For residential uses, replacement of gas and electric water heating appliances of equal or less Btu/cfh rating do not require a permit.
Section4-1-4 B(3)g
Replacement of gas air-conditioning units, direct-vented appliances, furnaces, and log lighters, of equal or less Btu/cfh, and minor modification to electrical, plumbing, and mechanical connections necessary to serve the appliance in R-1, R-2, R-3, R-4 and R-5 occupancies, manufactured homes, and recreational vehicles where the appliance serves an individual dwelling unit, provided the serving Gas Utility is notified prior to the appliance being energized. (4242, 4579)
Section 4-1-4B(5)d
Replacement of electric water heating appliances of equal or less amperage rating, and minor modification to electrical, plumbing, and mechanical connections to serve the appliance in R-1, R-2, R-3, R-4 and R-5 occupancies, manufactured homes, and recreational vehicles where the appliance serves an individual dwelling unit. (4242, 4579)