Unit 2
Burnout|A condition in which the breakdown of the motor winding insulation causes the motor to shout out or ground electrically.
Capacity control|Methods used in cooling systems to adjust system operations to match changes in the system cooling load.
Clearance volume|The amount of clearance between a piston at the top dead-center position of travel and the cylinder head.
Compliant scroll compressor|A version of the scroll compressor that allows the orbiting scroll to temporarily shift from its normal operating position if liquid refrigerant enters the compressor.
Compression|The reduction in volume of a vapor or gas by mechanical means.
Floodback|A condition in which there is a continuous return of liquid refrigerant in the suction vapor being returned to the compressor during operation.
Flooded starts|A condition in which slugging, foaming, and inadequate lubrication occur at compressor startup as a result of the oil in the compressor having absorbed refrigerant during shut-down. When the compressor starts and the pressure in the crankcase drops very quickly, the refrigerant boils out rapidly, creating a foam.
Line-duty device|A motor protection device that senses current flow and temperature in the motor windings. If an overload occurs, it opens the motor winding circuit to remove the line voltage.
Pilot-duty device|A motor protection device that senses current overload or temperature within the motor. If an overload occurs, it opens the motor contactor control circuit to remove power from the motor.
Positive-displacement compressor|Any compressor where the pumping action is created by pistons or moving chambers.
Pressure (force-feed) lubrication system|A method of compressor lubrication that uses an oil pump mounted on the end of the crankshaft to draw oil from the crankcase and force it to the compressor main bearings, lower connecting rod bearings, and piston pins.
Pump-down|The process of operating a compressor to clear most or all refrigerant from the low pressure side of the system, or a portion thereof. A pump-down cycle is used on some systems to clear remaining refrigerant from the evaporator and suction line that could condense to a liquid following each cycle. For service and repairs on the low side of the system, a valve on the high-pressure side can be closed and the compressor operated manually to pump the refrigerant out of the low-pressure side and into the high-pressure side.
Short-cycling|A condition in which the compressor is restarted immediately after it has been turned off;sometimes accompanied by very short run periods as well.
Single phasing|A condition in which a three-phase motor continues to run after losing one of the three phases while operating.
Slugging|The entrance of liquid refrigerant and/or a significant amount of oil into a compressor cylinder. Slugging may occur at startup or if there is a rapid change in system operating conditions.
Splash lubrication system|A method of compressor lubrication in which the crankcase oil is splashed up from the crankcase and onto the cylinder walls and bearing surfaces during each revolution of the crankshaft.