A. O. Smith now offers the shortest footprint in the most popular 199,000 Btu input sizes. At only 27 3/4" the Master-Fit Ultra-Low NOx from A. O. Smith can fit where others cannot. The BTL design keeps the gas connection near the bottom of the tank allowing for ease of replacement. The A. O. Smith design features a stainless steel air flapper inside the premix system that eliminates the need for an externally mounted mechanical damper. By not having a damper, it saves time at the install and avoids maintenance down the road. All BTL models feature top, front and rear water connection options to make retrofit applications as easy as possible. The BTL design incorporates a standard one-pass multi-flue design. This traditional flue design is time tested and will provide years of trouble-free service life. The full line of BTL models have been designed to easily connect directly to pre-existing water heaters. The Master-Fit® Ultra-Low NOx BTL series complies with California SCAQMD Rule 1146.2 and other air quality management districts with similar NOx emission requirements of 14 ng/J or 20 ppm. For ease of installation, all BTL’s feature water connections on the top, front and rear. BTL-199 uses up to 199,000 BTU/h of gas to deliver 191 GPH at 100°F rise. A. O. Smith offers the largest commercial product selection available, including the most specified commercial unit in the U.S. We offer more than 500 different commercial models, including gas fired, oil-fired and electric configurations, ranging in capacities from 5 to 10,000 gallons, with input range from 50,000 BTU to the equivalent of 4,000,000 BTU. Our comprehensive line is the natural fit for spec jobs requiring everything from the smallest commercial installation up to the largest multi-structure complex.