Though 30 amps can run a whole house, it can be dangerous for electrical appliances in the modern world. Choosing the accurate wire size for 30 amps is crucial to avoid overheating and electrical accidents.
According to the National Electric Code or NEC, the correct wire size for 30 amps is 8 to 10 AWG wire. But it will vary based on the wire material, distance, and voltage. You can also use a lower gauge, but 10 AWG is the minimum, and 8 AWG is the maximum.
The maximum wire gauge does not matter because the thicker the wire is, the better. You must ensure it is not thin. This article shares a detailed guide about the wire size of 30 amps based on the wire material, voltage, distance, and other aspects.
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In old times, 50 amps were considered the standard service to run a house with 1-2 electronic objects.
You can even run a house with 30 amps service.
Still, it is not recommended if you have modern electrical devices because one single device can draw around 30 amps of power.
In such a case, you will need a 30 amp circuit breaker and choose the wire.
Recently, the standard electrical service for running a house with a few modern electronic devices is 150 to 200 amps.
My house runs on 200 amp service.
I have some 30-amp circuit breakers to run substantial appliances like central air conditioners, ovens, dryers, etc.
Two wire sizes are recommended for 30 amps – 10 AWG and 8 AWG.
10 AWG wire is the most recommended wire and the minimum size for 30 amps. It has gained popularity because of its thickness.
The wire is often used in speakers, extension cords, home wiring, and other electrical systems.
Besides 30 amps, I sometimes use this wire for 10 amps and 20 amps.
Professionals recommend an 8 AWG wire as it is the maximum wire size.
With an 8 AWG wire, you can use the wire safely without any risk of electrical accidents.
NEC code compliance
When you are looking for a 30 amp wire size, you must take into account two NEC codes:
- NEC 220-2 Code: This code suggests that a conduit wire’s maximum load (30 amps) should represent 80% of the wire ampacity.
- NEC 310-16 Code: This code determines the wire size for 30 amps of service at a distance. Add 20% to the wire’s ampacity for every 100 feet away from the sub panel.
The 220-2 code will check the wire size usually required for a 30 amp circuit by looking at the AWG wire size chart in the NEC.
A 10 AWG wire is the most recommended wire size for 30 amps.
But most house owners ask how far we can run the 10 AWG wire for 30 amps.
A 10 AWG wire has a 35A ampacity.
It is expected to believe it can handle 30 amps. But you also need to follow the 80% rule here.
Following the 80% rule, the perfect wire size for 30 amps is 8 AWG wire with 50A ampacity.
Based on the material, 30 amps should represent 80% of the ampacity of the wire.
The calculation stands like this:
30 amp wire = 30A x 100% / 80% = 37.5A ampacity.
So, with 37.5A ampacity, an 8 AWG wire after 10 AWG wire will perfectly fit 30 amps.
The 310-16 code suggests adding an extra 20% of the wire’s ampacity for 30 amps every time the distance increases to 100 feet.
With this, you can take advantage of the wire’s capacity and maintain human safety at its best.
Wire size for a 30-amp breaker
It is possible to run an entire house for 30 amps services, provided you do not have any modern electrical devices.
These devices alone can draw current up to 20 to 30 amps.
It is still unsafe even if you have one electrical appliance that draws only 10-15 amps.
If you have such devices, you need higher amp service.
As for the 30 amps, you will have circuit breakers to run appliances like refrigerators or central air conditioning.
For such breakers, you need a 10 AWG wire.
If you use aluminum wires, use a 6 or 8-AWG wire for safety.
How many amps can a 30-amp breaker handle?
As I said, 10 AWG wire is the minimum requirement for a 30 amp breaker for operating each phase in the process.
Experts recommend using a thick wire with lower AWG that can carry enough current.
The wire size can be lower than 10 AWG, but it should not exceed 10 AWG. So, you can go for a 6 or 8 AWG, but not 12 or 14 AWG.
The 80% rule helps determine the amperage a 30-amp breaker can handle.
Usually, in a 30-amp breaker, you must use only 80% of the load and leave the remaining 20%.
This will keep the breaker safe and avoid overloading, breaking tripping, and short circuits.
When the load is over 80%, it will get stored in the remaining 20%, preventing short circuits and breaker tripping.
So a 30-amp circuit can easily handle 24 amps.
If you load the breaker up to 24 amps, a 10 AWG wire should be enough.
What size of wire is ideal for a 30 amp sub panel?
30 amp sub panels will need breakers to run correctly.
In that case, you can use a double pole 30A breaker in the sub-panel.
If the circuit is small, use thinner gauge wires for smaller appliances and thicker gauges for large appliances.
Ideally, the wire size for a 30-amp sub panel is 10 AWG.
But you can go for 8 AWG, like the service and breaker, if the distance is over 100 feet.
