Cutaway of La Marzocco saturated grouphead

[HB]

Often you'll hear the term "saturated group" bandied about, usually in the context of explaining the advantages of dual-boiler designs like La Marzocco's. But a picture is worth a thousand words:


"Gooseneck" extends the grouphead away from the boiler to the service area


Closeup of the grouphead itself; notice the copper water inlet

Thanks go to the folks at Counter Culture Coffee who use this cutaway as part of their barista training course.

[malachi]

Fantastic photos.

Keep in mind that this is the semi-auto version...

[barry]

Fantastic photos.

Keep in mind that this is the semi-auto version...

what's the difference between the one shown and the full-auto version?


--barry "btw, it's missing the diffuser"

[malachi]

Hunh
Actually... now that I look at the picture more carefully I don't think there is any difference.
The differences are all independent of the group I guess.
I stand corrected.

Are there any differences between the old, bolt on and the new, welded on groups?

[malachi]

Does the diffusion block just screw into those threads?

[malachi]

Oh... and I think now folks can see why:

1 - I prefer this design to the E61,
2 - Why I loved (in theory) the Hybrid group,
3 - and why that Hybrid group was (as Barry says) a total PITA to service.

[barry]

Actually... now that I look at the picture more carefully I don't think there is any difference.
The differences are all independent of the group I guess.
I stand corrected.

i just wanted to be sure i wasn't missing anything.

Are there any differences between the old, bolt on and the new, welded on groups?

apart from the stainless? i don't think so. i had someone tell me there was a change in the banjo tube/bolt interface, but they weren't able to describe it as anything other than "a change" and no one i've talked to who has a welded group has been able to verify that change. ask bill c.

[HB]

Oh... and I think now folks can see why... I prefer this design to the E61.

For those who joined late in the discussion, below is an excerpt from Lino's E61 Group Espresso Machine: Detailed Interior Schematics:

Cross Section, lever and valves in brew position (courtesy Verna Design Inc., please do not copy)

Comparing the two, you can see that the grouphead and indeed the backside of the La Marzocco dispersion block works as a direct extension of the boiler (hence why they call it "saturated"). In contrast, the E61 relies on circulation tubes leading to/from the boiler to bring water heated by the steam boiler to the grouphead and return cooler water (hence why it's called a "thermosyphon" and forms part of the HX circuit). The low-level details were covered in E61 Group Espresso Machine: Is its reputation justified?

That said, Chris will readily admit the La Marzocco design isn't without its own compromises. Ask him about the flowmeters on the automatics. Go ahead. I dare you.

[barry]

That said, Chris will readily admit the La Marzocco design isn't without its own compromises. Ask him about the flowmeters on the automatics. Go ahead. I dare you.

or the solenoids on either.


--barry "working on a cure"

[barry]

Does the diffusion block just screw into those threads?

yes, with a gasket between.

[malachi]

Cool.
So the Stainless replacement blocks are a easy retrofit. Very nice.

yeah - the flowmeters and the solenoids/pressure release are totall bulls**t.
Then again, the latter is true of most other machines as well and I'd never buy an auto machine, so...

[barry]

y'know, i never mess with the diffusion blocks, so it hadn't occurred to me to replace them with the stainless versions. that just got put way up on the list of things to do.


--barry "bought a welder today"

[malachi]

I love the idea of the stainless replacement blocks.
Figure a set of them, plus Terry's PID retrofit kit... a semi-auto Linea starts looking pretty good!
And if you really have a solution for the whole solenoid mess - then it starts looking REALLY good.

[barry]

current scheme:

retrofit PID in custom replacement housing, with real-time brew temp display (not just boiler temp);
retrofit preheat;
solenoid/flowmeter reconfiguration;
variety of... "novelty" housing designs.

things are progressing slowly, but they are progressing. being able to zap metal parts together at will should speed things up a bit. of course, now i'm bumping up against the insane holiday season.

[malachi]

solenoid/flowmeter reconfiguration;

would love to figure out a good solution for the 3-way valve location nonsense. if you have a plan...

[AndyS]

would love to figure out a good solution for the 3-way valve location nonsense. if you have a plan...

Are you familiar with Paul Pratt's modification? He put the body of the 3-way inside the group neck. Along with some of the other stuff that he did, it sort of brings the Linea up to the GS-1 standard.

[HB]

would love to figure out a good solution for the 3-way valve location nonsense. if you have a plan...

A quick recap for those following along who aren't familiar with the "valve location nonsense," at least as I understand it.

The multi-group La Marzoccos share a single rotary pump. Brew water is delivered to each diffusion block via a copper tube that momentarily exits the group, at which point a solenoid controls the flow, then re-enters to complete the pathway. Problem is, that little dash outside loses precious heat, and partially explains why barista competitions adamantly insist competitors flush the grouphead (not just to clear the dispersion screen, but also to clear the cooler water from this out-of-boiler portion of the delivery tubing).

For automatics, the situation is worse. A flowmeter works like a water wheel, spinning as the water passes to calculate the volume. There's a separate flowmeter per group, and once again, the brew water takes the long way home to pass by the flowmeter outside the group to reach the diffusion block (a single-group automatic wouldn't have this concern because the flowmeter is installed immediately after the pump, it isn't metering brew-temperature water, and thus doesn't contribute to heat loss). These two design choices earn the ire of those seeking uber-stable brew temperature.

(corrections are welcome)

Are you familiar with Paul Pratt's modification?

Very cool. Having only one group to deal with does simplify things though, which makes me wonder: Do any cafes use several well-capable one-group machines instead of a multi-group? Taking one machine offline for maintenance would be a lot easier. Or it is just a question of added space and potential maintenance (i.e., more parts means more potential failures)?

[barry]

partially explains why barista competitions adamantly insist competitors flush the grouphead (not just to clear the dispersion screen, but also to clear the cooler water from this out-of-boiler portion of the delivery tubing).

clearing the screen is the purpose of the flush. dumping water for a warming flush is a complex issue; it's not quite as straightforward as the cooling flush on a heat exchanger machine. if it was just the water in the exterior tubes that needed to be purged, that wouldn't be so difficult as it's not much water. the problem is the tubes themselves, and the solenoid body, and the flowmeter body, all need to be brought up to temperature before the water flowing through them can hit the coffee at the desired temperature. how much water to flush? a big "it depends".

[AndyS]

Do any cafes use several well-capable one-group machines instead of a multi-group? Taking one machine offline for maintenance would be a lot easier. Or it is just a question of added space and potential maintenance (i.e., more parts means more potential failures)?

Some people feel that the LMs get better as they step up in size from one to two to three groups. Bigger boilers run more stable temps, they say. Obviously, this doesn't solve the problem of the brew water flow path outside the temp stable zone.

[malachi]

While the 3 group machines have a bigger boiler, the issues with the length of the heating element make one of the groups nearly useless.

It looks like Paul's mod is similar to the Hybrid group design. Very cool.
That's the obvious solution but as Barry pointed out earlier, it's a PITA for servicing. And given that most folks seem to step down to a very small gicleur, servicing is actually something to be concerned about (small gicleur plus updosing equals potential service call).

I worked on a machine for a while that had the Blackwell/Schomer banjo tube mods done and actually found it to be far more stable. Of course, you want to talk about service PITA?!?