The CWNS series fully automatic fuel (gas) horizontal hot water boiler (utility model patent) adopts a horizontal three return wet back structure to improve the boiler operating environment, enhance boiler efficiency and service life; All smoke channels are placed in water, and the tail is equipped with a waste heat water tank and a complete insulation outsourcing design. The smoke box seal adopts a labyrinth structure to avoid smoke leakage. The boiler has a thermal efficiency of over 90%, using a combination of corrugated and conical furnace liners with good expansion performance. The size of the furnace liner matches the flame, and the flow area of the flue gas is reduced accordingly, ensuring that the flue gas flows at a constant speed and ensuring the heat exchange time of high-temperature flue gas in the furnace, achieving the best heat transfer effect; Adopting high-performance combustion engines that are perfectly matched with the boiler for comprehensive automatic adjustment, ensuring sufficient combustion, saving fuel, and reducing pollution; Using ultra-fine glass wool with high insulation performance, resulting in less heat loss; Adopting an intelligent energy-saving control system to control the boiler, water supply, heating, and automatic water temperature system, and adjusting fuel supply according to different loads for greater energy efficiency. The installation method is an integral quick installation boiler with minimal vibration and no special requirements for the foundation. It does not require anchor bolts for fixation and is easy to install. Adopting an active furnace head structure, it can match various burners, replace furnace heads, and repair furnace bodies conveniently and quickly. The front and rear smoke boxes adopt a movable and detachable structure, which makes it easy to inspect, maintain, and upkeep the interior of the boiler. It is simple and convenient, with a novel product design, reasonable structure, and good process performance, making this product have outstanding quality. It is the latest developed new product.