Wire size for 30 amps in terms of pole
The wire size for 30 amps is no different than that of the breaker.
Whether your breaker is a single pole or a 2-pole, you will need a minimum of 10 AWG wires in both cases.
Professionals suggest an 8 AWG wire for 30 amps for the best results.
The wire size can change if the distance increases.
Factors to consider while selecting the wire size of 30 amps
The ideal wire size for 30 amps is 10 gauge wire.
But several factors can affect the wire size for 30 amps.
The size can vary based on the wire material, distance, voltage, phase, etc.
Let’s talk about them in detail.
Wire material: Copper vs. Aluminum
The very first thing you should consider is the wire material.
There are several materials, but copper is considered the best after silver.
Copper wire has better conductivity, resistance, tensile strength, thermal expansion, and malleability than the other wires.
Copper wires do not overheat quickly and can carry enough current without issues.
Since the wire is malleable, you can mold and bend it without the risk of breakages.
If you use copper wire, you can utilize 10 AWG wire for 30 amps.
Next is the aluminum wire. It is good but not better than copper.
Aluminum wire does not have better conductivity or resistance than copper wires. So, you can’t use these wires for longer distances.
Additionally, it can overheat faster than the copper wires.
So, if you use aluminum wires for 30 amps, go for an 8 or 6-AWG wire.
There is another option: Copper-clad aluminum wires.
These wires are made of aluminum with copper fittings at the end.
You can receive some copper benefits from these wires, like conductivity and resistance.
The wire is cheaper than pure copper but costlier than pure aluminum.
Try this if you want the wire to provide better safety than aluminum.
The size will remain the same as aluminum wires.
I always prefer thick wires. But since copper wires are costly, I have both aluminum and copper wires for all breakers up to within 30 amps.
The size I use for aluminum wires has twice the smaller AWG than copper.
My house contains both wires based on current draw and distance.
For a shorter distance, we have aluminum and copper for long distance.
Keep reading to know how distance affects the wire size.
Voltage
The wire size stays mostly the same in terms of voltage.
The wire material can change at some voltages, for example:
- 110V-120V – 10 AWG
- 220V – 10-2 AWG copper wire
- 230V-240V – 10 AWG
- 480V – 10 AWG
- 3-phase – 10 AWG copper wire
This can change if the distance is too long and crosses 50 to 100 feet.
The next factor will clear this out.
Distance
With 30 amps, you can run the wire as far as you want.
But the wire size must be thick enough to carry the current through such a long distance.
The longer the distance, the higher the resistance, voltage drop, and chances of overheating.
To compensate for these elements, you need to increase the gauge size.
The wire’s ampacity should increase by 10% for every 50 feet.
Increase the amps by 20% for 30-amp wire 100 feet away from the sub panel and 30% for 30-amp wire size 150 feet.
If you run the wire 10 feet away, run a 10 AWG wire for 30 amps.
Do the same for 100 feet as well.
But after 100 feet for 30 amps, you will need a wire that can handle up to 35-45 amps, considering the 3% voltage drop.
After 100 feet, increase the gauge size to 8 AWG.
If you need to run a wire for 30 amps 200 feet away, you might need a wire that can handle 50-55 amps, i.e., a 4 or 6 AWG wire.
When the distance exceeds 50 feet, I prefer copper wire over aluminum.
Temperature rating
The temperature rating affects the ampacity of the wire gauges.
When you choose the wire gauge for your 30 amps, you should also cross-check the ampacity of the wires based on the temperature rating:
| Wire size | 140°F | 167°F | 194°F |
|---|---|---|---|
| Wire size | 140°F | 167°F | 194°F |
| 8 AWG | 40 amps | 50 amps | 55 amps |
| 10 AWG | 30 amps | 35 amps | 40 amps |
As you can see, both are safe to use, but 8 AWG is safer, especially at the temperature rating of 140°F.
Importance of proper wire sizing: Tips to remember while choosing the correct wire size for 30 amps
Choosing the correct wire for 30 amps or any other amperage is crucial.
Lower AWGs are safe, but higher AWGs can be dangerous as they are thin wires.
They will overheat, melt, trip the breaker, and even start a fire.
Below are some tips to help you understand the importance of the right gauge and select the correct wire size for 30 amps:
- Lower AWG is thicker than the higher AWG. A 10 AWG wire will carry more current than a 12 or 14 AWG wire. But it carries less current than an 8 AWG wire.
- The breaker needs to protect the wires. If the wires carry more current than they are rated for, they will overheat, melt, and start a fire. So, the wire size must match the breaker.
- Some contractors try to save money by using thinner wires only to end up with electrical accidents. Thicker wires are hefty and carry better current than thinner wires. When contractors use the wires, ensure they use the thicker gauge and the correct size.
