Can I Use 14 Gauge Wire On 20 Amp Circuit? (Or 12 Gauge)


using 14 gauge wire on 20 amp circuit

Are you trying to wire a 20A circuit? What is the best wire gauge for the circuit? Is 14AWG sufficient? You don’t want to get these questions wrong. You run the risk of burning your house down. That happens when you force a cable to carry more electricity than its rating permits. Don’t pair 20A circuits with 14-gauge wires unless you know for sure that 14AWG conductors can accommodate 20-amp circuits.

Can 14 Gauge Wire Be Used On A 20 Amp Circuit?

14AWG wire carries a maximum of 15 amps. If a load draws more than 15 amps on a 15A circuit, the breaker will trip, protecting the 14AWG wire. But if the circuit is 20A, the breaker won’t trip even when the current exceeds 15A. A 20A circuit breaker trips when the current passes the 20-amp threshold. Any volume of electricity below 20 amps is perfectly acceptable.

In other words, the 14AWG wire will overheat long before the breaker trips.

What does this mean for you?

You can use 14-gauge conductors on a 20A circuit if you keep the load under 15 amps. For instance, a 20-amp circuit that runs the lights in your house can make do with 14-gauge cables. But this pairing is risky. If an outsider checks the breaker and notices the 20A rating, they may attach a heavier load such as a 30A AC unit because they think the circuit can handle it.

Unless you attach a sign to the panel warning your friends and family about the 14AWG wiring on the 20A circuit, you run the risk of starting a fire.

You can add 14AWG wiring to a 20A circuit. No one will stop you, not in a residential setting. More importantly, you can use 14AWG wiring without suffering any severe consequences, but only if the load is 15 amps or less.

People expect circuit breakers to protect their electrical systems from overloading. However, such confidence is misplaced.

A 20-amp circuit works best when you pair it with 12AWG wiring. 12AWG has the thickness required to carry the current a 20A circuit will draw.

If you force the 12AWG wire to carry more than 20 amps, the breaker will trip. This is a good thing because it keeps the 12AWG conductors from overheating.

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How To Calculate If 14 Gauge Or Any Wire Is Good For 20 Amps?

If you know the wire gauge, you can determine the cross-sectional area of the wire. With this information in mind, you can start identifying the total wattage of all the devices in your home. By converting the wattage into amperage, you will know the load the circuit will carry. This helps you identify the correct circuit size to use.

This method sounds complicated, especially if you don’t understand the formulas for calculating the gauge and cross-sectional area.

But these processes don’t matter to the layperson. The layperson knows the amperage of their circuit (20A) because the breakers in their panels are labeled. More than likely, your contractor took the total wattage of your appliances into account before they selected the circuit size.

Therefore, you don’t have to calculate the total wattage of your devices. Additionally, you know the gauge of the wires at your disposal because they are all labeled.

But how do you identify the correct wire size for the circuit? You can check this table that shows the various gauges and their corresponding amp ratings.

CopperAluminum
Wire Gauge Size60˚C
NM-B, UF-B
75˚C
THW, THWN, SE, USE, XHHW
90˚C
THWN-2, THHN, XHHW-2, USE-2
75˚C
THW, THWN, SE, USE, XHHW
90˚C
XHHW-2, THHN, THWN-2
14152025
12 2025302025

A glimpse at that table will show you that 14AWG conductors can safely carry 15 amps. If you want to accommodate 20 amps, you need 12AWG or higher.

You don’t have to perform any calculations. Once you know the amperage, you can use a table to find the corresponding gauge. Leave the complex calculations to professional electricians.

What Is 14 Gauge Wire Used For?

14AWG wires allow consumers to use a maximum of 15 amps. 15 amps sound like a lot of electricity. However, I want you to use 14AWG for lighting circuits.

The size is insufficient for kitchen and bathroom appliances. You can use 14AWG for outlets as well as lights.

But Hunker prefers 12-gauge conductors because they give you more leeway regarding the kinds of devices you can connect to those outlets.

