Wiring installations in houses are very confusing. It can raise many questions about what to do and what to avoid. In today’s article, we shall discuss whether mixing a 12-wire gauge and a 14-wire gauge is possible.
You should only mix 12 and 14-gauge wires in the same circuit if the load is at most 15 Amps. The maximum load capacity of 12 Gauge wire is 20 Amps, whereas that of 14 gauge wire is 15 Amps. So, If you overload the wires, it can lead to overheating, melting, explosion, and serious fire hazards.
You may add two same gauges, like 12/2 and 12/3. If numbers are different, certain factors require consideration, the circuit being the most important. Stick till the end to know these factors and the dangers of mixing the two different wire gauges.
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This post includes some affiliate links.Why are wire gauges and circuits important?
The circuit breakers and fuses protect the wires from overheating and overloading. However, they do not completely protect them.
The devices are designed to detect and understand the current load and react to the overload by tripping or blowing before a dangerous condition occurs.
So, it would be best to guard the breaker and fuses against exceeding the amp rating.
The danger of overloading can happen anytime while plugging an appliance that consumes more current than the circuit can handle.
So, the wires also help in safeguarding the circuit breakers and fuses.
If you plug in a heater rated at 20 amps into a 15 amp circuit wired with 14 gauge wire, there is a chance of a hazard.
If the breaker fails, the heater will draw more power than the wire can handle.
It will end up melting the wire insulation and fire hazards.
You need to plug in an appliance that draws a limited amount of power wired with heavier gauges.
The appliance will draw the required wire without any overheating.
Common wires and their amp capacity
- 14 gauge wire – 15 amps
- 12 gauge wire – 20 amps
- 10 gauge wire – 30 amps
- 8 gauge wire – 40 amps
- 6 gauge wire – 55 amps
- 4 gauge wire – 70 amps
- 3 gauge wire – 85 amps
- 2 gauge wire – 95 amps
Can I mix a 12-wire gauge and a 14-wire gauge?
12-wire gauges are much better than the 14-wire gauges.
The 12 gauge wires are thicker, stronger, and heavier.
So, they are usually used in houses with 20 amp circuits.
The 14-gauge wires are thinner, weaker, and lighter than the 12-wire gauges.
So, you cannot use them in 20 amp circuits.
Combining the wires in the same circuit is not recommended because both wires serve different circuits.
Mixing them can cause a short circuit, wire melting, explosion, and fire hazards.
However, it completely depends on the circuit.
But, on one condition, you may join both wires.
It generally depends on the current draw of your circuit.
If you have a 15 amp circuit, you might be allowed to mix the 12 and 14-gauge wires in the circuit.
But, if you have a 20 amp circuit, please avoid the combination.
A 14-wire gauge is not the right size to be used in a 20 amp circuit.
Remember that though mixing the two wires is fine in a 15 amp circuit, it will be a waste of the 12-wire gauge.
You could have used it for the higher amp circuits.
Below are some things which you must keep in mind while combining them in the same circuit:
Select the correct gauge to avoid overloading.
Before you think of mixing two different wire gauges in the same circuit, you should know the importance of gauge numbers and their usage.
The gauge number will tell you the load your wire can handle.
If you force the wire to handle current flow more than its capacity, it will overheat and cause a short circuit and fire.
The 12 gauge wires are thicker, heavier, and stronger.
They have good conductivity and durability and are thus expensive.
On the contrary, 14 gauge wires are slightly thinner, lighter, and have less strength than the 12 gauge wires.
They have less conductivity and durability and are cheaper.
Also read: How To Tell If Wire Is 12 Or 14 Gauge?
Wire size and circuit breaker go hand in hand.
The 14 gauge wires are designed for 15 amp circuits and not beyond that.
If the amp exceeds 15, the wire will overload and melt.
On the contrary, the 12 gauge wire can handle up to 20 amp circuit breakers.
The 12 gauge wires are more durable than the 14 gauge wires.
Besides, 14 gauge wires cannot handle the load that 12 gauge wires can handle.
So, while mixing both wires, you need to choose a circuit that can protect the 14 gauge wire and not the 12 gauge wire.
Higher distances need smaller gauges.
It is sometimes unexpected that the distance can determine the mixing of the wire gauges.
Distance affects the amperage rating.
If the distance increases, the gauge’s conductivity needs to be high, but the number should be low.
For example, if you have a 14 gauge wire, you can use it for around 50 feet.
But, it cannot deal with distances crossing 200 feet, which will overheat the wire.
Can I solder both wires together?
You can solder the different wire gauges.
For that, you need a soldering iron to adjust the wires of two different gauges.
For soldering, the smaller gauge will require more soldering than the larger one so that the solder can flow well and make a strong joint.
While soldering two different wire gauges together, you should keep certain things in mind, one being the voltage.
If the wire’s voltage is higher, the wire should be thicker and stronger.
So, if you have a 12 and 14-wire gauge, the soldering of the 12-wire gauge should be stronger and can handle more current than the 14-wire gauge.
Why should we not mix two different wire gauges?
Mixing two different wire gauges is a common mistake, especially if the wires are connected in the wrong amp circuit.
Some wires are limited to some circuits. Using them in higher circuits will overheat the wires and result in short circuits and fire hazards.
Below are a few reasons for which it is not recommended to mix the 12 and 14-gauge wires:
Thickness
The different thickness levels of the wires are an important factor.
If the thickness level is different, but you still mix them in one circuit, it will heat the wires and melt them.
