In the past, low voltage wires and cables made of aluminum were widely used for house wiring. After a while, people realized how troublesome these cables can be.
Why these cables are even installed in the first place and why these cables are problematic will be answered later.
The term “aluminum building wire” refers to a specific type of electrical wiring used in residential buildings or homes that uses electrical conductors made of aluminum. Aluminum has a higher conductivity-to-weight ratio than copper, and as a result, it is used in wiring electrical networks such as power transmission lines and local power distribution lines.
It is also used in the electrical wiring of some airplanes. Aluminum wire has been used by utility companies to transmit electricity in power grids since the late 1800s and early 1900s. Copper wires cannot compete with it in terms of price or weight. Aluminum wire continues to be the material of choice for applications involving electrical power transmission and distribution.
For a brief period in the 1960s and 1970s, aluminum wire replaced copper wire in home construction across North America. The switch occurred at a time when copper costs were relatively high. At that time, electrical devices (sockets, switches, lighting, fans, etc.) were not designed according to the specific characteristics of the aluminum wire used.
In addition, there were some issues related to the characteristics of the wire itself, which made installations with aluminum wire significantly more prone to problems. In order to reduce the severity of the problems, updated manufacturing standards for wire and device have been devised. There is a potential fire hazard in older homes where older generation aluminum wiring is installed in branch circuits.
What is aluminum wiring?
Aluminum wire has been used as an electrical conductor for a considerable amount of time, particularly by utility power transmission lines long after the construction of modern electrical distribution systems began in the late 1880s.
These lines were used shortly after aluminum wire began to be used as an electrical conductor. Copper wire must have a larger wire gauge to carry the same amount of current as aluminum wire, however aluminum wire is still cheaper than copper wire for a specific application.
Aluminum has a density that is only 30.5% that of copper, but aluminum alloys used for electrical conductors are only about 61% as conductive as copper of the same cross-section. Consequently, the amount of current that one pound of aluminum can carry is equivalent to two pounds of copper.
Given that copper costs about three times the weight of aluminum (about $3/lb vs. $1/lb in 2017), aluminum wire with the same conductivity as copper wire costs one-sixth the price of copper wire.
The lighter weight of aluminum wires makes these electrical conductors particularly suitable for use in power distribution systems by utility companies. This is because the towers or supporting structures only have to support half the weight of the wires to carry the same current as the heavier wires.
When the North American housing boom occurred in the early 1960s and copper prices spiked, aluminum construction wire using AA-1350 grade aluminum alloy was made small enough for use in lower-load branch circuits. It was produced in homes.
This was done in the same period of time. In the late 1960s, problems and failures appeared related to branch circuit connections for construction wire made with aluminum alloy AA-1350. As a result, the use of that alloy for building wire was re-evaluated and it was determined that there is a need for newer alloys to produce aluminum building wire.
Complications related to aluminum wiring
When AA-1350 alloy aluminum wire was originally used in branch circuit wiring in the early 1960s, solid aluminum wire was installed in the same manner as copper wire using similar electrical equipment. This was done in order to ensure that there is no disruption to the electricity service.
Conventional connections of a power cord to an electrical device are usually made by wrapping the cord around a screw on the device, also called a terminal, and then tightening the screw. This method is usually used for smaller solid-wire branch circuits, such as 15-A or 20-A circuits. Around the same period, the use of steel screws, as opposed to brass screws, became more popular in the manufacture of electrical appliances.
Due to improper connection methods, different resistances of dissimilar metals, and very different coefficients of thermal expansion, as well as problems with the properties of solid wires, many of these terminals with solid aluminum wire began to fail over time.
This was because solid wires had problems with their properties. Overheated connections were a direct result of these connection failures caused by the heat generated by the electrical load.
Improper installation
Many aluminum wire terminals that were installed in the 1960s and 1970s continue to work without problems because they were installed correctly. However, complications may arise in the future, especially if the joints are not placed correctly in the beginning.
Improper installation, also known as poor performance, can be identified by: frayed wires, failure to use corrosion inhibitor, failure to wrap wires around terminal screws, wires wrapped around terminal screws in the opposite direction Incorrect and failure to apply sufficient torque to the connecting bolts.
Improper tightening of the connection screw with too much force can also lead to problems because it can damage the wire. This is especially true for the more flexible aluminum wires.
The ratio of creep and expansion coefficients
Most problems with aluminum wire are usually related to the older (pre-1972) AA-1350 solid aluminum alloy wire. This type of aluminum wiring is sometimes referred to as old-tech aluminum wiring.
This is because the properties of this wire cause significant expansion and contraction compared to AA-8000 series copper or aluminum wire. An older type of solid aluminum wire had particular problems due to a property called creep, which caused the wire to permanently deform or loosen over time under load.
Prior to the mid-1970s, aluminum wire had a slightly higher creep rate, but more importantly, aluminum wire had a critical coefficient of expansion that was significantly higher than that of steel screws, which were typically used instead of brass screws. It was different. Termination time in devices such as sockets and switches.
This was a problem because aluminum wire was critical because it had a coefficient of expansion that was significantly different from steel screws.
Due to the fact that aluminum and steel expand and contract at different rates when exposed to thermal loads, a joint may loosen over time. This is especially true for older terminals that were originally installed with insufficient torque on the screws, which when combined with aluminum creep, caused the connection to not install properly. Over time, securing loose joints becomes increasingly difficult.
Additionally, due to the large difference in thermal expansion rates of older aluminum wires and steel end screws, the connections tend to loosen over time, which in turn allows some additional oxide to build up on the wire. On the other hand, it was found that oxidation does not play an important role in the deterioration of the ends of aluminum wires.
Connecting aluminum wire to copper wire is another problem that may arise. In addition to oxidation on the surface of aluminum wires that can cause a poor connection, aluminum and copper are very different metals. As a result, galvanic corrosion may occur in the presence of an electrolyte and the stability of these connections may decrease over time.
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