Can You Connect Copper To Aluminum Wire?

Regarding home wiring, aluminum, and copper wires are ideal, and copper is considered the best. In the old times, houses used to have aluminum wires, but now, everyone has changed to copper. But can you join them together? 

Though there is a high risk of binding copper and aluminum, you can still join them by soldering, brazing, and splicing. The NEC permits customers to splice the copper and aluminum using an AL/CU-rated connector. 

When it is about electrical wiring, try to abide by the rules of the NEC. The article will explain everything about aluminum and copper wires and how to join them without violating any code.

Understanding the difference between copper and aluminum wires 

Copper and aluminum wires are very much different from each other. 

The old houses have aluminum wiring. But now, everyone prefers copper due to its properties. 

Let’s have a look at some significant differences between copper and aluminum wires:

Conductivity

The copper wires have more conductivity, around 60%, than the aluminum wires.

Copper is naturally high in conductivity. 

It can handle current loads better than aluminum. 

So, in most cases, you need a gauge size smaller than aluminum. 

For example, if you need a 2-gauge aluminum for some breaker work, you can use a 4-gauge copper wire. 

Thermal changes 

The aluminum wires contract at low temperatures and expand at high temperatures. 

It can further affect and interrupt the current flow.

But the copper wires don’t change because they can resist this thermal change. So the current can flow through the wires smoothly. 

Corrosion 

Aluminum wires are highly corrosive. So, the wires are prone to fire hazards. 

But, the copper wires are corrosion-resistant. 

Copper wires have a Patina, a green tarnish color formed by oxidation. It further changes the wire color. 

The layer protects the wires from corrosion and lessens fire risks. 

Oxidation 

The aluminum wires are more prone to oxidation than the copper wires. 

So, oxidation increases the resistance of the wires. 

And higher resistance means higher chances of overheating and fire. 

Malleability 

The copper wires are thin and highly malleable. 

You can bend and mold them whenever needed without any risk of breakage. 

However, I cannot say the same thing about aluminum wires. 

Aluminum wires have a high risk of breakage. 

The US Consumer Product Safety Commission staff have investigated accidents and fires in areas with aluminum branch circuit wiring. 

A survey has concluded that houses built with aluminum wires before 1972 are 55 times more likely to face fire hazards than those with copper wires. 

Resistance

The copper wires have higher resistance than the aluminum wires. 

People prefer copper wires over aluminum wires when they want to use wires for longer distances. 

Tensile strength 

The copper wires are more tensile than the aluminum wires. 

The tensility of copper wire is 150-300 mm2, and aluminum is 50-100 mm2.

Weight 

The aluminum wires are lighter than the copper wires and, thus, are easy to maintain.

Despite having so many demerits, you can still use aluminum wires for several purposes. 

Since they are lightweight, handling and installing the wires becomes easier.  

Cost 

Aluminum wires are cheaper than copper wires. 

Not all people can handle the high cost of copper wires. 

Since aluminum wires are cheaper, many people prefer them for wiring. 

Use lower gauges with thicker wires to avoid the risks associated with aluminum wires, or choose copper-clad aluminum wires.

Voltage

Since aluminum has a lot of drawbacks, it cannot be used for high-voltage purposes. 

But you can still use them for low-voltage work. 

There is no need to spend money behind copper wires for low-voltage if you can work it out with aluminum wires. 

As for the high-voltage works, copper suits the best. Copper wires are highly conductive, resistant, heavy, and durable. 

Safety considerations while connecting copper and aluminum wires

It is possible to join the copper wire to aluminum despite their differences. 

However, the connection can pose several safety hazards, including fire and other electrical hazards, if not connected properly.

So, here are some safety considerations that you must follow while connecting copper and aluminum and avoid fire and other risks:

Use AL or CU-rated connectors

When you splice or solder the copper and aluminum wires, use a suitable connector rated for AL(aluminum) or CU(copper) and UL-listed.

When something is UL-listed, the Underwriters’ Laboratories experiment with it and achieve success. Most contractors believe in UL-listed products and also recommend customers.

For example, AL7CU is an excellent connector to join the aluminum and copper wires at 75°F. 

A good option is an IDEAL TWISTERⓇ AL/CU WIRE CONNECTOR, MODEL 65, PURPLE, CARD OF 25.

This connector can prevent corrosion between the wires and maintain a secure connection.

By doing this, you can avoid the NEC code violation. 

The twist-on connector is also UL-listed and complies with NEC section 110.14. 

Use the correct connector size

When using a wire connector, ensure you use the right connector size. 

Correct connector size helps you to secure the wire connection and increase the safety of the connection between the two wires. 

Additionally, it also abides by the NEC rules. 

Use corrosion inhibitor paste.

