You may already know what a gauge is and how it works. If you don’t, we have a lot of valuable sections below on the topic to explore why you must choose the right product for your electrical needs. Scroll down if you want to look through NEC’s wire gauge amp chart table that we have included.
In a hurry? Buying recommendations
We spent more than 20 hours screening manufacturers and reviews to develop this list of products. The list will ensure you get the right extension cords, circuit breakers, and more. Any product needs to be rated to handle the electrical current you’ll be running through it. Products were chosen based on the National Electric Code. It is the safety standard used by pros. A copy of the electrical wire sizing chart included further down.
Table of content
- In a hurry? Buying recommendations
- A Rule of Thumb: What are the correct wire sizes for 20, 30, 40, 50 & 60 Amp Service & Breakers?
- AWG wire ampacity chart & gauge rating from NEC 310.16
- So, what exactly is the deal?
- Choosing the right one
- What Happens if You Use One That Is Too Small?
- Determining what breaker to use
- Circuit Breakers
- How Many Amps Can a 12 AWG Handle?
- How much does it take to handle 20 amp?
- How much does it take to handle 25 amps?
- How much does it take to handle 50 amps?
- How much does it take to handle 30 amps?
- How much does it take to handle 40 amps?
- Be part of the Atlantic Aspiration journey
A Rule of Thumb: What are the correct wire sizes for 20, 30, 40, 50 & 60 Amp Service & Breakers?
What wire do I need for various capacity requirements? The rule of thumb that techs will usually go by is that for a 30 amp circuit breaker, 10-gauge wire is the right one to go with. For a 40 amp, you need an 8-gauge wire. For a 20 amp, you will need a 12-gauge wire. For 60 amp, the correct wire size is 4. The right wire size for 50 amp is a 6 for both your breaker & circuit. However, there are certain essential assumptions that that rule of thumb relies on. We will expand on those in the rest of this article.
When you start comparing with the chart below, you will see that those numbers are conservative. It’s better to get a safer option, even if it may be marginally more expensive. Scroll down to our full NEC wire size chart to find the corresponding options for different temperatures. The one below simply summarizes the main recommendations based on conductor temperatures of no more than 140°F.
|Ground wire, service entrance, circuit, breaker size chart rating|
|Service or Feeder Rating, amps||Aluminum conductor, AWG||Copper conductor, AWG|
AWG wire ampacity chart & gauge rating from NEC 310.16
Looking for the NEC (National Electric Code) wire ampacity chart and size rating tables across the internet. These are the values that we have been able to find. They outline the values in slightly great detail than the previous charts did, as per the NEC 310.16 table. Scroll down further if you want a more detailed chart for the standard type.
As you can see from the graph, a 6 AWG is the safe choice if you have a 220v 50 amp that you need to power. A 12 gauge wire is perfect for your 220v 20 amp needs. Whether you’re finding out the option for your 1000 or 2000 watt needs, this is also the chart that the pros use. It can also be used for speakers, home theater, subwoofer, light fixtures, light bar, or subpanel.
Whether for a 20, 30, 40, 50, or 60 amp circuit or breaker, the AWG wire size chart can help you find what you need. It is the most accurate table to go with on this page and is the one that the pros use.
|Aluminum, Amp Rating||Copper, Amp Rating|
The detailed chart further down in this article is for copper with an ambient temperature rating of 60 ℃ or 140 ℉. It is what is considered the standard. The suitable selection for a specific capacity will change depending on the wire used and the ambient temperature rating. If you want to find the 50 amp wire size at an ambient temperature of 194°F, you look in the chart to see gauge 6. Respectively for 40 amp, it’s gauge 8. For 60 amp, the right wire is gauge 4 at an ambient temperature of 140°F. These numbers are assuming you’re going for aluminum.
In those situations, it’s important to think about what the conductor is made of. Copper or aluminum are the materials used for wires. The termination points and the ambient rating are other things you should be keeping in mind.
High ambient conditions like multiple conductors and the allowable voltage drop should be considered to ensure you don’t run into problems.
Copper is known to be able to carry more electricity than aluminum. That is why it can handle more at the same gauge than its aluminum counterpart. It means if you have a copper 6 AWG and the same made of aluminum, the copper will allow more current to flow through it.
Electrical components with a higher ambient temperature rating can be used at higher current requirements. This is why a copper 14 AWG wire size with a 60 ℃ or 140 ℉ ambient temperature rating is suitable for a 15 amp breaker. The same thickness but with an ambient temperature rating of 90 ℃ or 194 ℉ can be safely used with a 25 amp breaker.
