In an HVAC system, what types of valves are there?


In an HVAC system, various valves are used, each with its specific function and application. Some are used for protection, some for controlling liquid flow, some for quick opening and closing, some for balancing flow, and others for automatically adjusting the temperature of mixed hot and cold water to provide a constant temperature output. Let me first introduce various types of valves and their uses briefly. Then, I will focus on thermostatic mixing valves.


Types of valves in HVAC

  1. Control Valves: These include two-way control valves and three-way control valves, both of which are used to control water flow and simple temperature regulation.

  2. Shut-off Valves: These include ball valves, gate valves, and globe valves, which are mainly used to cut off or open water flow.

  3. Balancing Valves: Static balancing valves and dynamic balancing valves are used to control and adjust the flow in the system.

  4. Regulating Valves: Electric regulating valves and pneumatic regulating valves receive different signals to control and adjust the flow.

  5. Mixing Valves: Thermostatic mixing valves automatically adjust the ratio of hot and cold water to provide a constant outlet temperature.

  6. Check Valves: These prevent liquid backflow, affecting the entire system.

  7. Air Release Valves: These can be automatic or manual and discharge air from the system, preventing air locks.

  8. Pressure Reducing Valves: These lower and stabilize the pressure in the system to protect equipment.

  9. Safety Valves: These prevent system pressure from becoming too high by releasing excess pressure to protect equipment.

The choice of each valve depends on the system's needs and functional requirements. Understanding the functions and characteristics of various valves is crucial for the installation and use of HVAC systems.

Next, I will introduce the various aspects of thermostatic mixing valves. In an HVAC system, the primary function of a thermostatic mixing valve (TMV) is to automatically adjust the mixing ratio of hot and cold water to provide a constant outlet temperature. This valve uses an internal temperature-sensing element to detect and adjust the water temperature, ensuring that the output water temperature remains within the set range, even if the inlet water temperature or pressure changes.


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Function of thermostatic mixing valve

  1. Providing Constant Water Temperature: The thermostatic mixing valve can adjust the mixing ratio based on the set target temperature to ensure stable output water temperature. This avoids inconveniences or safety issues caused by temperature fluctuations.

  2. Enhancing Comfort: By maintaining a constant water temperature, the thermostatic mixing valve provides a more comfortable water experience, especially during showers and baths, avoiding sudden changes in water temperature.

  3. User Safety Protection: The thermostatic mixing valve can prevent excessively high water temperatures, avoiding scalding risks. This is particularly important in homes, hospitals, schools, and other places where water safety must be ensured.

  4. Energy Savings: By precisely controlling the water temperature, unnecessary heating or cooling can be avoided, saving energy and reducing operating costs.

  5. System Balance and Efficiency: In complex HVAC systems, the thermostatic mixing valve helps maintain system balance and efficiency. For example, underfloor heating systems ensure the supply water temperature is appropriate, preventing damage to floor materials or affecting heating performance due to excessively high temperatures.

  6. Simplified Control and Maintenance: The thermostatic mixing valve can automatically adjust the water temperature, reducing the need for manual intervention and complex control systems, thereby simplifying operation and maintenance.

To determine whether a mixing valve's material and functionality meet the requirements, there are many international certifications for valves, including TMV certification, WaterMark certification, UPC certification, CE, etc. Among these, the most difficult to achieve is the TMV3 certification, while most companies can easily obtain the TMV2 certification, TMV3 is relatively challenging. These certifications and standards are important indicators of the quality and performance of thermostatic mixing valves. Consumers should look for these certification marks when selecting products to ensure the purchased valve meets relevant safety and performance requirements.

In summary, mixing valves play a crucial role in HVAC systems by providing stable water temperatures, enhancing comfort and safety, and optimizing system operational efficiency.

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