Key Technical Differences Between Aluminum and CCA

The critical distinction between single-metal aluminum and Copper-Clad Aluminum lies in the metallurgical bonding process. Per ASTM B566-04, CCA conductors must feature a minimum of 10% copper by weight as a metallurgically bonded outer layer. Copperweld CCA conductors exceed this requirement with 27% copper by mass, consisting of oxygen-free copper (OFC) bonded to an 8000 Series aluminum core.

This copper layer eliminates the aluminum-oxide insulating layer that caused termination failures in 1960s-era single-metal aluminum wiring. The copper conducts current at the wire surface where skin effect concentrates AC current flow, while the aluminum core provides structural support and weight reduction.

Understanding the difference between aluminum and Copper-Clad Aluminum (CCA) conductors helps if you know the history. The two conductor materials are considered dissimilar metals in Code. From the very beginning, it's always been that way.

Timeline of How Aluminum and Copper-Clad Aluminum (CCA) Developed in the NEC:

• 1901:  Aluminum wire first recognized by the National Electrical Code as a conductor material.  Sees limited application as building wire for branch circuits.  Copper is the only other conductor material permitted as a conductor material of continuous current.
• 1958:  Aluminum wire for indoor residential applications first tested by Kaiser Aluminum Company in Ravenswood, West Virginia, a town where a Kaiser wire mill is located.  The apartment consists of 94 units.  Test results are mixed due to a statistically relevant sample size of deteriorating terminations (points of electrical contact with receptacles, switches and splices).  
• 1961:  Vietnam War Era begins. Copper Prices begin to rise due to the nation’s need for brass munitions.  Brass is a copper alloy.    
• 1964:  Gulf of Tonkin event escalates Vietnam conflict and causes copper shortages in the USA. Copper building wire becomes expensive and scarce.  
• 1965: Despite the mixed test results from the Ravenswood pilot program, Kaiser Aluminum Introduces KA-Flex NM cable into the US. Market.  KA-Flex NM cable is a type of residential electrical conductor made from utility grade aluminum.
• 1966:  Following Kaiser’s lead, other wire and cable manufacturers begin to produce NM cable made with aluminum.  Copper remains scarce and expensive.
• 1966 - 1970:  Due to a rash of hundreds of electrical fires in residences wired with aluminum NM cable, electrical inspectors from around the nation call for bans of aluminum wiring within their jurisdictions.  Run-away heating is reported at terminal screws of wiring devices at normal operational current ratings.  Splices are said to over-heat and melt.  The origin of the problem is traced to the natural aluminum-oxide layer inherent to aluminum that acts as an insulator at termination points.  The thermal instability of utility grade aluminum compounds the problem.
• 1967:  Research begins at Texas Instruments (USA) and Kabel Metal (Germany) to create an aluminum wire with the ability to maintain safe long-term electrical connections. Independently, cladding technology is invented by TI and KM to make Copper-Clad Aluminum wire. TI is more focused on markets serving electrical conductors; Kabel Metal is more focused on data conductor markets.
• 1969:  Mr. John Fan of Texas Instruments submits Public Inputs to the National Electrical Code to permit the use of Copper-Clad Aluminum (CCA) as a conductor material.  In the cladding process, the aluminum oxide layer naturally occurring on the surface of aluminum is removed and replaced with a thick layer (27% of the mass of the wire) of oxygen free copper.  The copper is metallurgically bonded to the aluminum core, creating a conductive and thermally stable bimetal.
• 1970:  Mr. Fan of Texas Instruments approaches Underwriters Laboratories to begin the testing of CCA to substantiate the safe performance of CCA for his Public Input submissions to the National Electrical Code.  Testing is successful, and safety at points of termination is proven.
• 1971:  The leadership of Underwriters Laboratories calls for the formation of an Ad-Hoc Committee to begin remediation and damage control of the single-metal aluminum NM cable.  The Ad-Hoc Committee consists of members from industry, regulators, aluminum cable manufactures, test labs, and industry associations.  The process of ceasing the production of Aluminum NM cables begins.    
• 1971:  The National Electrical Code (NEC) accepts the data on CCA provided by UL and Mr. Fan, and accepts CCA into the 1971 NEC Edition as one of only three conductor materials permitted to carry continuous current.  Texas Instruments scales up to build CCA cladding lines in its facility in Attleboro, Massachusetts.  
• 1971:  UL begins an extensive and independent fact-finding study of single-metal aluminum wire terminations.  More thermally stable grades of aluminum are tested, as well as utility grades.  Test results are inconclusive and distributed to the public upon request.  
• 1972:  The Consumer Product Safety Commission was founded by an act of congress, the Consumer Product Safety Act, to bring uniformity of regulation to all product standards at a national level, rather than have each individual state regulate standards independently.  The CPSC’s stated mission is to “protect the public against unreasonable risks of injuries and deaths associated with consumer products.”  The CPSC was created for all products.  The CPSC’s creation did not result from house fires caused by failing aluminum wire terminations.  
• 1972: Texas Instruments begins to sell CCA wire rod to wire and cable manufacturers to produce NM cables.  Copper remains scarce and expensive due to Vietnam.  Single-metal Aluminum wire is banned in most US markets by local authorities having jurisdiction.
• 1972 – 1975:  Copper prices hit new highs and copper building wire continues to be scarce. CCA NM-B cable is widely distributed and installed throughout the US. Most NM cable producers convert some of their production to CCA.
• 1974:  Kabel Metal sells the rights for CCA cladding lines to Copperweld primarily to support Copperweld’s customers making coaxial cables for the fledgling telecommunications industry.  Copperweld to build a new facility in Fayetteville, Tennessee which began production in 1976.
• 1975:  Vietnam Conflict Ends…Copper sees a sharp decline in price.  NM cable made with CCA sees drop in demand.
• 1976 - 1979:  Copper prices are choppy.  Copper scarcity is less.  CCA becomes ever less competitive against single-metal copper conductors.  Wire and Cable manufacturers begin to return to copper as price and supply make copper NM cable economical.
• 1980:  Copper prices plummet.  Texas Instruments ceases production of CCA.  Cladders are mothballed.  Electrical wire & cable manufacturers return to copper.  All production of NM cable made with CCA ceases.
• 1980 – 2004:  Copper prices remain too low for CCA to participate in the electrical conductor market.  However, CCA flourishes in data conductor markets against copper for key technical reasons.  Data conductor markets allow CCA to thrive.
• 2004:  Copper commodity markets begin to be securitized, allowing for stabilization and escalation of global copper pricing.  Rising copper prices allow for CCA electrical conductors to become economical again.
• 2006:  US manufacturers of CCA begin to explore export markets for electrical conductors made with CCA.  No consideration given, to reintroducing CCA back into the USA as an electrical conductor material.
• 2012 - Current  Export markets for CCA as an electrical conductor grow, mostly in those countries in Latin America and the Caribbean where the NEC is nationalized.  These markets served as test markets.  These markets utilize the same 120/240 Volt 60 Hz systems as the USA.  They use the same equipment and devices within their circuits as the USA.    
• 2015:  Copperweld buys the rights to the Texas Instruments CCA cladding technology through the acquisition of CommScope Bimetals.  
• 2016 - 2017:  Copperweld conducts a research project to study the feasibility of returning CCA to the electrical conductor market.  Nationwide, installations of NM cable made with CCA from the 1970’s are inspected to determine the state of safety.  Copperweld joins the International Association of Electrical Inspectors to learn more about how the NEC is regulated and how CCA is perceived by the regulatory community.  It is found that few inspectors have any experience with CCA.
• 2018:  After determining that CCA is still a safe and Code-compliant option for electrical contractors, Copperweld formally re-introduces NM-B cable (building wire) to the US market.

