You've raised some excellent and complex points about aluminum wiring and wire connectors! Let's break down the ideal #65 wirenut (and its alternatives) and address your concerns.

What Makes the Ideal #65 (or Similar) Wirenut Special?

You're right – the key differences between a standard wirenut and an AL/CU rated connector like the Ideal #65 (or equivalent from other manufacturers like Tyco/AMP/Polaris) are:1. No-Ox Compound (or similar corrosion inhibitor)

This is the crucial element. The compound serves several critical functions:

Breaks Down Oxide Layer

Aluminum readily forms an oxide layer on its surface when exposed to air. This oxide is highly resistant to electrical current. The compound helps break down this oxide, allowing for a better initial connection.

Prevents Further Oxidation

By excluding air and moisture, the compound prevents further oxidation of the aluminum.

Improves Conductivity

The compound bridges any small gaps between the conductors, increasing the contact area and improving conductivity.

Reduces Corrosion

Dissimilar metals (like copper and aluminum) in the presence of moisture can create a galvanic cell, leading to corrosion. The compound helps prevent this.2.

UL Listing for AL/CU Combinations

This is a crucial safety certification. It means the connector has been tested and approved for use with aluminum and copper conductors. The listing specifically validates that the connector with the compound can maintain a reliable connection under load and varying temperature conditions. The listing for CU-CU is different than a AL-CU connection.3.

Design for Proper Pressure

AL rated connectors may have a specific design (such as a tighter spring or internal ridges) to maintain consistent pressure on the conductors. Aluminum is softer than copper and can "cold flow" over time, reducing contact pressure. The pressure of a wirenut isn’t the only thing making the connection but the surface area of the strands.

Expansion/Contraction and the Role of No-Ox

You're correct that the no-ox compound alone isn't going to drastically change the expansion and contraction rates of the different metals. However, it mitigates the problems caused by those differing rates. Aluminum expands and contracts more than copper. This can lead to the connection loosening over time. The compound helps maintain a conductive pathway even as the conductors shift slightly.

Pre-Twisting Wires and Loose Connections

Pre-twisting wires can help create a more solid mechanical connection, but it's generally

not recommended for AL/CU connections using these types of connectors. Why not? The intent of the AL rated connector is to cold form the strands together and compress the entire bundle as the wirenut is tightened. Pre-twisting can make this more difficult and lead to uneven pressure distribution. The Focus is on Pressure

With aluminum, maintaining consistent pressure is paramount. The wirenut, when properly installed, is designed to provide that pressure.

Inspection is Key

The UL listing relies on specific installation instructions, and pre-twisting typically isn't part of those instructions. If you are pre-twisting, it is likely not properly inspected and not a safe connection.

Heating Problems with Same-Type Conductors

You're right – you can absolutely have overheating issues with copper-to-copper connections! This is usually caused by:

Loose Connections

The most common culprit. This increases resistance and generates heat.

Overloading the Circuit

Exceeding the ampacity rating of the conductors or the circuit breaker.

Corrosion

Even with copper, corrosion can occur, especially in damp or corrosive environments.

Poor Workmanship

Damaged conductors, insufficient insulation stripping, or improperly tightened connections.

Amperage, Time, and AL/CU Connections (Without No-Ox)

This is a tricky question because it depends heavily on the specific conditions:

Without no-ox (or a suitable compound)

An aluminum/copper connection will degrade rapidly. The oxide layer will increase resistance, leading to heat. The connection may initially carry the load, but it will quickly become unstable.

Within Hours/Days

Without proper protection, a significant load (close to the circuit breaker rating) could cause the connection to overheat and fail (melt, ignite insulation, or even cause a fire) within hours or days. Even a smaller load will cause gradual degradation.

The Danger is Unpredictability

The exact time to failure is unpredictable due to variations in the initial connection quality, ambient temperature, and load profile.

EC Practices: Pigtailing with Standard Wirenuts and No-Ox

This is a common point of debate. Many electricians have used the pigtail method with a standard wirenut and No-Ox for years with perceived success. However:

Not UL Listed

This method is not UL listed for AL/CU connections. It's a field-expedient method, and its long-term reliability is questionable.

Code Violation

Using a connector not listed for the specific application is a code violation in most jurisdictions.

Potential Liability

In the event of a fire or electrical failure, you could face increased liability if you used a non-listed method.

Aluminum Rated Connectors are Preferred

It is always better to use the UL listed Al-Cu connector for the job.

Residential Branch Circuit AL Wiring

With residential AL branch circuits, safety is paramount. Here's a summary of best practices:

Use UL Listed AL/CU Connectors

This is the safest and most code-compliant approach.

Follow Manufacturer's Instructions

This is critical for proper installation.

Anti-Oxidant Compound

Always use the specified anti-oxidant compound.

Do Not Pre-Twist

Let the connector do the work of compressing and forming the connection.

Tighten to Proper Torque

If the connector specifies a torque value, use a torque screwdriver to ensure proper tightness.

Regular Inspection

Have a qualified electrician inspect the connections periodically, especially in older homes with aluminum wiring.*

Consider Replacement

Depending on the condition of the existing wiring, consider replacing it with copper. This is the most reliable long-term solution.

In Conclusion:

While experience plays a huge role in electrical work, relying solely on anecdotal evidence and bypassing UL listings can be risky. While pigtailing may seem to work on the surface, the potential for failure and code violations make it a less desirable choice than using a properly installed, UL-listed AL/CU connector.Always prioritize safety and follow best practices when dealing with aluminum wiring. When in doubt, consult with a qualified and licensed electrician. Flag for review