What must be selected and assembled by the equipment manufacturer in a self-contained system?

In a self-contained refrigeration system, the equipment manufacturer is responsible for selecting and assembling all parts of the refrigeration system. This includes the compressor, condenser, evaporator, expansion devices, and any necessary piping and controls. The integration of these components is critical to ensure that the system operates efficiently as a cohesive unit.

When all parts are assembled by the manufacturer, they can ensure compatibility and proper functioning, which minimizes issues that could arise from mismatched components. Additionally, having the manufacturer handle the system assembly supports quality control and makes troubleshooting easier post-installation.

The other options are not comprehensive enough. Selecting only the cooling fluid or just the compressor unit would not provide a functional refrigeration system; both the fluid and the compressor are vital, but they must work in conjunction with other components. Similarly, only focusing on the electrical system is insufficient, as a complete refrigeration setup involves much more than just electrical components.