Description

Explains how to configure FHC for water mist calculations under NFPA 750, including choosing between Hazen-Williams and Darcy-Weisbach pressure loss formulas.

This technical data sheet explains how to set up Canute's FHC hydraulic calculation software correctly for water mist systems, across all three NFPA 750 pressure classifications: low (≤12.1 bar), intermediate (12.1–34.5 bar) and high (>34.5 bar).

It covers:

• When the Hazen-Williams pressure loss formula can be used for intermediate and high-pressure systems (water velocity below 7.6 m/s, minimum pipe diameter 20mm)
• Why Darcy-Weisbach is recommended for practical, lower-pressure results on high-pressure designs, and how to switch to it in FHC (project data > DWF button)
• Selecting the correct design authority (NFPA 750: 2010) in the FHC project data
• Water mist-specific settings: leaving density of coverage at 0.00, modelling a known water supply curve, and head area/density fields you can safely ignore
• Using FHC's automatic pipe sizing for tree-configuration water mist systems

For background on the underlying formulas, see the Hazen-Williams equation explained or try the free Hazen-Williams calculator. The hydraulics glossary covers related terms including the Moody diagram.