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My Rancilio Z9 Two Group Lever Machine will soon replace my Elektra T1 as my daily machine (and the Z9 will one day make way for my Model 80 LSM) - so I haven't much to offer in the way of experience with temperature management, yet. However, this thread got me thinking, looking at my Z9 more closely, and wondering about cooling flushes.

In theory (because I have little practice) it seems that I have little recourse in the way of managing the temperature coming out of the group other than through the pstat. The more I look at, the more it seems that a cooling flush would do very little to cool the group. Indeed, I think if anything it would heat the group. Whereas with my T1 I can clearly see and hear the HX heat flushing out like dragons' breath - there is no similar fire with my Z9 - it just remains a steady temperature reflective of the boiler temperature. For instance, if I open the water fill and leave the lever open, then the water cools out of the group as the incoming cold water cools the boiler.

This is a bit rambling and a bit of me thinking out loud, some of you might be saying, Well, DUH. However, it's all new to me. Below, are a couple of photos where you can see that the group is bolted directly to the frame, and (not so clearly) two tubes from each group are fed by the boiler. Oh, and FWIW, Clay's comment about 195 degrees had me measure the temperature in a cup that I kept overfilling - it was 190 degrees at 1.1 bar.

-phillip

phillip canuck wrote:The more I look at, the more it seems that a cooling flush would do very little to cool the group. Indeed, I think if anything it would heat the group.

Indeed it would, though that's why you'd instead think of it as a warming flush, true?

I was at Blue Bottle Mint Plaza on Wednesday and talked to Zack about the La San Marco lever. He says a flush heats the group. He clears the group with a purging flush and then prepares the grind, giving the group about a minute to cool. Not sure if that's a dipper machine. Warrior372 tells me for the Conti Prestina, which is a dipper group, you need a cooling flush if it's been idling.

Now I'm confused. 'Dipper group' means that you have no HX, the feed comes right from the boiler, right? If you don't have an HX to provide cool water I don't see how you can do a cooling flush. Now if the group idles on the cool side, then I can understand the need for a heating flush after a long idle.

P.S.
I was at a Santa Fe cafe (Downtown Subscription on Garcia street) this week, and had a very nice shot from a San Marco Leva. I noticed that their technique in a busy cafe involved a very small flush before prepping the dose. Was so far my best shot ever in Santa Fe (faint praise.) I found some interesting online info: http://www.couriercoffeeroasters.com/wordpress/?p=279 that shows the older (type 80) SM Leva did have an HX. I would think the new ones do also*, but don't know for sure about that.

*Edit addition: Later learned from posts on this forum (i.e., La San Marco 80, converting to 85 ) that the model 80 is an HX and the newer model 85 is a dipper.

homeburrero wrote:Now I'm confused. 'Dipper group' means that you have no HX, the feed comes right from the boiler, right? If you don't have an HX to provide cool water I don't see how you can do a cooling flush. Now if the group idles on the cool side, then I can understand the need for a heating flush after a long idle.

Ask Warrior372 until I can get hands-on experience with the Prestina. Perhaps it's because the group is bolted directly to the boiler and near the pocket of steam at the top of the boiler. At one time Conti put Teflon group to boiler gaskets there but have since abandoned that.

homeburrero wrote:Now I'm confused. 'Dipper group' means that you have no HX, the feed comes right from the boiler, right? If you don't have an HX to provide cool water I don't see how you can do a cooling flush. Now if the group idles on the cool side, then I can understand the need for a heating flush after a long idle.

You are correct - a dipper has no HX and the feed (two pipes for each group, in my case) come directly from the boiler. My Z9 group is bolted to the frame, not the boiler (Conti Prestina) so the cooling/heating flush is machine dependent, not dipper dependent.

Given that the pressure is fixed by the spring and the boiler is just for heating the water, it sure seems as if I should be able to keep lowering the pstat until I find a setting that works. This opposed to my T1 where I several variables to play with - and screw up.

Of course, as soon as I make this my daily machine in the very near future, I'll be able to come back here with some more definitive answers to these thoughts.

homeburrero wrote:I was at a Santa Fe cafe (Downtown Subscription on Garcia street) this week, and had a very nice shot from a San Marco Leva. I noticed that their technique in a busy cafe involved a very small flush before prepping the dose. Was so far my best shot ever in Santa Fe (faint praise.) I found some interesting online info: http://www.couriercoffeeroasters.com/wordpress/?p=279 that shows the older (type 80) SM Leva did have an HX. I would think the new ones do also, but don't know for sure about that.

The owner of Downtown Subscription is a member of HB. As for the Model 80, that is an entirely different beast. For the definitive video on the Model 80, see Doug and Barb of Orphan Espresso on their youtube channel, https://www.youtube.com/watch?v=eqcvMtYHpBA



-phillip

Here are some other comments on this topic:

The temperature profile of a commercial lever group

Chert: Thanks! I was thinking that these were questions that had already been easily answered. I see that's not the case. Having said that, I did read through the five pages and have solidly come to the conclusion that what I care most about is the taste in the cup. Once my z9 is running daily I'll post my experience.

-phillip

Just a addition here, as I'm finishing my Gaggia Tell (old Gaggia lever group) and doing some Scace tests, for the horror of some

I did some shots with 2 minutes interval, pstat around 0.9 bar, and the shots were getting hotter. The hottest was the last one, 96°C (and very little declining temperature). When I can I'll test 4-5 minutes interval, but it seems the group take some time to cool down (around 26-27°C ambient temperature here). Of course on a cooler room temperature it will be different.

Márcio.

the gaggia orione group heads (1949-1975 [?]) are very, very temperature stable. the group head housing is 26 pounds of (mostly) brass! flushing or not doesn't make much of a difference. see my temp log on the above mentioned thread.