Aluminum Branch Wiring

aluminum branch wiring

The image (above) is a perfect example of the problems that are associated with Aluminum branch wiring. Note letters A and B (the insulation jackets are melted), which I will explain "Why" in the third paragraph and C (mixing copper wiring with aluminum wiring on the same breaker). Aluminum branch wiring cannot be mixed with copper branch wiring, and breakers cannot be double-tapped with two wires unless specified by the manufacturer. In such cases, the breaker connection will include a special clip for double tapping. Aluminum branch wiring is easily identifiable by its distinct aluminum color. However, it should not be mistaken for tin-coated copper wiring, which has a similar appearance. A key distinction is that aluminum branch wiring is a solid conductor, whereas tin-coated copper has different structural characteristics.

During the 1970s, solid aluminum branch wiring became a popular alternative to copper and was widely used across the United States. However, over time, aluminum wiring was linked to numerous house fires, leading many jurisdictions to prohibit its use in new installations. I strongly recommend against using solid aluminum branch wiring for any new projects. That said, if your home already contains aluminum wiring, there is no need to panic. When properly installed, aluminum wiring can be just as safe as copper. However, it is far less tolerant of improper installation. In the following sections, I will explain the electrical risks associated with aluminum wiring and provide guidance on how to ensure your home's wiring remains safe.

The primary issue with aluminum branch wiring is a phenomenon known as "cold creep." As aluminum wiring heats up, it expands, and as it cools down, it contracts. Unlike copper, repeated warm/cool cycles cause aluminum to gradually lose its tightness at connection points. To make matters worse, aluminum oxidizes (or corrodes) when in contact with certain metals, increasing the resistance of the connection. This increased resistance leads to excessive heat buildup, which further accelerates oxidation and corrosion. Over time, the wire may become extremely hot, potentially melting the insulation jacket or the fixture it is connected to, increasing the risk of fire.

aluminum wiring at outlet

Since aluminum wiring is most commonly found in homes built in the 1970s, I will outline the key safety considerations for its proper use. If you are purchasing a home with aluminum wiring or have discovered it after moving in, I strongly recommend hiring a licensed electrician to inspect the wiring for the following:

1) Fixtures such as outlets and switches connected directly to aluminum wiring must be specifically rated for it. Approved devices will be stamped with "Al/Cu" or "CO/ALR," with the latter being the updated standard. However, both are considered safe for use. These fixtures tend to be more expensive than standard ones but are essential for maintaining a safe electrical system.

2) Wires should be securely connected, wrapping at least three-quarters of the way around the screw in a clockwise direction. All connections must be tight to ensure proper conductivity and minimize the risk of overheating. However, repeatedly tightening the screws can worsen the issue. During an inspection, it is beneficial to carefully check and gently snug each connection to maintain a secure fit.

{Note that stranded aluminum wiring is still commonly used for the main service entrance cable at the main panel and should be included in the inspection.}

3) Push-in terminals pose a serious hazard when used with aluminum wiring. Any connections relying on push-in terminals should be upgraded to proper screw connections immediately to ensure safety.

4) There should be no signs of overheating, such as darkened connections, melted insulation, or "baked" fixtures. If any such damage is found, a licensed electrician should repair it, and the connection should be upgraded to a safer alternative.

5) Connections between aluminum and copper wires must be handled with special care. Current codes require that connectors used for this purpose be specifically marked for aluminum-to-copper connections. The NEC mandates that these wires be joined using special crimping devices and anti-oxidant grease. The tools and materials required for this process are expensive, making it impractical to do it yourself unless you can rent the necessary equipment.

{Note that regulations in this area are evolving quickly. It is advisable to consult with an electrical inspector if you plan to make more than one or two connections.}

6) Any non-rated receptacles can be connected to aluminum wiring using a short copper "pigtail" as described in point #5 above.

If, during the inspection of the exposed wiring in the home you are considering purchasing, I find no issues, you can consider the wiring safe. However, if there are signs of electrical problems in multiple areas (which will be noted on page 16 of your home inspection report), I recommend having a complete electrical inspection and potentially upgrading all branch wiring throughout the house. If the wrong receptacles are used, you can replace them with the proper type or have the electrician install pigtails. Having this work professionally completed by a licensed electrician typically costs around $15 per receptacle or switch, plus hourly labor.

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Last updated on Mar 02, 2025

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Aluminum Branch Wiring

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