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CT HVAC practice questions

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Question 1Safety and Environmental Protection

Under Section 608 of the Clean Air Act, releasing refrigerant to the atmosphere while servicing a system is:

  1. Permitted for HFCs because they do not deplete stratospheric ozone
  2. Permitted when the appliance is going to be scrapped at the end of the job
  3. Prohibited for ozone-depleting refrigerants and their HFC substitutes Correct answer.
  4. Permitted whenever the system charge is below 5 pounds

Explanation

Section 608 prohibits knowingly venting ozone-depleting refrigerants and their substitutes, including HFCs, during service, maintenance, repair, and disposal. The compliant path is to recover the charge with certified equipment and then recycle, reclaim, or destroy it.

Question 2Safety and Environmental Protection

A recovery cylinder should be filled with liquid refrigerant to no more than what percentage of its capacity?

  1. 70 percent
  2. 60 percent
  3. 80 percent Correct answer.
  4. 95 percent

Explanation

Recovery cylinders are rated by weight and must be filled to about 80 percent of capacity so liquid has room to expand as temperature rises. Overfilling can generate hydrostatic pressure high enough to rupture the cylinder or lift the relief valve.

Question 3Safety and Environmental Protection

Why is dry nitrogen normally flowed through tubing while a joint is being brazed?

  1. To cool the joint so the filler alloy sets faster
  2. To carry away the flux residue from the outside of the fitting
  3. To displace air and prevent oxidation scale from forming inside the tubing Correct answer.
  4. To raise the pressure so the joint seals itself

Explanation

Heating copper in the presence of air forms copper oxide scale on the inside of the tubing. A slow nitrogen purge displaces the air so the internal surface stays bright, protecting the compressor, valves, and metering devices from contamination.

Question 4Safety and Environmental Protection

Which personal protective equipment is essential when there is a risk of liquid refrigerant contacting the skin?

  1. Refrigerant-rated gloves and sealed safety glasses Correct answer.
  2. Cotton gloves and a bump cap
  3. Leather work gloves and a dust mask
  4. Disposable examination gloves only

Explanation

Liquid refrigerant boils at extremely low temperature and can freeze tissue on contact, causing frostbite and eye injury. Gloves rated for refrigerant service plus sealed eye protection are the minimum protection for opening a system or transferring liquid.

Question 5Safety and Environmental Protection

Which method is appropriate for pinpointing a refrigerant leak on an operating system?

  1. Using an electronic detector calibrated for the refrigerant in the system Correct answer.
  2. Waiting for frost to form along the suction line
  3. Smelling for the odorant that is added to the refrigerant
  4. Holding a halide torch flame near each joint

Explanation

Electronic leak detectors and soap-bubble testing are the accepted methods for locating leaks. Halide torches produce toxic decomposition products when they contact refrigerant and should not be used, and HFCs contain no odorant to smell.

Question 6Safety and Environmental Protection

A lock and tag applied to a disconnect by a technician should be removed by:

  1. The building owner once the work area is clean
  2. The site supervisor at shift change
  3. The technician who applied it Correct answer.
  4. Any journeyman on the crew at the end of the shift

Explanation

Lockout/tagout rules require that the person who applied the lock and tag remove them, after confirming the work is complete and the equipment is safe to energize. Removing another worker's lock can expose that worker to a fatal re-energization.

Question 7Safety and Environmental Protection

Before servicing the blower motor circuit of an air handler, a technician should:

  1. De-energize the unit, apply a lock and tag, and confirm zero voltage at the motor terminals Correct answer.
  2. Turn the thermostat to the OFF position and begin work
  3. Open the blower compartment and check for airflow first
  4. Ask the homeowner to switch the breaker off while the work is done

Explanation

The circuit must be isolated at the disconnect, locked and tagged, and then verified dead with a meter before touching conductors. Motor circuits also store energy in run and start capacitors, which must be discharged as part of the same procedure.

Question 8Safety and Environmental Protection

How should refrigerant cylinders be carried in a service vehicle?

