All refrigeration systems have 4 major components , which function together to provide a complete solution. the 4 main components are the condensor, evaporator, compressor, and refrigerant flow device. So i would like to explain to you the most common type of refrigerant flow device used in commercial refrigeration.

the most common type of refrigerant flow device is a thermostatic expansion valve , it is usually called a TX valve . the tx valve controlls the amount of refrigerant that is allowed to enter the evaporator , it does this by passing the liquid refrigerant thru a very small orifice , the orifice is open and closed by a needle and seat arrangement . The value is set to automatically increase and decrease the flow of refrigerant gas based on several system conditions . the valve will open and allow more flow if the pressure of the gas increases the valve will also open if the temperature at the sensing bulb increases. the reverse is also true ie low pressure or low temperature will close The valve and reduce the flow.

All TX valves need to me set up (configured) for your system , this involves fitting the correct valve , each gas type has its correct valve ie R404a valves are used on R404a Gas and R22 vales are used on R22 gas. addition to this is that the orifice inside each valve is interchangeable based on the size of the system a small 2 door drink fridge would require a number 1 and a very large coolroom would need a number 6 , the orifices are sized from 00 to 06

Ok so now we have selected the correct valve based on gas type , and we have selected the correct size orifice based on system capacity. now we have to adjust the valve to optimum performance , this adjustment is called the superheat setting , there is an adjustment screw located on the valve and this is alter the maximum flow rate of the TX valve , there is a complex method of adjusting the valve and a qualified technician will need a pressure gauge, a thermometer, and a pressure-temperature chart to correctly calibrate the TX valve this will often take more than 1 hour to do but once calibrated the valve is set for life and should not require any further adjustment.