Checking refrigerant charge by superheat is typically done on systems using __________.___

Checking refrigerant charge by superheat is typically done on systems using fixed orifice metering devices. In systems with fixed orifice metering devices, the amount of refrigerant entering the evaporator is constrained by the size of the orifice, and it does not adapt to varying load conditions. This means that monitoring superheat becomes crucial for evaluating the refrigerant charge.

Superheat is the temperature of the refrigerant vapor above its saturation temperature at a given pressure. By measuring the superheat, technicians can determine whether there is the correct amount of refrigerant in the system. If the superheat is too high, it may indicate a low refrigerant charge, while low superheat may suggest overcharging or issues with the system.

This method of checking superheat is especially relevant for fixed orifice systems, as these systems do not possess the ability to modulate refrigerant flow based on the load, unlike systems with expansion valves or capillary tubes, which may require different approaches to assess refrigerant charge accurately. Therefore, the utilization of superheat as a charge verification tool is distinctively linked to systems employing fixed orifice metering devices.