what is thhn electrical wire
THHN vs THWN Wire. THHN Wire is a type of electrical wire most commonly used in conduit and cable trays for services, feeders and branch circuits in commercial applications. It can be used outdoors because it's water, gas and solvent resistant thanks to its PVC/Nylon insulation.HHN Dual Rating. 1  All of our THHN electrical wire is dual rated with THWN wire because they're manufactured very similar with almost no cost difference. 2  It's the most standard type of electrical wire on the market because it's used as a single condutor electrical wire and also used in most electrical cables as well.