New, old stock, unused and in original box. TX5N4 Expansion Valve Kit 3 1/2-5 Ton R-410A Thermostatic Expansion Valves (TXVs) are a requirement for 14 SEER or higher split system heat pumps, and an optional upgrade for other air conditioning systems. Your system will operate more precisely and with greater efficiency with a TXV. These valves offer more control over how much liquid refrigerant enters the evaporator coil. The valves only allow a precise amount of liquid into the evaporator coil to ensure that all liquid that enters fully evaporates. This prevents too little liquid from entering the evaporator making the system run less efficiently. It also prevents too much liquid from entering the evaporator which can cause excess liquid in the suction line. Thermostatic Expansion Valves can be mounted in any position on the evaporator coil inlet and are reliable, efficient and virtually trouble-free.