What safety mechanism prevents compressor damage during low outdoor temperatures?

The presence of low ambient temperature switches or locks is essential for protecting the compressor in heat pump systems when outdoor temperatures drop. These switches detect when the temperature outside falls below a certain threshold and subsequently inhibit the compressor's operation to prevent it from running under conditions that could cause it to freeze or sustain damage.

When the outdoor temperature decreases significantly, the risk of refrigerant in the system returning to the compressor as a gas rather than a liquid increases, potentially leading to inefficient operation or damage due to liquid slugging. Low ambient temperature switches act as a safety measure to prevent this scenario, ensuring that the system does not operate in conditions that could compromise the integrity of the compressor or overall system functionality. The activation of these switches effectively protects the equipment by avoiding operation during excessively low temperatures.

In this context, the other options do not specifically address the issues related to low outdoor temperatures and their impact on compressor safety. Low pressure switches and high pressure cutoffs are focused on maintaining safe operational pressures rather than temperature-related concerns. Thermostatic expansion valves, while crucial for regulating refrigerant flow, do not serve as a direct safety mechanism against low outdoor temperatures.