If an R404A system has a suction pressure of 29 psi and a head pressure of 239 psi, what is the superheat?

To calculate superheat in an R404A refrigeration system, both the suction pressure and the corresponding saturation temperature must be determined first. The suction pressure of 29 psi can be converted to temperature using a refrigerant pressure-temperature chart specific for R404A. At a suction pressure of 29 psi, the saturation temperature is approximately 18 degrees Fahrenheit.

Superheat is determined by the difference between the actual temperature of the vapor in the suction line (measured at the outlet of the evaporator) and the saturation temperature of the refrigerant at that suction pressure. If the measured vapor temperature incoming to the compressor is around 28 degrees Fahrenheit, the superheat can be found by subtracting the saturation temperature (18 degrees Fahrenheit) from the measured temperature (28 degrees Fahrenheit), which gives a superheat of 10 degrees.

Thus, the correct answer is based on the accurate application of superheat calculation principles, leading to the determination that the system's superheat is indeed 10 degrees.