HVAC Basic Electrical Practice Test 3

Question 1: Which of the following instrument detects the bubbles in refrigerant liquid line?

• Megger
• Electronic sight glass
• Electronic charging meter
• Halogen leak detector

Question 2: The battery cells connected in series produces …………..

• Higher voltages
• Higher currents
• High power
• High resistance

Question 3: A fuse in the electrical circuit protects the circuit from ……………..

• Excess power
• Excess current
• Excess voltage
• Excess impedance

Question 4: In parallel resistive network the voltage applied is equal to sum of voltages across the each individual resistor?

• True
• False

Question 5: Which of the following is the symbol of impedance?

• Z
• I
• R
• V

Question 6: What is the power flow in a circuit, if a 50 coulombs moved at a point in 20 seconds with an applied voltage of 8 Volts?

• 3.2 watts
• 20 watts
• 8 watts
• 16 watts

Question 7: Which of the following is produced around the conductor if an electric current passes through it?

• Magnetic field
• Negative field
• Static field
• Capacitance field

Question 8: If the resistance of the circuit is decreases keeping the voltage same, what happens to the current in the circuit?

• Increases
• Decreases
• Remains same

Question 9: Which of the following batteries action provides electricity?

• Chemical
• Electrical
• Mechanical
• Hydroelectric

Question 10: An ohm meter cannot simple connected to …………….

• Coil
• Motor winding
• Resistor
• Energized circuit

Question 11: What is the typical starting (inrush) current of a single-phase induction motor compared to its Full Load Amperage (FLA)?

• Equal to FLA
• 2 to 3 times FLA
• 5 to 8 times FLA
• 15 to 20 times FLA

Question 12: What is the primary purpose of a star-delta (wye-delta) motor starter used on large HVAC equipment?

• To increase motor speed above nameplate RPM
• To reduce starting current and starting torque
• To provide a controlled soft-stop capability
• To allow the motor to reverse rotation

Question 13: What is the key difference between a START capacitor and a RUN capacitor in a single-phase HVAC motor?

• A start capacitor stays in the circuit permanently to improve running efficiency
• A start capacitor is switched out after startup; a run capacitor stays in circuit permanently
• A start capacitor reduces running current while a run capacitor increases starting torque
• Start and run capacitors are interchangeable and serve the same function

Question 14: What does RLA (Rated Load Amps) represent on a hermetic compressor nameplate?

• The maximum current drawn during compressor startup (locked rotor)
• A calculated value for sizing circuits and overcurrent protection for hermetic compressors
• The current drawn when the compressor runs at minimum refrigerant pressure
• The current drawn at 50% of full compressor load

Question 15: Per NEC 440.14, where must the disconnecting means for an air conditioning or refrigerating unit be located?

• Within 10 feet of the equipment in the same room
• Within 25 feet and visible from the equipment
• Within sight from and readily accessible from the equipment (not more than 50 feet)
• At the main electrical panel regardless of distance

NEC Reference: 440.14

Question 16: When using a megohmmeter (Megger) to test a compressor motor winding's insulation, what reading indicates FAILED insulation?

• Greater than 100 megohms
• Greater than 10 megohms
• Greater than 1 megohm
• Less than 1 megohm

Question 17: Per NEMA standards, what is the maximum allowable three-phase voltage imbalance for motor operation without derating?

• 10%
• 5%
• 3%
• 0.5%

Question 18: What is the primary advantage of an Electronically Commutated Motor (ECM) over a Permanent Split Capacitor (PSC) motor in an air handler?

• ECM motors cost significantly less to purchase than PSC motors
• ECM motors operate at a fixed speed which simplifies controls
• ECM motors are significantly more efficient and can vary speed to maintain constant airflow
• ECM motors do not require a control board or electronics

Question 19: A condensing unit nameplate shows FLA = 18A and LRA = 108A. What is the primary use of the LRA value during electrical installation?

• LRA is used to size the wire gauge for the branch circuit
• LRA is used to select the maximum overcurrent protection device (MOP)
• LRA equals the steady-state operating current of the compressor
• LRA is used only to size the electrical disconnect switch

NEC Reference: 440.22

Question 20: What is the primary purpose of a crankcase heater on a refrigerant compressor?

• To warm the oil so it flows more easily during startup lubrication
• To prevent refrigerant from migrating into and diluting the compressor oil during the off cycle
• To reduce compressor vibration and noise during startup
• To prevent the compressor body from freezing in cold climates

Question 21: What occurs when a running three-phase motor experiences "single phasing" — the loss of one supply phase?

• The motor speeds up due to the reduced electromagnetic drag
• The motor continues to operate normally on two phases with no ill effects
• The motor draws excessive current on the remaining two phases and rapidly overheats
• The motor immediately trips the breaker with no risk of winding damage

Question 22: A condenser fan motor specifies a 5 µF run capacitor. What is the likely result of installing a 10 µF capacitor instead?

• The motor runs more efficiently since a larger capacitor stores more energy
• There is no significant difference — larger µF is always acceptable
• The auxiliary winding draws excessive current and the motor overheats, leading to failure
• The motor runs cooler because the larger capacitor smooths voltage fluctuations

Question 23: Per NEC 440.32, branch circuit conductors supplying a single motor-compressor must have an ampacity of not less than what percentage of the rated load current?

• 100% of rated load current
• 115% of rated load current
• 125% of rated load current
• 150% of rated load current

NEC Reference: 440.32

Question 24: When testing a single-phase hermetic compressor with an ohmmeter, what reading indicates an OPEN winding?

• A reading of 0 ohms between the winding terminal and common
• Infinite resistance (no continuity) between the winding terminal and common
• A reading of 1 megohm between the winding and the compressor shell
• Equal resistance readings between all three terminals (C, R, and S)

Question 25: In a single-phase hermetic compressor, what does the terminal labeled "C" represent?

• The control signal input terminal from the thermostat
• The common terminal shared by both the run and start windings
• The capacitor connection terminal
• The cooling terminal connected to the thermal overload protector only