The thicker wires hold more current. Mixing them with the thinner wires will melt them and cause an explosion.
Insulation
Due to the thickness, there is a difference in the insulation.
A 12 gauge wire has more insulation than 14 gauge wires, depending on how much current the wires can handle.
Insufficient insulation can overheat the wires and ignite and explode them.
Weight
The 12 gauge wires are heavier than the 14 gauge wires.
If the wires are not physically well-supported, the excessive current flow can stress the lighter wires and overheat them.
A 12 gauge wire will handle more current than a 14 gauge wire. Mixing the two will affect the latter.
Cost
The 12 gauge wires are more expensive than the 14 gauge wires.
So, if you can work with the 14 gauge wires, you do not have to waste money buying the 12 gauge wires.
Similarly, if you need only the 12 gauge wires for your 20 amp circuit, buying 14 gauge wires is a waste because they cannot handle the current drawn by the circuit.
Current ampacity
Before connecting two different wire gauges, it is essential to determine the amount of current ampacity a wire can tolerate.
If your circuit needs a 12 gauge wire, having a 14 gauge wire is meaningless.
If you mix the wires, the 14 gauge wire will melt and cause a short circuit, explosion, and fire hazards.
That is why it is better not to mix them both, especially if you have a 20 amp circuit.
The 14 gauge wire won’t be able to handle the current flow in a 20 amp circuit.
Confusion
Adding two wires together can create confusion.
If a person sees 14 and 12-gauge wires together in a circuit, they will think they can handle the circuit’s load.
When can I connect the different gauge wires?
In certain situations, you can connect two different wire gauges, but you cannot do that yourself.
You should consult an electrician before doing such dangerous things.
It would be best to have a circuit breaker or fuse for your protection and use the smaller gauge wire with the correct circuit.
The fuse must be of the same size as the smaller gauge wire.
Remember that the bigger the wire, the lower the gauge number.
So, do not get confused by the numbers.
The 12 gauge wire is thicker and stronger than the 14 gauge wire.
If you have a 15 amp circuit, you can use both wires and even mix them.
If you have a 20 amp circuit, a 12 gauge wire is the best option.
A 14 gauge wire will melt in this circuit.
Can I mix 10 and 12-gauge wires?
As I mentioned earlier, 12 gauge wires can handle 20 amp circuits.
But, it won’t be able to handle more than 20 amps.
On the contrary, a 10 gauge wire can withstand up to 30 amp circuits.
So, if you join the two wires in the same circuit, you need a circuit that protects the 12 gauge wire.
In that sense, you need a 20 amp circuit to join the two wires without any short circuits and fire.
If you join the wires in a higher circuit, like 30 amp, the 10 gauge wire will survive, but the 12 gauge wire will get overheated and start a fire.
The 20 amp circuit will protect the wires and shut off the power if the 12 gauge wire gets overwhelmed.
What about 10 and 14-gauge wires?
The logic is the same here.
The 10 gauge wires can handle 30 amp circuits.
On the contrary, 14 gauge wires are limited to 15 amp circuits.
If you mix the two wires in a 15 amp circuit, the wires will stay fine.
But if the circuit exceeds 15 amps, the 14 gauge wire will start a fire.
So, use a circuit that protects the 14 gauge.
Factors determining the wire gauge
The American Wire Gauge, or AWG, is a standard way to measure the wire sizes used for electrical purposes.
AWG is used to determine the different wire sizes, diameters, and thicknesses.
The lower the gauge number, the thicker and heavier the wire.
Three factors determine the wire gauge size:
- The physical feature of the wire material, i.e., the tensile strength, hardness, and flexibility.
- The thickness of the wire insulation. It is extremely important for safety purposes and other environmental reasons.
- The wire’s ampacity tells us how much current or loads the wire can tolerate.
Different wire gauges and their applications
- 18 AWG: Low-voltage cords
- 16 AWG: Extension cords
- 14 AWG: Circuits, appliances, and other light fittings
- 12 AWG: Small AC units and other indoor outlets
- 10 AWG: Water heater, cloth dryers, and large AC units
- 6 AWG: Cooktops for kitchen
- 4 AWG: Heaters and furnaces
What does the code say about mixing two different wire gauges?
The National Electric Code (NEC) does not mention mixing two different wire gauges.
They do not care about it and do not have any mention of it anywhere in the code.
However, the matter is different in the local codes.
So, you must contact the local authorities before connecting two different wire gauges.
Suppose your local authorities do not permit the homeowners to mix two different wire gauges on the same circuit.
In that case, you do not have a choice but to listen to them.
Final thoughts
Now that you are at the end of the article, you know why you should not mix 12 and 14-gauge wire in the same circuit. It will lead to overheating, wire melting, short circuit, and explosion.
However, it highly depends on the circuit you have. The rule is to join them in a circuit that can protect the higher gauge since it has lower durability.
So, if you ever want to join the two wires, consider the factors and reasons explaining why it is unsafe to join them.
With this basic knowledge, you can now ignore common electrical mistakes and prevent potential hazards in your home.
Call a professional if you want to join gauges but are afraid of electrocution.
FAQ
Can I use a 12 gauge wire in a 15 amp circuit?
The 12 gauge wires can handle circuits ranging up to 20 amps.
So, you can use 12 gauge wires in a 15 amp circuit.
And here, you can also join it with a 14 amp circuit since the breaker will protect the wire.
Data Source: National Electrical Code, Electrical wiring, Home wiring.
