A metering device with a fixed opening, such as a piston or capillary tube.
A fixed orifice meters refrigerant through an opening that does not change. Flow depends on the pressure difference across it and on the charge, so evaporator superheat moves with the charge and the load. That is why fixed-orifice systems are usually charged by superheat, using the manufacturer's chart for indoor and outdoor conditions.
Exam work areas
E · Commissioning and start-up F · Maintenance, service and troubleshooting