These factors make choosing the size for a 30 amp breaker not as straightforward as it seems. A copper 10 AWG copper with an ambient temperature rating of 60 ℃ or 140 ℉ is what you need from the chart above. You can also use an aluminum 10 AWG with a 90 ℃ or 194 ℉ ambient temperature rating and diameters larger than these two sizes.
Always remember that it is fine to get a higher rating electrical component than the recommended one for a circuit breaker. Still, you should never use one with a lower breaker rating.
So, what exactly is the deal?
This is the measure of the diameter you will be using in different measurements. People will usually refer to the gauge rather than the actual thickness. The number refers to a specific thickness.
The higher the number, the smaller the diameter. It may be contrary to logic, but that’s how it is. The easiest way to determine the thickness of some wire you may have lying around is by using a thickness tool. Sometimes the rating is indicated, sometimes it’s not.
You want to use the right diameter because the diameter determines the amount of current that can safely go through it, including the electrical resistance. Using the incorrect size could have serious consequences. Different amounts of current will require different diameters as well.
The unit of measure is AWG, the most popular measure in the US and is used in more than 65 countries. Other measures include the SWG and the IEC, the Imperial Standard Wire Gauge. The British Board of Trade introduced it. Since most of our readers are from America, we will be focusing on AWG for this article.
As the diameter determines how much electricity can be carried, not all diameters work with every single machine.
Choosing the right one
When you inspect your circuit breaker, a burned wire is a surprise that you do not want to get. Fortunately, this is an avoidable scenario if you know that having the right capacity for a circuit breaker is important. The bad news is, this is something that a lot of people do. People mistakenly believe that one wire is as good as any other. They attempt to make the connections themselves instead of calling for an electrician.
Anything involving breakers should be taken seriously because it has to do with electricity. It includes any sort of connectivity. You will avoid any electric hazards and issues common to circuit breakers and faulty connections if you have the right components. Many of these issues occur because of the wrong one being chosen and used for the breakers. It is important to know the right combination of the breaker and its compatible wires.
If you are clueless about the size of your 30 amp breaker for an air conditioner or water heater, allow us to help you understand the basics.
What Happens if You Use One That Is Too Small?
People believe as long as both ends of a wire fit a connector, they can use it for their connections with no issue. Unfortunately, this is not the case for breakers. Those unaware of its importance often use too small wires to connect their breakers. It is often because they want to save money since thinner products tend to be cheaper. This is partly because less material is used.
Sadly, this only leads to costly mistakes for them.
If you use larger ones on your breaker, the only effect is on your budget. This is because you ended up spending more than what you need to since larger wires cost more. It does not affect your breaker, nor will it cause damage to it. The wire can handle the current that flows through it.
But if you use one that is too small, the following can happen:
- Melting – the smaller the wire, the less current it can handle and the higher its resistance to the flow of energy. But if it is too small for your breaker and its rating, the current that flows is more than what it is designed to handle. Since they have a high resistance, heat is generated and this will eventually be enough to melt it if the power is too strong.
- Performance Drops – any appliance or equipment that is connected to the circuit with the too-small wire will not operate at peak efficiency. This is because it receives only a fraction of the energy it requires to run at full performance.
- May Damage Equipment – aside from affecting its performance, using a smaller diameter can eventually damage your equipment. Power being supplied improperly can cause them to go bust.
- Can Start Fires – this is the worst that can happen when it is too small to handle the current it receives. While circuit breakers can trip along wiwth other safety measures, an overload has the potential of causing fires if the wrong one is used.
These scenarios are avoidable if you use the right type for a circuit breaker.
Determining what breaker to use
Licensed electricians should ideally handle electrical work. It also helps to be personally aware of important aspects of your circuit breaker, such as having a good rating for the project. To select the right one, professionals use different charts as their reference.
In the USA, the chart that is considered standard is the American Wire Gauge, commonly referred to as AWG. Also known as the Brown & Sharpe, the AWG is a system that prescribes specific diameters of solid round wires. You’ll hear the rating referred to as the gauge used as electric conductors. The capacity is the maximum current that it can safely handle.
You should note that the AWG numbering system does not directly represent the actual size. This means the higher the AWG number, the thinner or smaller it is. The thinner it is, the less power it is rated to handle. It is why a 2 AWG can carry more current than a 14-rated one.
You can use the following chart to understand it better and determine the diameter of the AWG number. Whether you’re looking for 20, 30, 40, or 50 amp wire sizes, the chart below should help you out:
|AWG||Diameter (inches)||Diameter (millimeters)|
As you can see, the largest in terms of diameter is 0000. The smallest is 40. This means the 0000 has a bigger capacity than one with a 40-rating. It also means that the 0000 allows more energy to flow through it.
What is a circuit breaker?
This safety switch automatically interrupts electrical current when it senses an overload or short. It shuts down or ‘breaks’ the electrical flow of current to protect the rest of the electrical equipment from an electrical fire. Therefore, it is essential to have a good compatible breaker installed in your home or workplace.
What are the different types?
Three main types are used in electrical circuits – standard, GFCI, and AFCI. Let’s look at them in more detail below:
These are called standards for a reason. They are of the simplest type and monitor the flow of current indoors. Its job is to keep track of the current flowing through devices, wires, and outlets. Whenever the device senses an overload or a shortcoming, it stops the current entirely. It is done to prevent the wires from melting and prevent accidents like fires.
A Ground Fault Circuit Interrupter
This type is more complex and has more useful functions as well. A GFCI includes an outlet with a breaker built-in. But the most important function it provides is protection against electrical fires due to contact with water. For this reason, a GFCI is installed in kitchens, bathrooms, and other areas with frequent use of water.
Suppose you’re using a blender in the kitchen and the circuit overflows because it comes in contact with water. The breaker inside the outlet will trip. It will immediately stop all current from flowing to prevent any hazards. If something like this happens in your home, you should get the outlet checked by a professional before using it again.
Arc-Fault Circuit Interrupter
These are specialized devices designed to interrupt the current flow when they sense an arc or surge in the electrical flow due to damaged or worn-out wiring. This kind of surge goes undetected in other standard breakers since they react to heat and not sudden surges of electric discharge.
The latest Electric Code guidelines make it compulsory to have GFCI and AFCI breakers in the kitchen and laundry rooms. It is the place where electric fires are more likely to happen. You can also choose to install AFCI breakers in the living room or bedrooms.
Combination arc-fault circuit interrupter
These are ones with the combined power of both GFCI and AFCI protection. Not only do they sense any arcing due to damaged wiring, but also water contact. They can protect against both arc and ground faults. Installing CAFCI breakers can save you more money and fetch your one-time long-lasting protection for your home.
Make sure to test the GFCI and AFCI devices regularly to see that they are in good working condition. You can also schedule a servicing and get your electrical panels checked thoroughly.
Now that you better understand the relationship between the various parts of the equation, it is time to determine which is suitable. You may not necessarily be a licensed electrician. You still know some of the things you should be aware of to ensure safety in your home. At least when you’re dealing with electricity.
If you have no idea where to find the rating, look for the number on the breaker’s handle. It is the maximum capacity it can handle.
Once you find the rating, you can now determine which electrical components are the right ones for you to use. The most common ones and their corresponding ratings are:
|Wire Gauge (AWG Number)||Ampacity|
How Many Amps Can a 12 AWG Handle?
The amps that a 12 AWG can handle are:
- 20 for copper with an ambient temperature rating of 60 ℃ or 140 ℉, which is the most common connection
- 25 for copper with an ambient temperature rating of 75 ℃ or 167 ℉
- 30 for copper with an ambient temperature rating of 90 ℃ or 194 ℉
- 20 for aluminum with an ambient temperature rating of 75 ℃ or 167 ℉
- 30 for aluminum with an ambient temperature rating of 90 ℃ or 194 ℉
Ideally, an 8 gauge wire should only be handling about 40amp. It can take on 50 amp but might get too hot while doing so. If you’re looking to put a 50 amp load on a wire of 8 gauge, it should be thick so that it does not melt from the heat. This is necessary as a 50 amp current will lead it to become as hot as 75 degrees celsius.
Ideally, you should stick to 8 gauge wires or AWG8 for a 40 amp current. You would also require a size 8 gauge in solid copper for a 40 amp breaker. Additionally, 20 amps require 12 AWG. 6 AWG is ideal for 55 amp, while 10 AWG is ideal for 30 amp. These measurements are general rules of thumb for ampacity. You should double-check the type of insulation and the material of the wire. Check the thickness and other factors before purchasing. You should also refer to the National Electrical Code (NEC) before all kinds of electrical installations.
