If the evaporator coil horizontal return line of a container refrigeration system is less than 0.875" (2.21 cm) in diameter (considered small); the thermostatic expansion valve sensing bulb should be attached where on the return line?

Correct Answer: Option B — on the upper surface of the line

For small suction lines measuring under 0.875 inches, the thermostatic expansion valve sensing bulb is mounted on the upper surface of the horizontal line to prevent false readings caused by oil pooling in the bottom.