Aluminum wire was commonplace in residential building construction between the mid-1960s and the late 1970s as copper costs rose. Aluminum is a very good conductor, but its physical properties present specific problems that may result in overheating, connector failure, and even fire hazard if not handled well. The article discusses the unique problems inherent with aluminum wire in older houses and the recommended approaches to addressing them to ensure long-term reliability and safety.

Why Aluminum Wiring Was Utilized
In the 1960s and 1970s, copper costs skyrocketed, and construction professionals began using aluminum as an affordable substitute for home wiring. Aluminum provided a few perks in the following forms:
✅ Less expensive than copper
✅ Lighter and simpler to handle
✅ Excellent electrical conductivity

Aluminum possesses a unique set of physical and chemical characteristics compared to copper, which led to unforeseen problems in the long run.

Typical Issues with Aluminum Wiring in Older Homes
Thermal Expansion and Contraction

Aluminum expands and contracts further than copper when subjected to thermal changes.
This has the potential of loosening the wire over time at terminals, causing arcing, overheating, and fire hazards.
Oxidation

Aluminum reacts with air to create a layer of aluminum oxide.
Aluminum oxide is a poorer conductor than aluminum, which increases resistance and heat at the terminal point.
Galvanic Corrosion with Copper

If aluminum wires are wired directly to copper wires or copper terminals without connectors, a galvanic reaction is created.
The reaction speeds up corrosion, making the connection weak and more prone to failure.
Compatibility Problems with Typical Outlets and Switches

Electrical equipment that is made for copper wiring might not be rated for aluminum.
Typical switches and outlets can get overheated or fail when they are used with aluminum wiring.
Cold Flow

Aluminum is also softer than copper and more susceptible to "cold flow," in which the wire creeps or deforms under pressure of terminal screws.
This loosens the connection over time and raises resistance.
Symptoms of Aluminum Wiring Issues
Flickering lights
Discolored or warm switch plates and outlets
Tripped circuit breakers regularly
Burning odor near switches or outlets
Electrical panels or outlet buzzing sounds

Fixes for Aluminum Wiring in Older Houses
There are a number of safe and efficient ways to treat aluminum wiring problems in older homes:

✅ Utilize Aluminum-Compatible Lugs and Connectors

When connecting aluminum wires to copper or other metals, use Al/Cu-rated lugs or connectors specifically for mixed-metal connections.
Such connectors are normally pre-filled with an antioxidant compound to avoid oxidation and corrosion.
✅ Replace CO/ALR (Copper/Aluminum Rated) Outlets and Switches

Utilize switches and outlets specially rated for aluminum wiring.
CO/ALR devices are made to allow for the expansion and contraction of aluminum without loosening.

✅ Pigtailing with Copper Wire

Pigtailing a brief piece of copper wire (a pigtail) is one answer to joining aluminum wire to copper-only rated equipment.
Pigtails must be joined with approved Al/Cu wire connectors or crimped with a specialized tool.
✅ Use an Anti-Oxidation Compound

Before clipping the aluminum wire in a connector, apply a light coating of anti-oxidation compound.
This inhibits the development of aluminum oxide and lowers resistance where the connection is made.
✅ Rewire with Copper (If Possible)

Where there has been extensive failure or extensive remodeling, replacing the aluminum wiring with copper might be the best long-term solution to safety.
It is more costly but does away with the long-term hazards presented by aluminum wiring.
Safety Considerations
⚠️ Refrain from Standard Twist-On Wire Nuts – General wire nuts are not qualified for aluminum-to-copper terminations and will fail with the passage of time.
⚠️ Have a Licensed Electrician – Matters involving aluminum wiring demand professional skill and equipment. A skilled electrician can recognize and correct latent issues.
⚠️ Comply with Local Electrical Codes – Any work or replacement needs to meet current National Electrical Code (NEC) and regional building codes.

Conclusion
Old homes with aluminum wiring pose special problems, but they can be readily overcome with proper connectors, careful installation methods, and regular service. Al/Cu lugs, CO/ALR outlets, and effective pigtailing techniques are simple solutions to mixed-metal connections. By dealing with these problems now, homeowners can guarantee the reliability and durability of their electrical system.