Installation & Maintenance Practices Flashcards
7 cards from real CRST practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Installation & Maintenance Practices flashcards as text
What type of oil is required in systems using R-410A refrigerant?
Answer: Polyolester (POE) oil
R-410A and other HFC refrigerants require POE oil because it is miscible with HFCs, ensuring adequate lubrication and oil return throughout the system.
A refrigeration technician installs a new evaporator and notices the coil temperature is uneven across its face. What is the MOST likely cause?
Answer: Unequal refrigerant distribution due to a faulty distributor or plugged distributor nozzle
A faulty or plugged refrigerant distributor causes uneven flow to evaporator circuits, resulting in uneven coil temperatures and reduced capacity.
During a maintenance inspection, a technician finds that the compressor contactor contacts are pitted and burned. What is the correct action?
Answer: Replace the contactor
Pitted and burned contactor contacts indicate excessive arcing and wear; the contactor must be replaced to prevent premature failure and compressor damage.
What is the purpose of a hot gas defrost system in a commercial refrigeration installation?
Answer: Use high-pressure discharge gas to melt frost from the evaporator coil without electric heaters
Hot gas defrost diverts high-temperature discharge gas through the evaporator coil, efficiently melting frost accumulation without electric resistance heaters.
When installing multiple evaporators on a single condensing unit, which component ensures proper refrigerant distribution and independent temperature control for each case?
Answer: Individual EPRs (evaporator pressure regulators) or individual TXVs per evaporator
Individual EPRs or TXVs for each evaporator allow independent temperature control and proper refrigerant metering regardless of load differences between cases.
A technician measures 20°F of subcooling in the liquid line of a properly charged system. What does this indicate?
Answer: The liquid refrigerant has been cooled 20°F below its condensing saturation temperature, which is normal
Subcooling of 10–20°F is normal and indicates the liquid refrigerant has cooled below its saturation point, reducing flash gas at the metering device.
What safety precaution must be taken before performing brazing work on a refrigeration system that contains or previously contained refrigerant?
Answer: Ensure the system is fully recovered and purged with nitrogen before applying heat
Refrigerant must be fully recovered and the system purged with dry nitrogen before brazing, as heat applied to refrigerant can produce toxic decomposition products.