This is a follow-up to a post from a little over a year ago when I had a temperature problem with this machine due to a manufacturer's defect involving the HX. You can read that story here for additional background: Lessons in diagnosing brew temperature problems. Suffice it to say, in the end tech wiz Eric S helped me to figure it out.

Fixing the problem got me back to the point where the machine was in the right temperature ballpark, but it idled at only 200 F after a full hour warm up. This was okay for pulling a very nice first shot with a small cooling flush. But the problem was getting a decent second shot without waiting a long time for the machine to recover. Others have described similar problems with other HX machines: E61 grouphead thermometer and HX cooling flush recovery

This got me thinking recently that the idle temp was just too low and needed to be raised. First I tried increasing the boiler pressure, raising it from 1.25 bar to 1.35 bar and it had a negligible effect and I did not want to raise it any further. Then I remembered how the HX in this machine was designed and that I should be able to tune it to the desired effect. Below is a diagram (albeit crude) of the HX.



The thermosyphon loop is responsible for heating the group head, the stronger the flow the quicker the machine heats up and the hotter it gets. Machines with a thermosyphon restrictor limit the flow to attempt to prevent overheating of the grouphead and reduce the need for flushing and temperature surfing. These design differences are largely responsible for the characteristics of "dragon" vs "mixer" HX machines as described in this post: Ideal brew temperature management by HX espresso machine type

The ECM Technika is known as a "mixer" and this is due to the thermosphyon design in which the cool brew water enters through a tube inside the HX and exits the HX through another tube with a very small gap between them. This has the effect that the thermosyphon loop is weakened as the temperature differential between the top and bottom of the HX is reduced thereby slowing the flow induced by the temperature gradient. It also introduces more cool water into the shot when brewing as it has less chance to mix with the hot HX water before exiting to the grouphead.

In the Technika this aspect of the HX design is very easy to modify as the top tube is plastic and can be cut to shorten it (or replaced with a longer tube). My hypothesis was that cutting the tube shorter would have two effects that would both make the machine run hotter: (1) by increasing the gap the temperature differential in the HX thermosyphon will be increased, resulting in a stronger thermosyphon that will more quickly heat up the machine and a hotter grouphead idle temp, and (2) increasing the gap between the cool water inflow and hot water outflow will allow more hot water to mix with the cool water before it passes to the grouphead (this will mainly occur during a shot when cool water from the line or tank is introduced into the system). The diagram below shows how I modified it by cutting off about a centimeter of the plastic tube to increase the gap size.



Note that to do this on this machine you need to remove the upper thermosyphon tube from the top of the boiler to the grouphead and then remove the fitting in the top of the boiler. It's a relatively simple and pretty quick modification.

After doing this I tested the machine and it heats up about 15 minutes quicker than it used to and now reaches an idle temp of 203 at the grouphead in 45 minutes. When doing a cooling flush I now see some flash boiling which I did not see before. Before I could pull my first shot at 200, but subsequent shots dropped down to 197 or less. Now I can pull a shot at 203 and second shots are much better than before. Recovery is also quicker.

It's been said that the advantage of the HX design is the ability to modify temperature on the fly. I am now convinced that for that to be an actual advantage the machine must idle at a temperature sufficiently high and recover quickly enough to easily get to the desired temperature, since the HX design allows the operator to shed heat with a cooling flush but not to add heat (except by waiting for it to recover and some machines may take too long to recover for a reasonable morning routine for multiple drinks). HX tuning may help users of machines like the ECM Technika to ensure that the machine's idle temp allows for proper temperature surfing.

First off very interesting write up and discovery you have here. I myself had a heck of a time dealing with recovery issues with my Rocket Giotto Evo II. I knew like you mentioned raising boiler pressure was not going to be the most adequate approach. However what you have is different from what I saw in my Rocket Giotto the heat exchanger is essentially a bottle welded inside copper cylinder. In the picture below you can see the heat exchanger to right. Is that what yours looks like?

Yes, the copper "bottle" on the right side of your boiler is the HX. If you look at the bottom of your HX, the thicker tube on the top is the return of the thermosyphon loop and the thinner tube below is the brew line into the HX.

I am not familiar with the internals of the Rocket Giotto Evo II HX, so I can't say if the approach I describe would work or not. You might look for an exploded parts view or see if anyone else has opened one up.

Below is a picture of the Technika boiler and HX. The arrow points to the upper thermosyphon loop. The HX is to the left of that (my diagrams above show a cross-section from the side of the boiler and HX). Once the upper thermosyphon tube is removed the fitting sitting on top of the HX can be removed and the tube size modified.

