A thermostatic expansion valve (TXV) is designed to maintain a specific amount of superheat at the outlet of the evaporator. If the superheat value is too high or too low, the TXV may be the cause. However, before deciding the TXV is defective, all other system causes must first be investigated and ruled out.
The correct placement and installation of the thermostatic expansion valve (TXV) sensing bulb is important to its overall performance and reliability. An incorrectly installed or placed sensing bulb can lead to several different types of system problems. Here are some general installation concerns and tips to follow when installing a TXV.
The HVAC industry has seen a significant increase in thermostatic expansion valve (TXV) usage in the past decade. Even though TXVs are the most popular metering devices for residential air conditioning systems, there is still a lack of knowledge about TXV functionality in the market.
Bob and Tim were doing a routine service contract call. They had fastened gauges to the compressor at the condensing unit and had a temperature lead fastened to the suction line at the evaporator coil. They were observing the pressures and temperatures and Tim said, “The suction pressure is not stable. Isn’t it supposed to be stable during a long running cycle?”
One of the basic components selected when installing a walk-in cooler/freezer or any field-assembled refrigeration system is the metering device, typically the thermostatic expansion valve (TXV). The TXV needs to be selected to match the Btu capacity of the system’s evaporator and compressor.
This article explores how a restricted metering device will affect system performance and efficiency. The system is a commercial refrigeration system with a TXV as the metering device. The refrigerant being used is HFC-134a. Very similar results will occur if an automatic expansion valve (AXV) is used.