CRST Troubleshooting & Repair Techniques 4

Question 1

A technician suspects a leaking discharge valve on a reciprocating compressor. Which test can confirm this?

Accepted Answer

Perform a pump-down test and observe suction pressure rise after shutdown

Answer

After pump-down, a rapid rise in suction pressure with the compressor off indicates high-pressure gas is leaking back through the discharge valve.

Question 2

What is the purpose of installing a suction line accumulator on a refrigeration system?

Accepted Answer

To prevent liquid refrigerant from entering the compressor

Answer

A suction line accumulator traps liquid refrigerant and oil, allowing only vapor to enter the compressor, protecting it from liquid slugging.

Question 3

A scroll compressor has normal amperage but produces no cooling. What should the technician check FIRST?

Accepted Answer

Phase rotation — scroll compressors must rotate in one direction

Answer

Scroll compressors operate in only one rotational direction; incorrect phase rotation causes the compressor to spin backwards, moving little or no refrigerant.

Question 4

What condition is indicated when both suction and discharge pressures are abnormally low?

Accepted Answer

Large refrigerant leak or severe undercharge

Answer

When both pressures are low together, the system has lost a significant amount of refrigerant, reducing the overall pressure throughout the circuit.

Question 5

A technician is troubleshooting an intermittent low-pressure lockout on a system. The MOST likely cause is:

Accepted Answer

Refrigerant leak that worsens under load

Answer

A slow refrigerant leak may not trip the low-pressure control at startup but causes suction pressure to drop below cutout as the system runs under load.

(CRST) Certified Refrigeration Service Technician Practice Test

(CRST) Certified Refrigeration Service Technician Practice Test

CRST Troubleshooting & Repair Techniques 4