 Externally equalized valves must be used on multi-circuited evaporators with refrigerant distributors.Externally equalized TXVs can be used on all applications; however, an externally equalized TXV cannot be replaced with an internally equalized TXV.A type of externally equalized thermal expansion valve, known as the block type valve, which features an internal sensing bulb (often the valve's metal body, particularly when a stable and hunting-free refrigerant flow control is required), located inside the suction line connection and in constant contact with the refrigerant that flows out of the evaporator's outlet, is nowadays often used on automotive evaporators.