  1. Upright and secured so they cannot tip, roll, or strike one another Correct answer.
  2. Standing loose so they are easy to reach at each stop
  3. Laid horizontally in the cargo area so they cannot tip
  4. Wrapped in a blanket and placed next to the vehicle's heater vent

Explanation

Cylinders should ride upright and be restrained by straps or racks so valves are protected and the cylinders cannot become projectiles in a sudden stop. They must also be kept away from heat sources that would raise internal pressure.

Question 9Safety and Environmental Protection

A refrigerant classified as A1 under ASHRAE Standard 34 has which combination of properties?

  1. Lower toxicity and flame propagation
  2. Higher toxicity and flame propagation
  3. Lower toxicity and no flame propagation Correct answer.
  4. Higher toxicity and no flame propagation

Explanation

The letter designates health hazard, with A meaning lower toxicity and B meaning higher toxicity. The number designates flammability, with 1 meaning no flame propagation; the A1 group is therefore the least hazardous classification.

Question 10Safety and Environmental Protection

Carbon monoxide forms in a gas furnace when:

  1. The burner flame is starved of combustion air and burns incompletely Correct answer.
  2. The manifold gas pressure is set slightly below the nameplate value
  3. The blower runs at a lower speed than the nameplate specifies
  4. The flue carries more dilution air than the appliance needs

Explanation

Carbon monoxide is a product of incomplete combustion, typically caused by insufficient primary air, a blocked or undersized flue, or dirty burners. When the air-to-fuel ratio is correct, the burner produces carbon dioxide and water vapor instead.

Question 11Safety and Environmental Protection

Which container may be used to hold refrigerant recovered from a system?

  1. Any steel drum marked empty
  2. A propane cylinder fitted with an adapter
  3. A DOT-approved recovery cylinder in good condition that is within its test date Correct answer.
  4. A one-time-use refrigerant charge cylinder

Explanation

Recovery cylinders must meet DOT specifications, carry the proper markings, and be hydrostatically tested on the required schedule. Disposable charge cylinders and unrated containers are not built to be refilled and can fail under pressure.

Question 12Safety and Environmental Protection

Which precaution is required when brazing within a few feet of combustible material?

  1. Move the combustible material only after the joint is hot
  2. Rely on the torch flame being too small to ignite anything
  3. Use a heat shield, keep a fire extinguisher at hand, and keep a fire watch during and after the work Correct answer.
  4. Wet the material and begin brazing immediately

Explanation

Hot work near combustibles requires shielding the material, having extinguishing equipment within reach, and maintaining a fire watch that continues after the torch is shut off. Smoldering material can ignite long after the flame is gone.

Question 13Safety and Environmental Protection

When using dry nitrogen to pressure-test a system, the technician must:

  1. Connect the nitrogen hose directly to the cylinder valve
  2. Warm the cylinder to speed the test along
  3. Install a pressure regulator on the cylinder and stay within the system's rated test pressure Correct answer.
  4. Use oxygen instead of nitrogen so the pressure holds longer

Explanation

A full nitrogen cylinder can deliver well over two thousand psi, far above the working pressure of typical HVAC components. A regulator with a relief device lets the technician raise pressure in controlled steps to the test pressure the system can safely withstand.

Question 14Safety and Environmental Protection

A refrigerant classified as A2L is best described as:

  1. Non-flammable and non-toxic
  2. Mildly flammable with lower toxicity Correct answer.
  3. Non-flammable but highly toxic
  4. Highly flammable with higher toxicity

Explanation

In the ASHRAE 34 scheme, class A means lower toxicity and the 2L designation means a lower burning velocity, so the refrigerant is mildly flammable. Service procedures still require eliminating ignition sources and using equipment rated for flammable refrigerants.

Question 15Safety and Environmental Protection

A technician must enter a below-grade mechanical pit that is classified as a confined space. What is the first action?

