Field guides for HVAC pros.

These are written for people who already do this work. There is no “what is a BTU” section and no square-foot-per-ton table, because a tech reading about friction rate does not need either. Each one takes a question that comes up on real jobs — where a rulebook actually differs from another, why a field reading disagrees with a design number — and answers it at the level of detail you would want from a coworker who had already looked it up.

Where a guide touches a calculation you would otherwise do by hand, it links to the free browser tool that does it and to the offline app that does the full version. Every one of them states its sources and says plainly where the methodology stops and an assumption starts.

• Live Manual J block load vs room-by-room When a whole-house block load is enough, when room-by-room earns its keep, and how that choice shows up in equipment and duct decisions. Related app: Manual J load calculator
• Live CSA F280-12 vs Manual J What changes when you size to Canada’s heat loss standard instead of ACCA Manual J — climate data, basements, ventilation, and reporting scope. Related app: CSA F280 heat loss calculator
• Live Duct static pressure and friction rate Available static pressure, total effective length, healthy friction-rate bands, and how field TESP readings relate to Manual D design. Related app: Ductulator & static pressure
• Live R-454B / R-32 superheat, subcooling, and charging Bubble vs dew for glide blends, typical targets vs OEM procedure, and how room-based A2L max charge fits beside the nameplate. Cites ASHRAE 15 / UL 60335-2-40. Related app: R-454B superheat & A2L max charge

• Manual J load calculator app US MJ8 loads, Manual S sizing, ZIP climate data.
• CSA F280 heat loss calculator Canadian loads with NRCan design temps by postal code.
• Ductulator & static pressure Size runs, check TESP, design Manual D schedules offline.
• R-454B superheat & A2L max charge Charge A2L systems with glide handled correctly.