Tekmar Modulating Boiler Control. Boiler Control 265 is designed to stage multiple modulating boilers using Outdoor Temperature Reset. It can be used in applications ranging from baseboard or radiant heating systems, 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 control. It is capable of controlling (stage and rotate) up to 3 modulating boilers by using a native 4-20 mA (or 0-20 mA) signal that can be converted to 2-10 V (dc) or 0-10 V (dc), as well as system pump.