0.8 bar. The boiler would stop when the gauge readings reached about 1.3 bar. In fact I've not changed the pressure stat at the moment because I'm not sure it's actually the thermostat linked with the brew head heater, or the HX pstat that affected the brew temperature the most.

What I do now with the 95'C no flush brew temperature is: My beans are roasted no darker than City+ (all roast dropped below BT<= 220'C) for espresso. So, the same batch of roast is now good for espresso on Strega and also good for drip and siphon.

Well, something is not right with either your methodology or methodology Jim employed in his testing here: Bezzera Strega - Second Look
Somebody did not do it right.

another_jim wrote:Here is some temperature and pressure info:

Shot per one Minute; no Flush:


Shot per two minutes; no flush:


Shot per two minutes, short flushes

subq wrote:good thread...just wanted to say some of us like discussing such things and appreciate when people do such tests

I would say that most threads on this site are quite very much technical and science laden. Why we've obsessed over HX temp management (eric's thermometer, several FAQ write-ups, tons of graphs) and grind particles (titan project with microscope analysis and graphs) and then basket hole sizes and tolerances (VST threads) but for some reason are unwilling to dissect the Strega and its temp management?

I though we were off to a good start with the second look thread, let's keep it alive people. Gimme graphs, sections views, data tables, something! Let's keep the magic and voodoo in the lever thread.

In a few weeks is the Baltimore gathering; Barring bad weather, I'll be bringing my CMA lever group (dipper tube).
While not an HX, it would be interesting to compare the group against the Strega; don't have a thermofilter, but we'll certainly have Artisan running somewhere...

Let's design a protocol we can apply to both machines to gather data in a meaningful fashion to do a comparative study.

I'm not so hot on developing the protocol, but I can do my best to follow one.

Who's up for it?

A sectional drawing of the Bezzera Strega grouphead: