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SESK: Stuff Everyone Should Know · sesk.info/elec-insul-thhn-dry

Which conductor insulation type is typically used in dry and damp locations but not wet locations?

THHN is for dry and damp locations.

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  1. THHN ✔
  2. THWN
  3. XHHW

Why: THHN lacks the W for wet, so it is listed for dry and damp locations. THWN, THWN-2, THHW and XHHW types can be used in wet locations.

Huh, didn't know that: The temperature rating of insulation is the maximum temperature a conductor can withstand over a prolonged period.

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References

Answer: THHN. THHN lacks the W for wet, so it is listed for dry and damp locations. THWN, THWN-2, THHW and XHHW types can be used in wet locations.

  1. EC&M: Conductors for General Wiring www.ecmweb.com/national-electrical-code/article/20902784/conductors-for-general-wiring
    Insulated conductors typically used in dry and damp locations include THHN, THHW, THWN, or THWN-2
    Checked 2026-10-10.
  2. EC&M: Conductors for General Wiring www.ecmweb.com/national-electrical-code/article/20902784/conductors-for-general-wiring
    Insulated conductors typically used in wet locations include types THHW, THWN, THWN-2, XHHW, or XHHW-2
    Checked 2026-10-10.

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