Most people don’t understand the relationship between wire gauge and ampacity. Some might think 18-gauge wires can be used in any circuit, but that is not true. When voltage changes, the maximum amp value of that particular wire changes. Similarly, we cannot ignore the length of the wire and its effects. I’ve experienced this firsthand in many electrical projects. So, today, I’m focusing on breaking down and discussinghow many amps an 18 gauge wire can handle.
In general, 18 gauge wire can handle 14 amps at 90°C. This is the standard level that most electricians follow. However, depending on the distance and the voltage, the above amp value might change.
How Many Amps Can 18 AWG Handle?
AWG stands for American Wire Gauge. It is the standard method for measuring wire sizes in North America.
18 AWG Copper wire can handle 14 amps at 90°C. Usually, 18 AWG has a wire diameter of 1.024mm2 and a cross-sectional area of 0.823mm2.
Ampacity depends on various factors such as non-reactivity, voltage rating, flexibility, density, and flammability. However, the temperature can be labeled as the most significant factor. When the temperature is high the ampacity rating gets increased.
This is why most professionals point out a specific temperature with the wire size. In the above screenshot, you can find different wire gauges that fit certain temperatures and distances.
How Many Amps Can 18 Gauge Wire Handle at 12V?
As I mentioned earlier, the ampacity changes according to the voltage and length of the wire. So, when you supply 12V, the ampacity varies between 0.25A to 10A according to the distance. The voltage drop is the main reason for this change.
Voltage Drop
Whenever the resistance of the wire increases, the voltage drop increases accordingly. If you are having a difficult time grasping the above concept, this explanation might help.
Resistance depends on the cross-sectional area and the length of the wire. Follow the below equation.
R = ρL/A
Here, R is the resistance. ρ represents resistivity (constant value). A represents the cross-sectional area of the wire, and L represents the length of the wire.
So, when the length of the 18 wire gauge increases, the resistance increases accordingly.
According to Ohm’s Law,
V = IR
V represents voltage, I represents current, and R is the resistance.
Therefore, with higher resistance, the voltage drop is increased.
Acceptable Voltage Drop
The acceptable voltage drop should be under 3% for lights and 5% for other electrical appliances.
Considering the voltage drop, here are some examples for 12V and 18-gauge copper wires.
Example 1
As you can see, if the current is 5A, you can run an 18 gauge wire 5 feet.
Example 2
As you can see, if the current is 10A, you should run an 18 gauge wire under 3 feet.
Follow this link for the voltage drop calculator.
How Many Amps Can 18 Gauge Wire Handle at 24V?
When the voltage is 24V, an 18 gauge wire can handle a current range from 10VA to 50VA. Like in the above examples, these values have various distances.
Example 1
As you can see, if the current is 5A, you can run an 18 gauge wire 10 feet.
Example 2
As you can see, if the current is 10A, you should run an 18 gauge wire 5 feet.
How Many Amps Can 18 Gauge Wire Handle at 120V?
When the voltage is 120V, 18 gauge wire can handle 14 amps (1680 watts). You can run the 18 gauge wire 19 feet.
Keep in mind: Here, we are keeping the acceptable voltage drop below 3%.
How Many Amps Can 18 Gauge Wire Handle at 240V?
When the voltage is 240V, 18 gauge wire can handle 14 amps (3360 watts). You can run the 18 gauge wire a distance of 38 feet.
Uses of 18 Gauge Wire
Most often, 18 gauge wires can be located in 10A lamp cords. Apart from that, you can spot the 18 gauge wires in the following applications.
- 18 gauge wire is an excellent option for vehicle batteries and other automotive applications. For instance, most speaker wires range from 12 gauge to 18 gauge.
- Some people use 18 gauge wires for extension cords. For instance, in power tools such as drills and sanders, these 18 gauge wires are common.
