A heat exchanger for a boiler or similar heating device comprises a casing and a tube assembly inside the casing. The tube assembly includes a plurality of modules (6.sub.x, 6.sub.y) arranged in a juxtaposed configuration, each module (6.sub.x, 6.sub.y) having an at least approximately annular shape. The modules (6.sub.x,6.sub.y) each include a respective tube (7) that is at least partially embedded in a respective thermally conductive body (8) overmoulded to the tube (7). Each thermally conductive body (8) defines an upper face and a lower face of the respective module (6.sub.x, 6.sub.y), where at least at the upper face of a first module (6.sub.y) and the lower face of a second module (6.sub.x) the corresponding thermally conductive body (8) defines upper fins (24) and lower fins (23.sub.x), respectively, which extend in height substantially in an axial direction of the tube assembly and extend in length substantially in a radial direction of the tube assembly (5). The upper fins (24) of the thermally conductive body (8) of the first module (6.sub.y) are in an axially staggered position with respect to the lower fins (23.sub.x) of the thermally conductive body (8) of the second module (6.sub.x), with the upper fins (24), on the one hand, and with the lower fins (23.sub.x), on the other hand, which are at mutual distances such that the upper fins (24) of the thermally conductive body (8) of the first module (6.sub.y) are set between the lower fins (23.sub.x) of the thermally conductive body (8) of the second module (6.sub.x), or vice versa. In this way, between each upper fin (24) of the thermally conductive body (8) of the first module (6.sub.y) and each lower fin (23.sub.x) of the thermally conductive body (8) of the second module (6.sup.x), or vice versa, a respective radial passageway (P) is defined for the combustion fumes produced by a burner equipping the heat exchanger.

Embodiments include various water heaters. In one example, a water heater includes a burner, an exhaust vent, a corrugated baffle having a first slit having a first length and a second slit having a second length that is less than the first length, and a heat exchanger. The heat exchanger includes a first set of heat exchanger tubes arranged in a first row, and a second set of heat exchanger tubes arranged in a second row, the second set of heat exchanger tubes having a third tube having a first angled surface and a second angled surface, where the first angled surface and the second angled surface together form a fin. The third tube can be arranged such that the fin is disposed at least partially between the first curved outer surface and the second curved outer surface.

A control for a gas fired heater is configurable to operate at either a first voltage or a second voltage higher than the first voltage. The control includes an input voltage measurement circuit and an automatic voltage select circuit. The input voltage measurement circuit is configured to be operable for measuring an input line voltage to determine whether the gas fired heater is connected with the first voltage or the second voltage. The automatic voltage select circuit is configured to be operable for configuring the control for the correct input line voltage as measured by the input voltage measurement circuit.

A control for a gas fired heater is configurable to operate at either a first voltage or a second voltage higher than the first voltage. The control includes an input voltage measurement circuit and an automatic voltage select circuit. The input voltage measurement circuit is configured to be operable for measuring an input line voltage to determine whether the gas fired heater is connected with the first voltage or the second voltage. The automatic voltage select circuit is configured to be operable for configuring the control for the correct input line voltage as measured by the input voltage measurement circuit.