What is the first restriction when installing a manifold at the cross connection of the burner supply lines?

The first restriction when installing a manifold at the cross-connection of the burner supply lines being that the manifold piping must be as close to the shutoff valves as possible is crucial for safety and efficiency.

When the manifold is installed near the shutoff valves, it allows for easier access and quicker response during any maintenance or emergency situations. Keeping the manifold close to the shutoff valves minimizes the length of pipes that gas must travel through, which can reduce the risk of leaks and ensure that any potential hazardous conditions can be addressed swiftly. This configuration also helps in maintaining proper flow dynamics within the system, ensuring that the burner receives a consistent and reliable supply of fuel.

The other options offer different approaches but do not prioritize the same considerations for safety and operational efficiency that are embodied in the correct choice. For example, placing the manifold near the tank does not necessarily align with safety protocols regarding accessibility. Using plastic piping may not be suitable for all fuel types and could compromise system integrity. Allowing for the last fitting to be a distance from the tank may introduce risks that could otherwise be mitigated by following the guidelines for placement relative to shutoff valves.