Awesome work! I am waiting for my Technika to arrive and I am curious to see if it runs hot or not. I am getting the EU version, that could make a difference.

is this plastic tube attached to the upper thermosyphone tube inside the HX chamber,
the same you found bented by a too close contact with the lower copper tube of the cold water thermosyphon return?
at that time you cut it at 45 deg and this seemed to solve your problem;
so now you cut it further, to make a larger gap between the 2 tubes inside de HX chamber?

in this design of ECM Technika 4, the cold water injection, comming from the pump, is joined with the lower tube, as it enters the HX chamber;
quite different from Technika 3 (aka my Bezzera Magica design of an HX chamber as a mini boiler with all tubes into the 'cover');
this clever design of Technika 4, seems to solve many problems, making the machine a "mixer";
for example, the upper tube, so important in other designs - long and thick (12 mm diam, for lower idle temp in group), is quite short here;
seems that the interior design of HX has some more hidden resources...
I suppose you have checked both TS tubes for any flow restrictor inside?
in Magica, a kind of restrictor is the very elbow fitting of the upper TS tube (4 mm vs. 8 mm the internal diameter of the upper tube); enough to make this machine too a "mixer" with quite long recoveries, and no cooling flushes between consecutive shots:

radudanutco wrote:is this plastic tube attached to the upper thermosyphone tube inside the HX chamber,
the same you found bented by a too close contact with the lower copper tube of the cold water thermosyphon return?
at that time you cut it at 45 deg and this seemed to solve your problem;
so now you cut it further, to make a larger gap between the 2 tubes inside de HX chamber?

Yes and yes. Fixing it the first time when it was bent raised the idle temp from 190 to right about 200. The size of the gap is how you can tune it. By cutting off about an additional 5mm I raised the idle temp about 3 degrees Fahrenheit.

I don't believe the machine has any thermosyphon restrictor.

My ECM Technika arrived a few weeks ago. After playing around with the new machine I was getting some really nasty shots (extremely sour) and some times also nice ones. I was also using beans I ordered from a new vendor and I had the feeling that the decent shots were from the previous supply of beans, while the new ones were really bad. So I was attributing it to the beans or my roasting technique combined with the new beans.

Eric's thermometer has not arrived yet, but yesterday I started to think it could be the temperature. Perhaps some beans can withstand a bigger range of temperatures than others. My HX experience until now was all from YouTube and all I saw was people flushing it past the super heated point and then keep flushing it for 5 or so more seconds, pause a little and then flush some more. Also I remember reading here on the forum how surprised people were that they had to flush so much after having installed Eric's thermometer.

So yesterday I decided to put my thermocouple to use and made a basic temperature measuring device. Drilled a hole in an old single basket, put the thermocouple through and just started measuring shots doing flush & go. Now I haven't managed yet to slow down the shot enough to espresso speeds and I can imagine that the brew water will be a bit warmer at lower speeds, but I could see that the temperature was far too low, around 88C. So to get the water around 93C/94C I found out that pretty much I have to stop the flush after the flash boiling stops and can pull it straight away to hit the 93/94 mark. Then it needs a good 2-3 minutes to recover and pull another shot in the 93/94 range. After doing a shot it takes about 3.5 to 4 minutes to reach flash boiling point again. All of this is with a high pstat setting of 1.15-1.35 bar.

Keno, is this comparable to how you machine was behaving after you fixed the tube the first time?

This is how my thermosyphone tube looks like:


And inside the HX we can see the lower tube bringing in the the cold water from the pump:


I measured how deep the lower tube lies in the the HX and compared it to the length of the upper tube. I estimate the distance to be around 1 cm between the lower tube and the pointy end of the upper tube. Is this how far apart yours were also? And after you made the distance larger, did you increase it by about 1 cm total? Also did you keep the 45 degree cut that my tube currently has?

I'll wait for Eric's thermometer to arrive before starting making any mods. Perhaps I can make it to work as is with a different flushing routine, but it is good to know that it is possible to make the Technika less of a mixer if needed.

When you get your thermometer kit, give me a call at 301-587-5033 and we can make some more precise measurements from both a temperature and dimensions basis. As our daughter lives in Bolton Hill, I/we go to Baltimore all the time.

This machine is pretty good (all aspects) and is intended for a very short flush and go. Adjusting the pstat (down to maybe 1.00 bar max) would be the way to go.

edit - I would also buy a few spare copper washers for that upper heat exchanger ell. From the 1st line parts catalog, it LOOKS to be a 3/8" BSPP copper crush washer which is best used once.

Thanks Eric, I will get in contact when it arrives. We contacted by e-mail yesterday, this is the package you sent to the Netherlands. We moved back from Baltimore a few moths ago and I hadn't updated my profile yet.

I am also starting to think that as is the machine will be very capable, I just need to flush it a lot less than the advice that is given for HX machines in general.

Regarding the pstat setting, why would 1.0 bar max be better than 1.35 bar? Setting the boiler to a higher or lower temperature makes the recovery time between shots longer or shorter, are there any other considerations?

Man, you know what you are talking about, when I put the upper HX piece back I noticed that it could be screwed in much further than before, which wasn't good because in order for it to fit into the next tube it had to end in the same position. I was a little puzzled as to what had happened and fixed it temporarily by using a little thread tape. But now I know I need to replace a washer.

mr_pedro wrote:Regarding the pstat setting, why would 1.0 bar max be better than 1.35 bar?

Certainly, the lower pstat setting produces a lower grouphead temperature . . . it just needs time to acclimate. As far as I am concerned, these machines, along with the Rocket Hx models, are steaming "monsters" . . . a lot depends upon what you get accustomed to. "Playing" with pstat settings is so easy except for the patience necessary for the adjustment to take full effect.

It is absolutely true that a higher pstat setting will result in a faster recovery but the amount of flushing necessary to create an acceptable shot is also different.

So much depends on the typical duty cycle of the machine and the ability of the operator to discern differences while keeping all the other factors uniform as is reasonably possible.