The working principle of In a closed loop system, in order to guarantee the stability of the system pressure, you need to set up regulated expansion facilities. When the system pressure drops, and the water chamber pressure tank pressure drops, chamber volume expansion, the pressure also decreases, set limit to the control system, automatically open water pump, filling water to the system, until reach the set pressure cap, the pump stop running. When the water heating system, temperature, volume expansion, extrusion chamber, pressure, pressure system to the limit, the water in the system through safety relief device to the expander (or softened water tank), the system pressure drops to the set value, also stop the pressure. Performance characteristics: Economical use of land, a common floor-type expansion volume of expansion tank on shrinkage expansion capsule, the effective use of tank volume is only 20% ~ 30% of total volume of tank, relatively large tanks, and DBS type voltage stabilizing inflation unit with special technical measures, the inflation