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What is the Electrical Wire Capacity
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Summary: The amperage capacity of electrical wire is determined by a few factors. The insulation materials used to protect the actual wire conductor are an important factor when selecting an electrical wire or cable. The following table demonstrates Standard Over Current Devices with 75 Degree Rated Terminals.
© By: Dave Rongey |
Selecting Wire Sizes for Electrical Wiring
Electrical Wire Capacities
It is essential to understand that there are allowable ampacities of insulated wire conductors.
The insulation materials used to protect the actual wire conductor are designed for specific applications.
Some types of wire insulation protect the wire against overheating and external elements such as direct sunlight exposure, moisture as well as some corrosive substances, to mention just a few.
Not all wire insulation types are designed the same, therefore they have specific amperage capacities.
The wire or conductor size and type is determined by the by the specific application and the load requirement. Other considerations that will affect the wire size may be the total length of the run of wire to be installed and if the wire will be installed into conduit or in an open air environment.
This table shows the Amperage Rating for Home Electrical Wire Sizes
Although this is the most common table used to determine wire size, this is just one example.
| Standard Over Current Devices with 75 Degree Rated Terminals | |||
| Circuit Size |
Copper Cable Type NM, NM-B |
Copper Cable Type SE, USE |
Aluminum Cable Type SE, USE |
| 15 | #14 | - | - |
| 20 | #12 | #12 | #12 |
| 25 | #10 | #12 | #10 |
| 30 | #10 | #10 | #10 |
| 35 | #8 | #8 | #8 |
| 40 | #8 | #8 | #8 |
| 45 | #6 | #8 | #6 |
| 50 | #6 | #8 | #6 |
| 55 | #6 | #6 | #4 |
| 60 | #4 | #6 | #4 |
| 65 | #4 | #6 | #4 |
| 70 | #4 | #4 | #3 |
| 75 | #3 | #4 | #3 |
| 80 | #3 | #3 | #2 |
| 85 | #3 | #3 | #2 |
| 90 | #2 | #3 | #2 |
| 100 | #1 | #3 | #1 |
| 115 | 1/0 | #2 | 1/0 |
| 120 | 1/0 | #1 | 1/0 |