Both copper and aluminum wires are prone to corrosion. 

Copper wires are corrosion-resistant, but over time, they will eventually rust. 

The IDEAL Twister connector prevents the wires from corroding. 

But, for extra safety, use an antioxidant corrosion-inhibitor paste to prevent corrosion. 

For the flux paste, try IDEAL NOALOX ANTIOXIDANT JOINT COMPOUND.

To apply the paste:

• Clean the conductors with a wire brush or cloth.
• Apply the paste to the connector and the conductors.
• Connect the joint and remove the excess paste.  

The paste can also be used with the conductive metals and other equipment you use. 

Ensure the wires are secured safely.

When connecting the wires, ensure they are tightly connected and secured with the connectors. 

Loose connections increase the chances of fire and electrical hazards. 

With the IDEAL twist-on connector, you can connect the wires securely. 

Use the right tools

Use the right tools for the job for a perfect wire connection. 

Call a professional if you are naive. 

A professional will have the right tools to do the job, make the right connections, save time, and follow all the codes and regulations.

Standard methods to connect the copper and aluminum wires 

Connecting two different wires, like copper and aluminum, indeed has risks because both have entirely different properties. But you can do it.

The old houses are wired with aluminum wires. 

So people connect the wires to copper wire to upgrade and make it compatible with the electrical wiring system.

In this section, I will share some methods to connect both wires. 

Method 1: Splicing

I prefer this method the most to the other two explained later. 

You need less effort because the steps are easy.

Furthermore, the connectors are specially approved for such connections, and you don’t need heating, unlike soldering and brazing.

Things needed:

• Wire strippers
• Wire connectors or crimps
• Electrical tape 
• Sandpaper or wire brush 

Here is a detailed step guide for splicing:

1. Make sure the power is turned off. 
2. Go to the wire place where you want to connect them. 
3. Cut the aluminum and copper wires at the desired length with wire cutters. 
4. Since you will connect the wires, you need to remove some insulation. Strip around ½-inch or ⅜-inch of insulation. If you need to expose more, do it gradually as needed.
5. Clean the wires with sandpaper or a wire brush to ensure better connection and prevent corrosion. 
6. Bring one end of the copper wire and one from the aluminum wire into the crimp connector or wire nuts. 
7. If you use crimp connectors, squeeze the connector with pliers and secure the wires. 
8. If you use twist-on wire connectors, put the wires inside and twist them until it secures. If the wires need more twisting, but the exposure is insufficient, strip off a few more inches and twist them again. 
9. Pull the wires slightly to see if they are appropriately secured. 
10. Cover the ends of the connectors with electrical tape for extra safety to insulate them. 

Method 2: Soldering 

Soldering is a standard method of joining aluminum and copper wires.

Soldering brings two wires together and applies a filler metal with a lower melting point than the joined metals. 

Soldering will make an alloy at the joint and bind the wires when it cools down. 

Soldering is often used for electrical wire connections to make a strong bond between two metal pieces without compromising the wire’s integrity. 

Things needed to solder include:

• Flux paste
• Solder wire
• Torch or soldering iron
• Sandpaper or steel wool
• Tweezers 
• Protective gloves and safety glasses

Here are the steps to solder the aluminum and copper wires together:

1. Cut the wires at the desired length and strip off ½-inch insulation. 
2. Clean the wires with sandpaper or steel wool to ensure no debris remains and the connection is fast.
3. If any wire piece has a coating, like paint or varnish, remove it with a chemical remover before cleaning. 
4. Apply flux paste to both wire pieces. When heated, the flux paste will make a tight seal between both wires and prevent gas leaks.
5. Heat the metal parts with a torch or electric soldering iron until they reach their melting points. 
6. The aluminum wire will melt at about 1,120°F, and the copper will melt at 1,880°F. 
7. Before you solder, wear protective gear, like glasses and insulated gloves.
8. Once the wire pieces reach their respective melting point temperatures, add the solder wire to join them in a tight bond. 
9. Let the solder cool down for some time. 
10. You can put a shrinking tube over the soldering and heat-shrink it with a hair dryer to secure the bonding more. 

Method 3: Brazing 

Brazing is similar to soldering. The only difference is the high-temperature filler method that melts the soldering iron at a high temperature. 

Besides that, the brazing method needs a braze alloy. 

The Al-Cu braze alloy should have a melting range between 1,562°F and 1,652°F. 

Ideal braze alloys are BAISi-4, BAISi-3 (brazing wire), or AL 112.

Brazing helps make a stronger bond between two metal pieces. 

It is ideal for high-strength situations, like structural assemblies and repair work. 

The problem with brazing or soldering is that aluminum wires’ coefficient of Expansion (COE) is two times higher than in copper. 

