Re: Can someone explain?
The main reason aluminum is bad for house wiring, is that copper is 'springy' and aluminum isn't, at least far less than copper. When the wire is connected to the outlet, switch, etc., it is usually under a screw. The copper will push back when compressed, maintaining a good electrical connection, whereas aluminum doesn't. This leads to a connection that will degrade over time, and cause a 'hot spot' where the wire meets the outlet or switch, increasing the risk of fire.