Kraloy Expansion Fttings accommodate for conduit thermal expansion and contraction. Expansion joints are required when the temperature change is greater than 25°F (14°C). For conduit installed indoors, the range of expansion and contraction can be calculated using the maximum air temperature plus the heat contributed by the conductors inside the conduit and minimum air temperature expected. Expansion joints are not required indoors unless there are widely varying temperatures such as the attic of a building.