  1. Start the nearest fan and enter while it runs
  2. Have a coworker stand at the top while entry begins
  3. Test the atmosphere for oxygen, combustible gas, and toxic gas before entry Correct answer.
  4. Lower a light into the pit to see whether the air looks clear

Explanation

Atmospheric testing comes before entry in any permit-required confined space because refrigerant and carbon monoxide can accumulate in low areas and displace oxygen. Entry proceeds only when readings are acceptable and the required attendant and rescue provisions are in place.

Question 16Safety and Environmental Protection

For every 4 feet of working height, the base of an extension ladder should be set out from the wall by about:

  1. 3 feet
  2. 1 foot Correct answer.
  3. 2 feet
  4. 6 inches

Explanation

The 4-to-1 rule places the ladder base one quarter of the working height away from the wall, giving a stable climbing angle of about 75 degrees. Setting the ladder too steeply or too shallowly invites it to tip or slide.

Question 17Safety and Environmental Protection

How should a mercury-switch thermostat removed during an equipment upgrade be handled?

  1. Stored in the van indefinitely and discarded with other refuse later
  2. Tossed into the job-site dumpster with scrap metal
  3. Managed as hazardous waste through a recycling or household hazardous waste program Correct answer.
  4. Placed in the customer's household trash

Explanation

Mercury is a persistent neurotoxin, and mercury-containing devices are banned from ordinary trash in most jurisdictions. They must be segregated and routed to a recycling program or household hazardous waste facility.

Question 18Safety and Environmental Protection

Used refrigerant oil drained from a system should be:

  1. Poured into a floor drain that leads to the sanitary sewer
  2. Spread on gravel behind the shop so it can evaporate
  3. Collected in a labeled, closed container and managed as hazardous waste Correct answer.
  4. Combined with the shop's used motor oil tank

Explanation

Refrigeration oil can be acidic, can carry dissolved refrigerant, and may contain metal particles and other contaminants. It belongs in a labeled, closed container handled under the applicable hazardous waste rules.

Question 19Safety and Environmental Protection

Why must refrigerant recovered from different systems be kept in separate recovery cylinders?

  1. The resulting mixture cannot be returned to specification and may not be accepted for reclamation Correct answer.
  2. Combining refrigerants automatically overfills the cylinder
  3. Combining refrigerants lowers the pressure rating of the cylinder
  4. Mixed refrigerant causes recovery cylinder valve seals to fail

Explanation

Reclaimers must know exactly what a cylinder contains to reprocess it to AHRI standard. A mixed or unknown blend usually has to be destroyed rather than reclaimed, which increases cost and waste.

Question 20Safety and Environmental Protection

Portable electric power tools used on a job site should be connected to:

  1. A generator output that is not bonded or grounded
  2. The nearest convenience outlet inside the building
  3. A GFCI-protected receptacle or cord set Correct answer.
  4. An extension cord with the ground pin removed to prevent tripping

Explanation

A ground-fault circuit interrupter trips when it senses a small current imbalance to ground, protecting the user from a lethal shock. Temporary power on construction sites is required to have GFCI protection or an assured equipment grounding conductor program.

Question 21Safety and Environmental Protection

Why must oxygen never be used as a pressure-test gas for a refrigeration system?

  1. It reacts with atmospheric nitrogen to form a toxic compound
  2. It is too costly for systems with a large internal volume
  3. It cannot raise system pressure above atmospheric
  4. It can combine explosively with oil or other combustibles left inside the system Correct answer.

Explanation

Oxygen supports combustion, and a pressurized mixture of oxygen and oil residue can detonate when an ignition source such as a torch or a hot surface is present. Dry nitrogen is inert and is the accepted test gas.

Question 22Safety and Environmental Protection

Under EPA Section 608, a comfort-cooling appliance containing 50 or more pounds of refrigerant must have leaks repaired when the annual leak rate exceeds:

  1. 35 percent
  2. 10 percent
  3. 15 percent Correct answer.
  4. 20 percent

Explanation

Section 608 sets the leak-repair trigger for comfort-cooling appliances at 15 percent of the charge per year, with the obligation to repair, verify, and document the repair. The thresholds differ by appliance type, and failure to repair within the allowed period leads to additional requirements.

