Electrical wires can be very confusing. There are multiple wire sizes, and understanding their functions and capacity is tough. But today, I am here to simplify the number of amps a 12 gauge wire can handle.
As a general rule, a 12 gauge wire can handle a maximum amount of 20 Amps. However, the NEC code also allows you to handle around 25 Amps with the exemption of the motor loads. So, if you use the wire for power outlets of light devices, fans, and lights, it can handle up to 25 Amps.
This article will help you know the right amount of amps a 12 gauge wire can handle and whether it can tolerate other amperes or not. Besides, we will also share the factors to consider for ampacity shaping.
How many amps can a 12-wire gauge handle?
According to the National Electric Code (NEC), a 12 gauge wire can handle 20 amps.
It can also handle 25 amps, but with the exemption of the motor loads.
The amps may change depending on various factors.
For example, if you use copper wire, a 12 gauge wire can handle 25 amps at 60°C and 75°C and 30 amps at 90°C.
On the contrary, a 12 gauge aluminum wire can handle 20 amps at 60 and 75°C and 25 amps at 90°C.
However, you can use the maximum value to be 25 amps.
Pairing a 12 gauge wire with a 30 amp breaker will cause overloading because a 12 AWG won’t be able to handle 30 amps to a great extent.
The breaker will force the wire to transport, which can cause constant tripping if the load exceeds 30 amps.
The 20 amps are the best amperage to be handled by a 12 gauge wire.
Can a 12 gauge wire handle 15 amps?
A 12 gauge wire has the limitation of supporting up to 20 amps.
You can use it for 25 amps, but the wire can overheat.
Since the 12 gauge wires can easily handle 20 amps, they will also manage 15 amps safely without overheating them.
Sometimes, 12 and 14-gauge wires require mixing.
If you want them to mix and use, you can do so in this circuit.
Both wires will run safely in this circuit without overheating.
Can a 12-gauge wire handle 25 amps?
Though the maximum limit is said to be 25 amps by the NEC, it is mostly used in motor loads.
In general, the peak reading for a 12 gauge wire is 20 amps. It is the same in most house wiring systems.
Though you can use the 12 gauge wires in 25 amp circuits, the wires will overheat after some time.
Since it is about electricity, you should always try to stay away from heating.
So, if you have a 25 amp circuit, you should try some bigger gauges, like 10 gauge wires.
Can a 12 gauge wire handle 30 amps?
The 12 gauge wires are not safe for the 30 amp circuits.
It will overheat the wires and create a short circuit.
It will further lead the wires to melt, explode, and start a fire.
So, if you have a 30 amp circuit, do not use 12 gauge wires.
Instead, go for a bigger gauge, like 8 or 10-gauge wires.
However, if you have copper wires, you can use them if the temperature remains within 167°F.
But, it is better to avoid 30 amps.
Will the 12 gauge wires manage 50 amps?
The 12 gauge wires are not meant for 50 amp circuits.
A 50 amp circuit draws excessive current, which is impossible for the 12 gauge wires to handle.
You will receive a short circuit if you use a 12 gauge wire for your 50 amp circuit.
The wires will melt, explode, and start a fire due to excessive overheating.
For a 50 amp circuit, you can opt for 8 or 4 gauge wires.
The 8 gauge wires can handle up to 55 amps, and 4 gauge wires can tolerate up to 70 amps. So, these wires can easily handle 50 amps.
Factors to consider while installing 12 gauge wires in a circuit
The ampacity a wire can handle always does not remain the same.
It will change based on several factors.
So, before you decide and exact ampacity, you must consider the following factors for 12 gauge wires:
There are 3 types of wires commonly used for electrical purposes:
- Copper-clad aluminum
The ampacity will change depending on the wire types.
Copper wires can handle current much better than aluminum or copper-clad aluminum wires.
Copper has better conductivity, strength, and durability.
But, aluminum does not have good conductivity.
It overheats easily.
On the contrary, copper-clad aluminum is slightly better than aluminum because it contains copper fittings, giving some copper benefits.
So, a 12 gauge wire can handle up to 25 amps if you use copper wires.
But, if you opt for aluminum or copper-clad, 20 amps is the best option.
A 12 gauge copper and 12 gauge aluminum do not have the same conductivity and durability.
If you use 12 gauge wire for your 25 amps circuit, a 12 gauge aluminum will have the same qualities as copper.
To replicate the copper wire quality, you must use a 10 or 8-gauge aluminum or copper-clad wire for the same circuit.
Temperature also plays a great role besides the wire material.
The next point will make it clear to you.
Ampacity changes with temperature
The wire’s amperage capacity will change depending on the temperature rating.
If the temperature is high, the wire’s size will change.
The wire cannot withstand temperatures exceeding its capacity and start overheating. It will further cause short circuits and fire hazards.
The wire material and temperature come hand in hand.
If you have copper wires, then:
- The 12 gauge wires will handle 25 amps at 140°F and 167°F.
- At 203°F, a 12 gauge wire will handle 30 amps.
If you have aluminum or copper-clad aluminum wires, then the 12 gauge wire will handle:
- 20 amps at 140°F and 167°F.
- 25 amps at 203°F.
As you can see, the ampacity of 12 gauge wire changes depending on the temperature and material.
A copper wire can handle as close as 30 amps.
However, it is not recommended because that will overheat the wires badly.
It is always best to let the temperatures go up to 167°F.
