RACT unit 23 Review questions Flashcards
Which of the following best describes the function of a compressor?
a) the compressor restricts the flow of ref. that enters the evaporator
b) the compressor pumps liquid refrigerant into the condenser to transfer heat
c) the compressor is used to throttle a thermostatic expansion valve (TXV) open or closed
d) the compressor increases the pressure in the system from the low side pressure to the high side pressure
d) the compressor increases the pressure in the system from the low side pressure to the high side pressure
Five types of compressors are:
reciprocating
rotary
scroll
screw
centrifugal
Which of the following is true of HVACR compressors?
a) a compressor cannot compress liquid
b) a compressor can compress a liquid
c) a compressor requires liquid refrigerant for lubrication
a) a compressor cannot compress a liquid
What would be considered a higher than normal temperature of a discharge gas line on a reciprocating compressor?
a) 190F
b) 200F
c) 250F
d) 175F
c) 250F
Which compressor type uses pistons to compress the gas?
reciprocating
Which compressor type uses tapered, machined gear components to trap the gas for compressors?
a) scroll
b) reciprocating
c) rotary
d) screw
screw
What style of compressor uses belts to turn the compressor?
a) open drive
b) closed drive
c) chassis drive
d) hermetic drive
a) open drive
What would be done to increase the compressor speed on a belt-driven compressor?
a) decrease drive pulley size
b) increase drive pulley size
c) increase driven pulley size
d) both A and C
a) decrease drive pulley size
Which do the following design factors can affect the efficiency of a reciprocating compressor?
a) the two tapered, machined, screw type gears
b) the connecting rod and muffler
c) the piston and the internal springs
d) the valve plate design and clearance volume
d) the valve plate design and clearance volume
A medium temperature R-134A system that has a suction pressure of 22psig and discharge pressure of 185psig would have a compression ratio of:
185 + 14.7 = 199.7psia discharge
22 + 14.7 = 36.7psia suction
199.7/36.7 = 5.44:1
A direct drive compressor typically runs at _____rpm or _____rpm
1750rpm or 3450rpm
A piston, connecting rod, crankshaft, valves, valve plate are parts that may be found in a __________ compressor
reciprocating
What effect does a slight amount amount of liquid refrigerant have on a compressor over a long period of time?
it dilutes the oil and causes wear on any moving parts (liquid slugging)
What lubricates the refrigeration compressor?
a) refrigerant
b) moisture
c) desiccants
d) oil
d) oil
What can the service technician do to keep the refrigeration system operating at peak efficiency?
a) recover refrigerant charge and replace annually
b) replace compressor oil every 3 years or 3000hrs
c) replace crankshaft and connecting rods
d) clean the evap and cond coils to keep pressures within design parameters
d) clean evaporator and condenser coils to keep pressures within design parameters
