Knowing which size to pick is important, so you can use the right one for your equipment that requires electricity. If this is your first time reading about the topic, we cover some basic things to know about it.
In a hurry? Buying recommendations
We’ve got you covered if you want to buy a circuit breaker or a sub-panel. We can also help you with a transfer switch or fuse for your 70 to 600 amp service needs. We’ve found all the products we recommend based on NEC’s chart to ensure safety.
A Rule of Thumb: What are the correct wire sizes for 70 to Amp Service & Breakers?
What electrical components do I need for a project? The rule of thumb that techs will usually go by is that for a 70 amp circuit breaker, 4-gauge copper wire is the right one to go with. For an 80 amp, you need a 4-gauge copper wire. For a 100 amp service, you will need a 1-gauge wire.
For 125 amps, you will need a 1-gauge copper wire. For 150 amp, you will need a 1/0-size copper wire. For a 200 amp service, you will need a 250 kcmil-gauge copper wire. For a 400 amp service, you will need a 600 kcmil-gauge copper wire. For 600 amp, you will need a 1500 kcmil-gauge wire.
It’s important to realize that these rules of thumb come with certain limitations, such as the material and the ambient temperature.
We’ll get into it and share a wire ampacity rating chart for people who know what a gauge is and its importance. Use it to figure out what it is that you need. Scroll down a little bit.
This article was made due to the popularity of our original article. Choosing the right cord is crucial whether doing gasless MIG welding or welding aluminum. Any electrical activity has certain requirements.
The chart below can show you the wire size for 70, 80, 100, 125, 150, 200, 300, 400, or 600 amp of service. Scroll down the page a little bit further.
Table of content
- A Rule of Thumb
- What is a gauge?
- Choosing the right one
- What happens when you choose the wrong one
- But if you find yourself having the incorrect one, here are the things that might happen.
- Standard wire gauge chart
A Rule of Thumb
We encourage you to look at the chart below to find the right products for your project. There are general rules of thumb that techs go by, which we have included in the chart.
We’ve got the chart you need to see the electrical cable requirements for aluminum and copper.
Below is a table based on conductor temperatures of 140°F unless otherwise stated, taken from the NEC 310.16.
|Ground wire, service entrance, circuit, breaker size chart rating|
|Service or Feeder Rating (amp)||Aluminum conductor||Copper conductor|
|70||#2 AWG||#4 AWG|
|80||#1 AWG||#3 AWG|
|100||#1/0 AWG||#1 AWG|
|125||#3/0 AWG||#1/0 AWG|
|150||#4/0 AWG||#3/0 AWG|
|200||350 kcmil||250 kcmil|
|300||700 kcmil||500 kcmil|
|400||1,250 kcmil||750 kcmil|
|600||2,000 kcmil (194°F)||1,500 kcmil (167°F)|
Suppose you are unsure of which type of material you are dealing with or don’t know the right temperature. We always suggest erring on the side of caution. For that reason, our recommendations will always suggest a safe choice given the ambient temperature. It’s always better to choose a bigger diameter if you are unsure about any conditions that could influence the performance.
As you can see, you will want a 6 gauge wire for 60 amp. If you’re more cautious, a 4 AWG is great. That is assuming the right conditions, such as temperature.
Let’s say you have an 8-gauge and a 10-rated lying around at home. You want to know if you can use these with the circuit breaker. The 8-gauge nor the 10-gauge can be coupled with this breaker. Simply take a look at the chart further down the page.
For 70 amp, the right wire is either a gauge 3 aluminum or a gauge 4 copper. That is, assuming there aren’t other factors impacting the performance.
The requirement depends on whether aluminum or copper is used and the ambient temperature. For a circuit breaker with this rating, you can use 4-gauge copper at an ambient temperature of 140°F.
80 amp wire size
The right 80 amp wire size is a gauge 4 copper wire. 80 amp service will need to be a 2 AWG if you are going for aluminum instead. Be sure you get the right one for your subpanel and breaker!
What size wire for 100 amp service?
The right 100 amp wire size is a 1-gauge. However, that is only if you don’t consider the material. We’ll go into a little bit more detail below.
