What is the main difference between IMC and RMC?

The correct answer highlights that Rigid Metal Conduit (RMC) typically has a larger external diameter compared to Intermediate Metal Conduit (IMC). This difference in size stems from the fact that RMC is generally used for more demanding applications that may require a stronger and larger conduit to accommodate additional strength and larger conductors.

RMC is constructed with thicker materials to enhance durability and provide greater mechanical protection, which contributes to its larger external diameter. On the other hand, IMC is designed to be lighter and is generally thinner while still offering a substantial degree of protection for the electrical conductors it houses. Therefore, the distinction in external diameter between RMC and IMC reflects their intended applications and the environmental conditions they are designed to withstand.

Understanding these differences is crucial for selecting the appropriate conduit for specific installation needs, ensuring both safety and compliance with electrical codes.