NATE Cheat Sheet 2026

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

1. What does ACCA Manual D provide for HVAC installations? → Procedures for residential duct system design and sizing
2. What is the purpose of the metering device in a refrigeration circuit? → Reduce refrigerant pressure and control flow into the evaporator
3. Which component in an HVAC control circuit is used to sense thermostat demand and energize the compressor contactor? → Control relay
4. What is Manual J used for in residential HVAC design? → Calculating heating and cooling loads for a structure
5. At what temperature range does a medium-temperature refrigeration system typically maintain a reach-in display case? → 28°F to 40°F
6. What does a cracked heat exchanger in a gas furnace risk introducing into the living space? → Carbon monoxide (CO) and other combustion byproducts
7. What is the purpose of the electrodes in an oil burner? → Produce a high-voltage spark to ignite the atomized oil-air mixture
8. What is the standard line voltage for most residential HVAC equipment in the United States? → 240V/60Hz
9. What is the purpose of a high-pressure cutout switch in an HVAC system? → Protect the compressor from excessive discharge pressure
10. When a heat pump is in heating mode and the emergency heat is energized, what happens? → Only electric resistance strips provide heat; the compressor is locked out
11. Which EPA section requires technicians to be certified before purchasing refrigerants? → Section 608
12. What component in an oil burner atomizes the fuel oil and mixes it with air for combustion? → Nozzle
13. What does the ASHRAE 62.2 standard address in residential applications? → Ventilation and acceptable indoor air quality for residential buildings
14. What does a high discharge temperature on a refrigeration compressor typically indicate? → High compression ratio due to high head pressure, low suction pressure, or high superheat
15. What tool is used to measure air velocity in a duct or at a register? → Anemometer or flow hood
16. What unit is used to measure duct air leakage during a duct leakage test? → CFM25 (cubic feet per minute at 25 pascals)
17. What does the term 'MCA' (Minimum Circuit Ampacity) indicate on an HVAC nameplate? → Minimum wire ampacity required for branch circuit conductors
18. What is the function of the cad cell (cadmium sulfide cell) in an oil burner primary control? → Sense the presence or absence of a flame by its resistance to light
19. What does a suction line accumulator protect in a refrigeration system? → Compressor from liquid refrigerant slugging
20. What is the purpose of the oil filter installed in the oil supply line before the pump? → Filter sediment and particulates that could clog the nozzle or damage the pump
21. What is the typical voltage and frequency of the secondary side of an HVAC control transformer in the United States? → 24V AC / 60Hz
22. What initiates a defrost cycle on an air-source heat pump? → Time/temperature or pressure differential control sensing frost buildup on outdoor coil
23. What is the primary safety device that shuts off the gas valve if the pilot flame is extinguished on a standing pilot furnace? → Thermocouple
24. Which wire color in a standard NEC-compliant 120V residential wiring system is the grounded conductor (neutral)? → White
25. LP (propane) gas manifold pressure for residential furnaces is typically set to which value? → 7–11 inches WC
26. What is a common symptom of a stuck reversing valve in the heating position? → Both A and C
27. What component in an induced-draft furnace proves that combustion airflow is established before the gas valve opens? → Pressure switch
28. A heat pump's outdoor unit is making a hissing noise and the reversing valve solenoid is energized. What is the most likely cause? → Reversing valve internal bypass (leaking internally)
29. What is the function of a crankcase heater on a compressor? → Prevent refrigerant from migrating into the compressor oil during off cycles
30. What does COP (Coefficient of Performance) measure for a heat pump? → Ratio of heat output to electrical energy input