For 10 AWG THHN aluminum wire, it can carry up to 35 amps. This ampacity is based on its 90°C insulation rating, which allows for higher current carrying capacity compared to wires with lower temperature ratings.
Understanding THHN Wire Ampacity
THHN stands for Thermoplastic High Heat-resistant Nylon-coated. It's an insulation type commonly used for electrical wires due to its excellent heat resistance and durability, provided by the nylon outer jacket. While THHN refers to the insulation, the ampacity (the maximum current a wire can safely carry) largely depends on several factors, including the wire's gauge (AWG), the conductor material (copper or aluminum), and the insulation's temperature rating.
The provided information specifically details the ampacity for 10 AWG aluminum wire.
Ampacity of 10 AWG Aluminum Wire by Insulation Type
The current carrying capacity of 10 AWG aluminum wire varies significantly based on its insulation temperature rating. Here’s a breakdown:
| Insulation Type | Temperature Rating | Approximate Ampacity for 10 AWG Aluminum Wire |
|---|---|---|
| TW, UF | 60°C | 25 amps |
| RHW, THHW, THWN | 75°C | 30 amps |
| THHN, XHHW | 90°C | 35 amps |
As seen in the table, 10 AWG aluminum wire with THHN insulation falls under the 90°C category, allowing it to carry up to 35 amps.
Important Considerations for Ampacity
While the insulation rating provides a base ampacity, several other factors can influence the actual safe current-carrying capacity of any wire, including 10 AWG THHN wire:
- Conductor Material: It's crucial to note that the ampacities listed above are specifically for aluminum conductors. Copper wire of the same gauge and insulation type will generally have a higher ampacity. For instance, 10 AWG copper THHN wire typically has a higher ampacity than its aluminum counterpart. Always consult the National Electrical Code (NEC) for precise ratings based on the conductor material.
- Ambient Temperature: If the wire is installed in an area with high ambient temperatures (e.g., a hot attic), its ampacity must be derated (reduced) to prevent overheating.
- Number of Current-Carrying Conductors: When multiple current-carrying wires are grouped together in a conduit or cable, their individual ampacities must be derated due to accumulated heat.
- Installation Method: Whether the wire is run in free air, conduit, or direct buried affects heat dissipation and, thus, ampacity.
- Terminal Limitations: The lowest temperature rating of any connected device (e.g., breaker, switch, receptacle) often dictates the maximum current that can be safely carried by the circuit, regardless of the wire's higher temperature rating. Most common residential and commercial devices are rated for 60°C or 75°C terminations. Therefore, even if a wire has a 90°C rating (like THHN), the circuit is often limited to the 75°C or 60°C column ampacity based on the termination temperature ratings. You can learn more about these correction factors and guidelines in the National Electrical Code (NEC).
Always consult the latest edition of the National Electrical Code (NEC) and local regulations for definitive ampacity ratings and installation requirements to ensure safety and compliance.
