Essentially, the low pressure side float valve is a hollow, spherical or otherwise shaped container, connected by levers and hinges to a needle valve. It keeps the liquid in the evaporator at a predetermined level. When the refrigerant is evaporated, the liquid level is reduced, lowering the float. The connecting joint opens the valve, accepting more refrigerant. Then, when the liquid level rises to the required point, the float is raised, closing the needle valve.
This type of expansion valve offers very good control, maintaining the appropriate level of refrigerant regardless of load variations, no-load periods, load conditions and other operating variables. Any number of evaporators can work in the same system, as each valve flows only the amount of refrigerant needed for its own evaporator.
