Aluminum Building Wire 40 Years Later
Aluminum Building Wire
Today's aluminium building wire is both SAFE AND RELIABLE. However, the issues of the past continue to tarnish the reputation of aluminum building wire and hinder widespread acceptance of what is, in some ways, a SUPERIOR PRODUCT to copper.
Standards and requirements were put in place over 30 years ago, yes you read it correctly, over 30 years ago by the electrical industry. Governing boards of the industry took the appropriate steps that require and thus provide for safe and reliable aluminum building wire installations. Surely there are those reading this and thinking “it may be safe and reliable, but not as safe and reliable as copper.” The fact is that aluminum is just as safe and just as reliable as copper, and it actually provides certain advantages over copper.
THE PAST IS THE PAST…SO ARE THE ISSUES WITH ALUMINUM BUILDING WIRE
Because of a shortage of copper in the 1950’s, due to World War II and a housing boom in the 1960’s, an urgent need for a new residential and commercial building wire material arose. This urgent requirement was filled by aluminum. As often happens when there is an urgent need for something, there was a lack of due diligence such as appropriate testing and listing by the laboratories of the day. Instead, aluminum was made as a direct substitute for copper and began going into homes and businesses constructed at the time.
This first aluminum building wire was constructed from the same electrical grade aluminum being used in transmission lines. Consider the characteristics needed for electrical transmission lines:
• A lightweight conductor so transmission towers would not need to be too robust and expensive to build,
• The highest conductivity possible to minimize electrical losses over such long transmission lengths,
• A conductor with a high tensile strength so spans could be maximized and the number of transmission structures minimized.
This formula or mix of high tensile strength and high conductivity resulted in very low material elongation as well as other properties that are not desirable characteristics in a building wire conductor.
During this same time, and again due to materials shortages, the brass screws in electrical devices were replaced with steel screws. Once more due to the urgent nature and time constraints, driven by the need, this change also happened with a lack of appropriate testing and listings.
40 Years Later...
No one thought that a compatibility issue between steel screws and aluminum wire existed. However, the next decade would prove that a simple substitution of a screw without the appropriate testing can have consequences. The characteristics of each of the materials was such that under the heating and cooling experienced during operation, the device terminations could loosen resulting in high resistance connections and heating. Ultimately these connections resulted in residential fires, and the rest is history.
DURING THE 60’S AND 70’S PROBLEMS INVOLVED 10 AWG AND 12 AWG BRANCH CIRCUIT CONNECTIONS
The most likely and often identified reasons for aluminum branch circuit failures were:
Poor workmanship is generally recognized as the primary source of failed connections. Results of poor workmanship included incorrectly tightened connections, wires wrapped the wrong way around binding screws, and aluminum conductors used in push-in connections or with devices meant only for copper. If a connection was loose due to improper tightening torque, the connection would tend to loosen over time.
Thermal expansion differences
The coefficients of thermal expansion for aluminum and brass are similar while the thermal expansion for aluminum and steel is not. Copper’s thermal expansion is similar to both steel and brass. This is why the change to steel screws did not cause copper connector failures. Steel and aluminum have significantly different rates of thermal expansion. Because of this difference, the two materials expand and contract at different rates under load cycling. This causes the connection to gradually develop a smaller contact area resulting in increased resistance. As the resistance increased, the temperature at the termination point would also increase.
Creep of a conductor
Creep is a property of all metals, and each metal has a unique rate of creep. Creep is the measurement of the rate of change of a material’s dimensions over a period of time when exposed to a force at a particular temperature. The old aluminum conductors used EC grade aluminum (AA-1350) for building wire which has a higher creep rate than copper building wire.
The difference in creep between aluminum and steel resulted in connector failures.
A NEW ALUMINUM…
In 1968 Southwire Company led the way in aluminum building wire technology with the advent of triple e® aluminum alloy, resulting in the very first AA-8000 series aluminum alloy. This change resulted in the higher aluminum standards that are still observed today. Starting with a clean slate, metallurgists developed an aluminum alloy that possessed the characteristics desirable in an aluminum building wire. In 1972, and for the first time, aluminum building wire was manufactured with its own metal, not a poor fitting hand-me-down from electrical utility applications. One alloy does not fit all!