In that sense, 20-25 amps would be the best for 12 gauge wires.
If the temperature increases, the wire’s current carrying capacity will decrease.
Longer lengths will have overheating issues.
The gauge will increase with the length.
Longer wires have more resistance which makes them vulnerable to overheating.
It mostly happens when the wires carry currents more than their capacity.
If you increase the gauge, you can decrease the resistance and overheat.
A 12-gauge copper wire will carry 20 amps at 50 feet without overheating.
But the 12 gauge wire can’t carry 20 amps over 100 feet.
The voltage drop is worse in aluminum wires.
A 12 gauge aluminum wire won’t be able to carry such long distances.
They have more resistance and, thus, are prone to overheating.
Let me explain a bit.
At every 100 feet, a 12 gauge copper wire loses 3.3% of voltage.
So, if you have used 12 gauge wire in 20 amp 240 volts, it will drop to 232.08 volts. So, there will be a loss of 7.92 volts.
If you have used aluminum wires, at every 100 feet, the voltage drop will rise to 5.42%.
Using the wire at 20 amps at 240 volts will lose 13 volts, and your voltage will drop to 227 volts.
At 120 volts, the copper wire will have a voltage drop of 6.6%.
So, if you use the wire for 100 feet, there will be a significant drop at such a distance.
That is why it is not recommended to use 12 gauge wires over 100 feet.
If you cannot understand these things, consider checking the NEC table and using wires depending on your distance.
Does voltage affect the ampacity?
Though the voltage does not affect the ampacity of the 12 gauge wires, people still consider them to remain on the safe side.
The 12 gauge wires can handle up to 25 amps at 12 volts, 120 volts, and 240 volts.
The ampacity varies depending on the wire material, temperature, and distance.
In the case of voltage, it remains the same.
How far can I run a 12 gauge wire?
The distance to run with a 12 gauge wire depends on various factors.
There is no exact distance for 12 gauge wires.
It varies depending on the different volt circuits and phases.
If you have a single phase, you can run 12 gauge wires at the following distances:
- 41 feet at 120 volts
- 83 feet at 240 volts
- 167 feet at 480 volts
If you have 3-phase, you can run 12 gauge wires at the following distances:
- 48 feet at 120 volts
- 96 feet at 240 volts
- 193 feet at 480 volts
Here, I have considered copper wires and a 3% voltage drop.
Keeping the distance within 100 feet and not crossing it is always the best option.
I won’t suggest using 12 gauge aluminum wire here at such long distances.
It would be best to try lower number gauges.
What are the uses of 12 gauge wires?
The 12 gauge wires measure 2.05 mm in thickness and, thus, are called 2 mm wires.
They are 21% thicker and better than the 14 gauge wires and 26% smaller than the 10 gauge wires.
You can use these wires for kitchen and bathroom appliances.
The amount of current they draw can be handled by these wires.
Depending on the wire material and temperature rating, you can use 12 gauge copper wires.
These can handle at least 20 to 30 amps.
Take the appliance and convert its wattage into amps.
Divide the wattage by the voltage.
While using the appliance, the amp rating should not exceed the wire’s capacity.
Remember that freezers with 20A will use more than 20 amp current when it starts.
Below are some places where you can use 20 amp circuits:
- Electrical outlets
- Outdoor receptacles
- Indoor outlets
- Kitchen and bathroom exhaust fans
- Light fixture with outlets
- 120V air conditioners
Also read: Can You Mix 12 And 14 Gauge Wire? (When+Safety Guidelines)
How many watts can a 12 gauge wire handle?
To determine the amount of wattage to be handled by a 12 gauge wire, you need to multiply the amps by voltage.
A 12 gauge wire will easily handle 20 amps.
If your house has 120 volts of electrical services, multiply 120 volts by 20 amps.
The result is 2,400 watts.
If your house has 240 volts of electrical services, the result will be 4,800 watts.
If the voltage is 480V, it is 9,600 watts.
What does the NEC say about it?
The National Electric Code, or NEC, has a table in its rulebook.
It tells you the exact gauge number to use in different amperage circuits.
So, you do not have to calculate and find out any wire gauge size.
NEC recommends a 12 gauge copper wire for 20 to 30 amps.
They also recommend using aluminum wires for 20 to 25 amps.
However, you do not always have to follow the NEC rules every time.
If your local codes have something different than the NEC rules, you must prioritize the local codes and not the NEC codes.
The best amp for 12 gauge wire is 20 amps. 25 amps are suggested for motor loads.
30,40 and 50 amps are not good for 12 gauge wires. Consider using higher gauges, like 10, 8, or 6-gauge wires, if you have such amperages.
However, 12 gauge copper wires can handle a little 30 amps. But, since the wires can heat up after some time, it is better to avoid 30 amps.
Several factors require consideration while deciding the exact amp for the 12 gauge wires. The amp size varies depending on the wire material, temperature, and distance.
So, before you select a wire for any amp, consider the factors and then use it.
If you cannot understand anything about these things, go through the NEC or local rules and tables where things are already mentioned. Consult an electrician if required.
- How Many AMPS Can 8 Gauge Wire Handle?
- How Many Amps Can 14 Gauge Wire Handle?
- How To Tell If Wire Is 12 Or 14 Gauge? (+When To Use)
Data Source: National Electrical Code, NEC Wire Table, Electrical wiring, Home wiring.