You need to get a gauge 1 made of aluminum for a sub-panel, whereas a 3 will work if it is copper. It applies to both a breaker & sub-panel. These recommendations are based on conductor temperature ratings of 167°F.
Be sure to consider the table below to see the various products we recommend for sub-panels and entrance cables. When you click on the table, you may have to make the right selection to follow the electrical recommendations provided.
The right wire size for 125 amp service is a gauge 1 copper or a 2/0 aluminum to be on the safe side. Look at the table below to see the sub panel and breaker we recommend for 125 amps of service.
For 150 amp, you need a 3/0 wire size made of aluminum. Otherwise, a 1/0 is the smallest you can go with when looking at copper.
Suppose you have a circuit breaker at home with this rating, and you would like to use it.
You will need 1/0-gauge copper at an ambient temperature of 167°F or 2/0-gauge aluminum at an ambient temperature of 194°F.
What size wire for 200 amp service?
The right 200 amp wire size is 250 made of aluminum or a 3/0 made of copper. Here’s a table with the different sub-panel and breakers we recommend for this power level.
For 300 amp service, you will want copper wire of size 500 kcmil to handle the load.
What size wire for 400 amp service?
The right 400 amp wire size requires an aluminum wire size of 1000 kcmil. In contrast, a copper 600 kcmil can handle that amount of power. Take a look at the NEC electrical cable chart below.
The right wire size for 600 amp service is at least 1500 kcmil assuming a temperature of 167°F of the conductor.
Full wire size chart for 70, 80, 100, 125, 150, 200, 300, 400, & 600 amp
|Max amp for||Aluminum||Max amp for||Copper||Our recommendation|
What is a gauge?
The gauge is the diameter of the product. This determines how much electrical current it can safely carry. If you have ever been to the electrical section of a hardware store, you will notice it comes in several options.
Instead of referring to its actual thickness, people use its gauge. 6 and 4 are just some of the numbers you’ll encounter. You could also come across gauges like 1/0, 2/0, and 3/0.
It is inversely proportional to the diameter. It means the higher the number, the smaller the diameter. If it is not written on the product itself or is unclear, you can use a thickness tool to determine it. Getting the right diameter is important because it determines the maximum current it can safely handle. Using an incorrect one could lead to serious problems in the long run. So before deciding which to buy, consider how much electrical current it can handle by identifying the devices you will use.
The United States and 65 other countries use the AWG as the unit of measure. Other countries use the Imperial Standard, defined by the British Board of Trade.
Choosing the right one
They usually burn if you use the incorrect one. It is advisable to know the correct one to prevent this from happening. The bad thing is that most people are not aware that your choice makes a difference. People often make the connections themselves without consulting or calling a licensed electrician. It could lead to serious issues when done incorrectly.
When the setup involves the circuit breaker, you should take extra precautions. Installing the right components will greatly prevent common issues from happening. In most cases, issues arise because of an incorrect one. The different electrical components always need to be compatible with one another.
If you have a 60 amp circuit breaker for your water heater, read the next section as we guide you to understand the basics. We’ll ensure you know which products go with your clothes dryer or air conditioner.
What happens when you choose the wrong one
It is a common misconception for people to think that as long as the ends of the wire fit a connector, there will be no issues. It is not the case for circuit breakers. People unaware of their importance often use too small gauges to connect their circuit breakers. Smaller diameter ones are cheaper than the bigger ones. Unaware people often go for the cheaper ones, thinking it will not make any difference. Sadly, it will only cost them more in the long run.
Using a larger one for your circuit breaker is often the best way to go. The only negative effect this has is your budget, which will cost you more upfront. When picking a larger one, you spend more than what you may need. However, it will not cause any damage to your circuit breaker. Instead, it can better handle the electrical current flowing through it.
But if you find yourself having the incorrect one, here are the things that might happen.
|Drop-in performance||Melted insulation|
A drop in performance
If you connect appliances to a circuit breaker using too small one, achieving peak efficiency may be impossible. The appliances can only receive a part of the energy required to operate at peak performance. In effect, your appliances will be unlikely to achieve their optimal performance.
