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R-410A practice questions

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Question 1Refrigerant Properties, Safety, and Handling

R-410A is a blend composed of which two refrigerants?

  1. 50% R-32 and 50% R-125 Correct answer.
  2. 60% R-32 and 40% R-134a
  3. 50% R-22 and 50% R-125
  4. 100% R-32

Explanation

R-410A is an equal-part blend of difluoromethane (R-32) and pentafluoroethane (R-125) by mass. Because the two components have different volatilities, the mixture must be handled as a blend rather than as a single-component refrigerant.

Question 2Refrigerant Properties, Safety, and Handling

What is the ozone depletion potential (ODP) of R-410A?

  1. 1.0
  2. 0.6
  3. 0.05
  4. 0 Correct answer.

Explanation

ODP is assigned relative to CFC-11 and depends on the presence of chlorine or bromine in the molecule. R-410A contains only HFCs (R-32 and R-125), which carry no chlorine or bromine, so its ODP is zero.

Question 3Refrigerant Properties, Safety, and Handling

Compared with R-22 at the same saturation temperature, the pressure of R-410A is approximately:

  1. three times higher
  2. 50% to 70% higher Correct answer.
  3. nearly identical
  4. 10% to 20% lower

Explanation

R-410A has a much steeper pressure-temperature curve than R-22, so at any given saturation temperature its pressure runs roughly 50% to 70% higher. This is why R-410A systems, gauges, and recovery equipment must be rated for higher pressures.

Question 4Refrigerant Properties, Safety, and Handling

Which lubricant is used in most R-410A systems?

  1. Polyolester (POE) oil Correct answer.
  2. Mineral oil
  3. Polyalkylene glycol (PAG) oil
  4. Alkylbenzene oil

Explanation

HFC refrigerants are not miscible with mineral oil or alkylbenzene, so R-410A systems use polyolester oil to ensure lubricant returns to the compressor. POE is hygroscopic and must be kept sealed until use.

Question 5Refrigerant Properties, Safety, and Handling

R-410A cylinders are normally color-coded:

  1. green
  2. rose (pink) Correct answer.
  3. light blue
  4. orange

Explanation

Industry color conventions assign rose to R-410A so a cylinder can be identified at a glance. Light blue marks R-134a and green marks R-22, which prevents cross-charging mistakes.

Question 6Refrigerant Properties, Safety, and Handling

Under ASHRAE Standard 34, R-410A is classified as:

  1. A1 - low toxicity, no flame propagation Correct answer.
  2. B1 - higher toxicity
  3. A2L - mildly flammable
  4. B2 - higher toxicity, flammable

Explanation

R-410A is an A1 refrigerant: it has low toxicity and does not propagate a flame at atmospheric pressure. A2L covers newer mildly flammable refrigerants such as R-32 and R-454B, which require different handling procedures.

Question 7Refrigerant Properties, Safety, and Handling

A technician using a halide (torch) leak detector on an R-410A system will find that:

  1. it requires a different torch tip
  2. it reacts more strongly than with R-22
  3. it works only on liquid lines
  4. it cannot - R-410A has no chlorine Correct answer.

Explanation

Halide torches react to halogens, primarily chlorine, in the refrigerant. R-410A is chlorine-free, so electronic detectors, ultrasonic instruments, or soap bubbles must be used instead.

Question 8Refrigerant Properties, Safety, and Handling

When transferring R-410A from a cylinder into a system, the refrigerant should be removed as:

  1. either vapor or liquid, since there is no glide
  2. vapor first, then liquid
  3. liquid, because the blend can fractionate Correct answer.
  4. vapor only, to protect the compressor

Explanation

R-410A has a small but nonzero temperature glide, so the components vaporize at slightly different rates. Withdrawing vapor changes the composition of what leaves the cylinder and what remains, so the charge must be drawn as a liquid.

Question 9Refrigerant Properties, Safety, and Handling

Which personal protective equipment is essential when connecting or disconnecting R-410A hoses?

  1. A face shield only
  2. A dust mask and ear plugs
  3. A respirator and rubber apron
  4. Safety glasses and insulated gloves Correct answer.

Explanation

Liquid refrigerant boils at about -51°C (-60°F), so a splash can flash-freeze skin and eyes on contact. Gloves and eye protection are the standard protection against frostbite during hose work.

