Londinium Espresso wrote:with a dipper, as the ambient temp drops the group loses more heat to the environment, lets assume its at idle. the only way you can address this is to increase the boiler pressure, but then if you start pulling back to back shots the group quickly overheats

This makes a certain amount of sense.
An it got me thinking -- I found a great routine on my CMA single group dipper without flushing in the summer, but later (this fall) I discovered that a short flush worked better than no flush...

The only difference is ambient temperature.
I wonder if the flush/no flush is enough to compensate. I do not typically pull back to back shots so it might be enough, for my situation.

Discuss

Gwilym Davies, when he was in Chicago, explained his routine on the Victoria Arduino lever, which is set up as an HX without a thermosyphon. He advises pulling a shot every 3 to 4 minute per group. In effect, he prefers to let the group cool and the HX water heat, so the machine acts as like a sipper.

Given that the cooled off group will cool the water as it sits and preinfuses; the only difference will be that the preinfusion itself will be substantially hotter than if you pull in the more tempered HX water into a hotter group. So personally, I can't see this making a great deal of systematic difference if the temperature management is done properly.

I sure am looking forward to DrGary getting his Prestina up and running so we can get some fresh observations on commercial groups, temp management, etc...how's it going on that project?

I think that the group water delivery system on a commercial lever has more to do with overall design of the machine than temp stability, consistency, etc. Your Prestina has a dipper fed group and the group is bolted directly to lthe boiler. Since your Prestina is from the 1970s, it represents the vast majority of lever designs...bolt on boiler dipper group. Now to me the basic point of machine design has more to do with the intended use than anything else. The home machines were conceptualized to be filled with enough water for a couple of shots, turned on to heat up fast, make some coffee and turn off. They were not designed to be left on all day or to pull dozens of shots in one session so the overheating issue was (and is) not a big deal here. In fact the design parameter of small group to heat up quickly is a central theme. Move to the Prestina and look at what niche it was designed for....small footprint club machine that you turn on when you open the club or bar or small restaurant and serve the occaisional shot of espresso. If you need more volume (in a different setting) you got more groups on the machine. But you see, nowhere in this equation is there anything to do with group temp management since all that just naturally comes from the group, not the method of getting water to it or to how or where the group is hooked on to the frame or boiler or whatever.

Now there is this big rage about thermosiphon group setups going on. So does this mean that all of the bolt on the boiler groups or the dippers or the bolt on boiler/HX groups were or are just wrong or bad. Does it really suck that bad to not have a thermosiphon system as far as shot temp goes? Holy mackerel, I have a lever machine that the boiler is an actual PART of the group and manage to not have "sour or burned shots" unless I am using a coffee that just does not work in ANY lever machine!! I can pull a sourball and burn one with the best of them but if I am paying at least SOME attention to what I am doing I can pull "shot after shot after shot" and they are all in the ballpark. Same with a dipper, same with a bolt on HX, same with a thermosiphon.

The thermosiphon setup simply allows the machine to be designed in a slightly different format...boiler down low, case shorter....the decision of the water delivery system design or the group heating design is purely a matter of decision making on the part of the company or person creatiung the machine and has little to do with shot quality, temperature stability/consistency, or other considerations in the extraction of crema caffe. But if the owner/operator THINKS they have a superior system that nicely exploits some angle of the espresso equation to great benefit, then obviously they will be happy with the outcome much more than someone who feels that their coffee sucks because their machine sucks. But one can always then blame the grinder.

...The thermosiphon setup simply allows the machine to be designed in a slightly different format...boiler down low, case shorter....the decision of the water delivery system design or the group heating design is purely a matter of decision making on the part of the company or person creatiung the machine and has little to do with shot quality, temperature stability/consistency, or other considerations in the extraction of crema caffe

but separating the group from the boiler ,gives more potential for regulating the group temperature independent of the boiler, EG the adjustable thermosiphon valve, or the restrictors commonly put in the TS loop.

Yes, I agree that in theory the thermosiphon does allow for some level of temp control, but I just don't see , read, or hear about these difficult temperature problems in non thermosiphon systems. I don't think there is a body of evidence that points to direct boiler contact groups leading to inferior shots or thermosiphon systems resulting in superior shots. If there is any argument to be made of one system vs another it is highly anecdotal in nature and user specific as in user preference vs any solid temperature data.

There is always more than one way to achieve the desired result, it just a matter of which is simplest, easiest, cheapest, etc.

orphanespresso wrote:Yes, I agree that in theory the thermosiphon does allow for some level of temp control, but I just don't see , read, or hear about these difficult temperature problems in non thermosiphon systems. I don't think there is a body of evidence that points to direct boiler contact groups leading to inferior shots or thermosiphon systems resulting in superior shots. If there is any argument to be made of one system vs another it is highly anecdotal in nature and user specific as in user preference vs any solid temperature data.

Go on Doug admit it, Barb has caught you sneaking around datalogging at 4am with a secret Scace device you have tucked away

Well you bring up some good points, that perhaps the magic of levers is not all temperature related. I've long held the belief that the lever groups nice even dispersion and the column of water extraction makes up for a lot. Oh and of course the spring extraction "profile". Ahh that word profile starts to grate after a while...

Back to the subject at hand, I reckon that there are different horses for courses. For intermittent use like we do in the office/home/workshop you would be able to get away with any group+boiler arrangement whereas in a commercial environment I personally would be looking at a set up that would lean towards a heat exchanger.

Anyway we all have enough machines I am sure one day we can put some data together. But somehow datalogging the lever ladies just seems like heresy.

I tend to agree with Gary. I ran thousands of shots through my big commercial two group dipper in outdoor temperatures ranging from the 40's into the high 90's. I honestly didn't notice any difference in the cup. I don't have a sophisticated palate, but it works well enough to tell if the water temperature isn't right. Anytime I filled a 6oz cup off of the group, no matter what the outdoor temperature, and checked the temp with a digital thermometer, the water was around 195 degrees.

I tried an experiment...

The machine - single group CMA lever, dipper.

I typically do a short flush, then pull the shot.
When I do the short flush, the boiler refills - the autofill has very narrow deadband. As a result, the group heats up a little and the boiler cools down a little.

This time, I tried manual filling a little bit first, waited for the top of the temperature cycle (pstat click off, around 1.1 bar) then did a short flush and pulled the shot - no autofill and no cooling of the boiler.

I was able to taste a difference in the cup...it was much better with the autofill kicking in.

I guess I should also test with no flush, at the top of the temp cycle....