So, when you apply heat, the aluminum expands faster, for which there arises a chance of misfits or cracks in the joints. 

The thermal conductivity is 4 times higher than copper. 

The heat flows through the aluminum wires faster than copper. 

Here are the steps to join the wires by brazing:

1. Cut the wires and remove the insulation to expose the inner wires.
2. Clean the wire surfaces in the area where you will be joining them. 
3. Apply preheat on the wires. Use a higher preheat for copper as it has a higher melting point than aluminum. 
4. The melting point of copper is 1,981°F, and aluminum is 1,220°F.
5. Apply some flux paste on both wire surfaces and dip the brazing rod into the flux. 
6. Apply heat to where you will join them. 
7. Make sure to use a soft flame. Keep heating until the flux’s color changes. Most flux pastes are designed to change color once a sufficient temperature is reached. 
8. Touch the brazing rod to the joint and let it flow into place to fill the joining gap. 
9. Heat the joint until the rod has melted and flowed evenly into the right place. 
10. Let everything cool down. 
11. Clean the excess flux residue with a brush or a cloth soaked in water or rubbing alcohol. 

The pros and cons of each method for connecting the copper and aluminum wires

There are several methods of connecting copper and aluminum wires. 

But each method will have its pros and cons. 

Splicing pros and cons

Joining the copper and aluminum wires by splicing is recommended by the NEC, provided you use the correct connectors.

However, the method will have some pros and cons:

Pros:

Splicing the copper and aluminum wires are affordable than replacing the whole aluminum wiring with copper. Since the NEC approves it, there is no problem with it. 

Splicing ensures flexibility during repair and installation because you can use the wires in the same circuit. 

You can buy the approved connectors for splicing the aluminum and copper wires that provide a secure connection.

Cons:

• The slightest mistake can increase the chances of electrical accidents and overheating. 
• Splicing the copper and aluminum wires is difficult. So, you may have to spend money on consulting experts.
• There are chances where you can end up with a loose bond in the wires. 
• Splicing the copper and aluminum wires can be less visually appealing. Some heavy connectors require more space in the electrical boxes, breakers, and panels. So, it can be an eyesore. 

Soldering and brazing pros and cons

Since both are more or less the same except for the high-temperature filler, their pros and cons are similar.

Pros: 

• Soldering and brazing make a more robust bond between the two wires. 
• Soldering and brazing can help in making a low-resistance joint. It will further be beneficial for appliances with high performance. 
• Soldering and brazing are neat and clean jobs. You do not require any bulky connectors to connect the wires. 

Cons: 

• With soldering and brazing, the wires don’t get a proper joint due to the aluminum wires’ constant contraction and expansion during thermal changes. It can cause a loose connection or misfit. 
• When copper and aluminum wires are joined by soldering and brazing, a galvanic reaction can occur, increasing corrosion, damage, and fire hazards. 
• Soldering and brazing involve using heat and flames. So, they may create hazardous fumes and temperatures if you do not do it correctly. It is better to hire a professional for such work. 

The importance of using approved connectors and following the manufacturer’s instructions when connecting copper and aluminum wires

Connecting the copper wires to aluminum with wire nuts, connectors, or crimps is one of the fundamental ways. 

You need a wire connector when you connect two different types of wires. 

The wire connector should be approved for connecting copper and aluminum wires, which means it must be rated for AL/CU. 

Additionally, the wire must be UL-listed. As mentioned before, the contractors always trust such products. 

You can connect the copper and aluminum wires when the connectors are UL-listed.

Now, why is it essential to use the approved connectors? Here is what I researched. 

In the National Electric Code Section 110.4, Electrical Connections, the NEC has claimed that the splicing conductors of different materials should not be done where physical contact occurs unless the device is rated for it. 

It means you can do it if the connector is rated for the connection. 

So, if the connector is AL/CU rated, you can connect the two wires. 

Otherwise, you cannot connect them.

The connection can be dangerous; you must follow the manufacturer’s instructions about joining the wires. 

The instructions include:

• The right ways to connect the wires correctly.
• The right amount of torque to apply while securing the wire connectors.
• And several other things. 

These instructions are necessary for wire connections to be successful, and you may face fire hazards.

The impact of corrosion on copper and aluminum wire connections and ways to prevent it

When you connect the copper wire to aluminum directly, the contact surfaces of the wires develop electrolytes after contacting moisture and carbon dioxide in the air. 

The negative and positive electrodes from the wires can lead to galvanic corrosion of the aluminum wire. 

This corrosion eventually increases the contact resistance where both wires are connected. 

The difference in the COE of both wires is immense. 

So, after a few thermal changes, there will be a large gap between the two contact points.