You may have a 15 amp circuit breaker that you need to use for light fixtures at home. At best, using anything less than the recommended 14-gauge could lead to performance issues. For electric furnaces, you need at least a 4 because of the amount of current they consume.
It can start a fire
Fire is the worst-case caused by a burning electrical component that starts. Although modern circuit breakers have safety measures, they may not be enough if the load is too much.
A common safety measure for modern circuit breakers is the trip mechanism. When the circuit breaker experiences an overload, it will trip to cut the current from passing through. It helps prevent any damage from happening. However, having a trip mechanism does not fully prevent a fire from happening.
A smaller diameter can handle less current, making them more resistant to energy flow. If the diameter is way smaller for your circuit breaker, the current flowing is more than it can handle. Due to high resistance, heat generates and will eventually lead to melting.
Damage to the equipment
Aside from performance drop issues and the possibility of starting a fire, using a smaller one may damage your equipment. When the power supply is not stable, it may bust your equipment.
Standard wire gauge chart
You should know that it is important to have a licensed electrician handle any electrical work. It helps to know some basic electrical things, such as the right gauge. The chart electricians use as their reference will differ depending on the region.
Using a standard measurement instrument is easy to answer your questions about the product’s diameter. We use the AWG system in the United States to determine it. The AWG defines the diameter of solid round wires, otherwise known as the gauge. Given the various conditions, the capacity is the highest current it can handle. The material it was made from, and the ambient temperature is important factors.
When referring to the table below, note that the AWG value is opposite to the diameter. A higher AWG refers to a smaller diameter. It means an 8-gauge can support a higher capacity than a 10. The chart below defines the diameter in inches and millimeters. The chart should help determine which one to choose.
The one with the largest diameter is the 0000, while the smallest is the 40. The former lets more energy flow through it at any given time than the smaller ones will.
Frequently Asked Questions
Let us look at other queries and questions that commonly pop up in electrical work.
Wire versus Cable
Both of the above terms may seem interchangeable to many folks, but few know the significance of each. The basic wire is one conductor, whereas a cable has many different conductors grouped. An outer layer of the sheath protects the cables. The wire usually goes bare or has a PVC coating on top to protect and prevent accidents.
The wire unit is the gauge or thickness we have referred to above. In the case of the cable, the measuring unit is the total number of wires a cable consists of and their thickness.
Wires carry small electrical loads and transmit telecommunication signals and other small parts like bulbs and vehicle parts. On the other hand, the cables transport huge loads of electrical currents.
The cable types include coaxial cable and twisted pair cable. It can also include multi-conductor cable and fiber-optic cable. A multi-conductor table means joining many different cables. Its goal is to reduce noise and cross-talk. Coaxial cables consist of two conductors running parallel to them, one inside and one outside. These are generally used in televisions. You’ll generally find the twisted pair type wherever data and telecommunication transportation is required. Since the twisting of the two conductors reduces noise, it is perfect for transmitting data signals through long distances.
Is it ‘Gauge’ or ‘AWG’?
American Wire Gauge is often referred to as AWG. It is the standard used in most of North America and refers to thickness. It is used to denote the current carrying capacity of the wire and the cross-sectional area. Using this standard means you can purchase a 14 AWG wire from two different vendors. You will find they are the same thickness. The ‘gauge’ can be used as a shortened way of expressing AWG, but the seller must always confirm this. Sometimes manufacturers use the term ‘gauge’ to market cables that are certainly not in AWG units.
What is a breaker box/sub-panel? What is the difference between a Main Panel and Sub-panel?
The main panel is also known as the service entrance panel. Here the power company’s current first enters the home and is further distributed to the rest of the household. It’s also the first safety net that protects your home from any kind of electrical damage or fires. Suppose you suspect any faults in the circuit. You can directly switch off the main panel and take your home out of the power grid of the electricity supplier.
