Raceways shall be provided with expansion fittings where necessary to compensate for _____.

Raceways are conduits or channels designed to hold and protect electrical wires and cables. One of the key considerations in their installation is the impact of temperature changes on the materials. As the temperature fluctuates, materials tend to expand and contract, a phenomenon known as thermal expansion. If raceways are rigidly installed without allowing for this movement, they can experience undue stress, which may lead to damage or even failure.

Incorporating expansion fittings into raceways serves to accommodate these thermal changes. By allowing for a certain degree of movement, these fittings help maintain the integrity and safety of the electrical system. This is particularly important in environments where temperature variations are significant.

In contrast, structural support focuses on the stability and anchoring of raceways but does not account for the thermal changes these materials undergo. Cosmetic appearance pertains to aesthetics rather than functional aspects of raceway installation. Finally, while electrical faults can be critical considerations in electrical design, they do not directly relate to the need for expansion fittings in response to temperature variations. Thus, the correct answer regarding why expansion fittings are necessary is to compensate for thermal expansion.