NEC Classification and Requirements

The National Electrical Code recognizes three conductor materials for continuous current: copper, aluminum, and copper-clad aluminum. Per NFPA 70 (NEC) Article 310.106, these are distinct classifications with separate ampacity tables and installation requirements.

CCA conductors are sized using the aluminum column in NEC Table 310.16, but require devices rated CU/AL or CO/ALR for terminations. Single-metal aluminum requires the same device ratings but has different oxidation characteristics that led to its removal from the residential market in the 1970s.

CCA vs Copper: Ampacity and Sizing by Circuit Rating

Standards and Certifications

• NFPA 70 (NEC): National Electrical Code, defines CCA as a distinct conductor material since 1971
• ASTM B566-04: Standard specification for copper-clad aluminum wire, establishes minimum copper content and bonding requirements
• UL Listing E492024: Copperweld CCA building wire safety certification
• NEC Article 310.106: Conductors for general wiring, lists copper, aluminum, and copper-clad aluminum as permitted materials
• NEC Table 310.16: Allowable ampacities of insulated conductors, includes separate columns for aluminum and copper-clad aluminum

Copperweld CCA conductors meet or exceed all applicable NEC, UL, and ASTM standards for building wire applications. All Copperweld products are manufactured to ASTM B566 specifications with third-party NRTL certification.

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