Any owner of an E61 dual-boiler (w/PID) who finds temperature stability inadequate?

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boren

#1: Post by boren »

I'm about to pull the trigger on a Lelit Bianca. The only think I'm still not completely sure about is temperature stability (within the shot) and temperature repeatability (shot-to-shot). Does anyone here with this machine (or a similar dual-boiler E61) find either of these to be a big enough issue to consider upgrading away from an E61 grouphead?

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another_jim
Team HB

#2: Post by another_jim »

The truth of the E61 is that you can repeatedly get relatively cool, medium or warm shots. That is, around 90 to 92, 92 to 94, or 94 to 96. This is repeatable. The temperature during the shot depends on the configuration. It falls slightly for HXs and is flat or a very small rise (0.5C) during the shot for DBs.

With the exception of the NS Aurelia, no thermosyphon or simple bolted to the boiler group will do better. You need a flooded or actively heated group for greater accuracy than this.

The convenience of having a DB with a conventional group, like E61s or La Spaziales, is that no flushing or thermometry is required for this. It's walk up and make the shot. Many people will claim to do better; and with very close care they might. But I believe this is the accuracy if you let the machine do its own thing without forcing it.
Jim Schulman

JRising

#3: Post by JRising »

Adequate/inadequate is the operational choice of words. The E61 with a PID on a brew boiler is going to have slight temperature fluctuations at the head. If you need a more stable head temperature, things like a single-group Classe 9 with heated heads are available, but the other shortcomings of a Bianca are far greater "inadequacies" than its grouphead temp fluctuations.
Everyone's got their own opinions regarding what is adequate.

boren (original poster)

#4: Post by boren (original poster) »

@JRising - what other shortcomings do you see in the Bianca? The only ones I can think of a long warm up time, like other E61 machines (I can live with it), and lack of programable profiles like in Decent machines (I can't live with the other shortcomings of these machines). Am I missing anything else that's significant?

Giampiero

#5: Post by Giampiero »

I have not a Bianca, but on what info are based your doubt?
I have a Quickmill Carola with PID ( not the version with termopid), and i'm quite happy with its temperature stability, and it use the same boiler, and thermosiphon design of the Vetrano 2B, but it's a vibratory pump model.
I did a small change in the PID setting and even installed a gigleur that is slightly bigger than the original, a good configuration at least for my routine.

boren (original poster)

#6: Post by boren (original poster) »

@Giampiero - my doubts are based on my own measurements with my machine.

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Jeff
Team HB

#7: Post by Jeff »

As Jim points out, this is sort of "the nature of the beast". E61 groups were designed for use with HX machines and, as such, need to spill heat. The amount spilled varies with air currents and ambient temperature. There also has to be a significant temperature differential with the boiler or there is little flow through the thermosiphon. Neither of these characteristics is desirable for temperature accuracy or repeatability. People enjoy the appearance and/or tactile qualities of the E61 group. It is also a "commodity" part, so there are close to no development or tooling costs, nor ongoing parts stocking, as there would be for a purpose-specific design -- lower manufacturer cost for a price-driven market.

Close-coupled and saturated groups have been around for close to 50 years now, following soon after the E61 decade. They have the potential for better temperature control than a standard E61 attached to a PID-controlled boiler through a thermosiphon.

When I was running an E61 HX, with very attentive flushing, I could hit the same temperature within 0.5°C, shot after shot. My current machine is repeatable within 0.5°C as well. My experience with medium and medium-light coffees on the E61, and medium through light coffees on my current machine has been that at least a 2°C change in target temperature is needed for me to be able to believe that there is an impact on taste. Lots of "believe" in there. That experience leads me to believe that a machine that can reliably hit a 2°C window is probably "sufficient" for most people.

boren (original poster)

#8: Post by boren (original poster) »

Jeff wrote:That experience leads me to believe that a machine that can reliably hit a 2°C window is probably "sufficient" for most people.
This sounds reasonable, but my Quick Mill Alexia Evo (SBDU E61 with PID) couldn't reliably hit that 2°C window, see link above. The question is - would a machine like the Bianca would? I'm not interested in HX. My next machine for sure will be a dual-boiler, what's still somewhat open is whether I'll give E61 another chance.

JRising

#9: Post by JRising »

boren wrote:@JRising - what other shortcomings do you see in the Bianca? The only ones I can think of a long warm up time, like other E61 machines (I can live with it), and lack of programable profiles like in Decent machines (I can't live with the other shortcomings of these machines). Am I missing anything else that's significant?
Well, off the top of my head they used those crappy blue Y-connectors that can't handle steam knowing full well that they're using the same generic vacuum breakers that will leak steam if not serviced every couple of years. Most consumer-class machines use that valve for size reasons, it makes sense, but Lelit is the only one I am thinking of with the dissolving Y fittings, Though I believe Lelit is no longer putting those blue ones in anything.

As for not having "programmable profiles", I far prefer the user being in control of the flow-control rather than letting a player-piano type of script do it, but that's probably just my old-fashioned crotchitiness. Other little nits to pick include the second temperature sensor, while useful for comparative testing, it makes the boiler-fill probe that much less accessible and is not robust enough.

That said, I do adore the Bianca. A lot of really good ideas went in along with the few weird ones. Having a Plumb-in/Pourover choice machine where the entire machine becomes smaller when plumbed in and the user can choose between width or depth when the reservoir is on is great. In my opinion a shortcoming is something (non wear and tear) that actually breaks the machine or causes a leak or anything that makes it un-usable, less repairable than others in its class. Not something that allows a consumer-class machine to vary 1.5 or 2C at the brewhead.

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Jeff
Team HB

#10: Post by Jeff »

Maybe I'm missing something when I look at your data.

As I understand it, the first two measurement runs are without a pre-shot flush, the third includes a flush, so is arguably "different"

I'm looking at the "puck" temperature. I don't care what the boiler is doing, just the conditions under which the coffee is being extracted.

At 5 seconds, which would typically be somewhere in basket fill

* 93.5, 93.0, 94.9 -- within a 2°C window

At 10 seconds, typically early in high-pressure extraction

* 94, 93.3, 94.9 -- within a 2°C window

At 20 seconds, typically later in high-pressure extraction

* 92, 92.3, 93.7 -- within a 2°C window

Even with adding a 4-second flush on the third measurement run, it looks like you're within a 2°C window.