Radiant heating panels must be installed as what type of units when not listed and labeled for field cutting?

The correct choice indicates that radiant heating panels must be installed as complete units when they are not listed and labeled for field cutting. This requirement ensures that the system operates safely and effectively based on the manufacturer's specifications.

Installing radiant heating panels as complete units helps maintain the integrity of the design, including efficient heat distribution and safety. When panels are not specifically labeled for modifications like field cutting, it is crucial to use them in their intended configuration to prevent potential hazards, such as electrical shorts, inefficiencies, or even fire risks.

Their installation as complete units also ensures compliance with the International Mechanical Code, which emphasizes installation according to the manufacturer's guidelines to guarantee performance and safety. This practice aims to prevent any unintended consequences that may arise from altering the equipment in a non-standard way.