| When first used in branch circuit wiring, aluminum | | | | connections, wires wrapped the wrong way |
| wire was not installed any differently than copper. | | | | around the binding screws, and aluminum |
| Due to increased copper costs in the mid 1960's, | | | | conductors used in push-back connections or with |
| aluminum wiring became more prevalent in wiring | | | | devices meant only for copper. Because the |
| homes. It was known at the time that aluminum | | | | connections were made incorrectly, a chain of |
| wire requires larger wire gauge than copper to | | | | events of failures erupted. The connection was |
| carry the same current. | | | | loose to begin with due to improper tightening |
| For example, a standard 15-amp circuit breaker | | | | torque, and the physical properties of aluminum / |
| wired with No. 14 gauge copper requires No. 12 | | | | steel interface tended to loose the connection |
| gauge aluminum. Typical connections from | | | | over time. Aluminum and steel have significantly |
| electrical wire to electrical devices, also called | | | | different rates of expansion which would increase |
| terminals, are usually made by wrapping the wire | | | | the resistance and temperature at the termination |
| around the screw terminals and tightening the | | | | point. Similar problems occurred when aluminum |
| wire or pushing the wire through the back of the | | | | conductors were incorrectly terminated in the |
| outlet. Over time, many of these terminations to | | | | push-in connections intended only for copper wire. |
| aluminum wire began to fail due to improper | | | | Corrosion is often cited as a contributing cause of |
| connection techniques and dissimilar metals. These | | | | aluminum connections. In 1980 the National Bureau |
| connection failures generated heat under electrical | | | | of Standards performed a study to determine |
| load and resulted in overheated connections. | | | | what caused the high resistance at aluminum / |
| History of Aluminum Wire | | | | steel connections in receptacles. The study |
| Electricity is transmitted from the utility generating | | | | revealed that the formation of intermetallic |
| stations to individual meters using almost | | | | compounds (alloys of aluminum and steel) caused |
| exclusively aluminum wiring. In the U.S., utilities | | | | the high resistance terminations, not corrosion or |
| have used aluminum wire for over 100 years. It | | | | aluminum oxide. The thin, protective layer of |
| takes only one pound of aluminum to equal the | | | | oxide on aluminum conductors contributes to the |
| current carrying capacity of two pounds of | | | | excellent corrosion resistance of aluminum. When |
| copper. The lightweight conductors enable the | | | | terminations are made correctly, the oxide layer |
| utility to run transmission lines with half the | | | | is broken during the termination process allowing |
| number of supporting structures. The utility | | | | the necessary contact to be made between the |
| system is designed for aluminum conductors, and | | | | conducting surfaces. |
| utility installers are familiar with installation | | | | One of the most fundamental principles of |
| techniques for the types of aluminum conductors | | | | electrical safety for wiring buildings is that high |
| used in utility applications. Prior to 1972, the | | | | temperatures are hazardous. Heat is a major |
| aluminum wire was manufactured to conform to | | | | contributor to potential electrical hazards. A |
| 1350 series alloy. This alloy was specifically | | | | compromised connection creates additional heat. |
| designed for power transmission purpose. Due to | | | | The additional heat contribution can "snowball" |
| its mechanical properties the 1350 alloys were not | | | | problems. Sometimes if sufficient heat is created, |
| suitable for use in branch circuitry. At this juncture | | | | it can start a fire. Even if the heat does not |
| in time a "new technology" of aluminum wire was | | | | directly start a fire, the heat can melt and or burn |
| developed, known as AA-8000 series which is the | | | | away insulation, which can create a short that |
| current aluminum wire used today for branch | | | | may arc. Electrical arcs often reach temperatures |
| circuitry, however it is extremely rare to find in | | | | in excess of 10,000 Fahrenheit. Aluminum wired |
| branch circuit wiring. This type of wire when | | | | connections in homes have been found to have a |
| installed properly can be just as safe as copper | | | | very high probability of overheating compared to |
| wire. | | | | copper wired connections. |
| Problems with Aluminum Wires | | | | Upgrading aluminum wired homes |
| Aluminum wires have been implicated in house | | | | There are several "upgrades" that are commonly |
| fires in which people have been killed. Reports of | | | | done to homes with pre-1974 aluminum branch |
| fires with aluminum wiring generally show that | | | | circuit wiring:o Ensuring that all devices are rated |
| poor workmanship led to failures. Poorly made | | | | for use with aluminum wire. Many are not, since |
| connections were too often the cause. There | | | | they do not meet the CO/ALR specificationo |
| were several possible reasons why these | | | | "Pigtailing" which involves splicing a short length of |
| connections failed. The two core reasons were | | | | copper to the original aluminum wire for use with |
| improper installation and the difference between | | | | devices not CO/ALR ratedo COPALUM a |
| the coefficient of expansion between aluminum | | | | sophisticated crimping system that creates a cold |
| wire and the termination used in the 1960's. | | | | weld between copper and aluminum wire, and is |
| Feeder and branch circuit wiring systems were | | | | regarded to be a permanent, maintenance free |
| designed primarily for copper conductors. | | | | repair. These connections are sometimes too |
| Aluminum wiring was evaluated and listed by | | | | large to be installed in existing enclosures. Surface |
| Underwriters Laboratories for interior wiring | | | | enclosures or larger enclosures may be installed to |
| applications in 1946; however it was not used | | | | remedy this problem.o Completely rewiring the |
| heavily until 1965. At that time copper shortages | | | | house with copper instead. |
| and high prices made the installation of aluminum | | | | When deciding to repair or replace any electrical |
| branch circuit conductors a very attractive | | | | installation, a qualified professional should be |
| alternative. At the same time, steel screw | | | | consulted. The majority of homes wired with the |
| became more common than brass screws on | | | | general purpose circuits wired with aluminum are |
| receptacles. As aluminum wire was installed more | | | | now over 30 years old. The likelihood of |
| frequently, the industry discovered that changes | | | | experiencing any problems unique to having |
| were needed to improve the means of | | | | aluminum is slight. |
| connecting and terminating smaller aluminum wire. | | | | Any electrical system should be evaluated every |
| Installation methods for utility grade aluminum, or | | | | 10 years by a qualified electrical professional to |
| series AA- 1350 alloy were also different and | | | | determine if it is likely to operate safely under the |
| workmanship was an important factor in making | | | | increased loads in different rooms being used |
| reliable connections. | | | | differently, i.e. home office or bathrooms with |
| The most often identified culprits for poor | | | | larger dryers. |
| workmanship involved: incorrectly tightened | | | | |