The Boiler Control 274 is designed to stage multiple boilers using Outdoor Temperature Reset. It can be used in applications ranging from a single zone of baseboard, multiple baseboard and fan coil zones, to dedicated domestic hot water heating in commercial buildings. This control regulates a single heating water temperature through Outdoor Temperature Reset and/or setpoint/DHW target control. It is capable of controlling (stage and rotate) up to 4 on/off boilers as well as the system pump.