CRST Cheat Sheet 2026

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

1. What does a high-pressure control (HPC) do in a refrigeration system? → Shuts down the compressor when discharge pressure exceeds the set point
2. A walk-in freezer door gasket is worn and not sealing properly. Besides temperature loss, what additional problem can result? → Excessive frost buildup on evaporator due to warm, moist air infiltration
3. When a filter-drier becomes partially plugged, what is the MOST noticeable symptom? → Temperature drop across the filter-drier and bubbles in the sight glass
4. What minimum refrigerant velocity is generally required in vertical suction line risers to ensure adequate oil return to the compressor? → 700-1,000 fpm
5. How does root cause analysis improve repair effectiveness? → Identify underlying problems
6. A technician discovers a system leaking R-22 at a rate of 25% per year. What is the required response timeline under EPA regulations? → Repair within 60 days of discovery
7. When mounting a remote condenser on a rooftop, which installation requirement is most critical for proper oil return? → Pitch refrigerant lines toward the compressor and install traps on long vertical risers
8. In a refrigeration ladder diagram, what symbol represents a normally open (NO) contact? → Two parallel vertical lines with a gap between horizontal lines
9. What maintenance task should be performed on evaporator coil drain pans to prevent biological growth and drain blockage? → Add biocide tablets or clean and treat the pan and drain with approved algaecide
10. When a CRST professional encounters an unexpected result during a procedure, the FIRST action should be to: → Stop, assess the situation, and determine whether to proceed or seek guidance
11. Which type of fire extinguisher is appropriate for an electrical fire involving a refrigeration control panel? → Class C (CO2 or dry chemical)
12. What type of capacitor provides an extra boost of starting torque for a PSC or CSCR compressor motor? → Start capacitor
13. Under ASHRAE Standard 15, which refrigerant safety classification indicates the lowest toxicity and flammability? → A1
14. What label information is required on a recovered refrigerant cylinder before it can be sent to a reclaimer? → Refrigerant type, whether it contains oil, and whether it is mixed with other refrigerants
15. What is the PRIMARY purpose of obtaining CRST certification in Certified Refrigeration Service Technician? → To demonstrate verified competency and adherence to professional standards
16. What is the PRIMARY purpose of obtaining CRST certification in Certified Refrigeration Service Technician? → To demonstrate verified competency and adherence to professional standards
17. In what direction should horizontal suction lines be sloped to promote oil return? → 1/4 inch per foot sloping toward the compressor
18. Which refrigerant property determines the saturation temperature at a given pressure? → Pressure-temperature relationship unique to each refrigerant
19. A technician measures a 15°F superheat at the evaporator outlet and 80°F subcooling at the condenser outlet. What condition does this indicate? → Refrigerant overcharge
20. What safety precaution must be taken before performing brazing work on a refrigeration system that contains or previously contained refrigerant? → Ensure the system is fully recovered and purged with nitrogen before applying heat
21. Which OSHA standard specifically governs process safety management (PSM) for facilities using large quantities of ammonia refrigerant? → OSHA 29 CFR 1910.119
22. What does the OSHA permissible exposure limit (PEL) for ammonia (R-717) in the workplace? → 50 ppm TWA
23. When recovering refrigerant from a system with a hermetic compressor burnout, the technician should: → Use a dedicated recovery cylinder and filter to avoid cross-contamination
24. What is the minimum vacuum level (in microns) required before charging most commercial refrigeration systems to ensure proper moisture removal? → 500 microns
25. What is the standard voltage for a single-phase residential refrigeration compressor in the US? → 115V or 230V
26. After repairing a refrigerant leak and recharging a system, the technician should verify proper charge by checking: → Superheat or subcooling depending on the metering device type
27. Which refrigerant has an Ozone Depletion Potential (ODP) of zero and is commonly used in new commercial refrigeration systems in the US? → R-404A
28. Which condition makes it legal under EPA Section 608 to vent a small amount of refrigerant during service? → De minimis releases that occur during good-faith repair attempts
29. What role does proper diagnosis play in repairs? → Correctly identify issues
30. What refrigerant is classified as R-717 and widely used in large industrial refrigeration systems? → Ammonia (NH3)