Where are expansion fittings for PVC conduit required to compensate for significant thermal expansion or contraction?

Expansion fittings for PVC conduit are required where the length change is 6 millimeters (1/4 inch) or greater to effectively accommodate any significant thermal expansion or contraction. This requirement is based on the physical properties of PVC and the temperature variations that can cause thermal movement.

In situations where the temperature fluctuates, the length of the PVC conduit can change, and allowing for movement helps prevent undue stress on the conduit, joints, and fittings. Therefore, it is crucial to install expansion fittings at intervals where this level of movement is expected, which is identified as 6 millimeters (1/4 inch) or more.

Using expansion fittings minimizes the risk of damage, separation, or compromise of the electrical system housed within the conduit. By adhering to this rule, it ensures that the installation remains safe, functional, and complies with the necessary code standards.