30 Amp Wire Size: What AWG Wire You Need? (220/240V, NEC Code)

The 30 amp wire size is 10 AWG and is commonly used in house wiring. It is good to use for 240-volt larger devices and carries a higher current than thin-gauge wires for electrical outlets. According to American wire standards, the 30-amp circuit breaker needed ten gauges of minimum wire for a small distance. For larger distances, there is a need for larger wires, like 8-gauge, to handle voltage losses.

What Wire Size for a 30 Amp 240 Volt Circuit

For safety purposes, the minimum wire gauge used in a circuit with a 30 amp breaker is 10 gauge wire. A thick gauge wire for a 3-amp circuit can be applied, and a 10-gauge wire can be used as a thin gauge wire. The circuit breaker size is according to the wire gauge used in the circuit.

The breaker used for interrupting current before high current damages the conductor and causes serious effects. If the wire gauge is very low, the breaker will not trip the circuit before the current overload can damage the wire. The 30-amp circuit provides power to medium-sized devices connected in your home. These are high-power devices like space heaters, toasters, microwaves, etc. These electrical devices use high current, needing wire gauges to handle current needs. This instruction is needed if many devices are connected to the same circuit. So for these circuits, a 30 amp breaker with 10 gauge wire is best to use.

30 Amp Wire Size

What is a 30-amp breaker good for?

The 30-amp, 20-volt circuit can carry 7200 watts of power. The NEC provides one 30 amp 240 outlet for a 30 amp circuit. These circuits are used in homes. Their common uses are in electric furnaces, electrical systems of RV vehicles, AC units, dryers, etc. Normally, a 30-amp breaker is used for a single device. The receptacles for 30 amp circuits are different from normally used receptacles in homes and are required for single appliances or devices.

So they have different plug configurations. The 30 amp circuits are different from the 15 amp or 20 amp outlets that can be used for different devices. It is since 30 amp devices like electric clothes dryers, AC units, and water heaters are normally used.

Which cables are for a 30 amp circuit breaker?

The most common cable for a 30-amp circuit breaker is an NM-B Romex non-metallic sheath cable. If wet water affects the circuit, the best option is to use UF-B. Here, some commonly used cables for 30 AM service is explained.

NM-B Non-Metallic Sheathed Romex Cable: It is commonly used for 30 amp breakers in indoor and outdoor applications, and these cables also do not need additional protection.

UF-B cables are best used for devices that are completely or fully configured outdoors and for devices that are in contact with water and moisture, like RV hookups, water heaters, etc.

MC metal-clad cables: It is used for 30 amp circuit breakers if the cable faces mechanical damage. But this cable is not the best for moist conditions like water heaters. It is also used in damp conditions, and their installation is more difficult than UF-B cables.

What Size Wire Do I Need For a 30 Amp Sub Panel 100 Feet Or 150 Feet Away?

When power is transferred over a longer distance, 30 amp copper wire or 30 amp aluminum wire causes voltage losses. For distances less than 10 feet, the voltage loss has a value of less than 3 percent, and normally these losses are not considered. Voltage losses are calculated over distances of 50 feet, 100 feet, or more. So for these distances, there is a need to increase the ampere. According to NEC, there must be increases of about 20 percent for each 100 feet of distance from the 30-amp subpanel.

  • For 50 feet of distance, it increases by ten percent amps for a 30 amp wire size.
  • For 100 feet, the distance increases by 20 percent.
  • for 150 feet, the distance increases by 30 percent.

We can measure amperes for distance.

Suppose that there is a 30-amp service 100 feet away from the subpanel. The current value for zero-foot distance will be

30 Amp Wire = 30A × 100% / 80% = 37.5A Ampacity

So we will increase the 20 percent for the 100-foot distance that will be

30 Amp Wire at 100 feet distance = 37.5A × 1.2 = 45A Amperage

For a 30-amp service of 200 feet, there is a need for wire that can handle 45 amps. 8-gauge wire comes with a 50A ampacity, so we can use 8-AWG wire for subpanels at 50- to 15-foot distances. For 200 feet, the distance increases amps to 40 percent for controlling voltage losses.

30 Amp Wire Size AWG Wire You Need

What Happens If I Use the Wrong Length and Wire Size for a 30 Amp Circuit?

The use of a wire smaller than required can have a bad effect.

  • If overloading occurs in the circuit, the breaker can be affected due to overloading, resulting in wire damage.
  • At that time, the damaged wire can cause a fire that can damage wire features.

However, the use of thick wires will not affect the circuit. The circuit breaker also measures overloading, short circuits, and other faults in circuits. A thick wire is preferred for use.

Read Also:


Automotive Wire Size 5 Amps 30 Amps
12 Gauge Wire (AWG) 29.4 ft 4.9 ft


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