When connecting conductors, which should be placed over the other, aluminum or copper?

When connecting conductors, placing aluminum over copper is the preferred practice due to the differences in the properties of the two metals. Aluminum has a lower density than copper, which makes it lighter but also more prone to oxidation. When aluminum is placed over copper, the aluminum conductor's expansion and contraction during thermal cycling may create a stronger connection without damaging the underlying copper.

Furthermore, aluminum connections are less likely to suffer from galvanic corrosion when properly installed above copper, as this arrangement can minimize moisture retention and avoid direct contact with dissimilar metals that could lead to corrosion issues. This method ensures that the connection maintains integrity over time, promoting safety and reliability in electrical installations.

Using copper over aluminum could lead to potential issues such as overheating at the junction due to differing rates of thermal expansion and the possibility of creating a weak electrical connection in the longer term. Therefore, placing aluminum over copper is the appropriate choice in this scenario.