Hey everyone! Great to be here! I'm now also a proud owner of a Rocket Evo 2, after reading lots of positive stuff about it here.

I have a question about cooling flushes though, and I'm actually worried that something is wrong with my machine. I feel that my machine is running too hot. Is it normal that after 5-10 minutes without using the machine, you need to run water for about 12-20 seconds? I heard that cooling flushes are needed. But 12-20 seconds is really a lot, and I always need to refill the boiler.

Thanks for your help

Congrats on the machine, and Welcome to HB!

The flush will depend on your boiler pressure. A higher pressure will require a longer flush but will produce better steaming. A lower pressure = lower flush and lower steaming power.

Looks like you are just above 1.1 bar when the camera pans down to the boiler pressure gauge, but I didn't see your starting reading. You can always lower the boiler pressure via the pressurestat in .1 bar increments, allowing a few minutes for the machine to stabilize. Perform a cooling flush to see how much it's decreased while still delivering ample steam for frothing. Tweak as necessary until you find the proper setting for your usage.

In the future, if at all possible, you'll want to plumb in the machine. A very common complaint about tank-fed HX machines is the constant refilling of the reservoir (and dumping of the drip tray). My Vetrano was plumbed in, and this was heaven! Once you plumb in a machine, you'll never want to go back.

Get eric's thermometer while you are at it... will help tremendously.

uscfroadie wrote:Congrats on the machine, and Welcome to HB!

uscfroadie wrote:The flush will depend on your boiler pressure. A higher pressure will require a longer flush but will produce better steaming. A lower pressure = lower flush and lower steaming power.

+1

Your video looks and sounds fine to me. I think you will end up needing an even longer flush. On my old Giotto, which I believe is thermally similar to your machine and other Rocket Giottos and Evos I use a "flush-n-go"- for the first shot on an idle machine, I flush a lot (5+oz) then immediately lock in and pull. My pStat is currently set to ~0.97 ± 0.05 barg (and I'm at altitude, so that's a slightly lower temp than sea level.) After the first shot, shots in succession require nothing more than a short screen-clean flush.

You might want to consider adding an EricS E-61 thermometer to that group. I found it indispensable in getting my technique down, and still rely on it to decide when to stop my flush. You will find a ton of advice and opinion (and some graphs) on this forum that discuss flushing techniques in relation to that thermometer.

I do use a surprising amount of water, top it up at least once a day.

Note: Initial post had the wrong url for Eric's adapter. Fixed that right away.

wow so many replies in such a short time. thanks guys, you rock! so do you think I could decrease the pressostat a little, is there a lot that can go wrong? I'm just a little worried about voiding the warranty.

I just saw an ECM technika at a shop here around. They only need to flush for about 4-5 seconds (the guy said the machine idled for at least an hour). My pressostat is currently set to 1.0 - 1.2. It activates at 1.0 and deactivates at 1.2. I was thinking about reducing boiler pressure by 0.1.

BTW, that's exactly how it behaved: I really like this thermometer thing. But I love the design of the machine too much... I guess that's the curse of being a designer :/

Hard to compare across machines. And it looks to me like Dan did two 4-5 second flushes on his technika.

azumbrunnen wrote:I really like this thermometer thing. But I love the design of the machine too much... I guess that's the curse of being a designer

I was the same, and thought I would remove it after I got my technique figured out. But I've gotten to rely on it and decided that the appearance is OK.

Lately I've noticed reports of heat exchanger espresso machines with restrictors to slow down the thermosyphon. The group idles cooler, which means a shorter flush, but the recovery time increases. I alluded to this point in the ECM Technika IV Review:

HB wrote:The Technika is tuned to reduce the need to flush (hence the "short" and "mini" flush described in the video), but this increases its shot-to-shot recovery time to a minimum of 2 minutes. The temperature reproducibility is best with recovery time around 3 minutes. Keep in mind as you watch the video above that the "sss-s-s" sound is the best indicator of how long you should flush (long, short, or mini) rather than keeping track of idle time. To put it another way, long "sss-s-s" sound = long flush + mini flush, medium-short "sss-s-s" sound = short flush, no or little "sss-s-s" sound = little or no flush.

For those new to heat exchangers, the shorter or no flush routine is easier to manage. The main drawback is recovery time. If you read reports of some Expobars that are Dragons and others that behave more like Mixers, it's the introduction of a restrictor in the upper leg of the thermosyphon. It's easy to recognize the restrictor-free models: They flash vigorously for a long time and recover very quickly (hence the term "flush and go"). As a starting point, they typically stop flashing when the grouphead is around 206F, so you can count off one second for one degree from that point. At least that was true for La Valentina and a few other heat exchangers without restrictors that I've used.
As others have pointed out, Eric's thermometer adapter eliminates guesswork and narrows your target. It's not a "must have" if you're able to judge by taste, but it's certainly a "nice to have" for many baristas.

Thanks guys for the help

so would it possibly make sense to drop boiler pressure by 0.1 to have a better compromise between recovery time and the amount of cooling flushes?

Is it dangerous / hard to do that? I saw some videos. Looked pretty easy. But I'm afraid that I'll mess something up. My Evo 2 has the restrictor you're talking about. But that only means that the brew group doesn't overheat. You still need to make cooling flushes for the heat exchangers.

azumbrunnen wrote:My Evo 2 has the restrictor you're talking about. But that only means that the brew group doesn't overheat.

My understanding (based on EricS postings to this forum) is that most of these rocket Giottos and Evos have a 3mm restrictor. Also, I see that most of us tend to use the Flush-N-Go technique (same as Dan used in the video.) The restrictor affects the idle temp of the group in addition to how fast it comes back to temp.

Tweaking down the pStat is not difficult. Involves opening the machine and turning a little screw on the pStat, then plugging it in, letting it come back to pressure and seeing if you need to go a little further or back. If worried about warranty I guess you could call and ask - they may even tell you exactly how. But you are in a perfectly good ballpark now, so I think you should use it as is, get used to flushing and steaming, then consider turning it down 0.1 bar and deciding if that's better (as uscfroadie pointed out, there's a little steaming vs. flushing trade-off there.)

I would personally love it if you can somehow get the company in China who makes the parts for Eric to actually produce something tasteful, but you can't live without the thermometer.