A water heater includes a primary heat exchanger, a secondary heat exchanger disposed above the primary heat exchanger, a flow path member, and a flow restriction member. The secondary heat exchanger includes a case and heat transfer pipes arranged in the case. The case includes a wall having a gas inlet through which combustion exhaust gas discharged from the primary heat exchanger is introduced into the case. The flow path member connects the primary heat exchanger and the secondary heat exchanger and is disposed adjacent to the gas inlet and is configured to introduce the combustion exhaust gas discharged from the primary heat exchanger into the secondary heat exchanger through the gas inlet. The flow restriction member is disposed on the wall of the case to suppress upward flowing of the combustion exhaust gas that is introduced into the case through the gas inlet.

The present invention becomes possible to employ a main microprocessor with a relatively lower number of input ports, whereby while maintaining the performance and function of a water heater, the cost of a control apparatus is cut down. Some of sensors, adapted for measurement of various parameters which are for use in operational control of the water heater and in need of immediate response, are connected to a main microprocessor 31. The other sensors that are not in need of an immediate response, such as an ambient temperature sensor 36, are connected only to a sub microprocessor 32 if the main microprocessor 31 does not have any extra analog signal input port. The sub microprocessor converts an analog signal from the sensor 36 which is connected only to the sub microprocessor into digital data. And the sub microprocessor transmits the digital data to the main microprocessor through communication therewith.

Embodiments of the invention provide a pool heater including a housing, a first tankless heater, a second tankless heater, and a controller. The controller is configured to activate only the first tankless heater when a first condition is met, activate only the second tankless heater when a second condition is met, and activate the first and the second tankless heaters simultaneously when a third condition is met.

The disclosed technology includes carryover burner systems and methods for use with water heating system. The water heating system can include a burner unit having an outer sleeve, and an inner sleeve. The water heating system can also include an ignitor. The outer sleeve can include a carryover region having a first plurality of apertures and a combustion region which can be adjacent to the carryover region, the combustion region including a second plurality of apertures. The inner sleeve can comprise a dispersion region having a third plurality of apertures. The inner sleeve can be located substantially within the outer sleeve.

A heat exchanger arrangement, especially for a vehicle heater, includes a pot-like heat exchanger housing (12) with an inner wall (22, 24) and with an outer wall (18, 20). A heat carrier medium flow space is formed between the inner wall (22, 24) and the outer wall (18, 20). A first flow opening (54) is provided on the outer wall (18, 20) and, adjoining this, a pump housing (58) made integrally with the outer wall (18, 20) for a heat carrier medium pump is provided.

The plate-type heat exchanger includes blocks stacked on each other, each of the blocks including a heat exchanger body configured to exchange heat between a first fluid and a second fluid. A connection passage for the first fluid is formed between blocks adjacent to each other of the plurality of blocks, the connection passage allowing the outlet of one of the blocks adjacent to each other and the inlet of the other of the blocks adjacent to each other to communicate with each other, the first fluid in the blocks adjacent to each other having different flow directions between the blocks adjacent to each other, and a second connection passage is provided between at least one pair of blocks adjacent to each other among the plurality of blocks, the second connection passage being configured to cause the first fluid to flow to a position different from the connection passage.

Various implementations include a hot water heating system having a spine and two or more water heating units. The spine includes a top surface defining one or more top openings, two or more coupling areas, and cold water, hot water, and fuel manifolds. One or more top openings provide access to a cold water manifold inlet, a hot water manifold outlet, and a fuel manifold inlet. At least one of the coupling areas is located above another coupling area when the spine is oriented with the top surface facing upwardly. The water heating units are coupled to coupling areas such that a cold water inlet of the unit is fluidically coupled to the cold water manifold outlet, a hot water outlet of the unit is fluidically coupled to the hot water manifold inlet, and a fuel inlet of the unit is fluidically coupled to the fuel manifold outlet.

A fluid heating pre-start system includes a fluid circuit. The fluid circuit includes a circulating pump, a heat exchanger, and a fluid jacket coupled to a piece of equipment. The pre-start system includes a heater positioned to heat the fluid in the fluid circuit using the heat exchanger. The pre-start system includes a controller positioned to control the operation of the fluid circuit and the heater. The pre-start system may be run until the piece of equipment is preheated to a desired temperature before the piece of equipment is activated.

A secondary heat exchanger includes a case and a first heat transfer tube portion. The case includes a box body and a first closing member. The box body is provided with a second opening on one side in a third direction. A first assembly in which the first heat transfer tube portion and the first closing member are assembled integrally is mounted to the box body so that a plurality of first heat transfer tubes are is inserted into the box body from the second opening and so that the second opening is closed by the first closing member.

A water heater includes a first heater, a second heater, and a controller. The controller can enable different operational modes of the water heater, wherein only the first heater operates, only the second heater operates, or both the first and the second heaters operate. The controller can also be configured to enable a hybrid operational mode and a bypass operational mode. Further, in the different operational modes, the controller can direct water flow to at least one of a first conduit coupled to the first heater, a second conduit coupled to the second heater, and a bypass conduit. The controller can be configured to receive input signals relating to environmental conditions around the water heater and/or an aquatic system in which the water heater is installed.