How To Splice Heavy Gauge Wire? (Safety Caution+Steps)

Wire sizes are determined by gauge numbers or AWG (American Wire Gauge) numbers. The heavy gauge wires are mainly used for high-voltage applications. They are too heavy and thick. But what if you need to splice them? Is it safe? How to do it? Let’s see.

To splice heavy gauge wires, you need to strip the wire insulation, cut the wires, overlap the wire ends, and twist them together. Next, bind them with wire nuts, connectors, heat shrink tubing, and solder iron.

It may sound simple, but you must be careful about the wire splicing as they carry enough current and are heavy wire gauges. Splicing heavy gauge wires should always be done by experts. Read this article until the end to learn the splicing steps and the precautions to follow. 

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Understanding Heavy Gauge Wire: Characteristics and Applications

A heavy gauge wire is a thicker gauge with a small number representing the gauge thickness. 

For example, a 2-gauge wire is thicker and heavier than a 6 or 4-gauge wire. 

These types of heavy wires are used for electrical services that need to carry massive amounts of current.

 Thick wires have larger diameters compared to lighter gauges. As a result, they are robust and durable. 

Due to the thickness, the heavy gauges have much more tensile strength than the thinner gauges. 

So, these wires can tolerate higher mechanical stress than the thinner ones without breakage and deformation. 

Heavy gauges can also conduct electricity for long distances without increasing the resistance better than thinner gauges. 

Thinner gauges are mainly used for 50 to 100 feet, but heavier gauges can be easily used for distances above 100-150 feet. 

Since the resistance will be low, the risk of overheating in the thicker gauges is less. 

When talking about heavy wire gauges, consider voltage as well. 

Most Americans use 120V wires. 

But some heavy-duty appliances like electric stoves and cloth dryers will use 220V-240V wires. 

These wires are also heavy wire gauges and should be handled carefully. 

However, it is uncommon for such heavy wire gauges to wear out or tear. 

So, there will rarely be any requirement for splicing. 

You can splice or join them instead of rewiring the entire run. 

You will require heavy-duty junction boxes. 

Heavy gauges are used in high-voltage applications, for example:

  • Electrical power distribution
  • Industrial wiring
  • Structural support 
  • Kitchen cooktops
  • Furnaces and large air conditioning units
  • Water heaters
  • Cloth dryers and washers

There is no specific application of the thick wires. It depends on what size of wire gauge you are using. 

A 2 AWG wire is also a heavy gauge, as are a 2/0 AWG, 4/0 AWG, and 250 kcmil wire. 

A 2/0 AWG is thicker than a 2 AWG wire because 2/0 means 00 AWG.

As I said, the smaller the number, the thicker the gauge. 

A 250 kcmil is the thickest among these wires because it has a cross-section and diameter more extensive than the 4/0 AWG. 

When the wire gauge is larger than 0000 or 4/0 AWG, it is measured by MCM (thousands of circular mils) or kcmil. 

In the kcmil or MCM unit, the larger the number, the thicker the wire gauge. 

For example, a 300 kcmil wire gauge is thicker than a 250 kcmil wire. 

Also read:

Safety First: Precautions for Working with Heavy Gauge Wire

Heavy wire gauges are risky because they are mainly used for high-voltage appliances, where the current flow is much higher than thinner ones. 

So, you need to be careful to avoid electrocution and fire. 

You cannot commit any mistakes. 

That is why follow the following preventive tips while working with heavy wire gauges:

  • Wear protective gear before working with electrical wires, such as goggles, insulated rubber gloves, and insulated shoes. 
  • Turn off the main power source before you start splicing the wires. Use a multimeter or non-contact voltage tester to confirm the power is off. 
  • Use the right tools while splicing, for example, suitable strippers, heat shrink tubes, connectors, solder iron, etc. 
  • Keep a first aid kit near you to treat accidents, if any. 
  • Avoid working alone. Since you will cut, strip, and expose the wires, that too of heavy gauges, you will require assistance to help you out. 
  • Keep the surroundings clean and well-lit. There should be no obstruction or moisture around you. 
  • If you need to use a ladder, use wood instead of metal. 
  • Take permission from your region’s authorities so that you are allowed to do this work yourself. 
  • Get everything checked and inspected after the splicing by an expert. 
  • Try to follow the rules and local codes while splicing the wires. 

Tools and Materials: Essential Equipment for Splicing Heavy Gauge Wire

You will require specialized equipment to cut the wire for splicing the heavy wire gauges.

