Horizontal hot water boilers are equipment that provides heat energy for residential communities, villas, swimming pools, and bath centers, etc. They are categorized by fuel type into electric, oil-fueled, gas-fueled, and coal-fueled, and by structure into atmospheric (no explosion risk) and pressure boilers.

The unit features a horizontal layout, including the furnace chamber, flue, and water jacket, among other core components. Some models are equipped with an enamel lining for enhanced durability. The control system integrates microcomputer technology, supporting temperature presets, timed operation, and automatic adjustment, along with multiple safety mechanisms such as leakage protection and anti-dry-burn. The fuel/gas models utilize a three-pass full-wet-back design and threaded flue pipes to enhance thermal efficiency, while the coal-burning models optimize combustion through hand-cranked grate and secondary air intake technology. The atmospheric pressure boiler, due to its non-pressurized design with an open atmosphere vent at the top, does not fall under the category of special equipment, and its installation and use are not subject to regulatory restrictions.