313A Cheat Sheet 2026

The 30 highest-yield 313A facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. What is the unit of heat energy used in Canadian HVAC calculations? → Joule (J) or kilojoule (kJ)
2. What is the main advantage of a scroll compressor over a reciprocating compressor? → Fewer moving parts, quieter operation, and higher efficiency at part load
3. What does 'latent heat' refer to in refrigeration? → Heat absorbed or released during a phase change without a temperature change
4. What are the three types of condensers used in HVAC systems? → Air-cooled, water-cooled, and evaporative condensers
5. What is superheat in a refrigeration system? → The temperature of refrigerant above its boiling point in the vapour state
6. What is the maximum allowable refrigerant leak rate under Canadian ODSHAR for commercial refrigeration systems containing more than 10 kg of refrigerant? → 35% of total charge per year, with required repair within 30 days of detection
7. What type of condenser uses water as the heat rejection medium and is commonly used in large commercial systems? → Water-cooled condenser (shell-and-tube or plate heat exchanger)
8. What does a low superheat reading at the TXV sensing bulb indicate? → The TXV may be overfeeding the evaporator, risking liquid carryover to the compressor
9. Why must dry nitrogen be purged through copper tubing during the brazing process? → To prevent cupric oxide scale from forming inside the pipe
10. When recovering refrigerant from a system in Canada, what equipment standard must the recovery machine meet? → UL 1963 / ARI 740 standard for refrigerant recovery/recycling equipment
11. What is the ozone depletion potential (ODP) of R-22 (HCFC-22)? → 0.034
12. In a hermetic compressor, how is the motor cooled? → By the suction refrigerant vapour passing over the motor windings
13. What is the approach temperature of an air-cooled condenser? → The difference between condensing temperature and entering air temperature
14. When cutting copper refrigerant tubing, which tool provides the cleanest cut with the least internal deformation? → Wheel-type tubing cutter
15. What is the primary function of the evaporator in a refrigeration system? → To absorb heat from the refrigerated space or process fluid by evaporating the refrigerant
16. Under the Montreal Protocol, which class of refrigerants was phased out first due to the highest ozone depletion potential? → CFCs (chlorofluorocarbons)
17. Which type of electronic leak detector is best suited for detecting leaks of HFO refrigerants such as R-1234yf? → Infrared (IR) sensor detector
18. What refrigerant classification is R-717 (ammonia)? → B2L (higher toxicity, lower flammability)
19. A refrigeration system shows high discharge pressure, high suction pressure, and low superheat. What is the most likely cause? → Refrigerant overcharge
20. What is sensible heat? → Heat that changes the temperature of a substance without changing its phase
21. Per the Canadian Refrigeration Code, what is the maximum recommended support spacing for horizontal copper refrigerant suction lines? → 3 m (10 ft)
22. In the vapour-compression refrigeration cycle, at which component does the refrigerant absorb heat from the space being cooled? → Evaporator
23. What is subcooling in a refrigeration system? → The number of degrees the liquid refrigerant is cooled below its condensing temperature
24. Which flux is required when brazing copper tubing to a brass or steel fitting? → A proper brazing flux (AWS Type FB3-A or equivalent) must be applied
25. Which refrigerant leak detection method offers the highest sensitivity, capable of detecting leaks as small as 0.1 oz per year? → Electronic refrigerant leak detector
26. On a pressure-enthalpy (P-h) diagram, what does the area under the saturation dome represent? → The two-phase (liquid-vapour) mixture region
27. What is the purpose of a liquid receiver in a refrigeration system? → To store liquid refrigerant and ensure a steady supply to the expansion device
28. In the refrigeration cycle, what state change does the refrigerant undergo in the evaporator? → Liquid to gas (evaporation/boiling)
29. What does enthalpy represent in refrigeration thermodynamics? → The total heat content of the refrigerant per unit mass
30. What type of compressor uses pistons driven by a crankshaft to compress refrigerant? → Reciprocating (piston) compressor