8 gauge cables are commonly used to safely deliver electricity to home appliances. However, 8 gauge wire amp rating may vary depending on some factors.
To know how many amps can an 8 gauge wire handle, we have to look at its material and the maximum operating temperature. At 90 degrees Celsius, an 8 gauge copper wire handle up to 55 amps, while its aluminum counterpart handles up to 45 amps.
Table of Contents
The most common wire materials are copper and aluminum. Copper wires have greater current carrying capacities than aluminum, so an 8 AWG copper wire can hold more current than an 8 AWG aluminum wire.
Electrical wires may have different insulating materials. These materials must be able to withstand the heat caused by current flowing into the wire, and are rated to a maximum temperature. Generally, insulations have been rated at 60, 75 and 90 degrees Celsius in the US National Electric Code, or NEC.
The following table lists the different 8 AWG ampacity based on wire materials and operating temperatures of different insulators. These values are listed in the NEC for reference.
|Current rating of 8 AWG wire at different temperatures|
|Wire material||Copper||Aluminum or copper-clad aluminum|
|Temperature (⁰C/⁰F)||60⁰C (140⁰F)||75⁰C (167⁰F)||90 ⁰C (194⁰F)||60⁰C (140⁰F)||75⁰C (167⁰F)||90 ⁰C (194⁰F)|
|Insulating material (wire type)||UF
|Current rating (amps)||40||50||55||35||40||45|
Number of Wires
8 gauge cables usually come in either 8/2, 8/3, and 8/4 types, which indicate the number of 8-gauge wires in the cable. Usually, these come with one ground wire (which is not counted in the names):
- 8/2 cables consist of two 8-gauge wires.
- 8/3 cables consist of three 8-gauge wires.
- 8/4 cables consist of four 8-gauge wires.
The table above is only valid for a raceway that has up to 3 conducting wires (excluding the ground wire) like an 8/2 or 8/3 cable. The current that an 8/2 or 8/3 wire carry does not need a correction factor. However, 8/4 cables’ amperage or, for instance, 8 wire amperage, must be corrected using the values below.
Here is a list of correction factors based on the number of wires based on NEC:
|Conductor count||Correction for current rating|
|4 to 6||80%|
|7 to 9||70%|
|10 to 20||50%|
|21 to 30||45%|
|31 to 40||40%|
|41 and above||35%|
Wire lengths do not change how many amps is 8 gauge wire good for. It simply causes a greater voltage drop as the wire length increases and creates higher internal resistance. This may result in either of the two things:
- Appliances plugged into outlets with significant voltage drops may experience reduced performance and damage.
- Appliances may draw more current to meet their electrical requirement and may increase the current flowing through the wire, eventually exceeding the wire’s intended rating.
The NEC states that the voltage drop along the branch or feeder must not exceed 3%. Thus, 8 gauge wires of different materials may be limited to the following lengths at 120 volts and at 240 volts.
|Applicable wire material for 8 gauge wire amps 120v*|
|Current (amps)||25 feet||50 feet||100 feet||150 feet|
|15||Copper or Aluminum||Copper or Aluminum||Copper or Aluminum||Copper only|
|20||Copper or Aluminum||Copper or Aluminum||Copper only||Bigger wire needed|
|30||Copper or Aluminum||Copper or Aluminum||Bigger wire needed||Bigger wire needed|
|40||Copper only||Copper only||Bigger wire needed||Bigger wire needed|
|Applicable wire material for 8 gauge wire amps 240v*|
|Current (amps)||25 feet||50 feet||100 feet||150 feet||200 feet|
|15||Copper or Aluminum||Copper or Aluminum||Copper or Aluminum||Copper or Aluminum||Copper only|
|20||Copper or Aluminum||Copper or Aluminum||Copper or Aluminum||Copper or Aluminum||Copper only|
|30||Copper or Aluminum||Copper or Aluminum||Copper or Aluminum||Copper only||Bigger wire needed|
|40||Copper only||Copper only||Copper only||Bigger wire needed||Bigger wire needed|
Frequently Asked Questions
What is 8 gauge wire used for?
- 8 gauge wires are used for 40 amp circuits, like a dryer. For higher current needs, such as an electric burner, a 6 gauge wire may be a better choice than an 8 gauge wire to handle 60 amps.
- While the difference in current-carrying capacity of 8 gauge wire vs 10 gauge wire favors the former, 10 gauge wires are sufficient for receptacles or power outlets with 30 amps.
How far can you run 8 gauge wire for 30 amps?
Based on the tables above, we can run copper wires up to 50 feet at 120 volts and 150 feet at 240 volts. We can run aluminum wires up to 50 feet at 120 volts and 100 feet at 240 volts.
Can 8 gauge wire handle 50 amps?
Based on the table above, wires made of copper are rated 40 amps at 60 degrees Celsius, 50 amps at 75 degrees Celsius, and 55 amps at 90 degrees Celsius. Aluminum wires are rated 35 amps at 60 degrees Celsius, 40 amps at 75 degrees Celsius, and 45 amps at 90 degrees Celsius.
Can 8 gauge wire be used at 12 volts?
Yes, 8 gauge copper wires can be used for 12 volt applications up to 55 amps such as connecting a 1000 watt amp. However, 8 gauge aluminum wires are not recommended for the same amperage.
Different factors affect the current rating of 8 gauge wires. They may have varying ratings depending on the material, temperature, and number of connectors in a raceway. Moreover, the cable’s length has an impact on the delivery of electricity to a device.
The next time an 8 gauge wire is needed for a project, refer to this guide on how many amps can an 8 gauge wire handle. Doing so can ensure proper electrical installations.
I am Edwin Jones, in charge of designing content for Galvinpower. I aspire to use my experiences in marketing to create reliable and necessary information to help our readers. It has been fun to work with Andrew and apply his incredible knowledge to our content.