I've been wondering for a while why manufacturers are still sticking E61 style groups on double boiler machines. Granted, the E61 is a great group with built in pre-infusion and good temperature stability. But the problem in a double boiler (or single boiler) machine is that temperature stability - It's about 20 degrees too low, usually. Now, for an hx machine this is great, as the cooling flush will bring the group up to temperature, vice overheating it. But for a single or double boiler, a warming flush will affect boiler temperature and only have a transient effect on grouphead temperature.

On many non-E61 machines, the group is bolted to a boiler. For a double boiler, if the group was bolted to the steam boiler, the steam boiler could be tweaked to keep the grouphead temperature at 200 degrees.

This is really the only thing i have against machines like the brewtus, double domobar, and duetto II. Am I too critical? Does that 2-3 seconds of 180 degree water not have an effect on shot quality?

popeye wrote:Now, for an hx machine this is great, as the cooling flush will bring the group up to temperature, vice overheating it.

You're 180 degrees off. On an HX, you flush to cool down the grouphead as the thermosyphon has it sitting at a higher than ideal brew temp, unless of course you lower the boiler pressure so low that you can pull shots without flushing, but that will leave you with a machine that cannot steam.

Actually no the flush heats up the group and cools the HX simultaneously. It basically equalizes the brewing platform.

Based on my observations here and follow-up discussion.

Well.. As I understand it, pretty much any DB machine that is getting used or is meant for a home environment, needs a 2-4oz warming flush.. Whether it be the vivaldi, or an E-61 type. Since the E-61 DBs have PID's, I would imagine the boiler is a pretty stable temp.

So.. you walk up to your machine, pull your warming flush.
Build your shot
Pull at proper brew temp

The tests on the duetto showed pretty darn stable temps throughout the shot.

I too have questioned the need for an E-61 on a double boiler, and further questioning has led me to ask myself, if it is actually making things worse. Seems to be pretty stable, however. The first brewtus, IIRC, was an office lever with another boiler shoved inside...All things being equal, thats what all the E-61 Db's are.(VBM, Duetto, BrewtusIII). I was skeptical, and still am somewhat, but they seem to be pretty stable after a warming flush from a long idle. That, coupled with the pre-infusion of the E-61 makes them nice machines for home use. Total temp control, and 5-8sec PI.

However, Dalla Corte is on to something with their group design. I really like it. I was SOOOO disappointed when I found out the DC Mini doesnt have a hot water tap, but the DC Super Mini does. I really liked the Dalla Corte, based on the bench review, but I need a hot water tap, I love americanos, and drink them daily. But, that aside, What Dalla Corte did with the mini/super mini is awesome. The e-61 is without a doubt, a time-tested, solid, dependable group design. Its almost 50yrs old. Saturated groups now are only found on expensive machines.. Give it time.. Soon(ish) E-61's might be obsolete, replaced by a saturated type group.

popeye wrote:I've been wondering for a while why manufacturers are still sticking E61 style groups on double boiler machines.

No mystery here - cost and popularity.

Creating an unproven propriety design isn't cheap and convincing the world to adopt it isn't easy. As others have already pointed out, the E61 group works well on double boilers, is available from multiple parts manufacturers, and there's a plethora of off-the-shelf accessories/parts build around the platform. It does idle a bit cool, so you have to flush two ounces. So what? Most baristas flush the group prior to each extraction anyway to clear the screen; in fact, it's required in the SCAA competitions.

To be clear, I don't believe the E61 is the end-all be-all group. But as has been documented in abundant detail over the years, the E61 does have a lot going for it.

JmanEspresso wrote:Saturated groups now are only found on expensive machines.. Give it time.. Soon(ish) E-61's might be obsolete, replaced by a saturated type group.

Eh, I am less interested in the particulars of brew temperature control than the consistent quality/character of the group's extractions. But that's hard to quantify, so manufacturers ceaseless tout their equipment's impressively flat/reproducible brew temperature profiles. Yawn.

HB wrote:Eh, I am less interested in the particulars of brew temperature control than the consistent quality/character of the group's extractions. But that's hard to quantify, so manufacturers ceaseless tout their equipment's impressively flat/reproducible brew temperature profiles. Yawn.

Can I nominate that one as a "Quotable Quote"?

JmanEspresso wrote:Dalla Corte is on to something with their group design. I really like it.

I really love that Dalla Corte brewgroup as well. I really wanted to buy this machine when I first saw it. It's just too bad the rest of the machine seems like an afterthought.

I'm hoping they'll redesign the machine as a version II but use the same brew head (maybe chrome up the little pineapple as well).

If they could then drop the price a little, we'd have our E2009.

Endo wrote:Can I nominate that one as a "Quotable Quote"?

While I don't like quoting myself, I've nevertheless made it into the list a few times.

TimEggers wrote:Actually no the flush heats up the group and cools the HX simultaneously. It basically equalizes the brewing platform.

Based on my observations here and follow-up discussion.

Sorry Tim, but I think your test is flawed. You test measured the temp of the screen, not the grouphead. If you still have your equipment available, please perform the following test.

Attach your thermocouple to the inside of the grouphead where the portafilter is inserted. Do not let it touch the rubber gasket or the screen. Or, attach it to the outside of the grouphead and isolate outside air by throwing a think rag/towel on top. Allow it time to settle, and you'll probably find the temp of the group to be almost identical to your EricS themometer.

Now, perform a cooling flush. If your theory is correct, it will show the temp INCREASE on the grouphead, but I really don't think this will be the case. It'll probably drop, just as it does on the thermometer.