Question 10Refrigerant Properties, Safety, and Handling

R-410A vapor released in a basement mechanical room tends to:

  1. settle low and displace breathing air Correct answer.
  2. rise and vent through the roof
  3. form a visible fog that clears quickly
  4. break down into harmless gases

Explanation

R-410A vapor has a molecular weight of about 72.6, roughly 2.5 times that of air, so it sinks into low spaces such as pits and basements. In a large release it displaces oxygen and creates an asphyxiation hazard.

Question 11Refrigerant Properties, Safety, and Handling

A manifold gauge set used on R-410A systems must have a working pressure rating of at least about:

  1. 1500 psig
  2. 250 psig
  3. 500 psig
  4. 800 psig Correct answer.

Explanation

Standard manifold sets are rated around 500 psig, which is not adequate for R-410A. Gauges and hoses intended for R-410A are rated to about 800 psig to cover high-ambient standby pressures.

Question 12Refrigerant Properties, Safety, and Handling

Which recovery unit may be used to recover R-410A?

  1. An R-22-rated unit run at reduced speed
  2. Any unit that has a compressor
  3. A unit labeled for R-410A Correct answer.
  4. A unit with a water-cooled condenser

Explanation

Recovery equipment must be listed for the refrigerant being recovered so its components and compressor oil are compatible with the higher pressures and with POE lubricant. An unlisted machine can be overpressurized or damaged by oil incompatibility.

Question 13Refrigerant Properties, Safety, and Handling

Recovered R-410A should be handled by:

  1. transferring it into a disposable container
  2. putting it in a dedicated, labeled recovery cylinder Correct answer.
  3. adding nitrogen to the recovery cylinder
  4. combining it with R-22 to save cylinder space

Explanation

Each recovered refrigerant must go into its own properly labeled recovery cylinder so it can be reclaimed or destroyed. Mixing refrigerants creates an unidentified blend that cannot be reprocessed and may be unsafe.

Question 14Refrigerant Properties, Safety, and Handling

A recovery cylinder should never be filled beyond roughly what percentage of its capacity by weight?

  1. 100%
  2. 60%
  3. 95%
  4. 80% Correct answer.

Explanation

Liquid refrigerant expands substantially as it warms, so an 80% fill limit leaves a vapor space for expansion and prevents hydrostatic rupture. The limit is based on weight, not on the visible liquid level.

Question 15Refrigerant Properties, Safety, and Handling

To speed the transfer of R-410A from a cylinder, a technician may:

  1. set it in warm water no hotter than 125°F Correct answer.
  2. wrap it in a blanket set to 150°F
  3. play a torch briefly on the bottom
  4. place the cylinder on a hot plate

Explanation

Warming a cylinder raises its pressure and speeds transfer, but the cylinder must never exceed about 52°C (125°F). Warm water is the accepted method; open flame and uncontrolled heaters can overpressure the cylinder and decompose the refrigerant.

Question 16Refrigerant Properties, Safety, and Handling

When R-410A contacts a flame or a very hot surface, the decomposition products include:

  1. hydrogen fluoride and carbonyl fluoride Correct answer.
  2. carbon dioxide and water vapor only
  3. chlorine gas and phosgene
  4. ammonia and methane

Explanation

Fluorinated refrigerants break down at high temperature to hydrogen fluoride and carbonyl fluoride, both of which are highly toxic and corrosive. That is why a refrigerant fire produces intensely irritating fumes and requires respiratory protection.

Question 17Refrigerant Properties, Safety, and Handling

The global warming potential (GWP) of R-410A is approximately:

  1. 150
  2. 0
  3. 20,000
  4. 2,000 Correct answer.

Explanation

R-410A's GWP is about 2,000 times that of carbon dioxide, commonly cited as 2,088 on the AR4 basis. This high value is the main reason it is being replaced by lower-GWP refrigerants.

Question 18Refrigerant Properties, Safety, and Handling

An R-22 system cannot simply be recharged with R-410A because:

  1. R-410A has a lower heat capacity
  2. R-410A cannot carry lubricant
  3. its components and POE oil are not rated for R-410A Correct answer.
  4. R-410A freezes at a higher temperature

Explanation

R-410A is not a drop-in replacement: it operates at much higher pressures and requires POE lubricant, so the compressor, coils, and line components of an R-22 system are not suitable. Retrofitting an R-22 system to R-410A is therefore not permitted.

Question 19Refrigerant Properties, Safety, and Handling

The temperature glide of R-410A during phase change in a system is:

  1. between 5°F and 8°F
  2. about 10°F
  3. less than about 1°F Correct answer.
  4. exactly zero

Explanation

R-410A is a near-azeotropic blend with a glide well under 1°F, so it behaves almost like a single refrigerant in the evaporator. It is still treated as a blend and charged as a liquid to prevent fractionation.

