What helps keep condensers drained?

The option that accurately answers the question about keeping condensers drained is related to liquid receivers. Liquid receivers are components used in refrigeration and air conditioning systems to temporarily store the liquid refrigerant that has condensed in the condenser. Their primary purpose is to ensure that all the liquid refrigerant is collected and does not return back into the system, which helps maintain the proper functioning and efficiency of the condenser.

By holding the liquid refrigerant, the receiver allows for a steady flow to the expansion valve, preventing the condenser from flooding. This drainage is essential for the longevity and efficiency of the refrigeration cycle, as it prevents liquid refrigerant from entering the compressor, where it could cause damage.

The other options—mechanical filters, expansion valves, and evaporators—serve different functions within the refrigeration system. Mechanical filters are primarily used to remove contaminants from the refrigerant, expansion valves control the flow and pressure of refrigerant to the evaporator, and evaporators are involved in absorbing heat from the environment, where the refrigerant evaporates into gas. While all these components play critical roles in the system, they do not specifically assist in draining the condensate from the condenser like the liquid receiver does.