Thermostatic expansion valves (TEVs): Most factory settings target a superheat of approximately how many degrees Celsius at the evaporator outlet?

Introduction / Context:
The thermostatic expansion valve (TEV or TXV) regulates refrigerant flow to maintain a set superheat at the evaporator outlet, preventing liquid slugging of the compressor while ensuring good evaporator utilization.

Given Data / Assumptions:

• Superheat is defined as T_vapour_out − T_saturation at evaporating pressure.
• Factory or commissioning targets are sought for comfort cooling systems.
• Line losses and bulb placement are correct.

Concept / Approach:
A modest superheat ensures that all liquid has boiled off before the suction line, while not starving the coil. Industry practice typically targets about 5 K (≈ 5°C) at the evaporator outlet, with acceptable ranges often 4–8 K depending on application.

Step-by-Step Solution:

Verification / Alternative check:
Commissioning guidelines from OEMs and service manuals typically cite superheat in the 4–8°C band, with 5°C as a frequent nominal value for initial setting.

Why Other Options Are Wrong:

• 10°C or 15–20°C superheat is sometimes used for special cases, but “most” valves are not set that high by default.
• 2°C is too low and risks liquid carryover.

Common Pitfalls:
Measuring superheat at the wrong location; not correcting for pressure drops; or chasing charge issues with TXV adjustments.

Final Answer:
5°C