The expansion valve is the device in the air conditioning system that has the function of allowing the pressure from the compressor’s outlet to build up that helps in separating the high pressure as well as the low pressure part of the air conditioner. It is a somewhat a limit device used to enable the pressure to drop to or across the inlet or/and outlet lines.
This valve also is used to regulate the flow of liquid refrigerant in the expansion zone. This is because too much or too little liquid in the expansion zone is not good. So, what does it mean when there is too much or too little flow? This will depend on the size of the evaporator and the refrigerant that you use. Most evaporator and refrigerant are manufactured to give the desired heat removal capability to an air conditioning unit thus it is important that the expansion valve has to make sure that the amount of liquid used in the expansion zone has completely boiled down at the end of the such evaporator. If there is less that that it is considered too little and anything more that that is considered too much. Therefore, knowing how to maintain its parts will prolong the years of its existence that will definitely set you up for more time usage as well.
There are two most common types of expansion valve, the capillary tube and the thermostatic expansion valve. The first one is usually used in a small sized unit while the other one is generally used in larger sized units. Usually the capillary tube expansion device is not actually a valve but a simple tube with similar material which is usually used in the air conditioner tubing. Here, there is no actually device to control the flow but it has its tube’s internal diameter, spiral shape as well as length which create restrictions that allows refrigerant into the expansion zone.
On the other hand, the thermostatic expansion valve has sensing bulb which is connected to the tube, a spring loaded valve seat, a liquid outlet and inlet line, a diaphragm, a filter at the inlet line and an adjustable knob.
The expansion valve has a sensing bulb at the exit line of the evaporator wherein the pressure is connected to the tube that allows it to rise if such exit temperature is too high however the pressure in the connected tube will then drop if the exit temperature is too low as well. As a result, the rise and drop in the pressure will push and/or pull the diaphragm. While the diaphragm is connected to the spring loaded valve seat which is usually arranged so that it will increase the flow if it has a high pressure and so forth. As a result, the expansion valve has the capacity to operate in varying load conditions. There are also filters that are used to get solid particles from the equipment ordinary wear and tear. Furthermore, the adjusting knob is used to tune the valves as well.