Abstract: A hydronic heating system comprises a water line, one or more boilers, and a control. In operation, the water line facilitates a circulation of water through a building and the boiler(s) heat the water as the water flows through the water line. The control calculates a system energy load for operating boilers. The calculation of the system energy load is a function of a set-point water temperature for the hydronic heating system, a supply water temperature of water flowing relative to a supply point of the water line, a return water temperature of water flowing relative to return point of the water line and a flow rate of water flowing relative to a flow sense point of the water line.

Abstract: A hydronic heating system for a building includes condensing and non-condensing boilers in a hybrid arrangement. A control apparatus receives information from one or more condition sensors, such as air temperature or water flow, and calculates heating load requirements. The control apparatus then independently selects and operates the various boilers of the system to optimize boiler efficiency and operating characteristics.