The sub-panel is like a miniature main panel that doesn’t have a direct connection to the power utility company. It feeds off the main panel’s current. Its purpose is quite similar to the main panels in that it protects appliances from shorting or faulting. They also contain circuit breakers and fuses to detect any electricity surcharge and immediately stop the current to avoid fires. But then how are sub-panels different?
Sub-panels are different as they take their power from the main panel. Their main purpose is to help you organize your home’s electrical circuit in a manageable manner. You could also use a sub-panel to avoid overcrowding in the main panel. Overloading is a serious fire hazard. You can avoid this by distributing your home into the area, each having its sub-panel.
Subpanels can also isolate certain areas that have different power usage. For instance, a garage workshop will put a great load on the main panel with its heavy machinery. You can avoid this by setting up a separate sub-panel for the garage. You can isolate the area with the problem and turn off the respective area’s sub-panel in any short or fault. At the same time, the rest of the house can remain powered as usual.
What is the difference between Neutral and Earth lines?
The simplest way to explain the Neutral and earth lines is to look at a basic three-pin socket. Each pin corresponds to Earth, neutral, and phase. While the phase line carries the current, the neutral line makes for the return for balancing the flow. The earth line is the safety net during the entire process.
Earth line: The fluctuation of alternating current in household or workplace use can be dangerous if not directed elsewhere. That is why the earth line makes sure to take the extra current directly into the ground so that no shorts or accidents occur. A rod is used to direct the extra current under faulty conditions. During normal conditions, this line usually stays current-free.
Neutral line: This line is a return path for the alternating current, connecting the flow to its origin point. Even though it carries no current, the circuit is incomplete without this line. It is also known as the zero potential point. The return path provides a way to make the total of the current zero. In this way, both neutral and earth lines are safety lines. Preventive measures are taken to reduce the chances of a short scenario of a faulty current discharge.
What is a base meter? When is it time for a replacement?
A base meter is a protective enclosure around the electric meter to keep the machinery. It wires dry and in proper working condition. It is also responsible for receiving the supply of current from the power utility company and sending it to the main power panel of the house. Although the power utility company provides the meter box, the homeowner is responsible for all other attachments. Keeping the meter box and meter base in the appropriate condition is important for the house to be powered.
Suppose you spot any of the following signs. Your meter base may be in trouble, like flickering lights and devices not working. It could also be partial outages in the house. If you spot any visible damage to your meter box and base, it also may be time for a replacement. It can include corrosion on the inside or outside due to the weather conditions or torn and broken wires. Apart from all these conditions, updating meters to standard building and electricity codes is a major reason to get your meter base replaced. It is common for meter boxes to upgrade to a 200A capacity as older homes generally have 60A capacity meters installed. If you have a large home or property, a 400A capacity meter would be more appropriate.
What is the National Electrical Code?
The NEC is used as a benchmark for safe electrical installation and inspection in all 50 United States of America. It is part of the publication by the National Fire Protection Association. Although it is not established by federal law, all states commonly follow it.
Basic NEC rules and Codes
- Size of circuit breaker: For non-motor loads, the maximum loading for a breaker is cut off at 80%. Under no circumstances can the breaker be larger than the ampacity unless it is for motor loads.
- General design guidelines: lights and outlets should be set up on different circuits. This will allow maximum loading on light circuits and leave capacity for other outlets.
- Outlets circuits must have GFI protection if located in residential locations. Any place with portable equipment and machinery must also have GFI outlets. This includes any garage areas and workshops. It can also include shops and warehouses. Each piece of fixed machinery like drill presses or welding machines must also have its GFI-protected circuit.
- Service size: The minimum service for a very small building is 100 A and 20 circuits. It is advisable to do load calculations for larger places.
- Underground – Use XLP-USE for underground wiring, with AWG copper minimum.
- Protecting cables and conduits: Conductors must be inside a cord or trench. They can also be inside a raceway or cable tray.
- Outdoor receptacle: Each home must have one front and one rear receptacle, which is easily accessible. It is advised it should be located no more than 6 and a half feet above the ground.
- Receptacles used to supply power to the pumps and motors of spas and pools must be at least 10ft away from the pool if without GFCI. If the receptacle is GFCI protected, it can be located no closer than 6ft.
