The Booster Water Heater will operate at less than its sea level capacity due to either natural derating or code compliance derating. This means that the unit’s sizing selection should be checked for the intended altitude. Also, an orifice change may be required to achieve the maximum allowable burn rate. Charts are provided in the manuals to help achieve compliance with AGA's limits for our models. NFPA 54 and local codes should be checked to be sure they don't take precedence. A kit of blank orifices is available to allow you the flexibility to comply with the specific altitude regulation at your installation.