You’ve heard plenty about gauge and AWG, but what does it all mean? The gauge of a wire is just a fancy name for its thickness. The gauge is represented in numbers where the bigger the number, the thinner it is. In the United States, the standard method of measuring gauge is AWG. Through this standard, it becomes easier to communicate thickness between users. Companies and manufacturers use it all over North America.
The easiest way is to look at the insulation of the wire. Once you find the text, look at the last few figures. You’ll find the AWG size if it’s indicated. If you can’t find this, proceed to the following steps.
Start by measuring the diameter of a single wire. You can do this with a ruler, but if it’s too thin, you can use a conduit measuring device available at your nearest hardware store. Remember that you’ll measure a single strand in the bundle grouped in a single cable.
After you’ve measured the diameter, multiply the resulting figure by itself. The result should then be multiplied by the number of strands. The resulting figure is called the CMA or Circular Mils value. Once you’ve got the CMA value, all you need to do is consult an online table. Match the CMA with the AWG value. And voila! You’ve got your wire gauge size!
Before we get into the basics of reading a wire size chart, let’s see what factors affect the gauge. How much current it can carry will depend on various factors like the thickness and material. Sheathing and insulation play a role as well. Now let’s look at the steps needed to read wire size charts:
Time needed: 2 minutes.
How do you read wire size charts?
- Determine what ampacity you need
Once you calculate what ampacity will run through wires, you can easily determine the other factors. The ampacity will depend on the size of your circuit and the number of devices and types. Different devices require different amounts of current to power them. You’ll require a higher thickness and more insulation to avoid melting for something heavy like a refrigerator.
- Determine what metal and insulation you want
You’ll primarily be deciding whether you want aluminum or copper wiring in your home. Aluminum has the advantage of being super light and very malleable. Hence it is ideal for covering long distances. However, copper is more popular because it is quite strong and can carry almost double the amount of current. But keep in mind that copper will lead to a larger chunk being cut out of your savings.
- Pull up an online wire size chart.
Now for the final step: pull up any online wire gauge size chart. Now look for the material you are using and find the ampacity you are looking for the wire to carry. You’ll find the corresponding gauge value in AWG standard on the left-hand side. This is the gauge size you need for your project.
How much does it take to handle 20, 25 & 30, 35 amp?
The rule of thumb is that you at least need a 12 gauge wire for a 20 amp service. You could use an AWG 10 but not a 14-rated one. We still encourage you to refer to the detailed NEC table above to decide which to go for.
Say you have a 35 amps breaker and a 10-gauge wire lying around. You may be wondering if this particular one can handle that much current. It is possible, but it will depend on the type of material and its ambient rating.
A 10 AWG copper with either a 75 ℃ or 167 ℉ or 90 ℃ or 194 ℉ ambient temperature rating can handle 35 amps. The equivalent aluminum one with an ambient temperature rating of 90 ℃ or 194 ℉ can also work.
If you wonder if your extra 12 AWG can also be used for a 25 amp breaker, it is. In copper, it can be used if its ambient temperature rating is either 75 ℃ or 167 ℉ or 90 ℃ or 194 ℉. The equivalent aluminum one is compatible if its ambient temperature rating is 90 ℃ or 194 ℉.
How much does it take to handle 50 amps?
Looking at our chart above, you can see that this amount of power hasn’t been included. However, we’re still finding that many people are out there asking what the appropriate diameter is. The truth is that 8, 10, or 12 gauge can’t handle it. The 50 amp wire size is gauge 6 in this instance, given the same conditions stated earlier in the article. On the other hand, you need a wire size 4 for a 60 amp service, subpanel, or breaker.
How much does it take to handle 30 amps?
You must consider the previously noted conditions regarding ambient temperatures to answer this question. You can use a 10 AWG size wire for 30 amps, but you can’t use a 12 or 14 AWG for this amount of power. Consider a 10/3 cable for 220-volt outlets, which is a great residential option for a power circuit of this strength. It has a ground wire as well as 3 live wires.
When you have to power something like light switches, you will want a 10/2 wire instead, which is made for that purpose. The second number refers to the number of live wires. It also contains one for ground purposes. Because there is a distinction between the two, you must know what you’re powering to get the right electrical components.
Next time you’re working on wiring a 30 amp double pole breaker, you can refer to this guide. You’ll avoid crucial mistakes that could lead to severe consequences. If you are trying to hook up something larger like a double oven, you’re likely looking at a 6/3 or 8/3 option instead. These are rated for higher consumption than the 10/3 is.
How much does it take to handle 40 amps?
