If you have been to an electrical store, you will notice electrical wires come in several sizes. Most people would think that it does not matter and is pure aesthetics.
Its size greatly depends on other things, such as the electrical current passing through. We will be going through the different products in the following sections using the American wire gauge system.
Summary
The NEC, THHN, & AWG wire gauge amp chart is the easiest way to see the amp rating for different wire thicknesses. From it, you can see a list of things, including:
- The 6 gauge wire amp rating is 65 amps for copper, with 167°F ambient temperature.
- The 4 gauge wire amp rating is 85 amps for copper, with 167°F ambient temperature.
- The 2 gauge wire amp rating is 115 amps for copper, with 167°F ambient temperature.
Table of Contents
NEC, THHN & AWG Wire Gauge Ampacity Rating Chart
This section only serves as a guide when looking at a gauge chart. If you plan to install anything involving electricity, always call for a professional electrician to handle the work for you.
The table below shows that the AWG value is opposite the diameter. It means a higher AWG value would mean a smaller size. For example, a 12-gauge option can carry a higher amp than an 18-rated one.
| Wire Gauge Size | Aluminum, 75°C (167°F) THW, THWN, SE, USE, XHHW | Aluminum 90°C (194°F) XHHW-2, THHN, THWN-2 | Copper, 75°C (167°F) THW, THWN, SE, USE, XHHW | Copper, 90°C (194°F) THWN-2, THHN, XHHW-2, USE-2 |
| 14 | — | — | 20 | 25 |
| 12 | 20 | 25 | 25 | 30 |
| 10 | 30 | 35 | 35 | 40 |
| 8 | 40 | 45 | 50 | $55 |
| 6 | 50 | 55 | 65 | 75 |
| 4 | 65 | 75 | 85 | 95 |
| 3 | 75 | 85 | 100 | 115 |
| 2 | 90 | 100 | 115 | 130 |
| 1 | 100 | 115 | 130 | 145 |
| 1/0 | 120 | $135 | 150 | 170 |
| 2/0 | 135 | $150 | 175 | 195 |
| 3/0 | 155 | 175 | 200 | 225 |
| 4/0 | 180 | 205 | 230 | 260 |
| 250 | 205 | 230 | 255 | 290 |
| 300 | 230 | 260 | 285 | 320 |
| 350 | 250 | 280 | 310 | 350 |
| 500 | 310 | 350 | 380 | 430 |
| 600 | 340 | 385 | 420 | 475 |
| 750 | 385 | 435 | 475 | 535 |
| 1000 | 445 | 500 | 545 | 615 |
THHN vs. THWN
When looking at electrical wires, manufacturers use different types of material for the coating. The most common types are the Thermoplastic High-Heat Nylon-coated (THHN) and THWN. It stands for “Thermoplastic Heat and Water-resistant Nylon-coated.” Suppose you think about how these two are different.
The THWN can operate in an environment similar to the THHN without additional accessories. The Thermoplastic Heat and Water-Resistant Nylon-coated wire is a better version of the THHN. You can still find both across different infrastructures.
Thermoplastic High-Heat Nylon-coated (THHN)
The Thermoplastic High-Heat Nylon-coated wire is probably the more common option between the two. You can find this product in almost any commercial or residential building. Depending on the size, it comes in either a stranded or a solid wire. It uses either aluminum or copper as the conductive material.
Finally, polyvinyl chloride (PVC) wraps the conductive material and serves as insulation. THHN rates at 75°C in a wet location or 90°C in a dry location. Several options of this type carry a dual rating cable, which you can identify by a THHN / THWN marking.
If you think about distinguishing this from other types, you will observe its PVC insulation. In most cases, it uses a thinner one. It is important in electrical properties to determine its amp rating.
A negative effect of having a thin insulation layer is frequent current leaking, leading to a breakdown. When the insulation in THHN burns, it releases toxic smoke. It is highly undesirable.
Since this type uses nylon coating, it is not extremely flexible. It becomes an issue for some people, especially those who want to maximize saving time and energy during installation. Despite its cons, the THHN is still very popular because it is cheaper.
When you plan to wire an entire building, you will want to save money whenever you can. Having a cost-effective solution without sacrificing safety goes a long way, so several people still go for a THHN.
Thermoplastic Heat and Water-resistant Nylon-coated (THWN)
Thermoplastic Heat and Water-resistant Nylon-coated (THWN) are the least common of the two. According to the National Electrical Code, you can mostly find this type in industrial and commercial buildings. Its outer layer is tough yet easy to pull and bend.
When installing it, electricians will not have a hard time bending it. It saves them time and energy in the long run. The THWN is also resistant to common chemicals, such as gasoline and moisture.
Unlike THHN, you can commonly find the THWN in alternating current electrical distribution systems across the country.
It can be used during the installation of a range of things, including:
- Machine tools
- conduits
- feeders
- controlled circuits.
These systems typically have voltage levels that range from 110 volts to 600 volts. It uses copper or aluminum conductors, either solid or stranded.
It is suitable for use up to 90°C temperature in dry and wet locations. When it comes in contact with oil or coolant, the suitable temperature you can expose it to decreases to 75°C.
The THWN wire has approvals from several laboratories and regulatory boards, including:
- The Canadian Standards Association
- Underwriters Laboratories
- American Society for Testing
- Materials Miscellaneous
- Restriction of Hazardous Substances Directive
Is it dangerous to use the wrong one?
The short answer to this question is yes. It is dangerous to use an incorrect size. If you want to avoid unnecessary danger if you’re welding, you’ll want to make the right electrical choices.
A common misconception is that there won’t be any issues as long as the wire fits with the connector. When dealing with circuit breakers, pay much attention to the wire.
Those unaware often use an AWG below the recommended rating because it is cheaper. They think it won’t make any difference. In the long run, getting a smaller one than what you should be getting will only cost you more.
Professional electricians often recommend using a larger rating for your circuit breaker. You will greatly reduce the chances of using the incorrect option. You don’t want to pick one that can’t handle the necessary amount of amps you’re dealing with.
Picking a bigger one will not negatively impact performance or safety. The only negative effect it has is on your budget, which will cost you more than using a substandard option. Looking at it in the long run, you can save more because you will unlikely run into damage with your circuit breaker.
How to choose the right one?
It is important to know about compatibility across different scenarios when dealing with electrical components. Choosing an incorrect size could lead to burning or fire at worst. People think it does not play an important role, but it does. Pick the correct one to prevent any accidents from happening.
When dealing with a circuit breaker setup, extra precautions need to be in place. For example, the AWG needs to be compatible with the circuit breaker you plan to use. One that is too small for the circuit breaker could lead to a drop in performance. At worst, it can start a fire.
In the following sections of this article, we will discuss the maximum amps a particular AWG can support. If you have an 8-gauge, will a 30 amp circuit breaker work with it without any issues?
