Is it permissible for metal raceways to be installed in concealed locations under metal-corrugated roofing?

In this context, installing metal raceways in concealed locations, such as under metal-corrugated roofing, generally requires careful consideration. The correct choice indicates that such an installation is not permissible unless specified by regulations or standards. This is important because concealed locations can present various risks, including exposure to moisture, temperature extremes, and mechanical damage that could compromise the integrity of the electrical system.

Metal raceways are extensively used for protection and support of electrical conductors, but when installed in concealed spaces, additional requirements must often be fulfilled to ensure safety and code compliance. These requirements may include the need for specific approval or certain conditions to be met, thereby placing limitations on the general installation.

The other options suggest conditions under which such installation could be permissible. However, without explicit specification allowing it, as stated in the correct choice, it is safer and more compliant to view such installations as not allowed in the absence of clear guidelines. This is in line with best practices in electrical installation, which prioritize safety and adhere to codes.