Low-pressure floating ball valve is a low-pressure liquid level to control the amount of liquid into the control valve, it is combined with the following evaporative coil into a throttle and evaporator combination, float ball and valve needle is consist of lever, hinge connected into the liquid control valve. When the liquid level drops, the float drops, the valve needle is opened, the liquid volume increases. When the liquid level rises, the float rises with the liquid level, and the small valve is closed, the liquid level is reduced. So the float valve make the change of the liquid level as the power to adjust the flow.