CSLB C-10 Electrical ContractorWiring Methods and MaterialsMedium
A PVC conduit run is installed outdoors along a parking structure where temperature swings will cause significant thermal movement. According to NEC 352.44, when must an expansion fitting be installed in the run?
- AWhen the expected length change is expected to exceed 1/4 inch
- BOnly when the conduit crosses a building expansion joint
- CWhenever the run exceeds 50 feet in length
- DWhen more than four conductors are installed in the raceway
Show answer & explanationAnswer & explanation
Correct answer: A. When the expected length change is expected to exceed 1/4 inch
NEC 352.44 requires expansion fittings for PVC conduit where the length change due to thermal expansion or contraction is expected to exceed 1/4 inch, based on the temperature change and Table 352.44 expansion characteristics.
Why the other options are wrong
- B. Building expansion joints are a separate consideration, not the general trigger rule.
- C. Length alone doesn't trigger the requirement; expected expansion amount does.
- D. Conductor count relates to fill calculations, not thermal expansion requirements.
PVC Conduit Expansion Fittings
NEC 352.44 requires expansion fittings in PVC raceways where thermal expansion/contraction is expected to exceed 1/4 inch based on temperature change and conduit length.
- PVC has a much higher coefficient of thermal expansion than metal raceways.
- Table 352.44 provides expected expansion per 100 ft based on temperature change.
- Failure to use fittings can cause conduit buckling or joint failure.
Memory trick: 'A quarter inch triggers the joint' for PVC expansion.