Carlon Expansion Joints for PVC Rigid Nonmetallic Conduit - Manual (Page 6)

Use of Expansion Joints Where Concrete Encased or Direct Buried
In normal circumstances, expansion joints are not needed with concrete encased nonmetallic conduit
since the movement of the conduit will coincide with the expansion and contraction of the concrete.
The only place where an expansion joint would be utilized is where the concrete itself has an
expansion joint.
In direct burial situations, expansion joints are not needed because the ground has relatively constant
temperatures. In cold areas, buried lines must be below the frost line to prevent buckling during
freezing and thawing cycles. In warmer areas, the depth of cover protects against temperature
extremes.
Most Common Mistake
The most common error is not using enough expansion joints. When in doubt, use an additional
expansion joint. It is much more difficult and costly to insert an expansion joint once wiring has
been set up and in service.
This document is provided courtesy of:
This document was prepared by the NEMA PVC Polymer
Raceway Products (5TC) Technical Committee.
Gross Automation (877) 268-3700 · www.carlonsales.com · [email protected]