You're remembering correctly. There was a period when short EMT runs (typically under 3 feet) were often permitted without additional support beyond termination points. However, the NEC changed, tightening those rules. Here's a breakdown of the situation and the reasons behind the change

The Change and the Current Code
NEC 358.30 (A) and (B)

These sections outline the current support requirements for EMT. In essence:

(A) General

EMT must be securely fastened in place at least every 10 feet.

(B) Horizontal Runs

EMT must be supported at intervals not exceeding 10 feet.

Important Clarification

These are general rules. There are exceptions, but none of them allow for un-supported runs of 24 inches without regard to the terminations.

Reasons for the Change (Why the Looser Rules Were Tightened)



Safety and Reliability

The primary reason was improved safety and reliability of electrical systems. Even short, seemingly rigid EMT runs are susceptible to movement and damage over time.

Vibration

Vibration from equipment, machinery, or even normal building use can cause unsupported EMT to loosen at connections or even fatigue and break.

Physical Damage

Short, unsupported runs are more vulnerable to being bumped, hit, or accidentally pulled on, potentially damaging the conduit, conductors, and terminations.

Conductor Insulation Damage

Movement or vibration can cause conductors within the EMT to rub against the conduit edges at couplings or connectors, leading to insulation damage and potential short circuits or ground faults.

Strain on Connections

Without proper support, the weight of the EMT itself and any conductors within it can place excessive strain on the connections at the junction boxes or enclosures. This can lead to loose connections, arcing, and ultimately failure.

Consistency and Enforcement

Having a more consistent support requirement simplifies inspections and enforcement. It's easier to verify compliance when there's a clear rule applicable in most situations, rather than having to make judgments about whether a particular short run is "adequately" supported by its terminations.

Industry Best Practices

Over time, there was a growing consensus within the electrical industry that providing more robust support for EMT, even in short runs, was a best practice to improve the overall quality and longevity of electrical installations.

In summary: The change in the NEC requiring more consistent support for EMT, including shorter runs, was driven by a desire to improve the safety, reliability, and longevity of electrical systems by preventing damage from vibration, physical impact, and strain on connections. It also helps simplify inspections and enforce more consistent installation practices. Flag for review