CARO Cheat Sheet 2026

The 30 highest-yield CARO facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. According to the ASHRAE refrigerant safety classification system, what does the designation 'B2L' indicate about a refrigerant like ammonia (R-717)? → Higher toxicity, mildly flammable
2. A refrigeration system has high suction pressure and high discharge pressure. What is the most likely cause? → Dirty or fouled condenser reducing heat rejection
3. A flooded-type shell-and-tube evaporator is being used to chill brine. Where are the refrigerant and the brine typically located within this component? → The brine is in the tubes, and the refrigerant is in the shell.
4. A pilot-operated pressure regulating valve (PRV) in refrigeration is used to: → Automatically maintain a set downstream pressure regardless of upstream pressure changes
5. Which of the following conditions would most likely cause an evaporator to become 'starved' of refrigerant? → A dirty or clogged filter-drier upstream of the expansion device.
6. What is the function of an oil drain valve on an ammonia refrigeration vessel? → To drain accumulated oil from the vessel back to the oil pot or drain point
7. What does a check valve do in a refrigeration piping system? → Prevents refrigerant from flowing backward in the piping
8. In a standard vapor-compression refrigeration cycle, what is the primary function of the compressor? → To raise the pressure and temperature of the refrigerant vapor.
9. The primary purpose of the expansion valve (or metering device) in the refrigeration cycle is to: → Create a large pressure drop, which reduces the refrigerant's boiling point.
10. What tool is commonly used to detect refrigerant leaks? → Electronic leak detector
11. What is the primary function of a slide valve in a large screw compressor? → To provide a means of capacity control.
12. Why is the accumulator used in some refrigeration systems? → To prevent liquid slugging in compressor
13. Which of the following routine maintenance tasks is most critical for ensuring the long-term health and efficiency of a reciprocating compressor's moving parts? → Regularly checking and changing the crankcase oil and filters
14. When troubleshooting an ammonia system that is not reaching its design suction temperature, what should be checked first? → Refrigerant charge level and expansion device operation
15. Which type of valve is most commonly used as a stop valve (shutoff valve) in ammonia refrigeration piping? → Gate valve
16. What documentation is required when disposing of refrigerants? → Detailed logs and EPA forms
17. A thermostatic expansion valve (TXV) senses which two conditions to regulate refrigerant flow? → Evaporator outlet temperature and suction pressure
18. Why is proper ventilation important when working with refrigerants? → To avoid gas accumulation
19. What is the primary purpose of an oil separator in an industrial refrigeration system? → To remove entrained oil from the discharge gas and return it to the compressor.
20. High discharge temperature with normal suction pressure on an ammonia compressor most likely indicates what problem? → High suction superheat or discharge valve inefficiency
21. What is the benefit of regularly cleaning condenser coils? → Improves system performance
22. What should be done to refrigeration piping before leak testing with nitrogen? → Ensure all safety valves and relief devices are isolated or removed
23. Why are leak inspections required for refrigeration systems above certain charge sizes? → To minimize environmental impact
24. Which organization establishes workplace safety standards in the United States? → OSHA
25. What is the role of the evaporator in a refrigeration system? → Absorb heat and cool air
26. Why is preventive maintenance critical in refrigeration systems? → To extend equipment lifespan
27. An ammonia system's suction pressure gauge reads 0 psig. What approximate evaporating temperature does this correspond to for ammonia (R-717)? → -28°F
28. What is the purpose of a fusible plug installed on a refrigeration vessel? → To melt and release refrigerant if vessel temperature reaches a dangerous level
29. What is the main purpose of lockout/tagout (LOTO) procedures in refrigeration maintenance? → To prevent accidental equipment startup
30. Which component helps prevent moisture and debris from entering the expansion valve? → Filter drier