Arkansas HVACR NewsMagazine March 2025

HVACR NewsMagazine March 2025

Tech News

Solving Superheat

boiling/evaporating refrigerant in either the outdoor coil for heating or the indoor coil for cooling. To better understand this process, I recommend that you watch 3D How Refrigeration and Air Conditioning Works P1 – Components to learn more about the refrigeration cycle. There are three types of superheat measurements. The one discussed in this tech tip is the most common measurement; it's known as system superheat and is taken at the outdoor unit on the suction line. System superheat includes any additional heat added to the vapor in the suction line. Longer suction lines will be affected. There is also the evaporator superheat, which is taken at the evaporator coil outlet; this is what manufacturers use for TXV superheat settings. Finally, there is the discharge superheat, taken 6 ″ from the compressor discharge outlet. This third one will be discussed in a future article. Superheat is an important measurement for any metering device. If we don't have enough superheated vapor, we can flood the evaporator coil and end up with liquid in the compressor. If we have too much superheated vapor, we starve the evaporator of liquid needed for cooling and can overheat the compressor. Why Does Superheat Matter?

In this article, we'll discuss superheat while using this diagnostic sheet to help us better understand how it is calculated and from where it is derived. I want to thank Ty Branaman for helping me develop these sheets that will hopefully aid in a better understanding of some of the basic HVAC measurements that both new and experienced techs use day in and day out. To start with, let's make sure we have a general understanding of what superheat is. I am not going to go into great detail on the subject as there are already some great articles at https://hvacrschool.com/. Superheat, for the purposes of this article and as it pertains to HVAC, is the amount of heat gained by a refrigerant after it has completely changed state to vapor. Every degree of heat increase to the vapor is considered a degree of superheat. So, quite simply put, 10 degrees of heat above the saturated temperature (or the boiling point of the refrigerant) is considered 10 degrees of superheat. It is important to note that this process could happen in either the indoor or outdoor coil, depending on the type of equipment. For example, a heat pump, depending on what mode it is in, could be What is Superheat?