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.

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.