PVC Raceway Expansion Fitting
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).
Formula and source
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.
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