The thermostatic expansion valve (TXV or TEV) is a metering device located between the refrigeration system’s liquid line and the evaporator. It is a rather complex valve with a remote bulb feedback mechanism, which constantly tells the valve how full or void the evaporator is with vaporizing refrigerant. This article will explore the remote bulb and its proper placement on the system’s suction line.
The TXV is a dynamic valve that constantly modulates and meters just enough refrigerant into the evaporator to satisfy all heat loadings on the evaporator. A conventional TXV is shown in Figure 1. The basic TXV will control a set amount of evaporator superheat under varying heat loads. Three of the main functions of the TXV include: