NCCER HVAC 2 MODULE 2 EXAM QUESTIONS

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NCCER HVAC 2 MODULE 2 EXAM QUESTIONS

Qs and Ans - Expert- Explanation - ing score -25 Questions and Answers

-Format: Multiple-choice / Flashcard

Question 1: High- and low-pressure safety switches are installed in

Answer:

series in the compressor's control circuit

Question 2: Which compressor type has the motor sepa from the compressor?

Answer:

Opendrive compressor Question 3: Which type of compressor has no suction valve but does use a discharge valve?

Answer:

Rotary compressor Question 4: What unit nameplate value should be consulted to compare the measured compressor running current?

Answer:

RlA

Question 5: Oil scoops can be found in a

Answer:

Reciprocating compressor

Question 6: In a screw compressor, the motor drives the

Answer:

male rotor

Question 7: Throttling valves are used for capacity control on a

Answer:

centrifugal compressor Question 8: What is unique about the internal discharge-temperature safety devices in some scroll compressors?

Answer:

Some are ly valves that bypass refrigerant.

Question 9: To control capacity, scroll compressors have typically used a

Answer:

refrigerant bypass method

Question 10: For a single-phase compressor, which current-carrying lead does a

current-transformer (CT) monitor current in?

Answer:

Common Question 11: What happens in a reciprocating compressor when the piston reaches its lowest point?

Answer:

the suction valve closes

Question 12: Which statement about internal line-break overloads is correct?

Answer:

They automatically reset Question 13: The system condition that may cause a compressor motor's overload device to open is a(n)

Answer:

dirty condenser coil

Question 14: Flooded starts might be traced back to a

Answer:

Failed crankcase heater Question 15: A simple capacity-control method that provides capacity steps of 25 percent, 50 percent, and 75 percent using a plug valve would be found on a

Answer:

screw compressor Question 16: What capacity control method is popular with open and semi-hermetic reciprocating compressors?

Answer:

Cylinder unloading Question 17: About how many times above the normal running current value will be measured if a three-phase compressor motor is single-phasing?

Answer:

1.5 times Question 18: Slide valves allow screw compressors to vary capacity from full capacity (100 percent) to as low as

Answer:

10 percent capacity

Question 19: Purging refrigerant lines with nitrogen during brazing prevents

Answer:

Copper oxide formation Question 20: Which compressor often uses multiple stages of compression to increase the pressure difference?

Answer:

Centrifugal compressor

Question 21: The compressor displacement equals the rpm of the drive motor multiplied by the

Answer:

piston displacement Question 22: The system condition that can cause the vapor returning to the compressor to be superheated beyond normal is an)

Answer:

I insulated suction line Question 23: What type of oil-pressure safety switch is used on semi-hermetic compressors?

Answer:

differential pressure

Question 24: Freezing of the system's expansion device can be an indication of

Answer:

Moisture in the system

Question 25: For a three-phase system, the maximum voltage imbalance allowed is

Answer:

2%