30 Amp Wire Size: Wire & Breaker Size Guide

The 30 amp wire size is 10 American Wire Gauge (AWG) wire size and one of the most popular for powering household appliances. It’s excellent for powering 240-volt large appliances and carrying more current than thinner gauge wires for lights and electrical outlets.

According to the American Wire Standard, or AWS, a 30-amp circuit breaker requires a 10-gauge minimum wire size for shorter distances. For longer distances, you will need a bigger wire, such as 8-gauge, to account for voltage drop over the length of the wire.

Selecting the correct wire gauge for the circuit requires more care as the amperage rating of your breaker increases. What 30 amp breaker wire size do you need?

As the current demand on a circuit increases, a thicker conductor cable is necessary. The thicker wire gauge can be significantly more expensive than thinner wire.

Some homeowners or contractors may be tempted to use a thinner wire gauge to save costs. This perceived cost saving can be costly in the long run and potentially dangerous.

This article will cover what size wire for 30 amp circuit breakers and why you should not go too small or too big on the wire gauge!

What Wire Size for 30 Amp 240 Volt Circuit

For safety, the minimum wire gauge for use in a circuit with a 30-amp breaker is a 10-gauge wire. While using a thicker gauge wire than this on a 30-amp circuit is possible, you should consider 10 gauge as the thinnest possible gauge.

The sizing of circuit breakers is according to the wire gauge used in the circuit. The circuit breaker’s purpose is to interrupt the current flow before the excess current damages the conductor, resulting in a dangerous outcome.

If the wire gauge is too small, the circuit breaker will not trip the circuit before the current overload damages the wire. The AWS or American Wire Standard indicates standards with minimum wire gauges that can be used safely on circuits with a specific ampacity.

A 30-amp circuit intends to provide power to medium-sized appliances in the home. These are the more power-hungry devices such as:

• space heaters
• large microwave ovens
• electric dryers
• air conditioners

These electrical appliances draw a substantial current, requiring a wire gauge capable of withstanding the current demand. This requirement is especially true if multiple devices are on the same circuit. In this circumstance, a 30-amp breaker with 10-gauge wire for the conductor would be the appropriate solution.

Can You Use a 30-Amp Breaker on a 12-Gauge Wire?

You should not use a 30-amp circuit breaker on a 12-gauge wire. The circuit breaker installed on a circuit is of a specific size to protect a certain wire gauge. A larger breaker on a thinner wire will allow more current over the wire before tripping.

Your house’s electrical wiring code standards are there for excellent reasons. The standards resulted from experimentation on the ampacity that wires of various thicknesses could withstand before being compromised.

Testing results on solid aluminum wires found that copper wires were more conducive to less heat, making them safer.

This higher current can damage the thinner wire, melt the insulation, cause short circuits, electrical fires, and even lethal shock. A 12-gauge wire is safe up to 20 amps and should be used only on a circuit where the current will not exceed this value.

The correct wire gauge for each typical household circuit is as follows.

• A 15-amp single-pole breaker requires a minimum of 14-gauge wire.

• A 20-amp single-pole breaker requires a minimum of 12-gauge wire.

• A 30-amp single-pole and double-pole breakers require a minimum of 10-gauge wire.

• A 40-amp circuit double-pole breaker requires a minimum of 8-gauge wire.

• A 60-amp double-pole breaker requires a minimum of 6-gauge wire.

These minimum 30 amp wire size chart are safe for the current level flowing through the conductor.

What Gauge Wire for 30 amp 100 Feet Away?

What size wire for 30 amp breaker depends on the electrical load and voltage drop. For the longer run, you’ll need a larger wire size to compensate for a voltage loss. This will help reduce voltage drops and ensure a safe installation.

The correct wire gauge for a 30 amp circuit wire size with 100 feet of wire is 8 AWG (American Wire Gauge). At a 100-foot distance, there will be some voltage drop. This means that the voltage at the far end of the circuit will be lower than at the beginning, and it is important to compensate for this when wiring any electrical device or appliance.

Related reading: 80 Amp Wire Size: Breaker & Wiring Gauge Guide

What Happens if Wire Gauge is Too Large?

We have discussed that using a wire gauge too small for the circuit breaker’s rated current can be dangerous, but what about the opposite end of the scale? What happens if the wire used in the circuit is too large for the circuit breaker?

Using a larger gauge wire rated for higher amperage than the circuit breaker is possible. The circuit breaker will still trip the circuit when the maximum current for the breaker is reached. The tripping of the breaker will occur even if the current flowing is well below the wire’s rating.

It is best to install a thicker gauge wire for the circuit in certain circumstances. You can use this strategy for the future expansion of the circuit should additional tamper-resistant outlets be needed. Using a thicker wire gauge, you can add more outlets to the circuit and install a higher amperage breaker.

Using a larger wire will reduce the amount of heat build-up in the conductor as the current passes through it. While this is not a reason to install a thicker wire in a circuit, it is a beneficial side effect.

Remember that there will be a trade-off in cost for futureproofing the electrical system this way. The thicker the wire gauge, the more expensive the wire becomes and the more difficult it is to install through the conduits for the wiring.

How Many Amps Can a 30-Amp Breaker Handle?

You would assume that the amount of current a 30-amp breaker can handle would be 30 amps, which is technically correct. However, this is the maximum load the breaker can handle before tripping the circuit.

Running the circuit at maximum ampacity for extended periods is neither safe nor practical. This situation will cause the breaker to trip frequently and heat build-up in the conductor.

The NEC, or National Electrical Code, stipulates that a circuit must only conduct current up to 80% of its rated capacity for an extended period. This regulation protects from heat build-up in the conductor and prevents tripping the breaker when appliances turn on and generate a temporary spike in the current draw.

The number of outlets fitted to the circuit is formulated to prevent exceeding the 80% maximum draw of the circuit breaker’s capacity.

Related reading: 70 Amp Wire Size: Breaker & Wiring Gauge Guide

30 Amp Wire Guage FAQs

30a wire size depends on the electrical current and distance. Here are some frequently asked questions about the 30 amp wire gauge size you need.

Conclusion

The intention of the wiring standards stipulated in the National Electrical Code is not to be an inconvenience but rather to improve the safety standards of the electrical systems in our homes.

Older houses built and wired before these standards are known to burn down or result in fatal accidents because of the substandard wiring. An old breaker not replaced in time could also cause issues.

To prevent undesirable outcomes, it is always prudent to stick within the national and local wiring codes when installing electrical systems in your home. Modern standards also require electrical compliance certificates to ensure the electrical system is up to code before selling a house.

Taking shortcuts is dangerous and could cost you money in the long run when you must rectify these “shortcuts” before selling your house.

Always use the minimum 10-gauge wire on a circuit with a 30-amp breaker. If you are uncertain or have some concerns about the safety standards of your wiring and circuit breakers, always consult a professional electrician!