Aluminum wiring was used in residential homes primarily between 1965 to 1976. The wire is safe…it’s the connections that cause the problem. What happens is, because of the molecular properties of metal, when electricity passes through aluminum it heats up and expands. When the flow of electricity stops, it contracts and resumes it’s normal ambient temperature. This expansion and contraction can cause a loosening of the connection between the wire and the breaker or receptacle. Under load, once this connection is loose it starts to arc. The higher the electrical current of the device the more severe this problem may become. This problem is called “Cold flow”.
I remember being called to a residence here in Edmonton to investigate a problem with a power outage. I checked the panel and determined that there was aluminum wiring installed throughout the house. The master bedroom, half bath, second bedroom, and hallway were not working. The problem ended up being that the wall receptacle in the half bath was used primarily for hair dryers and curling irons. This was the first point in the circuit coming from the panel.
I opened the box and gently pulled out the receptacle. As I did, the sound of sizzling and a bright blue light filled the bathroom. When I finally got the receptacle fully extended to the end of the wires, I noticed that the only thing left was the plastic front face and the metal contacts of the plug. The remainder of the receptacle was in a puddle of plastic in the bottom of the box. “Cold Flow” had loosened the connection between the screw and the wire. With the high current draw from the hair dryer and curling iron the arcing had totally destroyed the bathroom receptacle. This is what was determined to be the cause of many fires in the past and that made aluminum wiring for residential construction a thing of the past.
Today, we have an acceptable method of solving this problem. We remove the original receptacle and switches, usually rated for Aluminum, and replace them with new devices, rated for Copper. We then pigtail (put two together under a wire connector or Marrett) the aluminum to a copper wire. This copper wire now gets put on to the new receptacle or switch and reinstalled. Copper and aluminum together will oxidize, so to prevent this problem we cover the aluminum wiring with a retail product that prevents oxidization. By doing this we have eliminated the problem of cold flow.
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