How does my heating system with solar thermal work?

First of all, thank you for your explanations! However, you are referring to a properly functioning system, right? If, as in my case for example, the control system incorrectly "thinks" that heat from the roof is available and accordingly activates the circulation pump, the cold water coming from the generator is heated using gas, isn't it?! I assume that a combination stratified tank consists of 2 tanks: One large tank (in my case probably 800 liters) to store the warm water from the solar thermal system and a smaller domestic hot water tank (probably ~150-200 liters). Now I wonder, how is it prevented during times without significant solar radiation that the large tank is kept warm by the heating system? Presumably there is a heat exchanger that is controlled by the solar thermal system controller to prevent exactly this, right? Thanks! Regards

No, you have a standard stratified storage tank with a large tank of 800l, no small extra one inside.

See:

Der Kombi-Schichtspeicher KWS ist ein Pufferspeicher mit Schichteinrichtung für das energieeffiziente Einschichten des Heizungswassers und mit integriertem Wärmetauscher zur direkten Erwärmung des Brauchwassers im Durchlaufprinzip. Der Speicher ist je nach Modell zum Anschluss von einer oder zwei weiteren Heizquellen - wie z.B. einer Solaranlage - zusätzlich mit einem (Modell KWS) oder zwei (Modell KWS R2) Wärmetauschern ausgestattet.

Morning

Your approximately 30 m3 in four days corresponds to about 7 liters of Heizöl EL per day. Whether that is a lot or little depends on the energy requirements of the building.

The pump in a solar system is located on the return flow; if installed on the supply flow, it would be damaged by the high temperatures of a solar system in summer.

With the 999 in the controller, I would suspect the sensor. As the technician himself says, "if nothing is plausibly measured" = sensor defective. PT 1000 = at 0° C 1000 ohms, at +10° C about 1040 ohms, at -10° C 960 ohms. You as an electrical engineer can certainly check this yourself.

Olli

Your approximately 30 m3 in four days corresponds to about 7 liters of heating oil EL per day. Whether that is a lot or a little depends on the building's energy demand.

Well, there are only 7 radiators connected on the ground floor and they are only set to frost protection because it is still a construction site and unoccupied. However, of course, the newly filled service water had to be heated first; in any case, I will definitely monitor the consumption.

The pump in a solar system is located in the return line; installing it in the supply line would damage it due to the high temperatures of a solar system in summer.

True, many thanks for the hint! I thought it was the supply line because it is the right pipe, but for idiots, the mixers have red and blue colors marked... -.- (so right is the return and blue with the pump)

At 999 on the controller, I would guess the sensor.
As the installer already says himself, "if nothing plausible is measured" = sensor defective.
PT 1000 = at 0° C 1000 Ohm, at +10° C about 1040 Ohm, at -10° C 960 Ohm.
As an electrical engineer, you can surely check that yourself.

Both sensors (sensor 1 is on the roof and sensor 2 in the storage tank) are fine. Of course, I have checked them myself again!
Yesterday the new controller finally arrived, directly installed, connected, and behold: sensors 1+2 now also show plausible values! What I don’t understand is why I cannot manually turn on the pump through the controller?! (According to the ESR 31 manual, this should be possible...)

Another question: Can someone tell me what these "mini junction boxes" are called, in which you can place a terminal block where 2+2 wires are clamped? Unfortunately, the heating engineer only installed one such "box" and the remaining connection points are flying terminals... :O
As an electrician, this is of course a thorn in my side!

Yesterday the new control finally arrived, installed and connected immediately, and lo and behold: Sensors 1+2 now also show plausible values! What I don't understand is why I can't manually run the pump through the control?! (According to the ESR 31 manual, this should be possible...)

How can I check if the pump is running? According to ESR 31 the pump is being controlled, but you can't hear or feel anything at the pump?! However, I have noticed that our "normal" circulation pump in the heating circuit (Wilo) also runs almost silently and vibration-free, but it conveniently has a display showing the current pumping power! So can it actually be that the pump is running without you hearing or feeling it? (Ear DIRECTLY on the pump...!) It is a Grundfos Solar PM2 15-105. Thanks in advance!

Clamp meter?

Possibly the circulation also occurs by gravity?