What is the primary function of the compressor? a) Increase refrigerant temperat

Question

What is the primary function of the compressor? a) Increase refrigerant temperature, pressure and pump refrigerant b) Pump liquid refrigerant to the metering device c) Increase the transfer of heat from the evaporator to the condenser Review Question #2 What is a reciprocating compressor? a) It has pistons that go up and down attached to a crankshaft that rotates b) It has a cam attached to a crankshaft c) It has a scroll that rotates with the crankshaft d) It has vanes which rotate at high speed .Review Question #3 What is the difference between a hermetic and a semi-hermetic compressor? a) The semi-hermetic has a motor with valves above the cylinders b) The hermetic has all parts enclosed in a welded shell c) The semi-hermetic has pistons and a crankshaftReview Question #4 What is a suction-cooled compressor? a) It has pistons and a crankshaft b) All its parts are enclosed in a welded shell c) It has suction valves in the cylinder head d) Suction vapor cools the compressor motor Question #5 Why is lubrication important to a compressor? a) Lubrication helps move refrigerant b) The more lubrication, the faster the compressor can go c) All moving metal surfaces must have oil between them d) Oil must mix with the refrigerant properly Question #6 What is the proper level of oil in the sight glass of a Copeland compressor? a) In the middle of the sight glass b) About ¼ of the sight glass shows oil c) About ¾ of the sight glass shows oil d) Anywhere in the sight glass as long as the top of the oil is visible Review Question #7 Why is a Copeland Discus® compressor more efficient than a standard reed valve reciprocating compressor? a) It has more horsepower b) It has bigger suction valves c) It has high compression pistons d) It has very little clearance volume Review Question #8 To check system pressures, the service valve stems should be in what position? a) Back-seated b) Front-seated c) Mid-seated or cracked Review Question #9 When the service is done and you are ready to go back home the service valves should be in what position? a) Back-seated b) Front-seated c) Mid-seated or cracked Review Question #10 Which position of the discharge service valve will cause damage if the compressor is running? a) Back-seated b) Mid-seated c) Front-seated Question #11 To isolate a semi-hermetic compressor from the rest of the system the service valves should be in what position? a) Back seated b) Front seated c) Mid seated or cracked Question #12 Which of the following is important about the position of the discharge service valve? a) Never run the compressor with it front seated b) Mid-seat the valve when the compressor is off c) Back seating the valve will damage the compressor Question #13 What is the compression ratio of a compressor operating at 10 psig suction and 235 psig head pressure? a) 5:1 b) 6.7:1 c) 10:1 d) 12.4:1 © 2012 Refrigeration Training Services - R2 Subject 2 Compressors v2 106 10 psig + 15 = 25 PSIA suction Convert psig to PSIA: psig + 14.7 (round to 15) 235 psig + 15 = 250 PSIA head CR = head pressure ÷ suction pressure in PSIA CR = 250 PSIA ÷ 25 PSIA = 10 (or 10:1 ratio) And the answer is… Review Question #14 If the compression ratio is too high, what is the effect on the compressor? a) Flooding or slugging b) High discharge heat c) Motor overheating d) Low amperage © 2012 Refrigeration Training Services - R2 Subject 2 Compressors v2 107 And the answer is… Review Question #15 What does the term “flooding” describe about the amount of refrigerant returning to the compressor? a) Small amount of liquid with the vapor b) Large amount of liquid to the compressor c) Too much vapor to the compressor © 2012 Refrigeration Training Services - R2 Subject 2 Compressors v2 108 And the answer is… Review Question #16 What does the term “slugging” describe about the amount of refrigerant returning to the compressor? a) Small amount of liquid with the vapor b) Large amount of liquid to the compressor c) Too much vapor to the compressor © 2012 Refrigeration Training Services - R2 Subject 2 Compressors v2 109 And the answer is… Review Question #17 How do you determine if there is liquid refrigerant returning to the compressor? a) Check the subcooling b) Check the suction pressure c) Check the superheat © 2012 Refrigeration Training Services - R2 Subject 2 Compressors v2 110 And the answer is… Review Question #18 What is the primary advantage of scroll compressors over reciprocating compressors? a) Fewer moving parts b) Radially compliant c) Axially compliant d) More efficient

Explanation / Answer

Q#1    the primary function of the compressor

ans

a) Increase refrigerant temperature, pressure and pump refrigerant

explanationThe function of a compressor is to increase the pressure, and corresponding saturation temperature (boiling point) of the refrigerant vapor to high enough level so the refrigerant can condense by rejecting its heat through the condenser.

Q#2 reciprocating compressor

ANS a) It has pistons that go up and down attached to a crankshaft that rotates

Q#3 What is the difference between a hermetic and a semi-hermetic compressor?

ANS The hermetic has all parts enclosed in a welded shell

Question #5 Why is lubrication important to a compressor?

ANS c) All moving metal surfaces must have oil between them

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