NATE Air Conditioning and Heat Pumps Practice Exam 2025 – All-in-One Guide to Master Your Certification!

In wiring diagrams, solid heavy lines typically represent factory-installed line-voltage wiring. This practice is grounded in the convention of using different line styles to indicate the source and type of wiring. Solid heavy lines are utilized to clearly distinguish high-voltage connections that come pre-installed from the manufacturer, which is vital for safety and clarity in installation and maintenance processes. Recognizing these lines helps technicians understand which parts of the system are powered by line voltage, allowing for proper handling when performing repairs or diagnostics.

The other options pertain to either low-voltage wiring or field-installed components, which would usually be depicted using different line styles such as lighter lines or dashed lines, emphasizing that they differ from factory-installed configurations.