What Size Wire for 30 Amps 200 Feet [2 Aspects Playing Role]

Understanding the significance of wire gauges becomes essential when working with circuits carrying specified amperage over long distances, regardless of whether you’re an experienced electrician or a DIY enthusiast. The type of wire and the voltage you’re using will determine the wire size you need for a 30-amp circuit over a distance of 200 feet. 

The voltage drop and overall effectiveness of the circuit will be more significantly impacted by the wire’s resistance over a longer distance. Typically, 8 or 6-gauge is advised. Let’s browse the wire gauge currents and identify the crucial factors influencing this critical decision.

Choosing the Right Wire Size for a 30-Amps 200 Feet

Typically, you want to pick a wire gauge that can support that current without overheating for a circuit with a 30 amp rating. The National Electrical Code (NEC), which bases wire size recommendations on current and distance, is available online. 

However, other parameters, such as the wire’s composition (copper or aluminum) and voltage level (120V or 240V), also affect the precise wire gauge you want. Even though a wire of size 10 can carry 30 amps, there can be a limit. The National Electric Code (NEC) states that the maximum load for a circuit should be 80% of the wire ampacity circuit rating.  

Given that you might not need to consider the 3% voltage loss, a 10 gauge cable might be sufficient for a 30 amp service located 10 feet away. However, you need a wire that can carry 52.5 amps if the distance to the 30 amp sub panel is 200 feet. So, it is safe to use a 6 gauge wire with a 65A ampacity. A table of wire gauge sizes according to the distance is given below.

Wire Material

The wire’s ampacity is also influenced by its substance. Because copper wire is more amphibious than aluminum wire, it can be utilized in smaller diameters for the same application. You can use a 10 AWG copper wire if you wish to keep the voltage drop to 3% when working with a 120V circuit. But 8 AWG is equivalent when it comes to aluminum wire.

Rated Voltage

The wire size varies according to the rating of the voltage. It’s possible that a kitchen oven and dryer don’t use as much power as a bulb. Wire gauges will differ for the two purposes as a result. A 10 gauge wire can be utilized for a 120-volt copper wire to span 200 feet. But an 8-gauge wire will be the best option. 

However, 10 gauge is not appropriate for 200 feet of distance for 240 volts. The needed wire size would typically be smaller for a 240V circuit since the greater voltage reduces the current for the same power. However, bigger wire gauges can be used for both cases. 

Let’s consider some technical aspects. We know, the formula for the wire diameter,

A = (2ILρ) / V

where:

A = Cross-sectional area of the wire in square meters

I = The current in amps

L = The length of the wire in meters

ρ = The resistivity of the wire material in ohm-meters

V = The allowable voltage drop in volts

The wire size can be determined as follows for a 30-amp circuit with a length of 200 feet using copper wire with a resistance of 1.68 10-8 ohm-meters and a voltage drop of 3%:

A = (2 × 30 × 200 × 1.68 × 10^-8) / 0.03

= 50.24 square meters

The closest AWG size for a 50.24 square meter cross-sectional area is 6 AWG.

Frequently Asked Questions

What Effect Does Distance Have on the Choice of Wire Size?

Increased resistance from longer wire lengths causes a bigger voltage drop. To reduce voltage loss over longer distances, thicker cable is typically needed.

Is It Ever Advisable to Use Wire That Is Larger Than What Is Advised?

Using a slightly bigger wire size might provide you further assurance that your system will work at its best in demanding applications or situations where there are substantial voltage drop restrictions.

Can I Use a Larger Wire to Update an Existing Circuit?

A professional’s help may be needed if you want to increase the wire size on an existing circuit because it can include adjusting the electrical panel and taking the right safety measures.

Conclusion

Depending on the particulars, the needed wire size could change.  However, by the general recommendation, 6 AWG copper wire is the appropriate wire size for a 30-amp circuit with a length of 200 feet.  The 65 amps of the ampacity of a 6 AWG copper wire make it more than adequate for this application.