A fully hermetic compressor on a 3 ton residential split system has three electrical terminals on the side of the compressor. An ohmmeter reads the following: terminal A to B = 20 ohms, A to C = 15 ohms and B to C = 5 ohms. There was a reading of infinity between all three terminals to ground. Which terminal is the common terminal?

NATE A/C exam questions focus on residential split systems, testing knowledge of refrigeration cycles, electrical troubleshooting, airflow, and installation, comprising a 50-question Core and 100-question Specialty exam. Key topics include diagnosing refrigerant pressures, superheat/subcooling, heat transfer, and electrical component testing (capacitors/relays).  Sample NATE A/C & Core Exam Questions Refrigeration Cycle: Which component is used to flood the condenser with liquid refrigerant under low outside ambient temperature? Answer: A head pressure control valve. Troubleshooting: A... Show more

NATE A/C exam questions focus on residential split systems, testing knowledge of refrigeration cycles, electrical troubleshooting, airflow, and installation, comprising a 50-question Core and 100-question Specialty exam. Key topics include diagnosing refrigerant pressures, superheat/subcooling, heat transfer, and electrical component testing (capacitors/relays). 

Sample NATE A/C & Core Exam Questions
Refrigeration Cycle: Which component is used to flood the condenser with liquid refrigerant under low outside ambient temperature?
Answer: A head pressure control valve.
Troubleshooting: A system shows high low-side superheat and low condenser subcooling. What is the most likely issue?
Answer: Refrigerant undercharge.
Airflow: What instrument is used to measure air velocity in ductwork?
Answer: Anemometer.
Electrical: What is the acceptable capacitance reading for a run capacitor?
Answer: Plus or minus 10% of the rating on the capacitor.
Concepts: What type of heat is removed in the condenser?
Answer: Sensible and latent heat.
Components: A grille equipped with a damper control is called a:
Answer: Register.
Safety: Which safety device prevents a furnace or air handler from overheating?
Answer: Limit switch. 

Key Exam Preparation Areas
Refrigerant Types: Understanding the use of R-410A in modern residential systems.
Electrical Theory: Applying Ohm's Law to electrical troubleshooting.
System Operation: Identifying 4 different pressure levels in a mechanical refrigeration system.
Tool Usage: Measuring voltage and resistance using a multimeter.

Show less