I have recently had two Viessman Vitodens 100 (120000 btu) gas boilers installed to supply radiant heat for our cast iron radiators, and which replaced our 40 year old 400,000 btu monster. So when I looked at my January gas bill I notice only 10% in fuel savings compared to January last year. Surprising especially since last January year was almost 5 degrees colder. Now the target temperature for the radiator water on the controller was was set to 170 F. Could this be too high?
We have also had some problems with the pressure dropping bellow 12kpa on about 6 occasions causing the system to shut down. While the source of the problem looks like it comes from the HBX controller, this issue has not been confirmed. Another contributing factor of the system shut down was that the water intake flow value's threshold was below 10kpa. The valve has been rectified to above a threshold of 15kpa and the system has not shut down in almost two weeks. There was some leaking from the poor welds in the old piping but I would say the total water loss would be less than 1 litre( 1/4 gallon) day
Is the pressure drops the cause of the inefficiency or is the low efficiency due to improper setting or other unknown problem on the HBX controller?