// 110.14(D) · Calibrated tool required
Terminal Torque Reference
Typical terminal torque by conductor size, converted three ways. Use it for orientation, then use the number the manufacturer printed on the device.
Since the 2017 cycle, 110.14(D) has required torque to be applied with a calibrated tool wherever the manufacturer provides a value. It is not a best practice anymore. It is a requirement, and inspectors ask about it.
If you want the reasoning behind the numbers worked all the way through, read the torque specification guide.
How this calculation works
What the rule actually says
110.14(D) requires that where a tightening torque is provided by the equipment manufacturer, the connection be made with a calibrated torque tool set to that value. “Good and tight” is not compliance, and neither is a screwdriver and experience.
The values on this page are typical figures for orientation. They are not a substitute for the label. When a breaker, lug or terminal block carries a torque marking, that marking is the specification.
Both directions are failures
Under-torqued. The connection has less contact area than it needs. Resistance goes up, and because heat rises with the square of the current, a marginal connection that runs warm at half load runs hot at full load. The heat oxidizes the contact surface, which raises resistance further. That feedback loop is how loose connections become fires.
Over-torqued. Strands get crushed and cut, which reduces the effective conductor area. Lug bodies crack. Screw threads strip or gall. On aluminum the damage is worse and shows up sooner.
There is no safe side to err on. That is the entire reason the Code went to a calibrated tool.
Practical notes
- Most branch-circuit devices are in inch-pounds. Feeder and service lugs go to foot-pounds. Check the units before you set the tool.
- Aluminum requires an antioxidant compound on most terminations, and it creeps under load — a retorque after the first heat cycle is common practice on large aluminum terminations.
- Torque screwdrivers need periodic recalibration. A tool that has been dropped or left wound up under spring tension does not read true.
- Mark what you have torqued. A paint pen stripe across the screw head tells the next person, and tells the inspector.
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Frequently asked questions
Is torquing terminations actually required?
Yes. 110.14(D) requires the use of a calibrated torque tool set to the manufacturer's value wherever that value is provided. It moved from recommended practice into an enforceable requirement in the 2017 cycle, and inspectors do ask to see the tool.
What if there is no torque marking on the device?
Then the requirement in 110.14(D) does not attach to a specific number, and you fall back on manufacturer literature or general industry values like the ones on this page. Most modern gear is marked, either on the device itself or in the packaged instructions.
Can I over-torque a connection to be safe?
No. Over-torquing crushes and severs strands, which reduces conductor area at the exact point where the current is concentrated, and it cracks lug bodies. It fails the same way under-torquing does — just from the other direction. There is no safe margin.
Do aluminum terminations need retorquing?
Aluminum creeps under sustained load and thermal cycling, and many manufacturers call for a retorque after the connection has been energized and heat-cycled. Follow the specific instructions with the equipment, and use an antioxidant compound where the listing calls for it.
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