If system pressure is significantly higher than the PT chart pressure, what does this indicate?

When system pressure is significantly higher than the PT (pressure-temperature) chart pressure, it indicates that the refrigerant is not behaving as expected under normal conditions. Specifically, this scenario suggests the presence of non-condensable gases in the system. Non-condensable gases, such as air or other gases that do not condense at the operating temperatures of the refrigerant, can elevate system pressure without contributing to the cooling process. This elevated pressure can prevent the refrigerant from condensing properly in the condenser, leading to inefficient cooling and possible damage to the system.

The other options pertain to different issues: being undercharged would generally result in lower pressures, a faulty compressor may lead to symptoms that entail variable pressures, and contamination of the refrigerant can cause other system malfunctions, but not necessarily a pressure higher than what is indicated on the PT chart. Therefore, the correct interpretation of significantly higher pressure is indeed linked to the presence of non-condensable gases.