Tekmar 263 Boiler Control Two Stage / One Modulating Boiler, DHW & Setpoint The Boiler Control 263 is designed to stage multiple boilers or operate a modulating boiler 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, setpoint, and DHW target control. It is capable of controlling (stage and rotate) up to 2 on/off boilers, a single 2 stage boiler, or 1 modulating boiler as well as the system pump.