If you want to install electrical wires in your home, your contractor probably encouraged you to buy 12AWG cables. The wire size is surprisingly common among electrical engineers. But is 12AWG appropriate for you? Can it handle your home’s load without overheating?
How many Amps Can 12 Gauge Wire Handle?
According to NEC, 12AWG copper wire can accommodate 25A at 60 degrees C, 25A at 75 degrees C, and 30A at 90 degrees C. If you have aluminum (or copper-clad aluminum), it can carry 20A at 60 degrees C, 20A at 75 degrees C, and 25A at 90 degrees C.
12 Gauge Wire Amp Rating Chart
|Wire Gauge Size
THW, THHW, THWN, USE, XHHW, ZW
THWN-2, THHN, XHHW-2, USE-2
THW, THWN, SE, USE, XHHW
XHHW-2, THHN, THWN-2
I suggest you use a maximum of 25 amps of electricity using 12AWG wire. Also, I don’t want you to pair 30A breakers with 12-gauge conductors because the conductors cannot carry the 30 amps. The breaker will force them to transport. As a result, it will trip when the load exceeds 30 amps.
Wire’s ampacity is however not necessarily fixed. Instead, the ampacity is shaped by several factors, including:
1). Ampacity Changes With Temperature
A conductor’s ampacity changes with the temperature. Higher temperatures limit a conductor’s current carrying capacity. This is because an increase in the temperature elevates the conductor’s resistance. From what electrical engineering has seen, a higher resistance equates to a lower volume of current.
This is why tables that compare and contrast different wire gauges show the ampacity of each wire size at different temperature ratings. Electrical engineers will take the ambient temperature of a given setting into account when they select wire sizes for a project.
2). Material (Aluminum Or Copper) Matters
The material is just as important as the temperature. Most people use aluminum or copper wiring. However, these two options have significant differences. Aluminum has a lower carrying capacity than copper.
For instance, you cannot replace a 12AWG copper conductor with a 12AWG aluminum wire. You need a thicker aluminum wire, maybe 10AWG or 8AWG, to replicate the capacity of a 12AWG copper conductor.
It is worth noting that the temperature will play a role in your selection here. Before choosing between aluminum and copper, you must first determine the temperature.
The ampacity of both materials will vary accordingly. Aluminum conductors might be appropriate for one temperature rating but not another. It may take you a while to select a suitable material because copper is more expensive than aluminum.
If these two options had the same price tags, everyone would simply use copper. But aluminum is cheaper, which is why consumers still flock to it. They only use 12AWG copper when 12AWG aluminum is insufficient for the setting or temperature.
3). Longer The Length, Higher The Resistance
The gauge has to increase with the length. This is because longer wires have more resistance, making them susceptible to overheating, especially if they have to carry larger volumes of current than their capacity permits.
You can prevent overheating by raising the gauge. A 12AWG copper conductor may carry 25 amps at 50 feet without overheating. But if you double the distance, the gauge (12AWG) may become insufficient.
The voltage drop is worse in aluminum conductors. 12AWG aluminum wiring carries far less current over long distances than 12AWG copper wire.
If you can’t wrap your head around all these variables and you still can’t determine whether or not 12AWG cables are appropriate for your application, look at the NEC’s tables.
They will show you the various wire sizes and ampacities at different temperatures. These tables take the material into consideration.
For instance, You can see that 12AWG copper wire can accommodate 25A at 60 degrees C, 25A at 75 degrees C, and 30A at 90 degrees C. If you have aluminum (or copper-clad aluminum), it can carry 20A at 60 degrees C, 20A at 75 degrees C, and 25A at 90 degrees C.
This may create some confusion. After all, a statement above suggested that increasing the temperature reduces the ampacity because it elevates the resistance. And that is true. This is not a contradiction.
Raising the temperature limits a conductor’s current carrying capacity.
Manufacturers are well aware of the negative impact the temperature can have on the ampacity.
For that reason, they make cables that can work at higher temperatures. Therefore, a wire with a higher temperature rating has a greater ampacity than a conductor with a lower temperature rating.
To clarify, the 12AWG copper cables in this NEC table do not have an ampacity of 30A at 90 degrees C. Instead, 12AWG copper cables with a temperature rating of 90 degrees C have an ampacity of 30A.
In other words, cables designed to work at 90 degrees C have a higher amp rating than conductors that work at a temperature of 75 degrees C. As you can see, a lot of thought goes into cable selection. You are better off leaving this decision in the hands of an expert.
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How Far Can You Run 12-Gauge Wire?
