FAQs
What is the lowest temperature recommended for pulling wire?
–40°F (–40°C) for XHHW‑2 and USE‑2 constructions; THHN/THWN‑2 is typically 14°F (–10°C). Thermoset XLPE insulations retain flexibility better than PVC in freezing conditions.
Why do THHN cables crack in the cold?
THHN’s PVC/nylon system stiffens below ~–10°C (14°F); bending and sidewall pressure during pulls can split the nylon or stress the PVC. Warming reels 24–48 hours prior to pulling and slower pull speeds help.
Do medium‑voltage EPR cables have different cold ratings?
Many MV EPR designs pass cold‑bend at ~–35°C, but the minimum installation temperature can be higher—often governed by the outer jacket (e.g., PVC). Always follow the specific datasheet for the cable you’re installing.
What code/standards should I consider?
NEC Article 310 governs conductor types/locations; manufacturer listings (UL/CSA) and cold‑bend/impact tests define low‑temperature performance and markings.
How cold is too cold to pull THHN wire?
THHN wire is rated for installation down to -10°C (14°F) when using standard methods. Below this temperature, the insulation can become stiff and prone to cracking. If you need to work in colder conditions, consider warming the wire before installation or using a wire type designed for extreme cold, such as XHHW.
Will wire get brittle below freezing?
Yes, most thermoplastic-insulated wires, including THHN, become less flexible as temperatures drop below freezing. This stiffness increases the risk of insulation damage during pulling. To prevent brittleness, store wire in a warm environment before installation and use proper pulling techniques with lubricant.
What lubricant helps cable installation in -20 °F?
Choose a polymer-based or low-temperature-rated pulling lubricant designed for cold conditions. These lubricants stay effective in sub-zero temperatures, reducing friction and preventing insulation damage. Always check the manufacturer’s specifications to ensure compatibility with your wire type and temperature range.
