The Viessmann 7819967 Temperature Sensor #3 Boiler #5 DHW is a precision temperature-sensing component designed to monitor domestic hot water (DHW) temperature in compatible Viessmann boiler systems. It works by detecting temperature changes and transmitting accurate readings to the boiler’s control system, allowing the equipment to regulate heating operation efficiently. https://www.partshnc.com/7819967-viessmann-sensor-35-boiler-dhw