How Far Can You Run 10 2 Wire (Length vs Resistance)

If you’re wondering how far you can thread a 10/2 wire in your wiring project without affecting amperage you are in the right place.

50 ft. or 15.25 meters at most. Running a 10/2 wire beyond 50 feet can reduce the amps and the overall power output of a 10/2 wire. As the wire length increases, so does the resistance that impedes a seamless flow of charge or electrons. As an electrician, I will teach you how far you should span a 10/2 wire in detail.

The farthest you can thread a 10/2 wire (i.e. two conjoined ten gauge wires with an additional ground wire) without appreciably affecting amperage is 50 ft. Running a 10/2 gauge beyond 50 ft. can tremendously extenuate or lower the amps rating of the wire. The length of the wire varies proportionally with resistance; so, as resistance increases the charge volume density reduces. Effectively, the current or amps diminishes.

I will go into more detail below.

10/2 Wires

10/2 wires are usually used to wire air conditioners which demand the use of specifically sized wires for efficacy. They (10/2 wires) are highly recommended for the AC units because they can handle the amps flowing in the circuits safely.

10/2 wires use two 10 gauge wires with a combined ampacity of 70 amps. The wire consists of one 10 gauge hot wire (black), one 10 gauge neutral wire (white), and one ground wire for safety precautions.

The ampacity of one copper 10 gauge wire is approximately 35 amps at 75 degrees Celsius. Implementing the 80 percent NEC rule, such a wire can be employed in a 28 amps circuit.

So, mathematically, 10/2 wires can contain 56 amps. In that vein, if your device, say an air conditioner, draws about 50 amps; then you can use a 10/2 wire to wire it.

However, in this guide, I will focus on how far you can span ten gauge wire without significantly affecting the amperage or any other functionality of the 10/2 wire.

Threading 10/2 Wire

The following are the properties that can be affected as the length of 10/2 wires, or any other wire gauge, are spanned:

Resistance & Wire Length

Resistance increases with length.

There is a direct relationship between the length a 10/2 wire must traverse and the amount of resistance the charge faces.

Essentially, as the 10/2 wire length increases the charge collision increases leading to an exponential increase in resistance to current flow. (1)

Amperage & Wire Length

The amp rating of a 10/2 wire can drop dramatically if it spans more distance.

As aforementioned, an increase in resistance will directly affect the flow of the electrical current. That’s because the electrons get prevented from flowing seamlessly through the wire.

Temperature & Wire Length

The table below lists the ampacity of various wire gauges at given lengths.

So, How Far Can You Span 10/2 Wire?

According to the AWG stipulations, a 10/2 wire can span 50 feet or 15.25 meters, and it can handle up to 28 amps.

Other uses of 10/2 gauge wire include speakers, home wiring, extension cords, and other electrical appliances whose amps ratings are in-between 20 and 30.

RELATED Can 10 Gauge Wire Handle 40 Amps

FAQs

Are 10/2 and 10/3 wires interchangeable?

10/2 wires have two ten gauge wires and one ground wire while 10/3 wires have three ten gauge wires plus a ground wire.

You may use a 10/3 wire on a 10/2 run, excluding the third ten gauge wire (in a 10/3 wire). However, you cannot use 10/2 wires on a device that requires 10/3 wires (two hot, one neutral, and a ground).

Can one use a four-prong twist lock receptacle with a 10/2 wire?

Yes, you can.

However, you will be breaching the wiring code regulation that requires all the terminals of a connector that uses AC power to be wired accordingly. So, it is best to avoid such incidence as they can cause confusion and potentially electrical accidents. (2)

Take a look at some of our related articles below.

References
(1) collision – https://www.britannica.com/science/collision
(2) electrical accidents – https://www.grainger.com/know-how/safety/electrical-hazard-safety/advanced-electrical-maintenance/kh-3-most-common-causes-electrial-accidents

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For 120 volts, 10 gauge copper wire can carry 30 amps at 140 ⁰F up to 57 feet, and for 240 volts, up to 114 feet. It can travel further at weaker currents. The circuit voltage and the electrical load it is carrying are two variables that affect how far a 10-2 wire can be run. 

You will experience more voltage drop along the line the longer the wire is run and the heavier the load. Particularly for delicate equipment or long-distance runs, the voltage drop can lead to lower efficiency and possibly dangerous conditions.

What Is the Approximate Distance a 10 2 Wire Can Cover

Calculate the voltage drop based on the current (amperage) and distance of the wire run to estimate the greatest distance a 10-2 wire can be run safely. Generally, for branch circuits, the National Electrical Code (NEC) suggests a 3% voltage drop limit. A table that displays the farthest distances 10 gauge wire can be run at 140°F and a power factor of 0.9 is given below.

CurrentCopper wire length at 140 ⁰FFor 120VFor 240V15 amps114 ft229 ft20 amps85 ft171 ft25 amps68 ft137 ft30 amps57 ft114 ft

Now, to calculate the distance, the given parameters are,

Source Voltage (V) = 120 volts

Voltage Drop Percentage (Vd%) = 3%

Current (I) = 20 amperes

Impedance per 1000 feet (Z) = 1.1 ohms (from NEC Table 9, assuming 10-gauge wire at 0.85 power factor)

Step 1: Calculate the Voltage Drop

Voltage Drop (Vd) = Vd% * Source Voltage / 100

Vd = 3% * 120 volts / 100

Vd ≈ 3.6 volts

Step 2: Determine the Distance

Length (feet) = Vd * 1000 feet / (2 * I * Z)

Length ≈ 3.6 volts * 1000 feet / (2 * 20 amperes * 1.1 ohms)

Length ≈ 3600 feet / (2 * 20 * 1.1) feet

Length ≈ 3600 feet / 44 feet

Length ≈ 81.82 feet

The maximum safe distance for the 10-gauge wire on a 20-amp circuit at 120 volts is calculated to be roughly 81.82 feet using this method.  It’s vital to remember that this method only provides a conservative estimate and ignores a number of additional variables, like temperature, power factor, and other circuit loads, that can affect voltage drop.

Frequently Asked Questions and Answers (FAQs)

Can I Use a Larger Wire Gauge to Increase the 10-2 Wire’s Maximum Safe Distance?

Yes, voltage loss can be reduced and the safe distance for electrical installations can be increased by utilizing bigger wire gauges, such as 8-2 or 6-2.

Are There Any Safety Concerns With Extending the Use of 10-2 Wires?

Yes, greater voltage drops over longer distances may have an impact on the functionality of electrical equipment. For safety, it is essential to follow voltage drop restrictions and refer to electrical codes.

Conclusion

The voltage drop limit, circuit current, and wire gauge all play a role in determining the farthest safe distance for running 10-2 wires. When planning electrical installations, it’s crucial to take these things into account and refer to local electrical codes in order to ensure safety and dependability.

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