Manual S HVAC Equipment Sizing Explained | Step-by-Step HVAC Selection

Learn how ACCA Manual S HVAC equipment sizing and selection works and how to use it after completing a residential Manual J load calculation. Manual J and Manual S perform two different jobs: Manual J → Calculates the building’s heating and cooling loads Manual S → Selects equipment capable of serving those loads Manual D → Designs the residential duct system In this quick HVAC training video, we walk through the Manual S equipment-selection process: starting with Manual J heating and cooling loads, establishing design conditions, obtaining OEM expanded performance data, comparing actual equipment capacity against the calculated load, applying the appropriate Manual S sizing criteria, and documenting the final equipment selection. One of the most important lessons is that nominal equipment tonnage is not the same thing as actual capacity under your project’s design conditions. ACCA specifically emphasizes manufacturer performance data because HVAC equipment capacity can change with indoor and outdoor operating conditions. The current ACCA Manual S also addresses equipment-specific sizing requirements, including updated provisions for variable-capacity heat pumps and dehumidification. This video is especially useful for: HVAC contractors • HVAC designers • Energy auditors • HERS raters • Home-performance professionals • Weatherization contractors • Building-science professionals For an actual project, use the applicable edition of Manual S, required OEM performance information, and applicable code/program requirements rather than relying on this short educational overview alone. Learn more about ACCA Manual S from the official ACCA Manual S resource⁠. Explore BPMS™ — Building Performance Modeling Systems™ at BPMSCloud.com⁠.

Originally uploaded October 7, 2026