PVC run along a pole barn
What's wrong here?
- The exterior PVC run has no expansion fitting
- The straps are too far apart for 1 in. PVC
- PVC conduit is not permitted in direct sunlight
- Nothing. This installation is compliant
Show the answer and the code reference
The answer
The 35 ft straight PVC run between the LB and the light box has no expansion fitting, and it is already bowing between straps from thermal growth.
Correct choice: 1. The exterior PVC run has no expansion fitting
PVC grows and shrinks about 4 in. per 100 ft for every 100 degrees F of temperature change (Table 352.44). On a sun-baked steel wall in Minnesota the conduit can see well over a 100 degree swing between a July afternoon and a January night, so this 35 ft run moves on the order of 1.5 in. or more. 352.44 requires an expansion fitting wherever the expected change in a straight run between securely mounted items is 1/4 in. or more, and 352.30 requires PVC to be fastened so that thermal movement is permitted. Without an expansion fitting, the run bows in summer and in winter pulls apart at glued joints or out of the LB and box hubs, exposing conductors to water and damage.
How to fix it
Cut in a PVC expansion fitting (one end of the run is a common spot), set its piston for the temperature at installation using the maker's chart, and use straps that let the conduit slide. Straighten or replace any sections that have taken a permanent bow.
Code references
NEC 2023 352.44 — Expansion Fittings
Expansion fittings for PVC conduit shall be provided to compensate for thermal expansion and contraction where the expected length change, determined from Table 352.44, is 6 mm (1/4 in.) or greater in a straight run between securely mounted items such as boxes, cabinets, elbows, or other conduit terminations.
Drills citing 352.44NEC 2023 Table 352.44 — Expansion Characteristics of PVC Rigid Nonmetallic Conduit
Gives length change for PVC by temperature change; the coefficient is about 3.38 x 10^-5 in./in./degree F, which works out to roughly 4.06 in. per 100 ft for a 100 degree F change.
Drills citing Table 352.44NEC 2023 352.30 — Securing and Supporting
PVC conduit shall be installed as a complete system (300.18) and fastened so that movement from thermal expansion or contraction is permitted. It shall be securely fastened within 900 mm (3 ft) of each box or other termination and supported per Table 352.30, which allows 900 mm (3 ft) spacing for trade sizes 1/2 through 1.
Drills citing 352.30
2026 NEC:same rule and number. No 2026 revision to the PVC expansion-fitting rule turned up in change summaries; the 1/4 in. threshold, Table 352.44, and the 2023 split into thermal (A) and earth-movement (B) provisions appear to carry forward. Based on absence of reported changes, not on the 2026 text. Confidence: low
Minnesota
Minnesota adopted the 2023 NEC as the Minnesota Electrical Code effective July 1, 2023 (Minn. Stat. 326B.35; Minn. Rules 1315.0200) and adopts the NEC without section-by-section amendments. No Minnesota change to 352.30 or 352.44 is known. Newer permits may fall under a later NEC edition; see the Minnesota page. The Board of Electricity adopted the 2026 NEC, also without amendment, for permits filed on or after Aug. 17, 2026 (exams moved to the 2026 NEC on Sept. 8, 2026); see the 2026 NEC note on this drill.
How Minnesota adopts the NECWhy the other choices are wrong
- The straps are too far apart for 1 in. PVC. The straps are about 3 ft apart, which meets Table 352.30 for 1/2 to 1 in. PVC; the waviness comes from thermal growth, not from missing supports.
- PVC conduit is not permitted in direct sunlight. 352.10 permits PVC for exposed work and in wet locations, and ordinary listed Schedule 40 and 80 PVC conduit is made for outdoor use in sunlight.
- Nothing. This installation is compliant. A 35 ft straight run of PVC between fixed points moves well over 1/4 in. across a Minnesota year, so 352.44 requires an expansion fitting.