Expansion Fittings

Expansion Fitting Intro

Expansion Fitting

Solar Design Calculator: Calculate thermal expansion and contraction of conduit runs to determine if expansion fittings are required per NEC 352.44. Supports PVC Schedule 40/80, RMC, IMC, EMT, and aluminum conduit with accurate thermal coefficients. Accounts for installation temperature, ambient extremes, and conduit length to prevent buckling, joint separation, and equipment damage in rooftop solar installations.

Conduit Configuration
Material affects thermal expansion coefficient
Total run length between fixed points
Temperature Conditions
Ambient temperature during conduit installation
Highest expected ambient (rooftop: 140-160°F)
Lowest expected ambient temperature

Expansion Fitting Results

Maximum Movement
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Expansion (Heating)
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Contraction (Cooling)
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Temperature Range
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Calculation Details
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About Thermal Expansion
Conduit expands when heated and contracts when cooled. PVC conduit has a thermal expansion coefficient approximately 5 times greater than metal conduit. Per NEC 352.44, expansion fittings are required when length changes exceed the capabilities of expansion joints in equipment or boxes. Rooftop installations commonly experience 100°F+ temperature swings, making expansion fittings critical for long PV runs to prevent buckling, joint separation, and equipment damage.