You can run 12 AWG copper wires for a maximum of 41 feet in a 120V circuit, 83 feet in a 240V circuit and 167 feet in 480V. This is for a single phase. In a three-phase, you can run 48 feet in a 120v, 96 feet in a 240v and 193 feet in a 480v with a voltage drop of 3 per cent. While I don’t suggest using 12 AWG aluminum wire.
For Copper Wire,
Does Distance Affect Its Amp Rating?
Every cable has resistance, and longer conductors have larger resistance. When electricity flows through a line, the resistance causes a voltage drop. In other words, you will lose some power.
Larger cables have less resistance than their smaller counterparts. Therefore, engineers reduce the voltage drop that usually occurs over long distances by using conductors with a greater diameter.
What does this mean? The amp rating of a 12AWG wire will not change? It will carry the same amount of current at 150 feet as it would at 10 feet. However, because the resistance changes with distance, the consequences will vary.
Even though the amp rating is the same, the voltage drop will increase with the distance, forcing you to get a thicker conductor to prevent overheating.
Does Voltage Affect Its Amps?
The voltage is concerned with the insulation. It has nothing to do with the wire gauge or ampacity. The gauge and ampacity go hand in hand because the diameter of a conductor determines the amount of current it can carry.
This is another area where an electrical engineer’s knowledge is necessary. They can use the variables surrounding the application you have in mind to identify cables with the appropriate insulation. For instance, conductors you have to bury underground require more robust insulation.
How many Amps can 12-Gauge Wire Handle At 12 Volts?
12AWG wire can handle a maximum of 25A at 12 volts. The amount of electricity the wire can take does not change regardless of the voltage.
How Many Amps Can 12-Gauge Wire Handle At 120 Volts?
12AWG cables can handle upto 25A at 120 volts. The voltage doesn’t matter. Or, at the very least, it won’t affect the ampacity. It will change the wattage because you have to multiply the amps by 120V instead of 240V. But the ampacity remains the same.
How Many Amps Can 12-Gauge Wire Handle At 240 Volts?
12AWG wire can handle upto 25A at 240 volts. Naturally, the ampacity will change depending on the temperature, material, and length. But the voltage doesn’t affect the ampacity.
Does Material Affect Its Amp Rating?
The material is important. Copper has a higher current carrying capacity than aluminum. Therefore, whenever you replace copper with aluminum, you must raise the gauge.
For instance, consumers need 6AWG aluminum conductors to replace 8AWG copper conductors. But the copper conductors are heavier (65lb) than aluminum (39lb). Additionally, aluminum is cheaper, which is why people still use it today.
If aluminum and copper had the same prices, people would flock to copper. You can buy thicker aluminum wiring if you don’t have the money. But again, you must consult an expert who can determine whether aluminum is a viable solution in light of factors such as temperature.
What Does The NEC Say About It?
The National Electrical Code has a table that shows the ampacity of a 12AWG conductor in relation to the material and temperature rating. They associate 12AWG with ampacities ranging from 20 to 30 amps.
You can check your local code to determine whether or not it matches the NEC’s regulations on this matter. Most local codes have adopted the NEC’s rulings. But it doesn’t hurt to check.
Uses of 12-Gauge Wire
12AWG wire has a thickness of 2.053mm (0.0808 inches), which is why people call it 2mm wire. It is 21 percent larger in diameter than 14AWG wire (1.628mm) and 26 percent smaller than 10AWG (2.588mm).
It can work with kitchen and bathroom appliances. The wattage will affect the applicability of the wire.12AWG conductors can handle 20 to 30 amps depending on the material and temperature rating.
Identify the appliance you want to run and convert its wattage into amps. You can do this by dividing the wattage by the voltage. Make sure the amp rating of the appliance doesn’t exceed the cable’s ampacity.
Don’t forget that devices like freezers have a starting amperage that significantly exceeds their operating amp rating. For instance, a 20A freezer will use more than 20 amps when it starts.
12 Gauge Wire Watt Rating
You have to multiply the amps by the voltage to get the watts. For instance, the average 12AWG cable has an ampacity of 20A. Where homes with a 120V electrical service are concerned, multiplying 120V by 20A will give you 2400 watts. On the other hand, multiplying 240V by 20A gives you 4800 watts.
12 Gauge Wire Vs Breaker Size
You can use 12-gauge wire on a 15, 20, 25 amp breaker. It will only be a problem if it exceeds 25 Amps.
12-Gauge Automotive/Stranded Wire Rating
12-gauge copper wire can handle 30 amps (90 degrees C).