You will need:

  • Voltage testers or indicators
  • Wire strippers
  • Crimpers 
  • Cutters
  • Connectors 
  • Heat shrink tubing
  • Terminals
  • Insulation tapes
  • Heavy-duty junction boxes

When you gather these supplies, consider the wire size

Different wire gauges will need different sizes of terminals and connectors to stay fit.

Preparation and Planning: Organizing the Wire Splicing Process

Since these are heavy wire gauges we are dealing with, proper preparation and planning are needed. 

Look at where the line comes from. Avoid testing or touching the wires.

Identify the circuit and turn off the breaker

If needed, turn off the main panel to avoid electrocution. 

Tag the wires and the circuit with a note that you are working on them and people do not touch them. 

You might require permission to work on the heavy-duty wires or add extra wires based on your region. 

You will also require permission before you start and get the wire inspected by experts after splicing. 

Now, consider the wire gauges you are going to splice. 

They must be the same gauge size and the original inside-out color. 

This ensures the safe splicing of the wires. 

The best way to match whether the wire matches is by cutting a piece and taking it to the local hardware. 

Make sure only to cut a damaged piece and not a good part. 

Clean the wires well and remove all dirt if they are corroded or dirty. 

Once you have the wire, check the insides to determine the hot, neutral, and ground wires

There will be two hot, one neutral, and one ground. 

Half of the time is spent ensuring their safety, ¼th is spent behind the actual work, and the remaining time is spent inspecting and fixing faults. 

Once you have identified the wires, turn off the power at the main breaker, gather all the supplies, and gear up. 

Check with a multimeter to ensure no electricity runs through the wires or breakers.

Stripping the Wire: Proper Techniques for Removing Insulation

The first step is to strip the wires and expose the insulation. 

You cannot just strip off wires as much as you want. 

There should be a proper measurement of how much insulation you should remove. 

If you need to fix and splice damaged wires, strip off and remove the damaged part first. 

Then you will have to remove the insulation. 

Be it a damaged wire or an additional new wire, stripping off the insulation with the correct measurement is a must. 

First, strip off the cable sheathing around 6 inches to expose the wire colors.

Generally, you should strip off only ½ to 1 inch of insulation. 

Insert the wire between the stripper’s shears and strip the wire insulation with one switch and decisive motion. 

Cut enough for the inner insulation to be visible. 

Strip so that you can see a bit of color on each wire. 

Repeat the same for the other one. 

There will be a ground wire. 

If the wire is bare, you do not have to mess with it. 

But if there is green insulation, strip off the insulation.

Sometimes, you will need to strip more than 1 inch. 

Connectors have a spring inside them. 

You have to keep twisting the wires until the wires tightly fix. 

So, if you need to twist more, expose the wire and strip off around 1.5 inches. 

Do not strip off too much, as that will impose an electrocution threat. 

Splicing: Using Connectors, Crimps, and Compression Fittings

Now comes the central part: splicing of the two wire ends. 

Several methods exist to connect the wire ends: connectors, crimps, or compression fittings. 

Wire connectors are one of the most common methods to splice wire gauges. 

In most cases, I have used wire connectors or nuts to splice thinner gauges. 

I have never tried heavy wire gauges. 

Even if I had the necessity, I would consult an electrician for it. 

I will share the steps to splice heavy wire gauges I witnessed in my friend’s house. 

Both of us were there when the electrician spliced the wires. 

The steps are more or less the same. 

But since the wires were too heavy, it was time-consuming, and the connectors were chosen accordingly so that the heavy wires could fit into it. 

Consider the wire gauge whenever you buy wire connectors, and then buy a suitable one that can fit the wire gauge perfectly. 

So, here are the steps:

  1. Once the wire stripping is complete, you must connect the wires with the connector. 
  2. Hold the wire ends in a way that they are touching each other. 
  3. Press the wire ends together to keep them right next to each other. Always begin with splicing the ground wires.
  4. Make sure to splice the same wire colors together. 
  5. Avoid twisting or coiling the wires. Hold them together to keep them secure inside the twist-on wire cap or connector. 
  6. Take the connector, put the wires inside, and twist the connector clockwise on the exposed wires. 
  7. Keep turning it for 5 seconds so the wires can wrap and coil inside the connector. 
  8. You have to expose the wire more than 1 inch, in case the twists are more. 
  9. For safety, you can layer electrical tape around the wire connector around the bottom. 

The other two methods with the same splicing steps are crimp connectors and compression fittings. 

But there is a slight difference between these two and twist-on wire connectors. 

