Information AboutAluminium Wire |
| CATEGORIES ABOUT ALUMINIUM WIRE | |
| electrical wiring | |
| aluminium | |
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HISTORY Usage within utilities In the mid 1956s , utility companies began using Aluminium Wire for transmission of Electricity within their Power Grids . It had advantages over the typical Copper Wire in that it was lighter, more flexible, and less expensive. Aluminium wire in power grid applications was very successful and is still used today. Increased copper prices In the mid 1960s , the price of copper spiked due to economic reasons and as a result, aluminium wire was manufactured in sizes small enough to be used in homes. One thing that was known at the time was that aluminium wire requires one Wire Gauge larger than copper to carry the same Current . For example, a standard 15- Amp branch circuit wired with No. 14 Gauge copper requires No. 12 gauge aluminium. When first used in Branch Circuit wiring, aluminium wire was not installed any differently than copper. Typical connections from electrical wire to electrical devices, also called Terminals , are usually made by wrapping the wire around screw terminals and tightening the wire. Over time, many of these terminations to aluminium wire began to fail. These connection failures generated heat under electrical load and the result was devastating in some cases. Some deaths due to fires were reported. In the late '60s, a device specification known as CU-AL (or AL-CU ) was created that specified standards for devices intended for use with aluminium wire. Larger screw terminals designed to hold the wire more suitably were the general improvement here. Unfortunately, CU-AL switches and receptacles failed to work well enough with aluminium wire, and a new specification, called CO/ALR (meaning copper-aluminium revised) was created. These devices employ indium-plated screw terminals which are designed to act as a similar metal to aluminium, to expand at a similar rate, and to form a gas tight seal against oxidation. CO/ALR applies only to standard light switches and receptacles; CU-AL is still an acceptable rating for high Voltage receptacles and circuit breakers. ACM, or NUAL, wire In the early 1970s , a new aluminium Alloy was created, known as 8000 series or "ACM" aluminium wire that is the current aluminium wire used today. It is also sometimes referred to as "NUAL." Many believe that this alloy of wire, when used with proper CO/ALR devices and aluminium rated twist-on connectors can be just as safe as copper wiring. It is, however, ''extremely'' rare in branch circuit wiring. Most likely, a home with aluminium wiring has the older 1350 series alloy. This alloy was specifically designed for power transmission purposes and did not suit branch circuit use very well. PROBLEMS WITH ALUMINIUM WIRES There are actually many reasons why these connections failed. The two core reasons are Oxidation of the aluminium itself, and aluminium's Coefficient Of Expansion . Aluminium oxidation All metals oxidize freely when exposed to open air. The only problem with aluminium is that its oxide is not an electrical Conductor , but rather an electrical Insulator . Consequently, the flow of Electron s through the oxide layer can be greatly impeded. This is known as a high Resistance connection and it will produce significant heat under electrical load. The oxidation of aluminium wire can be accelerated when it makes contact with a dissimilar metal. In many cases, the screw terminals initially used with aluminium wire were the same as that used with copper, and they were often made of Brass , which is a dissimilar metal. Coefficient of expansion Aluminium's coefficient of expansion is also a problem. It is possible to form a reasonably gas tight connection at terminals simply by ensuring that it is torqued properly. However, aluminium works against this because it expands and contracts under thermal load. As the wire expands under the screw terminal, it begins to deform slightly. Over time, this cycle results in the connection loosening slightly and allowing oxidation to occur on the wire between itself and the screw terminal. Joining aluminium and copper wires Another issue with aluminium wire is the joining of aluminium wire to copper wire. As aluminium and copper are dissimilar metals, oxidation occurs and these connections can become unstable after a very short time. Special connectors have been designed for the purpose of joining aluminium to copper wire, such as the Marrette No. 63 and No. 65 and the Ideal Twister No. 65. These wire nuts use a special antioxidant paste to prevent oxidation of the connection. There is some debate over whether these products are effective. Larger aluminium wires (No. 8 gauge) and larger are generally not regarded as a problem in any installation. The larger sizes offer better options for terminations and due to their use primarily in high voltage applications, are most often worked on by professionals. Properly terminated large-gauge aluminium wiring should be regarded as safe. It is still sometimes used today in homes and condos to power large appliances such as electric ranges and dryers. UPGRADING ALUMINIUM-WIRED HOMES There are several "upgrades" that are commonly done to homes with aluminium branch circuit wiring:
Always call electrical professionals when aluminium wire is found. The risk of fire with aluminium wire is said to be 55 times higher than that of copper. REFERENCES
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