Where should the sensing bulb on a TXV be located for accurate refrigerant temperature?

The sensing bulb on a thermal expansion valve (TXV) is critical for accurately measuring the temperature of the refrigerant in order to control the flow of refrigerant into the evaporator. Placing the sensing bulb at the 4 or 8 o'clock position ensures that it is in a location where it will be properly affected by the refrigerant temperature, allowing it to respond effectively to changes.

At these positions, the bulb is less likely to be influenced by external factors such as heat from the compressor or other components, which could lead to inaccurate readings. This placement allows it to accurately assess the refrigerant’s superheat, leading to optimal expansion valve performance and, consequently, improved system efficiency.

In contrast, positioning the sensing bulb at the 12 o'clock position can expose it to direct sunlight or heat sources, causing it to read inaccurately. The midpoint of the suction line may not always provide consistent temperature readings due to variations in refrigerant flow. Finally, placing the bulb only at the end of the suction line does not allow it to maintain continuous and accurate temperature feedback necessary for effective TXV operation. Therefore, the 4 or 8 o'clock position is recognized as the optimal choice for accurate refrigerant temperature sensing.