What type of collectors must be listed and labeled according to the specifications?

The correct answer is that factory-built collectors must be listed and labeled according to the specifications. Factory-built collectors are manufactured in a controlled environment and follow specific standards and testing protocols designed for safety and performance. The listing and labeling process ensures that these products meet the requirements established by applicable building codes and industry standards, providing assurance to consumers and professionals regarding their reliability and effectiveness.

When collectors are factory-built, they typically undergo rigorous testing for quality assurance and performance metrics before they reach the market. This process not only confirms that they are safe for use but also indicates that they will function as expected in a range of conditions, which is vital for any mechanical installation.

In contrast, custom-built, field-assembled, or permanent collectors may not undergo the same standardized evaluation or marking processes, making it essential for factory-built products to be explicitly identified as compliant. This distinction highlights the importance of certification and compliance in ensuring safe and efficient operation in mechanical systems.