What is 18 gauge Wire Rated For
18 AWG wires are rated for low voltage lighting.
Does Material (Aluminum/ Copper) Change its Amps
Yes, material type directly affects the amperage. Aluminum and Copper are the most common material used to produce these AWG wires. Before we dive into how the amperage changes according to the material, here are some unique features of these conductors.
Copper
Among the above two metals, most manufacturers use copper to produce wires. You can find copper wires in modern power distribution equipment and electronics. There are many reasons for this popularity. Here are some of them.
Higher Conductivity
One of the significant reasons for this popularity is conductivity. Copper has the highest conductivity among non-precious metals. That means copper is more conductive than aluminum.
Lower Thermal Expansion
Apart from that, the lower thermal expansion coefficient is also an advantage of using copper. Because of this, copper does not change easily during temperature changes.
Ability to Obtain Green Patina
Green patina is a chemical that forms naturally on bronze and copper. This chemical is a mixture of sulfides, copper chloride, carbonates, and sulfates. Because of the layer of green patina, the copper shows higher corrosion resistance.
Tip: Green patina does not disturb the copper wire’s performance.
Aluminum
Aluminum is the less popular metal compared to copper conductor wires. However, aluminum has some unique aspects that can be pretty useful. Here are some of them.
Less Weight
Even though aluminum has 61 percent lesser conductivity than copper, aluminum is equal to 30 percent of copper weight. Because of this, aluminum wires are easy to handle.
Inexpensive
Compared to copper aluminum is much cheaper. If you are looking for a low-budget wiring project, aluminum should be your choice.
Keep in mind: Aluminum reacts to water and produces hydrogen gas. This is a major concern among manufacturers. They can’t use the aluminum wires for tasks such as installing submarine cables. (1)
What About the Amperage?
For instance, if you use an 8 gauge copper wire for a given task, you would need a 6 gauge aluminum wire to perform the same task. Remember, with higher gauge numbers, the thickness of the wire decreases. So, you’ll need a thicker aluminum wire.
Benefits of Understanding Amp Values for 18 Gauge Wire
Knowing the amperage values for 18 gauge wire helps you pick suitable electronics and applications. With less thickness, the resistance of the wire gets increased due to the less cross-sectional area. This means the wires will heat up, and eventually, they will melt. Or sometimes it could affect your electronics. So, wiring with the correct gauge wire is crucial. Don’t use 18 gauge wires with a circuit that exceeds 14 amps. (2)
FAQs
Does Distance Affect Amps?
Yes. When the distance increased, the amp value decreases due to higher resistance. That is why you should run wires under acceptable voltage levels.
Maximum Current for 18 AWG Wire?
In general, 18 AWG wires can handle up to 16A. But the recommended level is 14A. So, keep the amp value in the safe zone.
What is the Amp Value for 18 Gauge Stranded Wire?
The average rating for an 18 gauge wire is 14A. However, solid wires are capable of carrying more current than stranded wires. Some professionals might limit the 18 gauge stranded wire to 7A.
What is the Amp Value for 18 Gauge Automotive Wire?
18 gauge automotive wires are unique. These wires can handle anything from 3A to 15A. When it comes to distance, you’ll be able to cover from 2.4 feet to 12.2 feet.
Wrapping Up
Indisputably, 18 gauge wires are an excellent choice for low voltage settings. Especially if you are using 10A lamps, 18 gauge wire will fit perfectly for those lamps.
However, remember to do your homework before making your final decision. Check the voltage drop level according to the distance. Also, check the type of wire; solid or stranded. Don’t use a stranded wire in place of a solid wire. Such a silly mistake might damage your electronics or melt the wires.
Take a look at some of our related articles below.
- How many watts can 16 gauge speaker wire handle
- What gauge wire for 20 amp 220v
- Where to find thick copper wire for scrap
References
(1) submarine cables – https://www.business-standard.com/podcast/current-affairs/what-are-submarine-cables-122031700046_1.html
(2) electronics – https://www.britannica.com/technology/electronics
Video References
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