What type of test must be performed and posted on-site during an installation?

The requirement for a combustion efficiency test to be performed and posted on-site during an installation is rooted in ensuring that the installed heating equipment operates safely and efficiently. This test evaluates how effectively the fuel is being converted into heat, which is crucial for both performance and safety reasons. A properly conducted combustion efficiency test ensures that appliances not only provide maximum heating output but also do so while minimizing harmful emissions, contributing to a safer environment for occupants.

Furthermore, this test gives valuable data about the air-fuel mixture and can help in adjusting the system to optimize performance. By having the results posted on-site, it provides transparency and allows inspectors and technicians to quickly verify that the installation meets required standards and operates efficiently right from the start. This is particularly important in adhering to regulations and maintaining optimal functioning throughout the lifespan of the heating system.

The other options, while relevant to heating system safety and performance, do not specifically meet the on-site posting requirement as defined in this context.