Trap 4 : A depression or dip in refrigerant piping in which oil will collect. A trap may be placed at the base of a suction or hot gas riser to improve oil return up the riser
EESiFlo North America, Terminology and Glossary: HVAC Terms, Pennsylvania, USA 2002. flowmeterdirectory.com/flowmeter_terminology, (Heat, Vent and Air Cond - Amer) {553}