Newbie Introduction to Espresso - Heat Exchanger vs. Double Boiler Espresso Machines [video]

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HB
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Postby HB » Dec 01, 2013, 9:40 pm

The previous video on Buying Advice discussed double boiler espresso machines, but largely skipped over heat exchangers (HX). As part of their buying decision, a shopper is confronted with lots of choices, but frequently doesn't know how these two types of espresso machines differ. This video explains how HX espresso machines work and how its design affects the barista's routine. The video ends with a side-by-side taste test.



Below is the HX hydraulics diagram by Eric Svendson and Lino Verna that I used in the video. If you're interested in the E61 thermometer adapter I mentioned in the video, please contact Eric directly via e-mail or PM. The shorthand terms for HX espresso machine characteristics that I mentioned in the video are described in more detail in the thread Ideal brew temperature management by HX espresso machine type.

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The earlier segments of the series are linked in the main thread, Espresso 101: Newbie Introduction to Espresso.
Dan Kehn

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keno

Postby keno » Dec 01, 2013, 10:40 pm

Great side by side comparison of DB versus HX. Thanks for posting!

One quick question about the taste test. It appears that you started the Alex shot first but cut it off last, so that pull might have been a few seconds longer. Could this contribute to the perceived greater fruitiness of the ECM shot since the bitters in the shot tend to come out in the latter part of the extraction?

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HB
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Postby HB » Dec 01, 2013, 10:53 pm

Pour time is possibly a minor contributing factor, but the taste difference was easily reproducible. Before we started the camera, I pulled two doubles for myself and Phillip handed me each at random to confirm I could discern the difference (and yes, I kept my eyes closed). To me, it was obvious which was which by taste, so I figured he'd have little trouble spotting the difference when the camera was rolling. Fortunately, he guessed correctly. :)
Dan Kehn

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keno

Postby keno » Dec 01, 2013, 11:12 pm

Interesting, just wondering about a few other variables. Did you compare brew pressure in each machine with a portafilter gauge? And how long since each machine was back flushed with detergent?

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HB
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Postby HB » Dec 01, 2013, 11:42 pm

I calibrated the brew pressure with a Scace II portafilter. The brew temperatures are harder to compare meaningfully when one profile is flat and the other is humped/declining, so I set them to be equal around the 20 second mark. Both espresso machines were backflushed within the last few days, though honestly I would spot the taste defect associated with a dirty grouphead right off.

I intentionally chose an espresso blend that has noticeable fruit flavors in the background (Rustico by Counter Culture Coffee), hoping that it would elicit a difference between the two espresso machines. Before I wrap up the reviews, I'll try side-by-side comparisons with a variety of blends in a group setting.
Dan Kehn

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keno

Postby keno » Dec 01, 2013, 11:54 pm

HB wrote:Before I wrap up the reviews, I'll try side-by-side comparisons with a variety of blends in a group setting.

I really like the controlled taste test format. Too often when comparing machines a lot of us have a tendency to obsess about technical specs and features, including DB versus HX, because we don't have the opportunity to compare taste in the cup among machines which is what really matters in the end.

Looking forward to the rest of this feature!

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TomC
Team HB

Postby TomC » Dec 02, 2013, 12:44 am

This was a very well presented video. That's a beautiful HX unit as well.

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damonbowe

Postby damonbowe » Dec 02, 2013, 8:18 am

Were the machines flushed prior to use and were the group heads at about the same temperature based on Eric's thermometer reading before you pulled the shots? I'm still not clear on why there would be a difference in these shots if the groups are showing approximately the same temp before pulling and the machines are both fully flushed. I don't know if it's because I'm OCD or whatever, but I immediately started to become nervous about the time period of the grinds sitting on the counter and no showing of group flushing in the video! Please enlighten me on the flush thing.

Thanks for putting together the videos. I'm currently still deciding between an ECM Technika Profi and Rocket R58, so I have a vested interest in this discussion.

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HB
Admin

Postby HB » Dec 02, 2013, 8:56 am

damonbowe wrote:Were the machines flushed prior to use and were the group heads at about the same temperature based on Eric's thermometer reading before you pulled the shots? I'm still not clear on why there would be a difference in these shots if the groups are showing approximately the same temp before pulling and the machines are both fully flushed.

I have been working on the Izzo Alex Duetto V3 Review for the last couple months and the ECM Technika IV Review for the last couple weeks; to the best of my abilities, the two espresso machines were dialed in similarly. The Technika doesn't have Eric's grouphead thermometer installed. I'll install it at some point in the review, but I prefer to start the research section of a review with the equipment as-shipped. As for the taste difference, I speculate that it's due to the hump/declining brew temperature profile (HX) versus flat brew temperature profile (double boiler).

damonbowe wrote:I don't know if it's because I'm OCD or whatever, but I immediately started to become nervous about the time period of the grinds sitting on the counter and no showing of group flushing in the video!

I'm betting on the former. :lol: The video had a cut while we setup for the taste test, so prep steps like dosing and flushing were not shown. Actually, that was the second take since one of the machines ran out of water mid-shot. D'oh!
Dan Kehn

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FotonDrv

Postby FotonDrv » Dec 02, 2013, 9:10 am

Dan: Thanks for the good video! I got a laugh out of you description of the Lever machine as a "Tea Kettle on steroids".

Thanks again

Stephen
That Light at the End of the Tunnel is actually a train