These gaps affect the contact line and increase the contact resistance.

When the resistance increases, the temperature will also increase while functioning, and if the temperature increases, the corrosion will increase. 

When you connect the copper and aluminum wires, the joining part becomes prone to oxidation, further increasing the resistance value.

Corrosion and oxidation will intensify at high temperatures, cause a vicious cycle, raise the temperature excessively at the contact point, and lead to electrical accidents, including fire hazards, smoking, and burning. 

To reduce corrosion and oxidation and prevent electrical risks, here are some ways:

• Use connectors approved for joining the aluminum and copper wires. The connectors should be rated for AL/CU and UL-listed. 
• Use an antioxidant corrosion inhibitor, for example, IDEAL Noalox Antioxidant Joint Compound. It can destroy oxidation and corrosion and connect both wires ends securely. 
• Make a thin barrier between the wires with some paint or specialized joint compound.

The role of electrical codes and standards regulating the use of copper and aluminum wires and how they affect wire connections

According to the National Electric Code, or NEC, you can splice the copper and aluminum wires, provided the connector is rated for AL/CU.

In the National Electric Code in 2020, the use of conductors is discussed in Article 110, Requirements for Electrical Installations. 

Article 110, Section 110.5 claims that the conductors used in the home wiring should be made of copper, aluminum, or copper-clad aluminum wires. 

The old houses used aluminum wires, but the new generation prefers copper. 

So people join the aluminum with copper wire to remain upgraded and compatible with the new electrical systems. 

But what do the electrical codes say about joining wires? 

In Section 110.4, Electrical Connections, the NEC talks about splicing and connecting wire conductors of different metals. 

It says that conductors made of two separate metals, for example, copper and aluminum, should not be spliced or joined together where they can physically contact each other. 

Joining them by physical contact is only possible if you use connectors rated for AL/CU and approved by the UL. 

So, use approved connectors to connect copper and aluminum wires. 

As for the soldering or brazing, it directly joins the wires, which the NEC does not recommend. 

I have shared the method because I have seen some contractors doing it. 

It is better to contact a professional if you want to do it.

The impact of temperature changes on wire connectors and how to account for them

Temperature changes have a significant effect on the wire connectors. 

Why? Because the COE of the aluminum wires is different from the copper wires.

For example, the aluminum wire will melt at about 1,120°F, and the copper will melt at 1,880°F while soldering.

The aluminum will melt faster before the copper begins to melt. It can affect the joining and lead to misfits. 

Aluminum wires contract and expand a lot during any thermal changes. But copper wires don’t change. 

This change can affect the joining. But you can avoid this if you use the correct wire connectors. 

Random connectors cannot control this change in the wires; the connection will become loose, leading to several serious issues. 

Also, different COE can crack and break the wire connectors, which can be a safety hazard. 

To prevent these things, use connectors rated for joining the aluminum and copper wires and are UL-listed. 

Also, apply some antioxidant corrosion inhibitors to prevent misfits, corrosion, and oxidation. 

Best practices for maintaining and inspecting the copper and aluminum wire connections over time to ensure safety and reliability

Maintaining and observing the condition of the wires regularly after joining will let you know if the connection is doing well and ensure electrical safety. 

Here are some best practices to follow to maintain and inspect the wire connections and ensure safety:

• Check the wire connections periodically. See if the connections are properly secured and whether there are any signs of damage or corrosion. The inspection frequency depends, but a yearly observation is a good start. 
• Check for frayed or damaged wires, loose wire connections, and corrosion. If you see any of these signs, call an electrician to get them checked to prevent potential damage. 
• Make sure the wire nuts or crimps are tightly connected to the wires. Loose connections can lead to electrical fire hazards. 
• Avoid overloading. Use the proper wire sizes. You have already taken a risk by connecting two different wire properties. So, avoiding more risks is better.
• Use the right type and size of connectors. You can only use connectors rated for aluminum and copper. 
• Debris can gather in the wire connections and cause electrical hazards. Cleaning the connections will improve the wire connection and prevent corrosion and electrical accidents. 
• Keep a record of the inspection and changes you have made so far. It will help you fix any issues in the future and keep it as evidence to use during any legal claims. 

Final thoughts

It can be risky to join the copper wires to aluminum as it imposes the risk of electrical accidents and severe fire hazards. But you can do it. Use connectors rated for AL/CU and UL-listed if you splice the wires. 

In soldering or brazing, be very careful because the melting point temperatures of both wires are very different, which can cause a misfit and connector breakage. Contact an electrician if possible. 

Follow the safety considerations and best practices I shared in the article. It will keep the connections secure in the long run. 

Reference: Copper conductor Wikipedia, Aluminum conductor Wikipedia

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