HVAC Level 2 03302 Compressors Exam
Questions with Correct Answers
Line-duty device - Answer-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 - Answer-A protection device that senses current overload or
excessive temperature within the motor and opens the contactor control circuit to stop
the motor.
Positive-displacement compressor - Answer-Any compressor in which the pumping
action is created by pistons or moving chambers.
Pressure (force-feed) lubrication system - Answer-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 - Answer-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 during the off cycle.
Short-cycling - Answer-A condition in which the compressor is restarted immediately
after it has been turned off; sometimes accompanied by very short run times as well.
Single-phasing - Answer-A condition in which a three-phase load receives power from
only two of the three phases.
Slugging - Answer-The entrance of liquid refrigerant and/or a significant amount of oil
into a compressor cylinder. Slugging can occur at startup due to condensed refrigerant
and/or collected oil near the compressor inlet.
Burnout - Answer-A condition in which the breakdown of the motor winding insulation
causes the windings to electrically short to ground.
Capacity control - Answer-The manipulation of compressor or system operation to
change the refrigeration capacity.
Clearance volume - Answer-The amount of clearance between a piston at the top dead-
center position of travel and the cylinder head.
Questions with Correct Answers
Line-duty device - Answer-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 - Answer-A protection device that senses current overload or
excessive temperature within the motor and opens the contactor control circuit to stop
the motor.
Positive-displacement compressor - Answer-Any compressor in which the pumping
action is created by pistons or moving chambers.
Pressure (force-feed) lubrication system - Answer-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 - Answer-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 during the off cycle.
Short-cycling - Answer-A condition in which the compressor is restarted immediately
after it has been turned off; sometimes accompanied by very short run times as well.
Single-phasing - Answer-A condition in which a three-phase load receives power from
only two of the three phases.
Slugging - Answer-The entrance of liquid refrigerant and/or a significant amount of oil
into a compressor cylinder. Slugging can occur at startup due to condensed refrigerant
and/or collected oil near the compressor inlet.
Burnout - Answer-A condition in which the breakdown of the motor winding insulation
causes the windings to electrically short to ground.
Capacity control - Answer-The manipulation of compressor or system operation to
change the refrigeration capacity.
Clearance volume - Answer-The amount of clearance between a piston at the top dead-
center position of travel and the cylinder head.
