The typical types of wire used for conduit are THHN and THWN wires.
Conduit is a protective tube or pipe used to route electrical wiring in commercial and industrial buildings and structures, and also in some residential applications. While conduits can support many types of wires and cables, certain types are specifically designed and commonly used within them due to their insulation and protective properties.
Common Wire Types for Conduit
Based on standard practices and the provided reference, the wires you typically run through conduit are THHN or THWN. These wires are suitable for conduit installations because of their insulation properties, which offer resistance to heat and, in the case of THWN, water.
Let's break down what these abbreviations mean:
- THHN: Stands for Thermoplastic High Heat-resistant Nylon-coated.
- THWN: Stands for Thermoplastic Heat and Water-resistant Nylon-coated.
THHN vs. THWN
Both THHN and THWN wires feature thermoplastic insulation and a nylon coating. The key difference, as indicated by their names, is water resistance.
Here's a quick comparison:
| Feature | THHN Wire | THWN Wire |
|---|---|---|
| Insulation Type | Thermoplastic Insulation | Thermoplastic Insulation |
| Heat Resistance | High Heat Resistance | Heat Resistance |
| Water Resistance | Not specified as water-resistant | Water Resistance |
| Outer Coating | Nylon Coating | Nylon Coating |
| Typical Use | Dry and damp locations | Dry, damp, and wet locations |
- THHN refers to wires with thermoplastic insulation, high-heat resistance, and a nylon coating.
- THWN wires have thermoplastic insulation and heat and water resistance.
Many wires are dual-rated (e.g., THHN/THWN or THHN/THWN-2), meaning they meet the requirements for both types. A THHN/THWN wire can be used in both dry and wet locations within conduit, while a THHN wire is generally restricted to dry and damp locations. THWN-2 indicates higher heat resistance in wet locations (90°C vs 75°C for THWN).
Using appropriate wires like THHN or THWN in conduit ensures the safety and longevity of the electrical system by providing necessary protection against heat, abrasion (from pulling through the conduit), and potentially water or moisture, depending on the environment.