- Copper is always better than aluminum wires. But if you can’t afford it, choose a smaller AWG for aluminum. For example, if a 30 amp breaker needs 8 AWG copper, use 4 or 6 AWG aluminum.
- The increase in the wire length and distance should also improve the size. For longer distances, you need smaller AWG wires. When the distance crosses 100 feet, use 6 or 8 AWG wires.
- If you are confused, look for the wire size chart in the NEC. If you have a separate local code, you need to follow the local code and not the NEC.
- Use the correct wire size. A wire should always be thick enough to handle the breaker’s current but shouldn’t be thinner. You can use 10 AWG, 8 AWG, 6 AWG, or even lower, but not higher than 10 AWG. If the cost bothers you, try aluminum or copper-clad with double the size of copper. For example, if you use 8 or 10 AWG copper, use 6 or 8 AWG aluminum.
Exploring 30 amps wire size charts at different phases, voltages, and distances
Let’s start with the single phase:
Single phase
120V
| Distance in feet | Copper wire size | Aluminum wire size |
|---|---|---|
| 50 feet | 10 AWG | 8 AWG |
| 75 feet | 8 AWG | 6 AWG |
| 100 feet | 6 AWG | 4 AWG |
| 200 feet | 4 AWG | 2 AWG |
| 250 feet | 3 AWG | 1 AWG |
| 300 feet | 2 AWG | 1/0 AWG |
240V
| Distance in feet | Copper wire size | Aluminum wire size |
|---|---|---|
| 50 feet | 10 AWG | 8 AWG |
| 75 feet | 10 AWG | 8 AWG |
| 100 feet | 10 AWG | 8 AWG |
| 200 feet | 6 AWG | 4 AWG |
| 250 feet | 6 AWG | 4 AWG |
| 300 feet | 4 AWG | 3 AWG |
480V
| Distance in feet | Copper wire size | Aluminum wire size |
|---|---|---|
| 50 feet | 10 AWG | 8 AWG |
| 75 feet | 10 AWG | 8 AWG |
| 100 feet | 10 AWG | 8 AWG |
| 200 feet | 10 AWG | 8 AWG |
| 250 feet | 8 AWG | 6 AWG |
| 300 feet | 8 AWG | 6 AWG |
3-phase
120V
| Distance in feet | Copper wire size | Aluminum wire size |
|---|---|---|
| 50 feet | 10 AWG | 8 AWG |
| 75 feet | 8 AWG | 6 AWG |
| 100 feet | 6 AWG | 6 AWG |
| 200 feet | 4 AWG | 3 AWG |
| 250 feet | 4 AWG | 2 AWG |
| 300 feet | 3 AWG | 1 AWG |
240V
| Distance in feet | Copper wire size | Aluminum wire size |
|---|---|---|
| 50 feet | 10 AWG | 8 AWG |
| 75 feet | 10 AWG | 8 AWG |
| 100 feet | 10 AWG | 8 AWG |
| 200 feet | 6 AWG | 6 AWG |
| 250 feet | 6 AWG | 4 AWG |
| 300 feet | 6 AWG | 4 AWG |
480V
| Distance in feet | Copper wire size | Aluminum wire size |
|---|---|---|
| 50 feet | 10 AWG | 8 AWG |
| 75 feet | 10 AWG | 8 AWG |
| 100 feet | 10 AWG | 8 AWG |
| 200 feet | 10 AWG | 8 AWG |
| 250 feet | 10 AWG | 6 AWG |
| 300 feet | 8 AWG | 6 AWG |
Final Thoughts
According to all the wire size table charts, 10 AWG wire is considered the best wire choice for the 30 amps. But experts suggest using 8 AWG wires for 30 amps. You can use both of them by considering the factors that affect the wire size, for example, the wire material and distance.
If you use copper wires, 10 AWG is enough. But you need 8 AWG for aluminum wires. The larger the distance, the more the wire length. With distance and wire length, the resistance and voltage drop will increase. You will need a thicker wire, like 6 AWG, 4 AWG, or even lower AWG than these two.
For example, if you plan to use the wire for 30 amps for up to 100 feet, you can use an 8 AWG wire. But when the distance is longer than 100 feet, jump to 6 AWG or 4 AWG.
How far can you run a 10 AWG wire on a 30 amp circuit?
Usually, you can run up to 50 to 100 feet with 10 AWG wires. But longer than 100 feet will require a 6 or 8 AWG wire.
What appliances use 30 amps circuit breakers?
You can use a 30 amps circuit for water heaters, dryers, refrigerators, electric heat pumps, air conditioners, and microwaves. You can even use lights and outlets.
Can I run 220V on a 30-amp breaker?
Yes, you can get both 220V 30-amp and 110/120V 30-amp. You can also apply the recommended wire size for a 30-amp 240V circuit.
Reference: Wire sizes Wikipedia
