14 AWG copper wire is the most common choice for a 15-Amp circuit. 14 AWG copper wire is ranked 20 Amps at 75°C. 

If you choose to use aluminum wire, the correct size for a 15 Amp breaker is 12 AWG. However, copper cables are a better choice for 15 Amp breakers due to safety and efficiency concerns. Aluminum wires work better for circuits with higher ampacity.

Can I Use a 12 AWG Copper Wire on A 15-Amp Breaker?

It is often asked whether it is fine to use a 12-gauge wire on a 15-amp circuit, and the answer is yes, it is actually fine. At 75°C, 12 AWG copper wire is ranked 25 Amps. 

However, there are several things to consider in this scenario. While the wire can handle the current, this doesn't mean you can put a higher amperage breaker on the circuit. The breaker must match the lowest-rated component on the circuit. This might confuse someone else working on the electrical system in the future, as they might assume the circuit is rated for 20 amps because of the wire size. All things concerned, it is best to use 14 AWG copper wire, which is perfectly suitable for this situation and is more cost-effective than 12 AWG wire. 

As for using a 10-gauge wire, while it is also possible and not a fire hazard, it is not practical for similar reasons that it is not practical to use a 12 AWG wire.

What Are The Applications Of A 15 Amp Circuit Breaker?

A 15-Amp circuit can be either a dedicated circuit or a shared circuit.

A 15-Amp circuit breaker can average between 1800 to 2000 watts. However, it is important to account for the 80 percent NEC rule that states you should load the breaker only to 80 percent of its capacity. This means that it is best to load a 15-amp circuit to 1600 Amp or less.

You can run up to 8 outlets on a 15-Amp circuit, the key is for them to have no more than 1600 Amps total.

When it comes to particular appliances used with 15-Amp circuits, the ones that need a dedicated 15-Amp circuit are:

• Microwaves: the 15-Amp dedicated circuit is enough for smaller countertop conditioners.
• Garbage disposals
• A 120V outlet for timer of a gas stove
• Small-window air conditioners or portable air conditioners

Other appliances that do not need a dedicated 15-Amp circuit but are often used on a shared 15-Amp circuit are:

• Small kitchen appliances include coffee makers, toasters, blenders, and food processors.
• Television sets, desktops, printers, and gaming consoles
• Hair dryers, curling irons, and electric razors. The dryers can actually hold significant power, but they are allowed for 15-Amp circuits because they are only being used for a short time.

electrical systems). 

15 Amp Outlet VS. 20 Amp Outlet

Aside from obvious things like current capacity and wire size, the main difference between a 15-amp outlet and a 20-amp outlet is the outlet design. A 20-amp outlet has one slot either turned sideways or T-shaped, while a 15-amp outlet does not.

It is possible to use a 15-amp outlet in a 20-amp circuit if there are more outlets in the circuit. UT is permitted in NEC 210.21(B)(3). Thus, a single receptacle installed on an individual branch circuit needs to have an ampere rating not less than that of the branch circuit. However, where multiple receptacles are installed on a higher rated branch circuit, it is permissible to use 15-ampere receptacles on a 20-ampere branch circuit.

However, doing this means taking into consideration the load that will be put on a circuit. Each 15-amp outlet is only rated to handle up to 15 amps of load. Plugging devices that draw too much current into a 15-amp receptacle could result in overheating. 

Why would you want to use a 15-amp outlet in a 20-amp circuit? There are a couple of reasons for that. First of all, many appliances are designed to plug into 15-amp outlets, and 20-amp outlets are less common for many appliances. 15-amp outlets are also more common. Using them might act as a built-in current limiter in a 20-Amp circuit.

Cables for 15-Amp Circuits

Here is a breakdown of how each cable can be used for a 15-Amp service:

• NM-B Non-Metallic Sheathed Romex® Cable: This is the most common cable for indoor applications in 15-amp circuits. It is applicable only for interior applications, which is the overwhelming majority of all 15-amp circuit applications.
• UF-B cables: This cable shares some similarities with NM cable, but it's designed to be buried directly underground without a conduit. It's often used for supplying power to outdoor fixtures or outbuildings.
• MC metal-clad cables: This cable has a green insulated ground wire and hot and neutral wires. It can be used in many of the same applications as NM cable but provides more protection to the conductors.
•  Copper and aluminum THWN in conduit for exposed applications: Instead of a pre-packaged cable like NM or MC, individual THHN/THWN wires can be run through a conduit of EMT or rigid steel metal. The conduit provides protection for the wires and can be used in exposed locations or where additional protection is required.