Electrical Connections & Torque
Terminals must suit the conductor material and be tightened to the manufacturer's torque spec — loose lugs are a top fire cause.
Why this code exists
Loose and mismatched connections generate heat. Standardizing terminations and, later, requiring torque values cut a recurring fire source.
Since 2017 the code explicitly requires tightening to the listed torque value where one is provided, effectively requiring a calibrated torque tool.
When it applies
Every termination point matters here, from a receptacle screw to a 1,000-amp switchgear lug. The connector has to be rated for the conductor material, and if you mix aluminum and copper on a device not marked for both, you are outside the listing. Torque is not optional either; each lug carries a value, and you meet it with a calibrated tool.
Common mistakes
- Guessing torque by feel instead of using a calibrated screwdriver or wrench.
- Landing aluminum on a copper-only terminal, or skipping the antioxidant where required.
- Re-tightening a lug repeatedly, which can strip threads or cold-flow the conductor.
In the field
I have thermal-imaged panels where one loose neutral ran forty degrees hotter than its neighbors. Torque it once, torque it right, and mark it so the inspector and the next tech both know it was done.
A torque screwdriver isn't optional on my jobs. Most of the 'mystery' hot spots I've chased with a thermal camera came back to a lug someone snugged by feel.
See full history
- 2017 — Explicit torque-to-spec requirement added.
Related codes
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