Optimal Settings for Junkers Cerapur Midi ZWB 24-1AR Boiler in 70m2 Flat for Efficient Heating

Hello fellow specialists

I would like to briefly describe the situation.

For the first time in my life I rent a flat with gas heating. 70 m2 flat, ground floor, ceilings at a height of 2.1 m. Building from what I know brick 40 and supposedly insulated with Styrofoam 10. Floor tiles and panels. The problem is that this is only the first heating season after the modernization of this building. 3 apartments in the whole building. One of my 70 m2, the rest above 100 m2. In all boilers Junkers cerapur midi ZWB 24-1AR.

Please advise what settings on the stove to make in the apartment from 20-21 degrees and at the same time economically went out heating.
I would like to mention that a room regulator is installed, but it is either badly connected or broken because when I set, for example, 21 degrees, the regulator stops at 20.9 and cannot finish this 1/10 so one night it burned 17 m 3 of gas. I set the hot water temperature 42 degrees and 45 co. the stove switches on every 3 minutes and heats the water to 50 degrees, then 3 minutes to cool to 35 degrees and so on over and over again. At these settings, the furnace works despite the indications of the room regulator, however, all the time daily consumption is 8 m3 of gas.

In the living room connected to the kitchen I have 2 heaters - 120x60 and 100x90
while in the bedroom where the temperature still does not exceed 20 degrees 120x60
I don't count the third room because it can be colder there

on the radiators I do not have thermostats, only plastic nuts for tightening the spire

In the apartment above, the neighbor heats to 22 degrees with similar settings, and his daily consumption comes out on average, after a month of use 7.5 m 3. With the apartment 100 m2 and a height of 2.5 m.

I am asking for advice on how to set this stove optimally.

Upper flats usually burn less gas even at a larger area, due to heat losses. Next, the regulator must be of good quality, well put on and it is worth setting several time intervals on it. Next thermostats on radiators are mounted and positioned. Then you can also make some changes on the boiler electronics to extend the periods of heating breaks or boiler power needed for your apartment. Further, based on experience, select the appropriate flow temperature to reach the desired room temperature ... Questions should be directed to the installer. What parameters did he use in calculations when selecting heaters? What heat loss he calculated. What heat capacity the boiler has calculated ... etc.

Thanks for the answer. I will try to apply the above guidelines. I just wanted to ask how many degrees should the circulation pump cool down from the furnace ?? A pump set to 2 gear lowers the temperature within 13 minutes by 13 degrees. After switching on the furnace, heating of this water at a setting of 55 degrees goes quickly to the temperature of let's assume 53 degrees and later he heats the remaining 2 degrees for a good several minutes. Is this a correct sign of pump operation ???

Everything Ok but the electronics allow some corrections in the settings. Heating power can be selected according to the surface of the apartment. You can also affect the tact and hysteresis ... First of all, a good regulator not to overheat the apartment and be able to consciously save.

Maybe switch the pump speed to Roman III then it should work longer on the pump itself. Enter the service settings and see what the settings are, i.e. how much the temperature should fall until the burner is switched on again or the burner blocking time