Question 23Safety and Environmental Protection

A system uses R-290 (propane), an A3 refrigerant. Which practice is required during service?

  1. Use standard recovery equipment, since all refrigerants are handled the same way
  2. Charge the system while it is running to shorten the exposure time
  3. Remove ignition sources, ventilate the area, and use recovery equipment and leak detectors rated for flammable refrigerants Correct answer.
  4. Purge the system with room air before opening it

Explanation

Class 3 refrigerants are highly flammable, so ordinary recovery machines and detectors whose switches and motors can arc must not be used. The work area must be ventilated and all ignition sources, including switches and open flames, eliminated before the circuit is opened.

Question 24Safety and Environmental Protection

In ASHRAE Standard 15, the refrigerant concentration limit (RCL) is used to:

  1. Cap the concentration a refrigerant can reach in an occupied space to limit health and flammability risk Correct answer.
  2. Set the maximum allowable working pressure of system piping
  3. Determine the minimum wall thickness for a machine room
  4. Establish the charging accuracy required for a system

Explanation

The RCL is the maximum concentration permitted in an occupied space, derived from oxygen-deprivation, toxicity, and flammability data for the refrigerant. The allowable charge is calculated from the RCL and the volume of the space being served.

Question 25Safety and Environmental Protection

Before a room air conditioner is discarded, the Clean Air Act requires that:

  1. The appliance be tagged as containing no refrigerant without verification
  2. The refrigerant be recovered from the appliance before it is dismantled or shredded Correct answer.
  3. The compressor oil be drained into the sanitary sewer before pickup
  4. The charge be released slowly through a service valve so nothing freezes

Explanation

Section 608 prohibits venting refrigerant and requires recovery from appliances before disposal. The technician or the final disposer must use certified recovery equipment and follow the applicable disposal requirements.

Question 26Tools, Instruments, and Measurement

In a standard two-valve manifold gauge set, what does the compound gauge measure?

  1. Low-side pressure and vacuum Correct answer.
  2. Refrigerant weight in the cylinder
  3. High-side pressure only
  4. Compressor operating current

Explanation

The compound gauge is the low-side gauge, and it is designed to read both positive pressure and vacuum. The high-side gauge is normally a pressure-only gauge.

Question 27Tools, Instruments, and Measurement

Which instrument indicates the level of vacuum reached during system evacuation?

  1. Voltage tester
  2. Air velocity meter
  3. Micron gauge Correct answer.
  4. Refrigerant scale

Explanation

A micron gauge measures very low absolute pressure and is used to verify evacuation. Micron readings decrease as moisture and air are removed from the system.

Question 28Tools, Instruments, and Measurement

A clamp-on ammeter is used to measure ___.

  1. Winding resistance
  2. Capacitor microfarads
  3. Current in a conductor Correct answer.
  4. Pipe surface temperature

Explanation

A clamp-on ammeter senses current by measuring the magnetic field around a conductor. It allows current measurement without opening the circuit.

Question 29Tools, Instruments, and Measurement

Which instrument is used to measure dry-bulb air temperature?

  1. Anemometer
  2. Manometer
  3. Thermometer Correct answer.
  4. Micron gauge

Explanation

Dry-bulb temperature is an ordinary air temperature reading taken with a thermometer. It does not account for humidity, unlike wet-bulb temperature.

Question 30Tools, Instruments, and Measurement

An electronic refrigerant scale is primarily used to ___.

  1. Read vacuum in microns
  2. Locate refrigerant leaks
  3. Measure duct static pressure
  4. Charge refrigerant by weight Correct answer.

Explanation

Charging by weight uses a scale to add a precise refrigerant mass. This method is more accurate than judging charge by gauge readings alone.

Question 31Tools, Instruments, and Measurement

A manometer is used to measure ___.

  1. Airflow in cfm directly
  2. Differential pressure Correct answer.
  3. Compressor current
  4. Relative humidity

Explanation

A manometer measures pressure difference, often expressed in inches of water column for duct static pressure. Airflow in cfm requires velocity and duct area.

