[Solved] Defro Komfort Eko - Too low return temperature to the central heating boiler

Hello, I have a problem with maintaining or actually reaching the temperature on the return to the central heating boiler. New installation, Defro Komfort Eko 15 kW boiler. The manufacturer recommends a minimum return temperature of 55 degrees, while my temperature is constantly around 32-37 degrees. I manage to get the maximum stroke on the return when the DHW pump is running, because then it forces circulation. When only the central heating and floor pumps are running, the return is practically cold and the water circulation in the boiler itself is rather negligible. I posted a diagram of my boiler room, red is the power supply, blue is the return. There is a four-way valve above the boiler and a three-way valve above the floor heating system. I did not draw check valves, but they do not affect this problem. Fully automated installation, valve actuators, temperature sensors installed. I am asking for information on the basis of the drawing whether the installer has made a mistake somewhere that causes excessive cooling of the boiler. I will add that the temperature of the boiler itself can jump by up to 20 degrees at the end of the support and start of operation.

The installer installed an additional pump on the return from the four-way line to the boiler. The return is warmed up but it burns me much more. The burner looks normal, there is no burnt crater, no sinters, very little ash. Boiler set at 65 degrees, floor heating 28, summer radiators 40 degrees. But for a day he burned almost half of the tank, can anyone advise where the reason lies?

If the pump is installed on the return in front of the boiler itself, you heat the tank 24 hours a day.
If the pump was installed at the outlet from the 4D valve to the boiler, then OK.

The pump is installed at the outlet from the four-way line to the boiler (from the valve to the right). My return is now perfectly warmed up, but the combustion has increased drastically...

Do you have a non-return valve downstream of the storage tank charging pump? If not, you still heat the tank all the time.
Also, fuel consumption will be higher because you weren't letting as much heat into the building before installing the pump. The boiler, protecting itself from too-nicky return, closed the 4D valve and did not let heat into the installation.

Yes, I have a valve behind each pump. I'll give it a few days, maybe it'll warm up. I will also try to put lagging on the pipes in the boiler room, maybe that will help

If it is a new installation in a new house, it needs about a week to stabilize and about a season to dry the building.
So the first season is always the most expensive, especially the first week before you heat the floor and walls.

The cottage has been standing and has been inhabited since April, it managed to dry out over the summer, so far I smoked and it was quite economical, but the return was cold and stuck to the stove inside. Therefore, the installer added this additional pump on a short circuit. Now I have a correct return but it eats fuel until it rumbles, every now and then the work starts. 4-way valve open to about 5-7%, so that the radiators are slightly warm, because the underfloor heating takes care of the whole living area. One more thing - what should be the optimal temperature of the boiler? I have it set to 60 degrees, but maybe it's not enough?

Maybe control the short circuit pump based on the return temperature.
Return lower than 45*C turns on the pump. It will turn on periodically.
Also set it to the lowest power.
Please post a photo of what it looks like if you can.
Maybe someone will notice something.

I close the topic, the pump behind the stove plus some time to stabilize helped.