Renovations and Aluminum Wiring
The electrical system is one of the most important components in a house because of the potential hazard faulty wiring creates. Aluminum wiring was used in much of the new home builds in Canada during the 60’s until the mid 70’s. Chosen for it’s cost effectiveness compared to copper, one can see houses entirely wired with aluminum and some with a combination aluminum and copper. A study conducted by the Consumer Protection Safety Commission concluded that 1 in 5 homes wired with aluminum had potentially dangerous connections.
How to recognize aluminum wiring
Aluminum wire is not as good of an electrical conductor as copper, so a larger wire is used. For example, aluminum wire No. 12 has about the same ampacity as copper wire No. 14. The ampacity is the maximum current that a wire can safely carry. The outer covering of the cable will be marked about every 12 inches with the word aluminum or an abbreviation such as “ALUM” or “AL. Where aluminum wire is pr
esent, special service connectors must be used. Wall switches and receptacles should carry the marking “CU-AL”. This indicates that the equipment is suitable with aluminum wiring. This marking would also appear on circuit breakers. Electrical receptacles, wall switches and fuse boxes designed for use with copper wiring are not satisfactory for use with aluminum wiring.
Hazards with aluminum wiring
Two chemical reactions that take place on the surface of pure aluminum. The result of both is exactly the same — the wire heats up and can reach temperatures high enough to ignite nearby combustible materials. The first chemical reaction causes corrosion when two dissimilar metals meet – in this case, between the aluminum wire and the standard brass outlet terminals. In the second chemical reaction, pure aluminum wire oxidizes as soon as its insulation is removed, exposing the wire to air. Either reaction coats the wire surface with a layer that increases resistance to current and generates heat. Also, aluminum wire expands and contracts at more than copper wire. It tends to “creep” out from under a terminal screw connection. This leads to a poor connection and overheating at the switch, receptacle or terminal.
Extremely warm cover plates, switches or receptacles. Mysteriously inoperative switches or receptacles, and smoke.
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