PVC Raceway Expansion Fitting

PVC conduit thermal length change, whether an expansion fitting is required (>= 0.25 in).

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Details, formula, and sources

PVC conduit thermal length change, whether an expansion fitting is required (>= 0.25 in), and the fitting count from the run length and temperature range (NEC 352.44).

dL = alpha * L * dT with alpha = 3.38e-5 in/in/F (NEC Table 352.44 PVC); an expansion fitting is required where dL >= 0.25 in in a straight run; fittings = ceil(dL / fitting_travel).

PVC raceway thermal expansion and expansion-fitting sizing - the length change over the run from the temperature range, the 0.25 in straight-run threshold, and the fitting count - per NEC Article 352.44 and Table 352.44 (rigid PVC conduit), by name; first-principles linear expansion.

NEC is free to read at nfpa.org/freeaccess. The 3.38e-5 in/in/F PVC-conduit coefficient is the NEC Table 352.44 figure, distinct from PVC pipe.

Estimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.

Field names used by the API: run_length_ft, temp_range_f, alpha_per_f, fitting_travel_in, length_change_in, fittings_needed

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