I say all this because the temp on the probe is reflecting grouphead temp until water starts hitting it. With the lever down, there is NO water in the path, therefore the probe will reflect the group's temps (not necessarily the brew path, but the group's temp).

Please don't take this the wrong way as it is not a personal attack. I'm interested in what is really going on as much as you and just think that the test you performed is not reflective of what is really happening. Perhaps it's all symantics, but I think your test shows that a cooling flush would bring the shower screen up to temp while also cooling down the grouphead.

Hi Merle please feel free to critique anything I do, I don't take things personally.

While I'm not going to conduct anymore tests I still stand by my interpretation of what happens in a flush. What I'm getting at is the water in the HX is even hotter than what the group is (hence the brief climb in the numbers on my group therm when the flush first starts). The super hot HX water is passing through the slightly cooler group (albeit very quickly). That super hot water (I presume) would have little affect on the massive group's temperature (but does serve to stabilize the entire brew path) but still throw hot on cold the cold becomes warm(er).

My "experiment" shows that the group (specifically the brew chamber/portafilter basket/screen) is cooler than the group (when idle) thats all, I made no comments or conducted any tests on the HX water's affect on the group temperature once passing through the group. Again the group therm shows how much warmer the HX water is when the flush first starts.

The HX comes down a little and the group goes up a little.

I'm not an expert on the numbers of thermal whatchmajigs but I think the important point that we both can agree on is that the flush is more about getting all the parts in the brew path as close to the same temperature pre-shot as possible. For me as long as that element is consistent I don't worry about what part is hotter when idle or what the machine does during a flush.

uscfroadie wrote:Now, perform a cooling flush. If your theory is correct, it will show the temp INCREASE on the grouphead, but I really don't think this will be the case. It'll probably drop, just as it does on the thermometer.

This video shows the temperature of the HX water measured at the point prior to the turn towards the brew chamber (smaller readout) and the thermofilter readout (larger readout):



The pressurestat was cranked up to the max, hence the very long flush. As you can see, the "pre brew chamber" water temperature doesn't coincide with the actual brew temperature during the extraction.

TimEggers wrote:While I'm not going to conduct anymore tests I still stand by my interpretation of what happens in a flush.

A quick way to verify this result without instruments is to touch the top outer part of the saucer once the machine has been idle for 20 minutes, then right after a "cooling" flush. I assure you it won't feel cooler.

Thanks Dan for sharing that video again. Its a great reminder of what really happens, I know I've seen that video before but it had been a long time. Impressive; the numbers certainly don't lie (that's my way of getting out of having to touch the saucer).

TimEggers wrote:...that's my way of getting out of having to touch the saucer.

Wimp! Lever owners are surely laughing since that's the standard way of dialing in the temperature for the first shot. It's surprisingly accurate/repeatable with a little practice.

For E-61 Hx owners.. Has anyone considered the little stick-on thermometers that Orphan Espresso has?

Penny's Hot Shot Group Strip Thermometer

Im thinking of purchasing it just to see if it helps me out with my flushes. Currently Im running "hot", P-Stat at about 1.35max reading, and the longer flush time needed gives me erratic group temp readings after I drop the lever and stop flushing. Meaning, If from idle, I flush to 208F, and stop, I get a group reading of 210-211F..pull shot. Then, about 4 minutes later, flush to 208F, and stop, group reads 203-204F. Weirdy weird. I almost think life was simpler before the group-therm.. but thats no fun is it?


So yeah, the stick on therm.. anyone consider it?

HB wrote:Wimp! Lever owners are surely laughing since that's the standard way of dialing in the temperature for the first shot. It's surprisingly accurate/repeatable with a little practice.

LOL...I still remember the video of one Michael Price touching the group of a Cremina to "verify" it was warm enough to pull a shot...."OUCH!!"
Funny, I had my friend Pete (whose Vario I was loaned these past 5 weeks). He just purchased an HX machine, and I suggested he order a temp strip. His is an Astra pro, and I'm not sure it has the same little screw in the group as my former Anita. Maybe so, as it is a form of E61.
Back on topic, I was always a bit confused as well with the terminology when performing a "cooling" flush, especially while watching all the steaming hot water dancing on the drip tray.

One of the advantages of the double-boiler design is that there is absolutely no need for a massive heat-sink. The brew water and steam water can be kept at their respective temperatures. Odd engineering to attach an E61 group on a double-boiler design. What you'd want to do is to minimize the heat-sinking character of the group. A small stainless group would be more energy efficient, and no less stable thermally.

This morning I performed the experiement I described earlier. With my machine up and idling for about an hour, my EricS shows a temp of 210.5. I took my digital meat thermometer (not a Fluke in accuracy, but it helps to illustrate a point) and held it against the top of the grouphead covering the temp probes with a rag in order to hold it in place without being burned. Temp on it rose to and settled on 180 degrees. I then performed a flush and watched the EricS rise in temp initially as the overheated water from the HX hit the probe, but the temp on the meat thermometer dropped, and by the end of the flush was reading 10 degrees less (170).

If the flush is bringing the grouphead up to temp, why did my temp drop? If I had a third hand, I'd post a video. Any thoughts/ideas? I'm stumped.

On a side note, just what is the EricS measuring when the machine is sitting idle? There is no water hitting the probe, so is it reflecting the headspace (not sure what to call it) above the water in the brew path, or is it measuring the brew path itself?

uscfroadie wrote:On a side note, just what is the EricS measuring when the machine is sitting idle?

It is measuring a temperature that is representative of the entire E-61 group. I do concur that it was not originally designed for that specific purpose but we have ALL learned (and are still learning) the heat intricacies of these machines.

Here are some measured temps on Anita: