Tempering valves and thermally actuated valves contain a thermal sensing component that opens or closes in response to temperature changes. They are used to regulate the temperature of hot water and prevent scalding. Thermally actuated valves and tempering valves consist of an operating valve and a thermostatically-controlled bypass valve. Water that enters a fixture at a desired temperature flows through the operating valve and then out the fixture. Water that enters a fixture at an excessively high temperature flows through a hot water tempering valve, bypassing the operating valve. Using a thermal actuator element, the bypass valve continuously senses the temperature of the water until a safe temperature is achieved. The bypass valve then closes, and water is routing to the operating fixture.

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 Selecting tempering valves and thermally actuated valves requires an analysis of performance specifications, actuation methods, and connection types. Performance specifications include valve size, pressure rating, number of ports or ways, media temperature, and valve flow coefficient. Suppliers specify valves according to metric or English (imperial) measurements. Some tempering valves and thermally actuated valves are actuated manually, by a hand wheel or crank, or with mechanical devices such floats and cams. Others are actuated by electric, pneumatic, electro-hydraulic, or electro-hydraulic methods. There are many connection types for tempering valves and thermally actuate valves. Examples include compression fittings, bolt flanges, clamp flanges, union connections, tube fittings, butt welds, and socket welds. Tempering valves and thermally actuated valves with internal or external threads for inlet or outlet connections are also available. AWWA certified valves meet the requirements of the American Water Works Association (AWWA).

Applications

Tempering valves and thermally actuated valves are often used in water supply applications. A watt tempering valve is a type of thermally actuated valve that mixes hot and cold water by using a hydraulically-operated thermostat in the tempering valve. The thermostat opens a spring-loaded valve in the cold water inlet, mixing cold water with hot water from a water heater or boiler. These thermally actuated valves and tempering valves can be preset to a specific temperature, usually between 80 to 120 degrees Fahrenheit. In some cases, a tempering valve may allow an installer to adjust the flow rate. Thermally actuated valves and tempering valves are also used to control the flow of steam from boilers to radiators in order to regulate heating or shut off the flow of oil to the crankcase in an engine in case of fire.