As used in NFPA 54, what does EHD stand for?

In the context of NFPA 54, EHD stands for Equivalent Hydraulic Diameter. This term is used in gas piping design and analysis, particularly regarding the sizing of gas distribution systems. The Equivalent Hydraulic Diameter is a valuable parameter that takes into account the geometry of non-circular pipes, allowing engineers to calculate pressure drop and flow rates more accurately.

Using the equivalent hydraulic diameter enables professionals to standardize the analysis of different pipe shapes and sizes, which is crucial for compliance with safety standards outlined in NFPA 54, ensuring that gas delivery systems function efficiently and safely. Understanding this concept is essential for effective design and troubleshooting in HVAC systems involving gas lines.