The drawing is for e61 thermosyphon double boiler, not a saturated group.

The delta between the boiler top and the group inlet is a few degrees, value depending on flow restrictor and pipe geometry.
The delta from group in to out is about 20°F
The delta from group out to boiler return in is another few degrees, again depending on flow restrictor and pipe geometry.

When the pump starts, cooler water flows back up the return line, mixing with hotter from the boiler top, averaging out at brew temp. It's possible to change intrashot profile by restricting either the upper or lower line and return and exit points on the boiler. The sensor could be at any depth, but typically the sensors are fairly short, measuring the upper temperature.

cafeIKE, it really news to me.
I have rising brew temperature profile, I would like to make a profile more flat.
The decision: to limit water stream which arrives from the top point of a boiler. I correctly think?

You may want to talk with Paul Pratt the premier rebuilder and refurbisher of LM in Hong Kong. He rebuilt a 3 group for me added a pid and preheat with copper tubing wrapped around the steam boiler before going into the steam boiler he will know for sure. http://www.espresso-restorations.com/
Good luck with the pre heater.

Rostik_KIEV wrote:cafeIKE, it really news to me.
I have rising brew temperature profile, I would like to make a profile more flat.
The decision: to limit water stream which arrives from the top point of a boiler. I correctly think?

From examining the Musica hydraulic circuit, it appears there is a lot of boiler temperature water in the thermosyphon circuit relative to the cooler group return water. Adding a restrictor in the group supply may reduce the group idle temperature.

How is the thermocouple inserted in the group?

What is the group idle temperature?

What is your flush routine?

cafeIKE wrote: How is the thermocouple inserted in the group?

cafeIKE wrote: What is the group idle temperature?

In the field of a head where the thermocouple is established, the group heats up to 88-90С. Can reach 92С, if idle time of 30 minutes.
It is interesting also that the copper tube from a thermosiphon to group has temperature 112-113С.

cafeIKE wrote: What is your flush routine?

Flush to 92-93С and go.
Flush, Flush, Flush and go.
Flush, pause and go.... all the same rising brew temperature profile.

Nice install

Rostik_KIEV wrote:It is interesting also that the copper tube from a thermosiphon to group has temperature 112-113С.

Is that temperature at the boiler or group end? On the Vibiemme with ~1.1bar boiler pressure, it's ~110°C right next to the group.

How much does the shot rise?
Do you have a plot or can you write down 2s interval temperatures?

That's a great idea!! Did you install the thermocouple into the bleed screw location?

mitch236 wrote:That's a great idea!! Did you install the thermocouple into the bleed screw location?

Has made a hole of 6,8 mm, carving М8.
Has made a head for the thermocouple.


I tried to arrange the thermocouple so that its end almost would adjoin to one of a hole group head dispersion plate (07300183). The thermocouple well reacts to water stream.

cafeIKE wrote:Nice install
Is that temperature at the boiler or group end?

Thanks.
~1.4 bar boiler pressure.
It is temperature in the middle of a way of a copper pipe.

How much does the shot rise?
Do you have a plot or can you write down 2s interval temperatures?

I will make exact record later, but I can inform that the first 10-12 seconds the temperature is stable. Then the temperature smoothly rises on 1 С each 2,5-3 seconds.

Why 1.4bar? A ~1.0bar is common for HX machies.
Do you steam a lot?

What is the reservoir temperatue?

cafeIKE wrote:Why 1.4bar? A ~1.0bar is common for HX machies.
Do you steam a lot?

I first of all investigated dependence of a profile of temperature at variables pressure in a boiler.
Character of brew doesn't change (rising brew temperature profile). Entry conditions change of flushing.
But steam is much more powerful at 1.4bar

What is the reservoir temperatue?

The water tank? At me direct connection to the water membrane filter.