Constant-pressure water make-up device

Schematic Diagram of Constant-Pressure Water Make-Up

　Constant-pressure water replenishment device

　　The YJDP pressure-stabilizing and make-up water unit, developed by our company’s Technology Research and Development Center, is designed for pressure stabilization and make-up water supply in heating systems, air-conditioning systems, and boilers. Its salient features include pressure stabilization, continuous make-up water supply, expansion management, and automatic overpressure relief, making it a next-generation replacement for bladder-type floor-mounted expansion tanks.

　　Technical Principle

　　In a closed-loop circulating water system, a pressure-stabilizing expansion unit must be installed to maintain stable system pressure. When the system pressure drops, the water chamber pressure of the connected pressure regulator—whether an bladder-type or diaphragm-type pressure tank—also decreases, causing the gas chamber to expand and further reducing the pressure. Once the lower setpoint is reached, the controller starts the water pump to replenish the system with make-up water until the set pressure is restored, at which point the pump shuts off. Conversely, as the water in the system heats up and expands, it compresses the gas chamber, raising the pressure; when the upper setpoint is reached, excess water from the water chamber is discharged through the safety relief valve into the expansion tank (or softened water tank), thereby reducing the system pressure. When the pressure returns to the set value, the relief process ceases.

　　Performance Features

　　Land-saving

　　Conventional floor-mounted expansion tanks rely on the expansion and contraction of a diaphragm to accommodate system expansion, but the effective usable volume of the tank accounts for only 20–30% of its total capacity. Moreover, these tanks are relatively bulky. In contrast, the YJDP-type pressure-stabilizing expansion unit employs specialized technical measures to separate the expansion section from the pressure-stabilization section. This design allows most of the system’s expansion volume to be stored in a dedicated isolation expansion vessel (or softened-water tank), increasing the volumetric utilization of the pressure-stabilization tank to over 85%. As a result, the overall footprint and height of the unit are significantly reduced, leading to a 50–60% reduction in land use. This not only simplifies equipment layout and installation but also lowers civil-engineering costs for the machine room.

　　● Safe and reliable

　　The advanced automatic control system features both dual-pump alternating operation and simultaneous dual-pump operation in the event of a leakage, as well as low-water-level protection and anti-undervoltage misoperation functions, thereby ensuring the safe and stable operation of the unit.

　　Energy-saving features

　　This product features a multi-stage stainless-steel pump and a specially designed, imported pressure regulator, which enhance the service life of the unit, ensure optimal performance under various operating conditions, and deliver superior energy efficiency.

　　●Easy installation

　　Conventional bag-type floor-mounted water tanks are typically shipped in disassembled parts for on-site assembly, which increases installation complexity and compromises equipment reliability. In contrast, this product is delivered as a complete unit, requiring only the connection of the outlet and power supply on site before it is ready for use—making installation simple and fast.

　　●A softened water tank may be omitted.

　　When the softened water equipment can consistently deliver the required flow rate without interruption, a separate softened water tank may be omitted to reduce capital investment; if a softened water tank is already installed in the system, it can simply be connected to the equipment’s designated connection port.

　　Selection Instructions

　　1. Provide the system’s thermal load or the system’s air-conditioning and heating area.

　　2. Specify whether the system includes a water tank.

　　3. Provide the flow rate and head of the water supply pump (or the elevation of the system’s highest point above ground level).

Constant-Pressure Make-Up Water System Selection Table: