Electrical wires are composed of either copper or aluminum conductors. Copper costs more and is heavier and less flexible.
Aluminum wire requires special anti-oxidant compounds at connection points. Most common house wiring uses copper. Between
1970 and 1973 or so, a small percentage of houses were wired with aluminum wire throughout the house. There are 2 issues with aluminum wiring:
Its conductivity changes when it oxidizes (rusts). This affects how well it carries electricity. If it resists conducting current too much, it will start to overheat.
It expands and contracts more when it heats and cools. This can cause connections to become loose and the problem gets worse.
For these reasons, aluminum wires are only to be connected to outlets and switches, etc. that have been tested, rated and marked "For
Aluminum Wire". Most switches and outlets are tested, rated and marked "For Copper Wire Only".
It should be noted that both copper and aluminum wiring could have loose connections that cause problems. We get calls to solve power problems for both copper and aluminum wired homes..
Helpful Hint: If a house has aluminum wiring, there are 5 options:
Do nothing? There are many houses with aluminum wire that have not experienced any problems. Knowing that your house has aluminum wires is no reason to panic but you should be alert to symptoms that may indicate problems: warm outlets or switches, flickering lights, etc..
Purple-wirenut pig-tailing. We find this method can be inconsistent. Using a special wirenut, the aluminum wires are connected to copper tail that is then used to connect to the normal outlets and switches. In the past, a special designed purple wire nut was used but there have been issues reported with the connections.
Pressure-crimp terminations. This is only available from a limited number of certified contractors who have have been trained with the process by the manufacture. This is also uses the special anti-oxidant compound but with a special tool to squeeze the connections.
Set-screw pressure-crimp terminations. Using special UL-listed set-screw connectors and a special tool, the aluminum wires are connected to copper wires. Then normal outlets and switches are installed. Connections that are too loose or too tight are not good. The special tool only lets you tighten up to the specified setting. We can do this type of installation for $65 per outlet, switch, light, etc.
Replace all aluminum wires with copper wires. The cost would vary depending on the house but roughly, expect a ranch house to be around $15,000 and a 2-story colonial to be around $25,000. A split level would probably be in between. Depending on basement and attic access, some holes and patching might be necessary.