Question 32Tools, Instruments, and Measurement

A psychrometer provides readings used to determine ___.

  1. Voltage drop across a contactor
  2. Refrigerant superheat and subcooling
  3. Dry-bulb and wet-bulb temperatures Correct answer.
  4. Vacuum level in microns

Explanation

A psychrometer measures dry-bulb and wet-bulb temperatures, which are used with a psychrometric chart. Those values allow calculation of humidity and related air properties.

Question 33Tools, Instruments, and Measurement

Which leak-checking method uses a soap solution applied to joints?

  1. Bubble testing Correct answer.
  2. Ultraviolet dye testing
  3. Electronic leak detection
  4. Ultrasonic leak detection

Explanation

Bubble testing applies soap solution to a suspected joint and looks for bubbles caused by escaping refrigerant or nitrogen. It is simple and useful for confirming a leak location.

Question 34Tools, Instruments, and Measurement

Suction line temperature is 55°F and the suction pressure corresponds to 40°F saturation. What is the superheat?

  1. 15°F Correct answer.
  2. 55°F
  3. 95°F
  4. 40°F

Explanation

Superheat is the difference between actual suction line temperature and saturation temperature at the same pressure. Subtracting 40°F from 55°F gives 15°F superheat.

Question 35Tools, Instruments, and Measurement

Liquid line temperature is 100°F and condensing saturation temperature is 115°F. What is the subcooling?

  1. 100°F
  2. 215°F
  3. 15°F Correct answer.
  4. 5°F

Explanation

Subcooling is the condensing saturation temperature minus the liquid line temperature. Subtracting 100°F from 115°F gives 15°F subcooling.

Question 36Tools, Instruments, and Measurement

Duct static pressure is commonly measured in ___.

  1. Inches of water column Correct answer.
  2. Pounds per square inch
  3. Microns
  4. Amperes

Explanation

Duct static pressure is usually a small pressure difference, so it is read in inches of water column. Microns are used for vacuum, and psi is used for higher refrigerant pressures.

Question 37Tools, Instruments, and Measurement

Air velocity in a duct is 400 fpm and the duct area is 2 ft². What is the airflow?

  1. 600 cfm
  2. 200 cfm
  3. 800 cfm Correct answer.
  4. 400 cfm

Explanation

Airflow in cfm equals velocity in feet per minute multiplied by duct area in square feet. Multiplying 400 fpm by 2 ft² gives 800 cfm.

Question 38Tools, Instruments, and Measurement

After evacuation, the vacuum pump is isolated and the micron gauge is watched. A rapid rise in microns most likely indicates ___.

  1. Excessive airflow
  2. A normal nitrogen holding charge
  3. Correct subcooling
  4. A leak or moisture in the system Correct answer.

Explanation

A standing vacuum test checks whether the system holds a low micron level after the pump is isolated. A rapid rise suggests air is entering or moisture is still vaporizing.

Question 39Tools, Instruments, and Measurement

When pressure-testing a system with dry nitrogen, a pressure regulator is used to ___.

  1. Raise cylinder pressure above source pressure
  2. Control the test pressure to a safe setpoint Correct answer.
  3. Remove moisture from refrigerant
  4. Measure the vacuum level

Explanation

A nitrogen regulator reduces cylinder pressure to a controlled test pressure. This protects the system from overpressurization during leak testing.

Question 40Tools, Instruments, and Measurement

To measure voltage across an operating component, the voltmeter leads are connected ___.

  1. In series with the component
  2. Around the thermostat only
  3. In parallel with the component Correct answer.
  4. From the component to ground only

Explanation

A voltmeter is connected in parallel with the component so it can compare the potential on each side. Connecting it in series would place its high resistance in the current path.

Question 41Tools, Instruments, and Measurement

Before testing a compressor winding with an ohmmeter, the technician should ___.

  1. Set the meter to amps
  2. Disconnect only the thermostat
  3. De-energize and isolate it Correct answer.
  4. Energize the circuit first

Explanation

An ohmmeter supplies its own small voltage and must not be used on a live circuit. The circuit should be de-energized and isolated to protect the meter and obtain a valid resistance reading.

