In an externally equalized expansion valve, is the external equalizer connected upstream or downstream of the sensing bulb?

In an externally equalized expansion valve, the external equalizer is connected downstream of the sensing bulb. This configuration ensures that the pressure at the equalizer line accurately reflects the pressure in the evaporator after the expansion process has occurred.

When the sensing bulb detects the temperature of the refrigerant in the evaporator, it responds to changes by adjusting the valve opening to control the flow of refrigerant. By connecting the external equalizer downstream, the pressure feedback helps the valve to maintain the desired superheat at the evaporator outlet. This design enhances the valve's ability to react to load changes and stabilize performance, promoting efficient refrigeration operation.

In contrast, if the equalizer were connected upstream of the bulb, it would receive pressure readings from the higher pressure side of the system, which would not provide an accurate representation of the conditions within the evaporator, potentially leading to improper valve operation. Thus, positioning the external equalizer downstream is critical for optimal system performance.