You've hit on a great question, and one that goes beyond just "because it's a circle." Here's a breakdown of the history and reasoning behind the 360-degree rule, along with why it's so important

The History and Development of the 360-Degree Rule:
Early Days and Initial Concerns

In the early days of electrical wiring, conduit use was less standardized and less prevalent. As conduit systems became more common, the need for rules governing bends became apparent. The primary concern was wire pulling tension. Without limits on bends, pulling long runs of conductors through multiple severe bends became extremely difficult, potentially damaging the insulation and making future wire replacements impossible.

Evolution of the Code

The 360-degree rule wasn't initially a fixed number. It evolved through experience and testing. Early codes might have had more vague language about "excessive bends" or "bends that unduly increase pulling tension."

The Rise of the 360-Degree Limit

Over time, practical experience and experimentation demonstrated that exceeding 360 degrees of cumulative bend in a run significantly increased the force required to pull conductors. This threshold seemed to be a reasonable balance between allowing for practical conduit routing and preventing excessive stress on the wires. This limit was incorporated into the NEC.

Standardization and Enforcement

As the NEC became more widely adopted and rigorously enforced, the 360-degree rule became a standard requirement.

The Reasoning Behind the 360-Degree Limit (Why It Matters)



Wire Pulling Tension

This is the primary driver. Every bend increases friction. Exceeding 360 degrees of bends dramatically increases the cumulative friction, making pulling very difficult and risking damage to the conductor insulation.

Insulation Damage

Excessive pulling force can stretch, abrade, or even tear the insulation of the conductors. This can lead to: Short circuits Ground faults Reduced conductor lifespan Fire hazards

Future Wire Replacements

If the original installation required extreme pulling force, replacing those wires later will be equally difficult or impossible without damaging the new conductors. This limits the system's flexibility and lifespan.

Code Compliance and Safety

The NEC is a safety document. Enforcing the 360-degree rule helps ensure a safer electrical installation.

Heat Dissipation

While not the primary driver, bends can also slightly impede heat dissipation from the conductors, especially in densely packed conduits.

Why 360 Degrees and Not Some Other Number?

While it's impossible to definitively pinpoint the exact experiment that solidified 360 degrees, here's what likely happened: Empirical Data

Engineers and electricians likely experimented with different bend configurations and measured the pulling force required. They likely found that the tension increased significantly around the 360-degree mark.

Practicality

360 degrees allows for reasonable routing around obstructions while maintaining pullability.

Simplicity

The round number "360" is easy to remember and enforce.

Why People "Cheat" (and Why They Shouldn't)



Convenience

It's often easier and faster to add a bend than to properly plan and offset a conduit run.

Lack of Understanding

Some installers may not fully understand the implications of exceeding the limit.

Ignoring the Code

Some installers simply choose to disregard the code for various reasons.

Why Cheating is a Bad Idea



Safety Risk

As explained above, exceeding the 360-degree limit creates safety hazards.

Liability

If a problem arises from an installation that doesn't meet code, the installer could be held liable.

Poor Workmanship

It reflects poorly on the quality of the installation.

In summary, the 360-degree rule in conduit bending isn't arbitrary. It's based on decades of experience, testing, and a desire to ensure safe, reliable, and maintainable electrical systems. It is not a rule that should be broken. Flag for review