Question 42Tools, Instruments, and Measurement

Which temperature sensor produces a voltage when two dissimilar metals are joined at a measuring junction?

  1. Resistance temperature detector
  2. Thermistor
  3. Thermocouple Correct answer.
  4. Bimetal thermometer

Explanation

A thermocouple uses the Seebeck effect: two different metals joined at a junction generate a small voltage that changes with temperature. The other sensors rely on resistance change or mechanical expansion.

Question 43Tools, Instruments, and Measurement

An infrared thermometer aimed at shiny metal may give an unreliable reading because ___.

  1. The meter is reading vacuum instead
  2. Infrared meters work only in ducts
  3. Low emissivity affects accuracy Correct answer.
  4. The metal is always at absolute zero

Explanation

Infrared thermometers infer temperature from emitted radiation, and shiny surfaces have low emissivity. That can make the indicated temperature lower or less reliable unless emissivity is adjusted.

Question 44Tools, Instruments, and Measurement

A combustion analyzer is used to ___.

  1. Test capacitor capacitance
  2. Measure register air velocity
  3. Analyze flue gas and efficiency Correct answer.
  4. Weigh refrigerant into a cylinder

Explanation

A combustion analyzer samples flue gases to measure oxygen, carbon monoxide, and related values. Those readings are used to evaluate combustion safety and efficiency.

Question 45Tools, Instruments, and Measurement

A digital multimeter with a capacitance setting is used to ___.

  1. Detect refrigerant leaks
  2. Measure duct static pressure
  3. Measure capacitor microfarads Correct answer.
  4. Read vacuum in microns

Explanation

The capacitance function charges and discharges the capacitor internally to determine its value in microfarads. The capacitor must be discharged and isolated before testing.

Question 46Tools, Instruments, and Measurement

In a duct traverse using a pitot tube, velocity pressure is calculated as ___.

  1. Static pressure minus total pressure
  2. Total pressure plus static pressure
  3. Static pressure divided by velocity
  4. Total pressure minus static pressure Correct answer.

Explanation

Velocity pressure is the difference between total pressure and static pressure. It represents the pressure energy due to air movement and is used to calculate velocity.

Question 47Tools, Instruments, and Measurement

For the most accurate evacuation reading, the micron gauge should be ___.

  1. Connected at the pump inlet only
  2. Connected directly to the system Correct answer.
  3. Left on the manifold center port
  4. Installed after the recovery cylinder

Explanation

A micron gauge should sense the system itself, using a short, large-diameter connection when possible. Reading at the pump inlet or through long manifold hoses can make the vacuum appear better than it is in the system.

Question 48Tools, Instruments, and Measurement

On a fixed-orifice system, charging by superheat is used because the orifice ___.

  1. Uses only liquid-line temperature
  2. Controls subcooling directly
  3. Does not regulate superheat Correct answer.
  4. Maintains constant superheat at all loads

Explanation

A fixed orifice has a fixed flow area, so superheat changes with load and conditions rather than being held constant. A thermostatic expansion valve actively modulates flow to control superheat.

Question 49Tools, Instruments, and Measurement

Which instrument is best suited for measuring low air velocity at a supply register?

  1. Thermal anemometer Correct answer.
  2. Micron gauge
  3. Dry-bulb thermometer
  4. U-tube manometer

Explanation

A thermal anemometer is sensitive to low air speeds and is useful at registers and grilles. A manometer measures pressure, and a thermometer measures temperature.

Question 50Tools, Instruments, and Measurement

A gauge gives repeated readings that are close together but consistently 3°F higher than the true temperature. The readings are ___.

  1. Precise but not accurate Correct answer.
  2. Neither accurate nor precise
  3. Accurate but not precise
  4. Both accurate and precise

Explanation

Precision describes how close repeated readings are to each other, while accuracy describes closeness to the true value. Repeated readings with a consistent offset are precise but biased.