- Light fixtures located outdoors do not require GFCI protection.
- Low voltage light fixtures should not be any nearer than 5ft to indoor water structures like spas and pools.
- Telephone and other types of wiring should be located at least 10ft away from the top of the water surface of indoor water structures.
- Underground wiring must be covered with conduit.
- Buried underground or exposed wiring must always be listed for its use. UF cable type is best known for underground purposes as it can be dug and settled underground without the use of a conduit.
- Wiring carrying equal to or less than 30 volts must be located 6 inches deep underground.
AWG4 in copper is the usual size to use. The panel is also known as the breaker box. You will need a sturdy and well-insulated wire to prevent loss of current and accidents in this area. You will need both a ground wire and a neutral wire running from the meter box. The neutral wire will improve the effectiveness of the circuit and push back any straying current back into the circuit. The ground wire is run for protective measures to prevent the current fluctuations from damaging the circuit wiring. For this purpose, you can use AWG4 in copper material.
You’re going to need something thick and durable for something of this voltage. This is why it’s best to stick to AWG2 in copper or AWG4 in aluminum material for a 200 amp service. For something slightly lower like 150amps, AWG1 in copper and AWG2 in aluminum.
For 400 amp service, you will need 400AWG or 350copper amps between the pole and the new electrical service and circuit breaker box. For a 400 amp service, you will require a size 3 conduit. Don’t fret! Using a service of this size should be no different for you cost-wise.
This should be more than enough for small and medium-sized homes. It is ideal for larger homes with many electrical appliances and cooling devices like air conditioners or heating appliances. A 400 amp service is recommended where the heat load exceeds 20000 watts.
Solid and stranded versions see a lot of use in electrical equipment, but how are they different? A solid type consists of a single solid core wire. The stranded type consists of an assembly of thinner wires.
Stranded wires are more flexible since they consist of many smaller sub-parts. It is also significantly more malleable and does not split or get damaged in devices and control panels. They are frequently used in small and cramped spaces where sub-parts must be connected and fit together regardless of the awkward positions.
The solid type is thicker and ideal for spaces requiring high durability and heavy current. This can include porch areas and backyards. It can even be set up in the garage where you need to power heavy equipment like drill presses and chainsaws. The thick size and high resistance to weather conditions mean it can be used widely in the electric parts of vehicles and big buildings.
Both of these are used as safety nets to completely stop the flow of the circuit if there is an overload. However, there are some differences between the two.
The biggest difference between the two is a fuse is a self-destructing metal piece. It melts when there is an overload to protect the circuit. A Miniature circuit breaker has a switch that trips when there is an overflow of current or a fault.
It essentially means that a fuse will have to be replaced every time there is an overload. An MCB can be used again and again. Another disadvantage of the fuse is that it doesn’t indicate an overload and must be checked every time.
The working principles of the fuse and MCB are also very different. While a fuse detects thermal and electrical properties, an MCB works on electromagnetic principles.
A fuse is significantly cheaper than an MCB. It is ideal for homeowners who require a cheap, low-breaking capacity option.
Therefore a Miniature circuit breaker is preferable over a fuse for your home.
How do you read wire size charts?
- Find out the requirement of amps.
You’re going to have to work out the voltage requirement. This factor is essential in determining the thickness of wires you’ll need in the project. This will be calculated using the number of devices and their corresponding volts.
- Find the ideal type of wiring.
When it comes to the type of wiring, there are plenty of options in the market. You can go the cheaper route with aluminum or choose the more sturdy and high current-carrying copper. Some people even choose precious silver in some places. While aluminum is more flexible, copper is tougher.
- Read a wire size chart using the above values.
In the row section, look for the material. It can either be copper or aluminum. In the column section, look for the voltage section to find the ampacity you require for your project. After you have done this, look for the intersection of the two. You’ll easily find the wire size or AWG you need to purchase. Voila! You’re one step closer to becoming an electrical expert!
It is an essential skill if you’re just getting into electrical wiring and systems know-how. Now you know the basic steps to reading an online wire size chart.
Read a wire size chart using the above values.