Markus, thanks a lot for your answer.
Another issue appeared to this Heating only system - Baseline modeling of DHW (Domestic Hot Water).
The Proposed model is having a gas fired boiler to provide hot water for heating and for preparation of DHW
The Baseline system for this project is system 9. There are no boilers there, just gas fired furnace.
The question is: How to model the DHW for the Baseline? Should this be Gas instantaneous water heaters or some other approach is to be applied? Also, how to model the circulation pump associated with the DHW device?