Abstract: A commercial water heater apparatus, including a housing, a radial-fired burner within the housing, a single continuous, multiple loop, finned coil tubing heat exchanger for circulating water around the burner, having at least a first set of inner coils forming a coil trough therebetween and a second set of outer coils nested within the coil trough formed by the inner set of coils, the outer set of coils forming a second coil trough around the exterior thereof, and a coil baffle interposed in the second exterior trough for deflecting heat adjacent to the second set of coils.

Abstract: A radially fired water heating apparatus (10) having a plurality of stacked segments of multiple-loop, finned coiled tubing (58) separated by inner and outer support baffles (86, 88), all contained within a cylindrical baffle (20) which cooperates with the coiled tubing (58) and support baffles (86, 88) to direct combustion by-products into an annulus (24) promoting heat transfer to a countercurrent flow of inlet air, the water being supplied to and recovered from the stacked segments of coiled tubing (58) through inlet and outlet headers (54, 56) disposed outside cylindrical baffle (20) that can be selectively modified by installing or removing baffles (90, 92) for either single-pass or multiple-pass operation.