What Size Wire for 70 Amp Breaker? | Wiring Size Guide for 70 Amp Circuit Breaker

A gauge 3 aluminum or a gauge 4 copper makes a perfect choice for a 70 Amp breaker assuming there aren’t other factors impacting the performance, such as material and temperature.

What Size of Wire do You Need for 70 Amp Breaker?

Before you decide to upgrade the breaker you need to consider whether your wires can take the load or not. Considering there aren’t other factors impacting the performance, the right wire is either a gauge 3 aluminum or a gauge 4 copper for 70 amp. At an ambient temperature of 140°F,  you can use 4-gauge copper for a circuit breaker with this rating.

Rule of Thumb

General rule of thumb is an uncomplicated way to measure and choose wirings. Have a look at the chart below to find the right wirings, based on conductor temperatures taken from the NEC 310.16.

Ground wire, service entrance, circuit, breaker size chart rating:

Service or Feeder Rating (amp)	Aluminum conductor	Copper conductor
70	#2 AWG	#4 AWG
80	#1 AWG	#3 AWG
100	#1/0 AWG	#1 AWG
125	#3/0 AWG	#1/0 AWG
150	#4/0 AWG	#3/0 AWG
200	350 kcmil	250 kcmil
300	700 kcmil	500 kcmil
400	1,250 kcmil	750 kcmil
600	2,000 kcmil (194°F)	1,500 kcmil (167°F)

Check out the list below to check which wires are best for you regarding different voltages, distances, and materials.

Volt with 70 Amps	Max Distance	AWG(Copper)	Aluminum
120V	95 ft	4AWG	2AWG
240V	191ft	4AWG	2AWG
480V	383 ft	4AWG	2AWG

Volt with 70 Amps	Max Distance	AWG(Copper)	Aluminum
120V	120 ft	3AWG	1AWG
240V	241ft	3AWG	1AWG
480V	483 ft	3AWG	1AWG

Volt with 70 Amps	Max Distance	AWG(Copper)	Aluminum
120V	152 ft	2AWG	1/0AWG
240V	302ft	2AWG	1/0AWG
480V	609 ft	3AWG	1/0AWG

Voltage Drop is 3%, Line=Single phase

Wire size for 70 Amp 3 Phase

Volt with 70 Amps	Max Distance	AWG(Copper)	Aluminum
120V	150 ft	2AWG	1/0WG
240V	150ft	4AWG	2AWG
480V	150ft	4AWG	2AWG

Voltage Drop is 3%, Line=3 phase

To Conclude

After you select the right size of your wire you can select either the flexible aluminum option or high-conducting and robust copper. Make sure to consider price and safety measures before buying the wires and other components for your project.