Danfoss Thermostatic Valves

A thermostatic radiator valve (TRV) is a self-regulating valve mounted on radiators hot water heating system. The TRV controls the temperature of a room by adjusting the flow of hot water to the radiator. radiator thermostatic valves (air valves) are also available for steam radiators.

Several years ago the first ideas for heating controls has emerged, but it was not until 1943 when Mads Clausen, Danfoss' founder, invented the radiator thermostat, first, that the development of VTR has become serious. However, from the first invention to mass production for the European market, it took almost 15 years, and not until 1973 when the first oil crisis hit the world that the installation of TRVs really took speed.

VTR now have a market distribution and worldwide acceptance as an energy efficient technologies and competitive. Despite this there is still a huge potential for the implementation of that new VTR replacing older manual valves for the benefit of the environment and reduce energy costs for people around the world.

A TRV is composed of two parts: a valve that opens or closes to control the flow of hot water and a sensor that controls the opening of the valve. The sensor contains an actuator with sensitive material, which adjusts the valve opening as a function of temperature in the room via a physical connection between the cylinder and pin valve-spindle/cone.

The sensors are mostly plastic in various designs and shapes. The actuator typically includes a detection substance, such as wax, liquid or gaseous.

The valves are mainly made by the brass or bronze and have different sizes, shapes and connections to the radiator. Most manual valves radiator are mounted on the pipe connected to the radiator, but the valves can also be mounted as part of the radiator.

VTR devices are self-regulating, which control the temperature in the room temperature based on an individual setting of the heat load. VTR can work together with the external temperature controls, controls the flow of supply temperature, pressure and time control devices back.

The principle of self-regulation is shown in this animation. The general principle can be described this way:

1.The actuating device in the sensor is a steel container containing a substance detection, or wax, liquid or gaseous. All three substances expand or contract depending on the temperature in the room.

2.A spindle system in the sensor transfers the axial movement of the valve actuator by the interaction between the sensor rod and the valve stem. In the valve of a rubber cone attached to the valve stem interacts with the valve seat and thus regulates and controls the flow of hot water through the valve at the entrance of the radiator.

The process is completely autonomous and without complex electronic control. VRT keeps the room temperature at a desired level, even through fairly wide swings in indoor temperature due to external conditions such as sudden drops in temperature, solar radiation, wind speed or wind direction.

After installing TRVs, owners must get used to the principle of self-meaning they do not turn the thermostat up and down. When the ambient temperature varies, the valve opens or closes automatically to regulate the flow of hot water until desired temperature is reached. Only if the desired room temperature must be changed or if the windows are open or closed for the EV.