Which of the following best describes a low-pressure appliance?

A low-pressure appliance is specifically defined in the context of refrigeration and air conditioning systems as one that utilizes refrigerants that have a saturation pressure below 45 psia (pounds per square inch absolute). This classification is important because it identifies the operating pressures at which these systems function, distinguishing them from high-pressure appliances.

Understanding this classification helps technicians apply proper handling and recovery techniques, as low-pressure handles refrigerants differently from high-pressure types, especially in terms of safety and compliance with regulations. Low-pressure systems typically involve refrigerants that evaporate and condense at lower pressure levels, which can influence system design and efficiency.

The other choices do not correctly describe a low-pressure appliance. While a saturation pressure above 170 psia fits into the definition of a high-pressure appliance, claiming that an appliance operates with a full charge of refrigerant does not pertain to the classification of pressure at all, as it speaks to operational status rather than pressure type. Lastly, saying that an appliance exclusively uses R-12 doesn't universally apply to all low-pressure systems, nor does it encompass refrigerants that may also be classified under low-pressure categories outside of just R-12.