www.pmmag.com/articles/86522-efficient-water-heater-a-o-smith
Efficient Water Heater - A.O. Smith
January 1, 2003

The new A.O. Smith Cyclone XHER BTH-400 is the first commercial gas water heater to achieve 99 percent thermal efficiency. When manifolded together, four Cyclone units provide 540 gallons of total hot water storage and 1.6 million Btu input, to serve the needs of high-demand applications.
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