Which metering device is most commonly used in commercial refrigeration systems over 3 tons?

The thermostatic expansion valve (TXV) is commonly used in commercial refrigeration systems that are over 3 tons due to its ability to adjust to varying load conditions effectively. The TXV controls the flow of refrigerant into the evaporator based on the temperature of the refrigerant and the load requirements of the system. This adaptability is crucial in larger systems where the cooling demand may fluctuate significantly.

By maintaining the proper superheat, the TXV optimizes refrigerant use and enhances system efficiency, preventing issues such as flooding of the evaporator and ensuring that heat absorption is maximized. In contrast, devices like capillary tubes or fixed orifices have fixed flow rates and lack the flexibility needed for larger, more variable refrigeration applications. While electronic expansion valves provide precision similar to TXVs, they are often more expensive and may not be as commonly implemented in all commercial refrigeration scenarios compared to the traditional use of TXVs in systems over 3 tons.