Thermostatic Expansion Valves (TXVs) are:

• A requirement for 14 SEER or higher split system heat pumps
• A requirement for many condensers or heat pump systems that use the new R-410A refrigerant
• An optional upgrade for any other air conditioner or heat pump system

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. Select the TXV to correspond with the tonnage of your air conditioner or heat pump, as well as to match the type of refrigerant your systems uses, R-22 (standard) or R-410A (new alternative). 

When using a TXV, manufacturer's recommend also installing a hard-start capacitor in your heat pump or condenser. This capacitor gives an extra "jolt" of electricity upon startup to push the refrigerant against higher head pressures that are present with a TXV system. If a hard-start capacitor isn't installed, the equipment compressor may sometimes have difficulty starting.