___________________ wire is never allowed in the DC system of an RV.

In the DC system of an RV, aluminum wire is not permitted due to its inherent properties compared to copper. While aluminum wire is lighter and less expensive than copper, it has a higher electrical resistance, which can lead to excessive heat generation under load. This can increase the risk of electrical failure or fire hazards, especially in a confined space like an RV where safety is paramount.

Copper wire, whether stranded or solid, is preferred because it has superior conductivity and lower resistance, providing a more reliable and safer electrical system. Additionally, stranded copper wire is often used in RVs due to its flexibility, making it easier to handle and install in tight spaces. The use of appropriate wire gauge, such as 12 gauge for many applications in DC systems, ensures that the wiring can adequately handle the required current without overheating.

By prohibiting aluminum wire in DC systems, safety is prioritized, minimizing the risk of electrical issues that could arise from using materials that are not suitably conductive or reliable for RV applications.