1. Ball Valves: These are used for on/off control of water flow in HVAC systems. They are durable and provide a good seal.

2. Gate Valves: Used primarily for isolation purposes, gate valves control the flow of liquids by lifting a gate out of the path of the fluid.

3. Globe Valves: These are used for regulating flow in a pipeline. They offer good throttling capability and are used in applications where precise flow control is required.

4. Butterfly Valves: These are used for isolating or regulating flow. The closing mechanism is a disc that rotates to open or close the valve.

5. Check Valves: These allow fluid to flow in one direction only, preventing backflow. They are used in various HVAC applications to ensure fluid flows in the desired direction.

6. Thermostatic Expansion Valves (TXV): Used in refrigeration cycles, TXVs control the amount of refrigerant released into the evaporator, based on the temperature and pressure.

7. Solenoid Valves: These are electrically controlled valves used for fluid or gas flow. They are commonly used in HVAC systems for automatic control.

8. Pressure Relief Valves: These are safety devices that release pressure if it exceeds a certain limit, protecting the system from damage.

9. Zone Valves: Used in hydronic heating systems, zone valves control the flow of heated water to different zones or areas of a building.

10. Control Valves: These can include various types (like modulating valves) and are used in HVAC systems to control the flow of liquids or gases according to the signals from a control system.

11. Mixing Valves: These combine hot and cold water to achieve a desired temperature and are used in various heating applications.

12. Needle Valves: Known for precise flow control, needle valves are used in applications where accurate flow measurement is critical.

Each type of valve serves a specific purpose and is selected based on the requirements of the HVAC system, such as the type of fluid, pressure, temperature, and the level of control needed.