RSES Cheat Sheet 2026

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

1. A refrigeration system has high discharge pressure and high suction pressure. What is the most likely cause? → Overcharge of refrigerant
2. A technician measures equal suction and discharge pressures on a running compressor. What is the most likely diagnosis? → Completely failed or broken compressor valves
3. When decommissioning a system with a refrigerant blend, which recovery method is preferred to minimize fractionation? → Liquid recovery followed by vapor recovery
4. Which refrigerant class poses the greatest immediate danger of chemical burns and respiratory damage at low concentrations? → Natural refrigerants — ammonia (R-717)
5. In a shell-and-tube water-cooled condenser, refrigerant typically flows: → Through the shell side around the tubes
6. What role does documentation play in RSES compliance? → It provides evidence of adherence to standards
7. What does a pressure-enthalpy (P-h) diagram compliance check verify in a refrigeration system? → That operating pressures and temperatures match design conditions within code limits
8. What is the recommended first step when a RSES professional identifies a compliance violation? → Document and report through proper channels
9. What does a pressure-enthalpy diagram primarily help a refrigeration technician determine regarding safety? → Whether system pressures are within safe operating limits for the refrigerant
10. What is the function of a crankcase heater on a compressor? → To prevent refrigerant migration into the crankcase oil during the off cycle
11. When sizing an evaporator for a walk-in freezer, which heat load component is often the largest contributor in a busy retail application? → Infiltration heat gain from door openings
12. What role does the evaporator play in the refrigeration cycle? → Absorbs heat
13. In a flooded evaporator system, refrigerant level is maintained by a: → Float valve that admits liquid to maintain a set liquid level
14. What is the purpose of a suction line accumulator installed between the evaporator and compressor? → To prevent liquid refrigerant slugs from reaching the compressor
15. Why is it important to pitch evaporator drain pans toward the drain outlet? → To prevent water from accumulating and refreezing on the pan, causing blockages
16. What role does calibration play in maintaining technical accuracy for Refrigeration Service Engineers Society Certification professionals? → It ensures instruments and methods produce accurate, consistent results over time
17. The short-tube orifice (fixed orifice) expansion device is commonly used in which type of system? → Residential heat pumps with scroll compressors
18. Which type of overload relay automatically resets after cooling down without requiring manual intervention? → Auto-reset bimetallic relay
19. According to ASHRAE 34, what refrigerant safety group classification indicates the highest flammability? → A3
20. Subcooling in a condenser is measured as: → Saturated condensing temperature minus liquid line temperature
21. When performing an oil change on a hermetic compressor, how is oil typically added to the system? → Through the suction service valve using an oil injector or pre-charged compressor
22. A potential relay used for starting a single-phase compressor motor opens the start circuit based on: → Back-EMF voltage across the start winding reaching a set threshold
23. When must an EPA Section 608 technician certification card be presented under federal regulations? → Upon request by the refrigerant seller or EPA enforcement officer
24. A condenser pressure too low in cold ambient conditions can cause which operational problem? → Liquid floodback to the compressor due to low pressure differential
25. What happens in the condenser unit? → Releases heat and condenses
26. A SPDT (single-pole double-throw) thermostat is used in a heat-cool system. In the heating mode, which terminals are typically energized? → R and W
27. Under EPA Section 608, which action is specifically prohibited when servicing refrigerant-containing appliances? → Knowingly venting refrigerants to the atmosphere
28. Which type of refrigerant cylinder is used exclusively for shipping and cannot be refilled with refrigerant for resale? → Disposable/non-refillable cylinder
29. In an evaporative condenser, Legionella risk is primarily controlled by: → Proper biocide treatment and water management program
30. A technician measures 20°F superheat at the evaporator outlet on a system designed for 10°F. What adjustment should be made to the TXV? → Open the valve (decrease spring tension) to allow more refrigerant flow