HVAC Basic Electrical Practice Test 4

Question 1: To protect an electrical circuit a fuse should be placed in ………………….

• Series
• Parallel
• Both series and parallel

Question 2: If there is no deflection in a voltmeter which is used to measure voltage between two electrical contacts it indicates ...

• Two contacts are shorted
• Two contacts are opened
• Two contacts are driven by same voltage source
• Same current is flowing across two contacts

Question 3: The primary winding of a transformer has 1000 turns and secondary coil has 400 turns. What will be its secondary voltage if 480 volts is applied at primary?

• 192 volts
• 240 volts
• 480 volts
• 1200 volts

Question 4: A magnetic field seeks the path of ………….

• Low reluctance
• High reluctance
• Less resistance
• High resistance

Question 5: Which of the following meter is used to measure electrical pressure in the circuit?

• Voltmeter
• Ammeter
• Ohmmeter
• Wattmeter

Question 6: Which of the following is used to measure high resistance of circuit?

• Series ohmmeter
• Shunt ohmmeter
• Impedance meter
• Wattmeter

Question 7: Battery cells connected in parallel produces ………….

• Higher current
• Higher voltages
• High power

Question 8: Which of the following battery cell can be recharged?

• Primary cell
• Secondary cell

Question 9: How many 1.5 volts cells should be connected in series to form a 9 volt battery?

• 4
• 6
• 9
• 2

Question 10: A primary cell is a device which converts …………………

• Chemical energy into electrical energy
• Electrical energy into chemical energy
• Mechanical energy into electrical energy
• Electrical energy into mechanical energy

Question 11: Why are transformer cores constructed from laminated silicon steel sheets rather than solid steel?

• To reduce the manufacturing cost of transformer cores
• To reduce eddy current losses and improve transformer efficiency
• To increase the core operating temperature for better flux density
• To increase the air gap between primary and secondary windings

Question 12: What is the primary functional difference between a contactor and a relay in HVAC control systems?

• A contactor measures current; a relay measures voltage in the circuit
• A contactor switches high-current power loads; a relay switches low-current control circuits
• A contactor uses only AC coils; a relay uses only DC coils
• A relay has multiple poles while a contactor has only a single pole

Question 13: What is the primary function of a diode used as a "flyback" or "freewheeling" diode across an HVAC control relay coil?

• To amplify the 24V control signal to operate the high-voltage contactor
• To absorb the voltage spike generated when the coil is de-energized, protecting electronic controls
• To regulate the coil voltage to a precise DC level
• To measure coil resistance and detect a failed coil winding

Question 14: In most heat pump systems (Carrier, Trane, Lennox), during which operating mode is the reversing valve solenoid ENERGIZED?

• During heating mode only
• During cooling mode (most brands)
• Continuously in both heating and cooling at all times
• Only during the defrost cycle, not during normal operation

Question 15: How does a Variable Frequency Drive (VFD) control the speed of an AC induction motor?

• By varying the supply voltage amplitude while keeping frequency at 60 Hz
• By varying both the output frequency and voltage supplied to the motor
• By rapidly switching the motor between star and delta connections
• By inserting variable resistance in series with the motor windings

Question 16: What controls the opening and closing of a liquid line solenoid valve in an HVAC refrigeration system?

• Refrigerant pressure differential across the valve body seats
• An electromagnetic coil that magnetically opens or closes the valve plunger
• A temperature-sensing bulb similar to a thermostatic expansion valve
• A mechanical float that rises or falls with refrigerant liquid level

Question 17: Why do most residential and light commercial HVAC systems use a 24VAC control circuit rather than operating controls directly at 120V or 240V?

• Because 24V components cost significantly less to manufacture than 120V components
• For technician and homeowner safety — 24V is below the dangerous electrical shock threshold
• Because 24V signals travel farther through thermostat wire without voltage loss
• Because thermostats cannot be manufactured for voltages above 24V

Question 18: What does an "HACR-type" rating on a circuit breaker mean, and why is it required by NEC 440 for HVAC equipment?

• The breaker is rated for use in outdoor HVAC enclosures exposed to weather
• The breaker has a time-delay characteristic to tolerate HVAC motor startup inrush without nuisance tripping
• The breaker automatically resets itself after clearing an overcurrent fault
• The breaker provides built-in GFCI protection specific to refrigeration equipment

NEC Reference: 440.22

Question 19: What condition triggers a motor overload relay (OL relay) to open and shut down the HVAC motor?

• An instantaneous high fault current caused by a short circuit
• The motor drawing more than rated current continuously for long enough to risk winding overheating
• Supply voltage rising above the motor's rated voltage
• The three supply phases arriving in the wrong sequence (phase reversal)

NEC Reference: 430.32

Question 20: A high-pressure safety switch protecting an HVAC compressor is wired as a normally _____ contact in the control circuit.

• Normally Open (N.O.) — the switch closes only when a fault condition is detected
• Normally Closed (N.C.) — current flows through normally; the switch opens on fault to shut down the compressor
• Normally Open in cooling mode and Normally Closed in heating mode
• There is no standard — N.O. or N.C. varies by manufacturer preference

Question 21: Per NEC Article 100, what is the fundamental difference between "grounding" and "bonding"?

• Grounding applies to AC systems only; bonding applies to DC systems only
• Grounding establishes a connection to earth; bonding connects metallic parts to ensure equal potential
• Grounding connects the hot conductors; bonding connects the neutral conductors to ground
• Both terms describe the same action of connecting metallic enclosures to the earth electrode

NEC Reference: 100

Question 22: When testing an HVAC run capacitor with a digital multimeter set to capacitance (µF) mode, what result indicates the capacitor is GOOD?

• A reading of 0 µF indicates the capacitor is fully charged and healthy
• A reading close to the capacitor's rated µF value (within ±10%) indicates a good capacitor
• The meter always reads OL (overrange) for a healthy capacitor
• Any non-zero reading indicates the capacitor is shorted and must be replaced

Question 23: In a three-phase 480V wye (Y) connected system, what is the voltage measured between a single phase conductor and the neutral?

• 480 volts
• 277 volts
• 208 volts
• 240 volts

Question 24: Per NEC 110.3(B), when installing listed or labeled HVAC equipment, what instructions must be followed?

• The National Electrical Code only — manufacturer instructions are suggestions only
• The local building department's approval only, overriding manufacturer specifications
• The manufacturer's installation instructions included with the listing or labeling
• The installing technician's professional judgment and local trade standards

NEC Reference: 110.3

Question 25: When using a clamp-on ammeter to measure the running current of a single-phase HVAC compressor, which conductors should be clamped?

• Clamp around both the hot and neutral conductor together inside the same jaw
• Clamp around only one conductor (either the hot or the neutral — not both)
• Clamp around the equipment grounding conductor (green wire) only
• Clamp around all conductors of the supply cable simultaneously for accuracy