Myself and 2 neighbors have Buderus's. They are a "cold start" boiler. They do not maintain kettle temperature when there is no demand. They will only reach the aquastat temp when there is a call for heat, and the temp of the water in the boiler has dropped below the differential. I run my aquastat at 160 in the winter and 130 in the summer. I have a Buderus indirect hot water storage tank for domestic hot water. The tridicator gauges provided with these units are not particularly accurate so this may be why you saw the lower temp. It is possible for the unit to have a call for heat and never turn on the oil gun. The water jacket is insulated and they have a fair amount of thermal mass because of all the cast iron.
The 115 does not have a mixing chamber as whistlenut mentioned. The hot water leaves the top of the boiler and returns to the bottom. The 215 is where they have the mentioned mixing chamber thereby making for a unit that is almost impossible to "thermal shock". Also if the boiler has the Logomatic it will behave differently as well. Myself and my neighbors optioned ours up with typicla Honeywell controls and Riello burners.
My installed costs around 3K materials only. Did the job myself, about 6 years ago.
Last edited by 2001Sierra
on Sun Mar 14, 2010 11:00 pm, edited 1 time in total.