You should always aim for the thickest wire you can find. Though, 12-gauge wiring is somewhat irritating because it is less flexible than 14AWG. This is not a problem if flexibility doesn’t matter to you.

What Happens If You Use 14 gauge Wire On A 20 Amp Circuit?

The gauge shows you the volume of current a wire can safely carry. For instance, you need 12AWG to carry 20 amps. Technically speaking, 14AWG can carry 20 amps of electricity. But it cannot do so safely. The wires will overheat because of the elevated resistance.

This is why the NEC has published tables revealing the appropriate amp rating for each wire size. A breaker is supposed to defend against overheating by tripping and switching the power off whenever the current exceeds the capacity of the wire.

But I don’t want you to rely on breakers because they can malfunction. If the breaker fails to respond, a heavy-duty appliance will start a fire because it is pulling more current than the 14AWG cables can handle.

The insulation will melt, and the combustible objects in the area will ignite. Heavy-duty devices can exceed the capacity of 14AWG wires without tripping the 20A circuit.

You can’t trust the members of your household to avoid appliances that exceed 15 amps because they may forget about the limitations of 14AWG conductors. If you added the 14AWG conductors to a 20A circuit in a commercial setting, an inspector may fine you.

You don’t want to incur unnecessary financial penalties. Do yourself a favor and use the correct wire size.

Can You Use 12 Gauge Wire On A 20 Amp Circuit?

12AWG is the smallest size that can safely carry 20 amps. You can use 12 gauge wire on a 20 amp circuit but I suggest using larger sizes such as 10 and even 8AWG. In fact, many homeowners use bigger wire sizes than their circuit rating calls for because they want to plan for the future.

using 12 gauge wire on 20 amp circuit

For instance, a 10AWG wire can handle 30 amps of electricity. If you have a 20A circuit, you can install 10AWG conductors just in case you decide to upgrade to 30 amps in the future.

If your 20A circuit uses 12AWG, you cannot upgrade to 30 amps without changing the wiring to 10AWG. Re-wiring a home is expensive, especially for people in large houses. You are better off using wire sizes that can accommodate future upgrades. Admittedly, thicker wires are also more costly, which is why homeowners with 20A circuits prefer to use 12AWG instead of 10 or 8AWG.

The type of material matters as well. Copper carries more electricity, but it is more expensive. Aluminum is the cheaper option. But you must use a higher gauge for aluminum wires to replace a copper wire of a lower gauge.

For instance, you cannot replace 10AWG copper conductors with 10AWG aluminum conductors. You need at least 8AWG (Aluminum) to match the capacity of 10AWG (Copper).

How Far Can You Run 12 Gauge Wire On 20 Amp Circuit?

Voltage DropSource VoltagePhaseDistance
3%120Single Phase52 feet (Copper)
3%120Single Phase33 feet (Aluminum)

You can run 12 gauge copper wire on a 20 amp circuit for 52 feet with an allowable voltage drop of 3% of the source while aluminum wire is only capable of running 33 feet.

Electrical technology has published a formula that shows consumers how to calculate the allowable voltage drop. They understand that the voltage drop affects the wire size.

The voltage drop increases with the length. This is because the resistance also increases with the length. The higher the resistance, the greater the voltage drop. You have to calculate the voltage drop before selecting the wire size.

The correct wire size can reduce the voltage drop. If a conductor is thick enough, it can reduce the resistance, permitting the current to flow unimpeded. This prevents overheating in the long run.

If you want the line to exceed 52 feet, you should jump to 10AWG to compensate for the resistance.

If you cannot determine whether or not 12AWG is appropriate for the length of your circuit, consult a professional electrician. They can calculate the voltage drop. This will tell them whether or not you need a thicker wire.

Can I Mix 12 Gauge and 14 Gauge Wire On A 20 Amp Circuit?

You can use 12 and 14-gauge wires on the same 20A circuit. But the wire size should match the load. For instance, you can’t use 14AWG wire (15 Amps) in an outlet that powers appliances whose rating exceeds 15 amps.

You must consult a professional electrician. They can identify the correct application for each wire size.

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