To splice the wires with crimp connectors and compression fittings:

  1. Put the exposed parts into the connector’s openings. 
  2. With a crimper tool, squeeze the crimp connector to let the wires fit. Use the same for the compression fittings to fit the wires. This will create a strong bond between the wires and the connector. 
  3. After crimping, inspect the connectors to ensure the wires have properly been joined with the connector. 
  4. Perform a continuity test to ensure the connection is solid. After that, you can start running it. 

If you use butt splice, a type of crimp connector, slide in heat-shrink tubing for extra security.

Heat-Shrink Tubing: Insulation and Protection for Spliced Wires

Splicing the wires with heat-shrink tubing is another standard and straightforward method. 

You use a shrinkable plastic tube to cover and insulate the exposed wires. 

To shrink the tube with heat, you can use a hair dryer. 

The shrink tube should be slightly more extensive than the wire’s diameter. 

At the same time, the shrunken diameter of the tube should be smaller than the wires.

For example, let’s suppose the diameter of the tube is ½ inch and a shrink ratio of 2:1. 

It should become ¼ inch after shrinking. 

This way, find out the suitable one for your wire.

For better splicing, use heat shrink tubing with a solder ring. 

Soldering creates a secure and water-resistant connection for the wires. 

Let’s get to the steps:

  1. Use a suitable shrink tube for your wire. 
  2. Cut the tubing ½ inch longer than the wire part you must cover. Slide the tubing into the wire cable.
  3. Now, strip off the wires’ insulation, and twist the wire ends. Do not just randomly make any twists. It should be done so that the tube perfectly fits the exposed area. If needed, check for online videos or consult your electrician. 
  4. Begin splicing with the ground wire and then the hot and neutral wires.
  5. Bring the tubing over the exposed wires. 
  6. Use a heat gun or a hair dryer and blow the heat over the tubing. Hold the dryer 3 to 6 inches away. It should be neither too close nor too far away. 
  7. Keep moving the dryer’s nozzle or gun back and forth and rotate the wire. This will ensure that the tubing fits perfectly into the wire. 
  8. For the perfect shrinking temperature, check the tube’s packaging. 
  9. Let the tube cool down for 5 minutes, and then check the wires to see if you can flexibly use it. 

Please consult an expert to ensure whether heat shrinking a heavy wire gauge is possible. 

Soldering Heavy Gauge Wire: Techniques for Reliable Connections

Another way to splice the heavy wire gauges is to solder them. 

It provides a permanent solution for damaged wires or joining new wires. 

But the process can be time-consuming. 

You need to be very careful and patient during the whole process. 

The method’s efficacy depends on your ability and experience. 

The slightest mistake will lead to the failure of the wire splicing. 

Here are the steps to splice by soldering:

  1. Take a shrink tube and slide it inside the cable. After soldering, this serves as a shrink tubing for secure splicing. The tubing should be slightly thicker than the wire to fit perfectly after heat-shrinking.
  2. Now, take a solder to join the wires. Make sure to use a solder suitable for the heavy wire gauges. While buying, ask the expert for the ideal solder type for your wire gauge. 
  3. Turn off the power at the main breaker. 
  4. Strip off the insulation from the wires and expose the inner wires. Based on the conductor type, there might be different wire colors. You need to twist the wire ends with the correct color. 
  5. Apply some rosin flux on the wires before splicing. This will help the solder to attach better. 
  6. Melt the soldering iron over the top of the exposed wires and coat them well. Begin with soldering the ground wires first.
  7. Hold the solder’s tip at a 45-degree angle. Ensure that only the solder iron is melting and not the wires. 
  8. Once done, let the solder cool down for a few minutes. Please do not touch it. 
  9. Apply some silicone paste on the solder for waterproofing. 
  10. Now bring the tube you have inserted before in the soldered area and shrink the tube with a heat gun or hair dryer. 
  11. Inspect the connection and ensure everything is secured well. 
  12. Test the wires’ continuity and resistance before you start running them. 

Since you are dealing with heavy wire gauges, I suggest leaving it to the hands of an expert. 

They know the right tools and equipment. 

Besides, soldering is quite a risky process. Choosing professionals is a wise choice. 

Testing and Verification: Ensuring the Integrity of the Spliced Connection

After splicing the heavy wire gauges, consider performing a continuity test to verify that the splicing is done correctly. 

A digital multimeter will suffice for the testing and verification. 

It will determine the continuous path between two points and ensure that the spliced wire is successfully joined and there are no breaks in the circuit. 

Turn on the continuity function in the multimeter and use a dedicated tester if needed. 

