F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
F24H1/22—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating
F24H1/40—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating with water tube or tubes
F24H1/41—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating with water tube or tubes in serpentine form