23 Flashcards
(26 cards)
Of the five types of compressors, which one is kinetic displacement?
Centrifugal
What is the purpose of a crankcase heater?
Prevent refrigerant from migrating under the compressor oil
Connecting rods connect the
crankshaft to the piston
Calculate the compression ration for a system that uses R-407C when the suction side temperature is -45°F and the high side manifold gauge reads 43.3 psig. Use 14.7 for the conversion to psia.
5.32
An open-drive belt-driven compressor is attached to a motor with four belts. What type of belts must be used?
Matched set, same length and width
What would affect the shaft seal on a belt-drive compressor?
Belt tension
What temperature is the discharge line considered to be at a danger level and why are high temperatures dangerous to a compressor?
Temperatures starting at 210° up to 250° can break down the oil and form carbon, which will lead to the formation of acid. Acid and degraded windings and cause shorts and also electroplating of copper on bearing surfaces may take place.
What are three types of motor protection used on reciprocating compressors?
Thermal overload in or near windings, hermetically sealed overload in the winding, high pressure switch, low pressure switch, 3 phase internal overload, 3 phase internal thermistor.
The reciprocating compressor is used most frequently in
Window ac and small and medium refrigerator systems
At what compression ratio does oil in a hermetic compressor become overheated?
12:1
An open drive compressor can be either belt or direct drive. T/F
T
centrifugal compressor is an example of a positive displacement compressor. T/F
F
A metering device that is overfeeding an evaporator may cause liquid
slugging to a compressor. T/F
T
Dirty condenser coils cause compression ratios to rise but not as fast as with a dirty evaporator coil. T/F
T
A dirty evaporator will cause suction pressure to rise. T/F
F
A compressor that has its motor mounted external of the compressor shell
is an open-drive compressor. T/F
T
Rubber can be used inside hermetic compressors because it is not
affected by refrigerant. T/F
F
The motor shaft and the compressor crankshaft are one shaft in a hermetic compressor. T/F
T
Suction and discharge pulsations can be transmitted into the compressor piping if they are not muffled. T/F
T
The physical state of the refrigerant at the exit of the compressor discharge port is high-pressure, high-temperature liquid. T/F
F
Angular and parallel misalignment is a concern with open-drive belt driven compressors. T/F
T
How is a hermetic compressor normally cooled?
Suction gas internally
What is the difference between rigid mounting and spring mounting for a hermetic compressor?
Rigid mounts use external springs that are locked down (compressed for shipment and must be decompressed to loosen them before the compressor is operated. The spring mounted compressor is used internally on hermetic compressors.
What does the semi-hermetic compressor on your module use to dampen vibration?
Springs and a vibration loop in the suction line.
