What happened to the water in the heating and water supply tank? The exhaust is not good

There may be four reasons. Check it out: 1. The make-up water tank shall be connected to the return water pipe. 2. The length of the connecting pipe between the water supply pipe and the furnace should be greater than1.5m ... 3. The cooker is large, the radiator is few, and the load is small, resulting in high water temperature. 4. The supply tank is too small. After replenishing water, water expands with heat and contracts with cold, resulting in overflow.