Place the multimeter’s probe on each end of the spliced section. 

If there is continuity, the multimeter will make a beep sound or display readings close to Ohms. 

If there is no continuity, the splice is done incorrectly and requires thorough inspection and fixation. 

To check the resistance, set the multimeter to resistance mode and again connect each end of the spliced wire to the multimeter’s probes. 

Check the measured resistance with the expected resistance. 

Generally, the resistance should be zero or near zero. 

High resistance means you have made some faults while splicing the wires. 

Common Mistakes to Avoid: Pitfalls in Splicing Heavy Gauge Wire

While splicing the wires, it is common to make mistakes. But when it comes to splicing the heavy wire gauges, you must avoid these mistakes for safe splicing. 

Here are some common mistakes I have seen some of my friends make during splicing:

  • When you splice the wires, you expose the wires. After the splicing, properly insulating these wires is paramount to avoid fire and electrocution. So, always use high-quality materials to insulate these wires. 
  • When splicing the wires, avoid overlapping them too much. That causes an interruption in the current flow and creates hotspots, causing fire and other safety hazards. Use proper wire connectors and splicing methods to ensure a secure connection. 
  • Do not simply twist the wires while splicing. Proper twisting is required. You can watch videos of DIY enthusiasts and figure out how to do it. Also, confirm the process with an expert. 
  • Use the correct wire gauge for splicing, especially when adding extra wires. Smaller gauges will lead to overheating and fire. 
  • When stripping the wires, try to make a clean cut. 
  • Clean the wire before splicing for secure splicing and interrupted current flow. 
  • Instead of randomly starting to splice any wire, always begin splicing with the ground wires for safety.
  • Use the correct splice method, for example, soldering, connectors, crimps, and heat shrink tubes. Use the right kind of solder iron, the correct types of connectors and crimps that suit the heavy wire gauges, and the right size and type of shrink tubes that perfectly fit and insulate the wires. 
  • Since the wire gauges are heavy to handle, use some support to support the wires and secure the splicing. 
  • You will be dealing with heavy wire gauges. So, be patient and take your time to do the job. Do not rush it.

Seeking Professional Help: When to Consult an Electrician for Wire Splicing

The best decision for splicing heavy gauge wires is to leave it to the experts. 

When experts do the job, they will do it faster. 

Experts know the correct methods of splicing heavy wire gauges, using the right tools and equipment, and know the rules and regulations. 

Some professionals also receive detailed training about wire splicing for light and heavy wire gauges separately. 

So, they will perform the perfect methods of splicing the wires. 

Besides, electricians have proper licenses for electrical work. 

So, you do not have to struggle with the electrical inspection or pay any fine. 

When experts do the job, they follow the rules and regulations. 

So, you can also save yourself from penalty fees. 

Furthermore, electricians also provide you with insurance. 

This ensures that if any accidents occur during splicing, the electricians can cover up the accidents. 

So, do not hesitate for once to seek professional help. 

Final thoughts

There are several methods to splice heavy wire gauges. But since the wires are thick and heavy, you must handle them carefully and be patient while doing the work. Using wire connectors or caps, crimp connectors, and compression fittings is one of the easiest methods. 

You can use heat shrink tubes to splice the wires for more security. However, soldering is by far the most efficient and reliable splicing method. Prepare your wire before you start splicing, and take permission to do the work yourself. 

Additionally, inspect the spliced wires after you have done it to ensure proper security. Instead of doing it alone, I suggest hiring an electrician and getting the job done by them for perfect splicing and security.

Can I use a butt splice to connect heavy wire gauges?

A butt splice connector may look like a heat shrink tubing but is a kind of crimp connector. You can use it but you must choose the butt splice size based on the gauge size. Ask the expert for the correct type and size.

Can I use machine splice?

Performing a crimp connection using an auto-splice machine is as reliable as soldering. The machine cuts a spool of brass-coated copper into a blank, then stamps and forms a crimp around the wires. Once this is done, cover the splice with heat shrink to seal it.

Reference: Splicing Wikipedia

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Arthur Smith

Howdy! I am Arthur Smith, an electrical engineer who is extremely passionate about electronics. I have lived in different parts of the US and currently reside in Wisconsin. I am one of those rare children who knew what he wanted to study and do in life right from the start. I was a curious child who wanted to know how switches work and how the AC works, and I would always observe my dad whenever he would handle the wires and fix things around the house. I currently work as an electrical engineer at a reputed company and write for this blog. And I read loads of books or play video games in my free time.

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