Thermostatic Expansion Valves (TXVs) are a requirement for some higher efficiency split system heat pumps, and an optional upgrade for other air conditioning systems. However, they are not needed with an Alpine brand system if you purchase a new indoor evaporator coil or air handler, since the TXV is already built into the coil 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

When using a TXV manufacturers 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.