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NYC Thermostat Repairer (CUNY) Practice Questions
1. What is the primary function of a thermostat in an HVAC system?
A. To increase air pressure in the system
B. To regulate temperature by sensing room temperature and controlling the
heating/cooling system
C. To filter air contaminants
D. To measure humidity only
Answer: B
A thermostat monitors ambient temperature and signals the HVAC system to heat or cool to
maintain the desired setpoint .
2. Which type of thermostat uses a bimetallic strip to sense temperature changes?
A. Digital thermostat
B. Programmable thermostat
C. Mechanical thermostat
D. Smart thermostat
Answer: C
Mechanical thermostats rely on a bimetallic strip that bends with temperature changes,
activating or deactivating the circuit .
3. What voltage is most commonly used in low-voltage thermostat control circuits?
A. 120V
B. 240V
C. 24V
D. 480V
Answer: C
Most residential and commercial HVAC thermostats operate on 24 volts AC, supplied by a
step-down transformer .
4. What does the "R" terminal on a thermostat represent?
A. Return air
B. Refrigerant
C. Power supply (24V hot)
D. Relay signal
Answer: C
The R terminal provides 24V AC power from the transformer to the thermostat .
5. What is the purpose of the "C" wire (common wire) in modern thermostats?
A. Cooling signal
B. Common return path for continuous power
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C. Compressor control
D. Condenser power
Answer: B
The C wire provides a continuous 24V return path, supplying constant power for smart
thermostats with Wi-Fi and displays .
6. What does the "Y" wire typically control?
A. Heating
B. Cooling (compressor/condenser contactor)
C. Fan
D. Humidifier
Answer: B
The Y terminal signals the air conditioning compressor/condenser contactor to turn on for
cooling .
7. What does the "W" terminal control in a thermostat system?
A. Cooling
B. Fan
C. Heating (furnace/heat relay)
D. Power supply
Answer: C
The W terminal signals the heating system (furnace or boiler) to turn on when the
thermostat calls for heat .
8. What does the "G" wire control in a thermostat system?
A. Cooling
B. Heating
C. Fan (blower motor)
D. Power supply
Answer: C
The G wire signals the fan/blower motor to operate .
9. Which instrument is most appropriate for measuring voltage in a thermostat circuit?
A. Clamp meter
B. Multimeter
C. Megohmmeter
D. Manometer
Answer: B
A multimeter measures voltage, current, and continuity, which are essential for testing
thermostat operation .
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10. What is the correct method for testing a thermostat's continuity?
A. Use a voltmeter to measure voltage
B. Measure air flow across the unit
C. Use a multimeter set to ohms
D. Adjust the setpoint and wait
Answer: C
A multimeter in the ohms setting tests if the thermostat contacts are closing properly when
calling for heat or cool .
11. What component reduces line voltage to 24 volts in a thermostat circuit?
A. Relay
B. Contactor
C. Step-down transformer
D. Thermistor
Answer: C
A step-down transformer converts higher line voltage (120V or 240V) to 24V for safe
thermostat control circuit operation .
12. Short cycling of an HVAC system can be caused by:
A. Proper anticipator setting
B. Oversized equipment
C. Clean air filters
D. Correct thermostat placement
Answer: B
Oversized equipment heats or cools the space too quickly, causing frequent on/off cycling .
13. A mercury-bulb thermostat must be mounted:
A. Vertically only
B. Level to function correctly
C. Near a radiator
D. In direct sunlight
Answer: B
Mercury thermostats rely on gravity for accurate operation. If not level, the mercury bulb
may not tilt properly, causing inaccurate temperature control .
14. If a thermostat display is blank, the first step in troubleshooting should be to check:
A. Compressor pressure
B. Outdoor coil
C. Power supply and batteries
D. Duct insulation
NYC Thermostat Repairer (CUNY) Practice Questions
1. What is the primary function of a thermostat in an HVAC system?
A. To increase air pressure in the system
B. To regulate temperature by sensing room temperature and controlling the
heating/cooling system
C. To filter air contaminants
D. To measure humidity only
Answer: B
A thermostat monitors ambient temperature and signals the HVAC system to heat or cool to
maintain the desired setpoint .
2. Which type of thermostat uses a bimetallic strip to sense temperature changes?
A. Digital thermostat
B. Programmable thermostat
C. Mechanical thermostat
D. Smart thermostat
Answer: C
Mechanical thermostats rely on a bimetallic strip that bends with temperature changes,
activating or deactivating the circuit .
3. What voltage is most commonly used in low-voltage thermostat control circuits?
A. 120V
B. 240V
C. 24V
D. 480V
Answer: C
Most residential and commercial HVAC thermostats operate on 24 volts AC, supplied by a
step-down transformer .
4. What does the "R" terminal on a thermostat represent?
A. Return air
B. Refrigerant
C. Power supply (24V hot)
D. Relay signal
Answer: C
The R terminal provides 24V AC power from the transformer to the thermostat .
5. What is the purpose of the "C" wire (common wire) in modern thermostats?
A. Cooling signal
B. Common return path for continuous power
, 2
C. Compressor control
D. Condenser power
Answer: B
The C wire provides a continuous 24V return path, supplying constant power for smart
thermostats with Wi-Fi and displays .
6. What does the "Y" wire typically control?
A. Heating
B. Cooling (compressor/condenser contactor)
C. Fan
D. Humidifier
Answer: B
The Y terminal signals the air conditioning compressor/condenser contactor to turn on for
cooling .
7. What does the "W" terminal control in a thermostat system?
A. Cooling
B. Fan
C. Heating (furnace/heat relay)
D. Power supply
Answer: C
The W terminal signals the heating system (furnace or boiler) to turn on when the
thermostat calls for heat .
8. What does the "G" wire control in a thermostat system?
A. Cooling
B. Heating
C. Fan (blower motor)
D. Power supply
Answer: C
The G wire signals the fan/blower motor to operate .
9. Which instrument is most appropriate for measuring voltage in a thermostat circuit?
A. Clamp meter
B. Multimeter
C. Megohmmeter
D. Manometer
Answer: B
A multimeter measures voltage, current, and continuity, which are essential for testing
thermostat operation .
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10. What is the correct method for testing a thermostat's continuity?
A. Use a voltmeter to measure voltage
B. Measure air flow across the unit
C. Use a multimeter set to ohms
D. Adjust the setpoint and wait
Answer: C
A multimeter in the ohms setting tests if the thermostat contacts are closing properly when
calling for heat or cool .
11. What component reduces line voltage to 24 volts in a thermostat circuit?
A. Relay
B. Contactor
C. Step-down transformer
D. Thermistor
Answer: C
A step-down transformer converts higher line voltage (120V or 240V) to 24V for safe
thermostat control circuit operation .
12. Short cycling of an HVAC system can be caused by:
A. Proper anticipator setting
B. Oversized equipment
C. Clean air filters
D. Correct thermostat placement
Answer: B
Oversized equipment heats or cools the space too quickly, causing frequent on/off cycling .
13. A mercury-bulb thermostat must be mounted:
A. Vertically only
B. Level to function correctly
C. Near a radiator
D. In direct sunlight
Answer: B
Mercury thermostats rely on gravity for accurate operation. If not level, the mercury bulb
may not tilt properly, causing inaccurate temperature control .
14. If a thermostat display is blank, the first step in troubleshooting should be to check:
A. Compressor pressure
B. Outdoor coil
C. Power supply and batteries
D. Duct insulation
