Which type of refrigerant system is least likely to leak refrigerant into the building space being cooled?

• A. The indirect system
• B. The direct expansion system
• C. The cascade system
• D. The open-drive system

Answer: (A)

The key idea is keeping refrigerant out of the building air by using a secondary cooling loop. In an indirect system, the refrigerant stays in a separate plant and only transfers cooling to the building through a secondary fluid (like water or glycol) that runs through coils inside the occupied space. Since the space itself isn’t tied to the refrigerant circuit, a leak would release the secondary coolant rather than the refrigerant, making refrigerant entering the living or working space unlikely.

In contrast, direct expansion systems have the refrigerant in the evaporator coils inside the cooled area—so any leak would release refrigerant directly into the room air. Cascade systems involve refrigerant loops that include equipment in the space being cooled as well, so leaks can still introduce refrigerant into that space. Open-drive systems, by their nature, involve configurations where refrigerant handling isn’t fully contained, increasing the chance of refrigerant entering the space. So, the indirect system best minimizes the likelihood of refrigerant leaking into the building space.