TL;DR
THHN wire is a single-conductor building wire with thermoplastic insulation and a slick nylon jacket, rated 90 degrees Celsius in dry locations and pulled through conduit or raceway rather than run exposed. Nearly all of it sold today is dual-rated THWN-2, extending the 90-degree rating to wet locations.
What it means
THHN wire is a single-conductor building wire with thermoplastic insulation and a slick nylon jacket, rated 90 degrees Celsius in dry locations and pulled through conduit or raceway rather than run exposed. Nearly all of it sold today is dual-rated THWN-2, extending the 90-degree rating to wet locations. It fills panels, EMT runs to garages and EV chargers, and commercial branch circuits, with the nylon skin existing mainly to survive the friction of long conduit pulls.
Where it sits in the glossary
THHN wire is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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