NATE Refrigeration 3

Question 1

What does a sight glass with bubbles in the liquid line typically indicate?

Accepted Answer

Insufficient refrigerant charge or restriction causing flashing in the liquid line

Answer

System is operating normally

Answer

Excessive superheat

Answer

Overcharged system

Question 2

What is flash gas and where does it occur in the refrigeration cycle?

Accepted Answer

Refrigerant that vaporizes as pressure drops across the metering device before reaching the evaporator

Answer

Hot discharge gas from the compressor

Answer

Gas released from compressor oil at high temperature

Answer

Vapor formed in the condenser

Question 3

What is the purpose of a liquid line solenoid valve in a refrigeration system?

Accepted Answer

Stop refrigerant flow to the evaporator when the thermostat is satisfied or during pump-down

Answer

Control condensing fan speed

Answer

Regulate refrigerant pressure in the liquid line

Answer

Prevent liquid refrigerant from returning to the compressor

Question 4

What is the significance of the dewpoint temperature in refrigeration system diagnostics?

Accepted Answer

Suction pressure converted to temperature gives the evaporating (saturation/dewpoint) temperature for superheat calculation

Answer

It determines the oil viscosity required

Answer

It measures the ambient humidity at the condenser

Answer

It indicates the minimum compressor discharge temperature

Question 5

What type of compressor is most commonly used in large commercial refrigeration rack systems?

Accepted Answer

Reciprocating (semi-hermetic)

Answer

Scroll

Answer

Centrifugal

Answer

Absorption

Question 6

What does it mean when a refrigeration system has non-condensables present?

Accepted Answer

Gases such as air or nitrogen are trapped in the system and raise head pressure without contributing to refrigeration

Answer

Refrigerant charge is too low

Answer

The system is properly charged with nitrogen for leak testing

Answer

Moisture has entered the refrigerant circuit