CRST Refrigeration Systems & Components 3

Question 1

What condition is indicated when frost forms uniformly across the entire evaporator coil?

Accepted Answer

Normal operation with adequate airflow

Answer

Uniform frost across the full coil typically indicates normal operation with proper refrigerant flow and adequate airflow.

Question 2

A brazed-plate heat exchanger used as an evaporator offers which advantage over a shell-and-tube evaporator?

Accepted Answer

Compact size with high heat transfer efficiency

Answer

Brazed-plate heat exchangers provide very high surface area-to-volume ratios, offering superior heat transfer in a compact package.

Question 3

What is the effect of non-condensable gases on condenser performance?

Accepted Answer

They raise condensing pressure and reduce efficiency

Answer

Non-condensable gases (air, nitrogen) blanket condenser tubes, raising head pressure and reducing heat transfer efficiency.

Question 4

A scroll compressor produces a rattling noise on startup. What is the most likely cause?

Accepted Answer

Reverse rotation of the compressor

Answer

Scroll compressors are rotation-sensitive; reverse rotation causes the scrolls to separate and produces a characteristic rattling or grinding noise.

Question 5

What is the function of a hot gas bypass valve in a refrigeration system?

Accepted Answer

Maintain minimum evaporator pressure during light loads

Answer

A hot gas bypass valve routes hot discharge gas to the low side to maintain minimum evaporator pressure and prevent coil freeze-up at light loads.

(CRST) Certified Refrigeration Service Technician Practice Test