Open hot water heater

摘要

A hot water heater includes a water tank defining a tank space for accommodating water; a cold water inlet and a hot water outlet connected to the tank; a hot water tap in the hot water outlet for controlling flow of hot water from the water tank; a cold water valve in the cold water inlet for controlling flow of cold water into the water tank; and a volume altering device for changing the tank space. The volume altering device comprises an expandable and collapsible chamber situated in the tank space and defining a chamber space hermetically separated from the tank space; and a volume varying arrangement connected to the chamber and exposed to pressure of inflowing cold water for increasing the chamber space by a predetermined volume while correspondingly reducing the tank space when the hot water tap and the cold water valve are open and for reducing the chamber space by the predetermined volume while correspondingly increasing the tank space subsequent to closing the hot water tap and the cold water valve to obtain a water-free space having the predetermined volume and forming part of the tank space.