You are commissioning a new refrigeration system with R-404A. The manufacturer specifies a target superheat of 5-7°C. After initial startup, you measure the suction pressure at 450 kPa gauge and the compressor inlet temperature at -2°C. What adjustment should you make to the TXV?

Question: You are commissioning a new refrigeration system with R-404A. The manufacturer specifies a target superheat of 5-7°C. After initial startup, you measure the suction pressure at 450 kPa gauge and the compressor inlet temperature at -2°C. What adjustment should you make to the TXV?

Answer options: ✅ Increase the superheat setting (turn adjusting stem clockwise).

• Decrease the superheat setting (turn adjusting stem counter-clockwise).
• No adjustment is needed, as the superheat is within range.
• Increase the subcooling setting at the condenser.

Correct answer: Increase the superheat setting (turn adjusting stem clockwise).

Explanation: For R-404A, at 450 kPa gauge (551 kPa absolute), the saturation temperature is approx. -5.5°C. Actual superheat = -2°C - (-5.5°C) = 3.5°C. This is below the target range, so the TXV needs to be adjusted to increase superheat, meaning turning the adjusting stem clockwise to close it slightly. This ensures proper evaporator feeding and compressor protection.