Novel clean water circulation central heating system

The utility model relates to the technical field of central heating, and discloses a novel clean water circulation central heating system which comprises a heat exchange unit and a standby heat exchanger, the primary sides of the heat exchange unit and the standby heat exchanger are connected with a primary water supply pipeline and a primary water return pipeline, and the secondary sides of the heat exchange unit and the standby heat exchanger are connected with a secondary water supply pipeline and a secondary water return pipeline. The secondary water return pipeline is connected with a purifying and water replenishing pipeline, the purifying and water replenishing pipeline comprises a tap water pipeline, the tap water pipeline is communicated with a water tank through a softened water pipeline, the output end of the water tank is connected with a plurality of water replenishing pipelines, and each water replenishing pipeline is communicated with the secondary water return pipeline; a water softening devic