Mixed Deck — All CRST Topics Flashcards

A refrigeration system uses a flooded evaporator. What distinguishes it from a dry-expansion evaporator?

Answer: Refrigerant fills the entire evaporator with liquid

In a flooded evaporator, the entire heat exchanger is filled with liquid refrigerant, maximizing heat transfer surface contact.

What refrigerant is classified as R-717 and widely used in large industrial refrigeration systems?

Answer: Ammonia (NH3)

R-717 is ammonia (NH3), a natural refrigerant with excellent thermodynamic properties and zero ODP/GWP widely used in industrial cold storage and food processing.

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.

What is a common cause of refrigeration system failure?

Answer: Refrigerant leaks

Refrigerant leaks are a very common and critical cause of refrigeration system failure. A loss of refrigerant reduces the system's cooling capacity, increases energy consumption, and can eventually lead to compressor damage due to overheating. Detecting and repairing leaks promptly is vital for system longevity, efficiency, and environmental protection.

What is the correct procedure before working on energized refrigeration electrical panels according to NFPA 70E?

Answer: Perform an arc flash risk assessment and wear appropriate PPE

NFPA 70E requires an arc flash risk assessment and appropriate arc-rated PPE before working on or near energized electrical equipment.

When brazing copper-to-copper refrigeration joints, which brazing alloy family is self-fluxing and most commonly used in the industry?

Answer: Silver-phosphorus-copper (BCuP) alloys

BCuP (silver-phosphorus-copper) alloys are self-fluxing on copper-to-copper joints because phosphorus acts as its own flux, making them the industry standard for refrigeration brazing.

Which statement BEST describes the relationship between Certified Refrigeration Service Technician certification and industry evolution?

Answer: Requirements evolve periodically to reflect advances in knowledge and practice

Certification requirements evolve to keep pace with professional and technological advances.

When new equipment is introduced in Certified Refrigeration Service Technician, what is REQUIRED before staff use it?

Answer: Formal training, competency verification, and documentation

Formal training, competency verification, and documented training completion are required.

How should Certified Refrigeration Service Technician professionals handle procedures that have been updated or revised?

Answer: Review updates, complete required training, and implement revised procedures

Professionals must review changes, complete training, and implement revised procedures.

Which tool is used to measure the depth of a vacuum during system evacuation?

Answer: Micron gauge (electronic vacuum gauge)

An electronic micron gauge accurately measures deep vacuums in microns of mercury, which standard manifold gauges cannot resolve.

When recharging a system with an HFC blend refrigerant (such as R-410A), how must the refrigerant be added from the cylinder?

Answer: As a liquid (cylinder inverted or using a liquid valve)

HFC blends like R-410A must be charged as liquid to maintain the correct blend ratio, as vapor-charging can cause fractionation and alter the refrigerant composition.

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.

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.

Which electrical test instrument is used to measure the insulation resistance of a compressor motor winding to ground?

Answer: Megohmmeter (megger)

A megohmmeter (megger) applies a high DC voltage to measure insulation resistance in megohms, detecting winding-to-ground faults.

A heat pump in heating mode has frost building up on the outdoor coil when outdoor temperature is above 40°F. What is the MOST likely cause?

Answer: Low refrigerant charge reducing evaporating temperature

A low refrigerant charge drops the evaporating temperature below the frost point even in mild weather, causing premature frost accumulation on the outdoor coil.

A refrigeration technician discovers a system running with extremely high compression ratio. What is the most likely consequence?

Answer: Excessive discharge temperature and reduced volumetric efficiency

High compression ratios cause discharge temperatures to rise sharply and reduce volumetric efficiency because re-expanded gas from clearance volume occupies more cylinder space.

What does a high suction superheat combined with normal or low head pressure indicate in a refrigeration system?

Answer: Low refrigerant charge or metering device starving the evaporator

High superheat with normal or low head pressure points to insufficient refrigerant flow through the evaporator, typically from a low charge or restricted metering device.

Which OSHA standard specifically governs process safety management (PSM) for facilities using large quantities of ammonia refrigerant?

Answer: OSHA 29 CFR 1910.119

OSHA's PSM standard (29 CFR 1910.119) applies to facilities with 10,000 pounds or more of ammonia, requiring formal safety management programs.

What is the refrigerant charge method used when a manufacturer specifies charging by weight?

Answer: Use a refrigerant scale to add the exact specified weight of refrigerant to the system

When charging by weight, a refrigerant scale is used to measure and add the exact factory-specified charge weight, which is the most accurate method for sealed system charging.

Which condition makes it legal under EPA Section 608 to vent a small amount of refrigerant during service?

Answer: De minimis releases that occur during good-faith repair attempts

EPA allows de minimis refrigerant releases that unavoidably occur during good-faith attempts to recover, recycle, or reclaim refrigerants.