You will need an 8 gauge wire for 40 amps. A 10 AWG will not be able to handle this amount.
How to install a circuit breaker?
Now that we’ve gotten you familiar with circuit breakers and gauges let’s look at how to install a circuit breaker if you decide to go DIY. Remember, only perform this under the supervision of a licensed electrician until you learn to do it yourself.
- Turn off the main power
There should be no current in any wires in the panel. Turn off the main power and then open up the breaker panel. Main breaker wires will still be live, so it’s important to test them and ensure no current flows for safety purposes. Once this is done, you can begin the process.
- Screw on the cable clamp
You’re going to need a new cable clamp if you want to install a new breaker. For this, use a hammer on the knockout and make room for the new cable clamp. Find the new wire and run it through the panel and to the clamp.
- Install the ground wire
Affix the ground wire into the ground bar. This should be done with care since this is the only one with no insulation and thus carries more safety risks.
- Connect the neutral wire
Next, the neutral wire must be connected to the neutral bus. This can be done easily if you simply remove a little bit of insulation around the end of the wire. Feed this tip into the bus and tighten it.
- Circuit breaker installation
Look for a screw on the bottom of the breaker. Affix the last black wire under this screw. When this is done, tighten the screw and hold it steadily. There are prongs on the back that you can use to align it correctly.
- Take out the knockouts
Now you can safely place the knockouts over the newly installed circuit breaker. This will ensure that they are shielded carefully.
Safety measures to follow with all types
Dealing with electric repair work should always be left to a professional. If you’re a beginner in that field, here are some tips you should always keep in mind when dealing with industrial or commercial breakers.
- Never forget to shut off the main breaker
Here it’s useful to follow the Lockout/ Tagout procedure or LOTO protocol. The LOTO protocol involves the following eight safety steps:
- Good preparedness and training – Everyone affected by the shutdown must be appropriately informed and trained to deal with hazardous energy sources.
- Notifying affected personnel – All persons on site who will be affected by the shutdown/ lockout must be notified of its timing and reasons.
- Shutting off equipment – All operating manual procedures must be done to shut off the running equipment in a timely and safe manner.
- Isolate the power origins and sources – This will mean any valves that are supplying power to the equipment and machinery must be cut off temporarily.
- Lock out all power sources – this can mean through a physical padlock or other tools so that no one can access or physically turn on the equipment during the shutdown time.
- Release the stored power – Some machinery hold air or energy or electric charge which must be released.
- Double check the LOTO process – This means ensuring all the steps above have been followed and checking off the checklist.
- Control the LOTO – Appropriate personnel must be appointed to overlook and ensure the shutdown is in place all the while the maintenance work is being done.
Following this LOTO protocol isn’t just part of circuit breakers. It is a common practice followed in major electrical maintenance work in any factory unit or industrial area.
- Wearing safety clothing
Electricians must always wear safety gear when working with circuit breakers or any electrical equipment. This includes personal protective equipment like PPE suits and safety goggles.
- Make sure all the constituents match with each other
Match the wiring with the appliances and the switchboards and ensure it aligns with the load requirements.
- Watch your hands!
Even though the power may be off, the main bus bar and other parts may still be hot to the touch. Ensure sufficient time between shut down and handling for the bus bar to cool off. Even the conductors could have excess electrical charges and therefore must only be handled after proper isolation procedures.
- Take count of your tools
The tools, wires, and other fittings must be thoroughly counted before and after maintenance. This ensures that no damaged parts are being used in the installation. Counting the tools will ensure nothing is left inside the control panel and switchgear during the maintenance work.
Your circuit breaker should be routinely serviced to maintain its long life and ensure its proper working. You can take advantage of yearly servicing packages and ensure that your system gets enough attention and care. It can keep your whole factory or workplace running smoothly.
- Meet code requirements
Especially when any new electrical parts are installed, it’s essential to check on whether you’re meeting local electrical code standards. National Electrical Manufacturers Association (NEMA) or Institute of Electrical and Electronics Engineers (IEEE) guidelines are great. They have control procedures to help you set electrical maintenance standards in your workplace.
- Only the right person for the job
We cannot stress this one enough. Make sure you hire a skilled and experienced technician or electrician for the job. Under no circumstances should an employee be allowed to handle the electrical panels. Handling electricity and current can prove dangerous. All the safety precautions above must be read and followed carefully.
Following these tips can provide you and your family or co-workers with long-lasting protection against any fire or electric hazards. It’s always better to stock up on prevention measures than regret later!
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