What is the installation requirement for mechanical fasteners in radiant heating systems?

The correct answer highlights that mechanical fasteners in radiant heating systems are required to be installed in a manner that only engages the unheated portions of the system. This specification is important for a few reasons.

Primarily, unheated portions of a radiant heating system refer to areas where the risk of heat distortion or damage to materials is minimized. By limiting fasteners to these areas, the integrity of the heated components can be preserved, ensuring optimal function and efficiency of the heating system. Properly managing the placement of fasteners prevents issues such as thermal expansion or contraction, which could lead to malfunctions or a decrease in the system’s effectiveness.

This installation requirement reflects standard practices in maintaining both the safety and functionality of radiant heating systems, which involve careful consideration of heat distribution and material reactions to varying temperatures.

In contrast, other options either suggest unnecessary penetration of heated areas or don't provide the clarity needed for proper installation, which can lead to complications in system performance.