The Danfoss AVTB DN 25 is a direct-acting combined thermostatic temperature controller designed for automatic control of water temperature in hot water storage tanks, heat exchangers, oil preheaters and other heating equipment. The valve operates completely independently – without the need for electrical power or compressed air – solely on the principle of thermal expansion of the thermostatic actuator.

The controller closes as the temperature rises and opens as it falls, thereby maintaining the set medium temperature in the system. It consists of a control valve, a thermostatic head with bellows element, a capillary tube and a temperature sensor. The supply includes a sensor with an external diameter of 9.5 mm and a length of 180 mm for accurate temperature sensing at the installation point.

Version 003N5116 is equipped with an external thread (R 1"), is intended for a temperature range of 20–60 °C and a capillary tube length of 2 m. This version is referred to as “fast” – the insulating disc is fitted to the controller directly at the factory, ensuring protection against the influence of the valve temperature on control accuracy. The valve must be installed in the return line (the sensor temperature must be higher than the temperature in the valve body).

Features

• Direct-acting control without the need for an external power supply (neither electrical power nor compressed air is required)
• Closes as temperature rises – ideal for protecting the system against overheating
• Thermostatic actuator consisting of a bellows, capillary tube and temperature sensor
• Can be installed in any position – flow direction indicated by a cast arrow on the valve body
• Insulating disc factory-fitted for stable control within the 20–60 °C temperature range
• Fast response to temperature changes (“fast” version)
• Adjustable temperature by means of a manual knob directly on the controller
• Robust construction with the long service life typical of Danfoss products
• Service kits available for easy maintenance and repairs