Tekmar Mod Boiler Control (tN4, 4-stg mod + DHW). Boiler Control 275 is designed to stage up to four condensing or non-condensing, modulating or on-off boilers using P.I.D. staging to accurately maintain temperature. Water temperature is controlled by Outdoor Temperature Reset for space heating applications or a fixed setpoint for Domestic Hot Water (DHW) tank heating or industrial process heating applications. control will also accept an analog 0-10 V (dc) signal from an Energy Management System (EMS) to control water temperature. Boiler Equal Run Time Rotation, pump exercising and stand-by system pump operation increase boiler plant reliability. control is tekmarNet?communication compatible allowing for internet connectivity using an optional Gateway 483.