What is another method of rating a low pressure heating boiler aside from btu/hr input?

The method of rating a low pressure heating boiler using Equivalent Direct Radiation (EDR) is significant because it provides a means to quantify the heating capacity of a boiler based on its ability to support a certain amount of connected radiant heating surface. EDR represents the square footage of radiation (like radiators or convectors) that the boiler can effectively heat, thus linking the boiler's capabilities directly to the radiator's output.

This concept is particularly useful because it allows for a clear understanding of how much heat the boiler can deliver to the systems connected to it based on the types and sizes of radiators being used. Essentially, it bridges the gap between the boiler's technical specifications and the real-world application in a heating system.

In contrast, while other options like boiler horsepower measure the installed steam capacity, temperature rise assesses temperature differences in the heating medium, and combustion efficiency relates to the performance of the burner, they do not provide a direct correlation to the heating capacities in terms of radiation output in the same manner as EDR does. Therefore, EDR remains an essential metric when evaluating how well a low pressure heating boiler will perform in a specific heating application.