This new aluminum alloy, developed and patented by Southwire, bridged the gap in key metal characteristics between copper and aluminum. In AA-8000 series aluminum alloy characteristics such as elongation, thermal stability, compressive creep and flexibility were much closer to that of copper. In addition to a new aluminum alloy, aluminum building wire and devices were being tested and listed for compatibility. The use of compatible materials, proper testing and listing resulted in a reliable aluminum electrical wiring method. In 1981, the NEC® began requiring aluminum alloy conductors for 12, 10 and 8 gauge conductors. In 1987 NEC® began requiring AA-8000 series aluminum conductors. This has remained unchanged and can be found in the 2008 NEC® Section 310.14. AA-8000 series aluminum alloy conductors have properties that are significantly different from the old AA-1350 aluminum conductors. To confirm your cable has these conductors, look for the designation “AA-8176” on Southwire’s cable print legend. For other aluminum building wire products, make sure there is an “AA-8…” followed by three other digits.
In addition, copper/aluminum compatible (CO/ALR) devices were required for aluminum wire branch circuits and listed by UL. These devices were developed to be compatible with 10 and 12 AWG aluminum conductors. Due to the cost of these connectors and devices, it is no longer economical to use these sizes in aluminum.
Today, aluminum AA-8000 alloy is fully recognized by industry standards and is required in all aluminum building wire installed per the NEC.® This new aluminum is generally compact stranded according to ASTM B-801. Compact stranding reduces the diameter of the conductor by 9-10%. Equal ampacity AA-8000 aluminum and copper conductors can usually be installed in the same size conduit because of the compact stranding. Annex C in the 2008 NEC® includes tables for determining conduit fill when using compact stranded conductors. These tables can be used for both compact stranded aluminum and copper conductors.
FIRST IMPRESSIONS ARE HARD TO CHANGE
Even though aluminum was poised for the comeback it deserved, market conditions and lack of understanding prevented it from reaching it’s full potential. Copper prices at the time were relatively low so little motivation existed to try something new. First impressions are hard to change and although some considered it as a new alternative, others still perceived it as the same wire used in the 50’s and 60’s.
Aluminum building wire is something few people in the residential and commercial electrical industry don’t have a passionate opinion about. More often than not, you will find this opinion is based on 40-year-old facts, and a misunderstanding of those facts. Aluminum building wire, through the efforts of manufacturers like Southwire, and organizations such and the NEC® and UL,® is a proven safe and reliable system.
And don’t forget about the advantages of aluminum building wire over copper, particularly in the larger sizes (6AWG- 900kcmil). It is much lighter and more economical. This means easier installations, fewer injuries, and pound-for-pound more conductivity. Those that have embraced feeder sized aluminum building wire, are reaping the benefits, and may very well be hoping you walk away from this information clinging tight to your old misconceptions since they could be bidding their next job against you.
So why tell this story? With the rise in copper prices over the past few years renewed interest in aluminum building wire is gathering. Many contractors and owners find themselves looking for an alternative to provide relief from rising copper prices. Unfortunately, they are still being misinformed that the very solution they hope for does not exist. Well it does and it has for over 35 years. It’s called AA-8000 series aluminum alloy. And Southwire Company developed it in 1968. So now when you hear someone say “aluminum causes fires” you can reply with the facts about today’s aluminum building wire:
A problem that happened 40 years ago, failure of utility grade aluminum and a simple steel screw, is simply not relevant to the aluminum building wire installed today. With the development of an improved aluminum alloy, AA-8000, increased NEC® and UL® requirements, and a proven track record of over 30 years, aluminum building wire is just as safe and just as reliable as copper.
DID YOU KNOW?
• Material shortages after WWII and a housing boom in the 1960’s caused the switch from copper to aluminum in building wire.
• Pre-1972 aluminum wire is referred to as either AA-1350 aluminum, EC aluminum or utility grade aluminum because it was the same construction used in utility wire.
• The National Electrical Code® has permitted the use of aluminum wire since 1901.
• Southwire developed and patented the first AA-8000 Series aluminum alloy in 1968 setting a standard for the manufacturing of aluminum building wire that exists today.
• In the 80’s, UL® and NEC® required new connectors and devices assuring reliability of aluminum building wires performance.
• It takes only one pound of aluminum to equal the current-carrying capacity of two pounds of copper.