Condensing boilers and baseboard hydronic heating systems

Condensing boilers offer the potential for significant improvements in the efficiency of heating systems. However most of the market for these boilers is existing homes where hydronic heating systems use baseboard convectors. These are designed for operation at higher circulating water temperatures than will allow condensing operation of these boilers. This study explores the use of an outdoor reset control in combination with condensing boilers in which to quantify the fraction of the heating season actual operation in the condensing mode can be achieved. The study involves both experimental work with one oil-fired condensing boiler in the lab and in the field as well as development of a method that can be used to estimate the fraction of the year that condensing can be achieved for any application. Results are dependent upon fuel type and existing baseboard oversize factor.