A.O. Smith Water Products Co. has added the BTH-400 model to its Cyclone XHE (Extra High Efficiency) line. In addition to combining the delivery capacity of a 130-gallon tank with 400,000 Btu input, the BTH-400 can achieve 99% thermal efficiency. The unit features a new cyclonic combustion system that distributes heat more evenly, and a longer heat exchanger coil with more heat transfer surface area. The BTH-400 delivers 475 gph recovery at 100 degrees F temperature rise. The unit also offers powered anodes that are guaranteed to last the life of the tank. Six models are available: BTH-400 (130-gal/400,000 Btu), BTH-300 (130-gal/300,000 Btu), BTH-250 (100-gal/240,000 Btu), BTH-199 (100-gal/199,000 Btu), BTH-150 (100-gal/150,000 Btu), and BTH-120 (60-gal/120,000 Btu).A.O. Smith Water Products Co.