While copper and aluminum can work together, they require special connectors to join these different metals.
The problem begins when two dissimilar metals meet; a chemical reaction takes place that causes them to oxidize. Oxidation causes a high-resistant connection to develop with an unwanted voltage drop across the connection. Voltage drop leads to three potential problems: low voltage resulting in equipment damage, wasted energy and poor efficiency -- and the most dangerous of all -- the connection heats up and can contribute to fires at high-ampere loads.
Expansion and Contractions
Aluminum and copper do not expand and contract at the same rates as they heat up and cool down. This difference can cause wire splices or connections to work loose. A loose connection, whether at a splice in a junction box or at a terminal screw on a switch or receptacle can cause arcing. Loose connections are forerunners to arc faults, arc flash and fires in electrical systems.
Copper and Aluminum Connections
Electricians can splice copper and aluminum wires together by using special copper-aluminum connectors.
You cannot splice them using a standard wire nut without dire consequences.
Connectors identified with a "Cu/Al" splice contain a chemical compound that combats the oxidation that would normally take place when joining aluminum and copper.
