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Aluminum Wiring
By Nick Gromicko, Rob London
and Kenton Shepard / Reprinted with permission
Between approximately 1965 and 1973, single-strand aluminum
wiring was sometimes substituted for copper branch-circuit wiring in residential
electrical systems due to the sudden escalating price of copper. After a decade
of use by homeowners and electricians, inherent weaknesses were discovered in
the metal that lead to its disuse as a branch wiring material. Although properly
maintained aluminum wiring is acceptable, aluminum will generally become
defective faster than copper due to certain qualities inherent in the metal.
Neglected connections in outlets, switches and light fixtures containing
aluminum wiring become increasingly dangerous over time. Poor connections cause
wiring to overheat, creating a potential fire hazard. In addition, the presence
of single-strand aluminum wiring may void a home’s insurance policies.
Inspectors may instruct their clients to talk with their insurance agents about
whether the presence of aluminum wiring in their home is a problem that requires
changes to their policy language.
Facts and Figures
| On April, 28, 1974, two people were killed in a house
fire in Hampton Bays, New York. Fire officials determined that the fire was
caused by a faulty aluminum wire connection at an outlet. |
| According to the Consumer Product Safety Commission (CPSC),
"Homes wired with aluminum wire manufactured before 1972 ['old technology'
aluminum wire] are 55 times more likely to have one or more connections reach
"Fire Hazard Conditions" than is a home wired with copper." |
Aluminum as a Metal
Aluminum possesses certain qualities that, compared with copper, make it an
undesirable material as an electrical conductor. These qualities all lead to
loose connections, where fire hazards become likely. These qualities are as
follows:
| higher electrical resistance. Aluminum has a high
resistance to electrical current flow, which means that, given the same
amperage, aluminum conductors must be of a larger diameter than would be
required by copper conductors. |
| less ductile. Aluminum will fatigue and break down more
readily when subjected to bending and other forms of abuse than copper, which
is more ductile. Fatigue will cause the wire to break down internally and will
increasingly resist electrical current, leading to a buildup of excessive
heat. |
| galvanic corrosion. In the presence of moisture,
aluminum will undergo galvanic corrosion when it comes into contact with
certain dissimilar metals. |
| oxidation. Exposure to oxygen in the air causes
deterioration to the outer surface of the wire. This process is called
oxidation. Aluminum wire is more easily oxidized than copper wire, and the
compound formed by this process – aluminum oxide – is less conductive than
copper oxide. As time passes, oxidation can deteriorate connections and
present a fire hazard. |
| greater malleability. Aluminum is soft and malleable,
meaning it is highly sensitive to compression. After a screw has been
over-tightened on aluminum wiring, for instance, the wire will continue to
deform or “flow” even after the tightening has ceased. This deformation will
create a loose connection and increase electrical resistance in that location.
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| greater thermal expansion and contraction. Even more
than copper, aluminum expands and contracts with changes in temperature. Over
time, this process will cause connections between the wire and the device to
degrade. For this reason, aluminum wires should never be inserted into the
“stab,” “bayonet” or “push-in” type terminations found on the back of many
light switches and outlets. |
| excessive vibration. Electrical current vibrates as it
passes through wiring. This vibration is more extreme in aluminum than it is
in copper, and, as time passes, it can cause connections to loosen. |
Identifying Aluminum Wiring
| Aluminum wires are the color of aluminum and are easily
discernible from copper and other metals. |
| Since the early 1970s, wiring-device binding terminals
for use with aluminum wire have been marked CO/ALR, which stands for
“copper/aluminum revised." |
| Look for the word "aluminum" or the initials "AL" on the
plastic wire jacket. Where wiring is visible, such as in the attic or
electrical panel, inspectors can look for printed or embossed letters on the
plastic wire jacket. Aluminum wire may have the word "aluminum," or a specific
brand name, such as "Kaiser Aluminum," marked on the wire jacket. Where labels
are hard to read, a light can be shined along the length of the wire. |
| When was the house built? Homes built or expanded
between 1965 and 1973 are more likely to have aluminum wiring than houses
built before or after those years. |
Options for Correction
Aluminum wiring should be evaluated by a qualified electrician who is
experienced in evaluating and correcting aluminum wiring problems. Not all
licensed electricians are properly trained to deal with defective aluminum
wiring. The CPSC recommends the following two methods for correction for
aluminum wiring:
| Rewire the home with copper wire. While this is the most
effective method, rewiring is expensive and impractical, in most cases. |
| Use copalum crimps. The crimp connector repair consists
of attaching a piece of copper wire to the existing aluminum wire branch
circuit with a specially designed metal sleeve and powered crimping tool. This
special connector can be properly installed only with the matching AMP tool.
An insulating sleeve is placed around the crimp connector to complete the
repair. Although effective, they are expensive (typically around $50 per
outlet, switch or light fixture). |
Although not recommended by the CPSC as methods of permanent repair for
defective aluminum wiring, the following methods may be considered:
| application of anti-oxidant paste. This method can be
used for wires that are multi-stranded or wires that are too large to be
effectively crimped. |
| pigtailing. This method involves attaching a short piece
of copper wire to the aluminum wire with a twist-on connector. the copper wire
is connected to the switch, wall outlet or other termination device. This
method is only effective if the connections between the aluminum wires and the
copper pigtails are extremely reliable. Pigtailing with some types of
connectors, even though Underwriters Laboratories might presently list them
for the application, can lead to increasing the hazard. Also, beware that
pigtailing will increase the number of connections, all of which must be
maintained. Aluminum Wiring Repair (AWR), Inc., of Aurora, Colorado, advises
that pigtailing can be useful as a temporary repair or in isolated
applications, such as the installation of a ceiling fan. |
| CO/ALR connections. According to the CPSC, these devices
cannot be used for all parts of the wiring system, such as ceiling-mounted
light fixtures or permanently wired appliances and, as such, CO/ALR
connections cannot constitute a complete repair. Also, according to AWR, these
connections often loosen over time. |
| alumiconn. Although AWR believes this method may be an
effective temporary fix, they are wary that it has little history, and that
they are larger than copper crimps and are often incorrectly applied. |
| Replace certain failure-prone types of devices and
connections with others that are more compatible with aluminum wire. |
| Remove the ignitable materials from the vicinity of the
connections. |
In summary, aluminum wiring can be a fire hazard due to inherent qualities of
the metal.
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