SkillCat EPA Universal Practice Test

When air ends up in the refrigerant circuit, it becomes a non-condensable gas that doesn’t liquefy in the condenser. This gas collects around the condenser tubes and forms an insulating layer, which greatly reduces the condenser’s ability to reject heat. With poorer heat rejection, the condenser pressure (the head pressure) rises, and the compressor has to push against that higher pressure, causing the discharge pressure to climb. This is a common and direct way discharge pressures can go up. While other factors can influence pressures—for example, an overcharged refrigerant system, slower compressor speeds, or higher ambient temperatures—the presence of air in the system specifically leads to a rise in discharge pressure by hindering heat transfer and raising the condensing pressure.