How Many Amps Can a 10/3 Wire Handle?

If you use a 10/3 wire, how many amps can it handle?

Generally, this type of wire is suitable for handling up to 30 amps in most cases, as long as it is made of copper and, depending on its insulation, whether it is encased in a conduit or not, the length of the wire, and the ambient temperature. This should be treated as the maximum, whereas around 24 amps should be considered the safer standard current capacity for continuous use.

This is a standard household wiring configuration in Canada and the United States for a 10/3 wire (white, black, red, and bare ground). Read more about the 10/3 wire and for further considerations, including the length of the wire.

A 10/3 Wire

In specifying a ‘10/3’ wire, the 10 indicates the gauge in AWG, and the 3 indicates the number of insulated conductors in the cable (4 wires in total, including the ground).

From the information in the Wire Gauge Reference Table (AWG), the 10 AWG has a bare diameter of 0.101900” (2.58826 mm), a circular mil area of 10,383.311783 mm, and is equivalent in other wire size systems to 12 SWG and 12 BWG.

30A circuit breaker

Considerations

Type and Length of Wire

Copper wire has very low resistivity, enabling it to handle higher currents more efficiently than aluminum wire.

If you consider the length of the wire, a 10 gauge copper wire 10 meters long would have a resistance of around 0.032 ohms. The 10/3 wire should be acceptable for appliances within 55 feet of the main breaker panel for a voltage drop not exceeding 3% in a 110V system. For a 240V system, this length can be doubled. If you need to wire over a longer distance, you must consider the voltage drop the appliance can tolerate.

Applications

Some air conditioners, electric laundry dryers, and other appliances that need up to 30 amps can be run safely on 10/3 wiring using a 4-prong plug.

The 10/3 wire would not be adequate if connecting, for example, an electric stove (which would need an 8/3 wire). Only in controlled outdoor or industrial situations can a 10/3 wire be used for a little higher current than 30 amps. Going lower, the 10/3 wire is unnecessary, for example, for services controlled by multiple switches, such as lighting on a stairway.

Use of a Conduit

A conduit would lower this rating depending on its size and what other wires run alongside it. In free air, the wire can potentially handle more without overheating. Regardless, the 10/3 wire should be on a 30-amp circuit breaker.

Circuit Breaker and Maximum Load

The 10/3 wire must be protected by a 30 amp circuit breaker or fuse. The maximum wattage load is 2,880 watts for a 120V system (5,760 watts for 240V).

However, the current should not constantly exceed 80% of the 30 amps, which is 24 amps. This means that although the 10/3 wire can handle up to 30 amps, this should be treated as the maximum, whereas around 24 amps should be considered the safer standard current capacity for continuous use.

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About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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