CRST Installation & Maintenance Practices 5

Question 1

What type of oil is required in systems using R-410A refrigerant?

Accepted Answer

Polyolester (POE) oil

Answer

R-410A and other HFC refrigerants require POE oil because it is miscible with HFCs, ensuring adequate lubrication and oil return throughout the system.

Question 2

A refrigeration technician installs a new evaporator and notices the coil temperature is uneven across its face. What is the MOST likely cause?

Accepted Answer

Unequal refrigerant distribution due to a faulty distributor or plugged distributor nozzle

Answer

A faulty or plugged refrigerant distributor causes uneven flow to evaporator circuits, resulting in uneven coil temperatures and reduced capacity.

Question 3

During a maintenance inspection, a technician finds that the compressor contactor contacts are pitted and burned. What is the correct action?

Accepted Answer

Replace the contactor

Answer

Pitted and burned contactor contacts indicate excessive arcing and wear; the contactor must be replaced to prevent premature failure and compressor damage.

Question 4

What is the purpose of a hot gas defrost system in a commercial refrigeration installation?

Accepted Answer

Use high-pressure discharge gas to melt frost from the evaporator coil without electric heaters

Answer

Hot gas defrost diverts high-temperature discharge gas through the evaporator coil, efficiently melting frost accumulation without electric resistance heaters.

Question 5

When installing multiple evaporators on a single condensing unit, which component ensures proper refrigerant distribution and independent temperature control for each case?

Accepted Answer

Individual EPRs (evaporator pressure regulators) or individual TXVs per evaporator

Answer

Individual EPRs or TXVs for each evaporator allow independent temperature control and proper refrigerant metering regardless of load differences between cases.

(CRST) Certified Refrigeration Service Technician Practice Test

(CRST) Certified Refrigeration Service Technician Practice Test

CRST Installation & Maintenance Practices 5