High-Altitude Appliance Input Derate

From the nameplate input and installation elevation, the derate factor (default 4% per 1000 ft above 2000 ft, both editable) and the derated input, with a high-altitude-kit flag. Field orifice drilling is generally prohibited; use a listed kit and the AHJ governs.

steps = max(0, (elevation - threshold) / 1000); factor = max(0, 1 - (derate-per-1000ft / 100) x steps); derated input = nameplate x factor. A high-altitude-kit flag is set above the threshold.

NFPA 54 (National Fuel Gas Code) / IFGC high-altitude provision (by name, not reproduced); the derate basis is an editable convention.

The derate arithmetic is public; the exact basis varies by edition and AHJ. Free read-only at nfpa.org/freeaccess.

Estimate. AHJ and licensed professional govern.

Field names used by the API: nameplate_input_btuh, elevation_ft, derate_pct_per_1000, threshold_ft, steps_1000, factor, derated_input_btuh

• Derate basis default 4%/1000 ft above 2000 ft, both editable; the exact basis varies by edition and jurisdictionNFPA 54 / IFGC high-altitude provision
• Field drilling field orifice drilling is generally prohibited; use a listed manufacturer high-altitude conversion kitmanufacturer instructions
• Floor the derate factor is floored at zerofirst principles