Question 20Refrigerant Properties, Safety, and Handling

The critical temperature of R-410A is about 160°F, which means that:

  1. it solidifies when cooled below 160°F
  2. it becomes flammable above 160°F
  3. it boils at 160°F at atmospheric pressure
  4. it cannot be liquefied by pressure alone above that point Correct answer.

Explanation

Above the critical temperature a refrigerant exists as a supercritical fluid regardless of applied pressure, so no liquid phase can form. Cylinders must be kept well below this temperature so that liquid and vapor remain in equilibrium and pressure stays predictable.

Question 21Refrigerant Properties, Safety, and Handling

Under Section 608 of the Clean Air Act, R-410A:

  1. may be vented if the charge is under one pound
  2. must be recovered and may not be knowingly vented Correct answer.
  3. may be vented if released outdoors
  4. may be vented because it does not deplete ozone

Explanation

The venting prohibition covers ozone-depleting refrigerants and their HFC substitutes, including R-410A. Knowing venting during service or disposal is prohibited regardless of the refrigerant's zero ODP.

Question 22Refrigerant Properties, Safety, and Handling

To remove moisture and non-condensables, a new R-410A system should be evacuated to a standing vacuum of at least:

  1. 500 microns Correct answer.
  2. 10,000 microns
  3. 5,000 microns
  4. 2,000 microns

Explanation

A standing vacuum of 500 microns or lower confirms that the system has been dehydrated and is leak-free. Higher readings indicate residual moisture or an incomplete evacuation.

Question 23Refrigerant Properties, Safety, and Handling

POE oil left exposed to air reacts with moisture to:

  1. evaporate completely
  2. turn the refrigerant flammable
  3. thicken into a harmless gel
  4. form acids that can damage the compressor Correct answer.

Explanation

POE is hygroscopic and hydrolyzes in the presence of water to form organic acids, which attack motor windings and produce sludge. Containers must stay sealed, and system exposure to air should be minimized.

Question 24Refrigerant Properties, Safety, and Handling

A cylinder of liquid R-410A sitting at 70°F will show a pressure of approximately:

  1. 70 psig
  2. 200 psig Correct answer.
  3. 160 psig
  4. 120 psig

Explanation

Reading the R-410A pressure-temperature chart at 70°F gives a saturation pressure near 200 psig. That is roughly 80 psig above R-22 at the same temperature, which is why R-410A equipment is built for higher pressures.

Question 25Refrigerant Properties, Safety, and Handling

Pressurizing an R-410A system with air for leak testing is hazardous because:

  1. air dissolves the copper tubing
  2. the refrigerant breaks down instantly
  3. R-410A/air mixtures at high pressure can ignite Correct answer.
  4. air causes the POE oil to freeze

Explanation

R-410A does not propagate flame in air at atmospheric pressure, but refrigerant-air mixtures at elevated pressure can become combustible. Dry nitrogen is the accepted medium for pressure testing because it is inert and leaves no moisture.

Question 26Refrigerant Properties, Safety, and Handling

R-410A is a blend composed of:

  1. 50% R-32 and 50% R-125 Correct answer.
  2. 75% R-32 and 25% R-125
  3. 60% R-22 and 40% R-125
  4. 50% R-32 and 50% R-134a

Explanation

R-410A is a binary near-azeotropic blend of equal parts R-32 (difluoromethane) and R-125 (pentafluoroethane) by weight. Because the ratio is fixed at 50/50, it is not the same as other HFC blends such as R-407C or R-404A.

Question 27Refrigerant Properties, Safety, and Handling

The ozone depletion potential (ODP) of R-410A is:

  1. About 0.2
  2. Zero Correct answer.
  3. About 0.05, similar to R-22
  4. Roughly half that of R-12

Explanation

ODP is driven by chlorine and bromine atoms, and R-410A contains neither, so its ODP is zero. This is one reason it was adopted to replace ozone-depleting HCFC refrigerants such as R-22.

Question 28Refrigerant Properties, Safety, and Handling

Liquid R-410A escaping onto a technician's hand causes severe frostbite mainly because the refrigerant:

  1. reacts chemically with the proteins in the skin on contact
  2. carries a static charge that damages exposed tissue
  3. is forced into the tissue by the pressure in the cylinder
  4. boils at a very low temperature and absorbs heat rapidly Correct answer.

Explanation

R-410A boils at roughly minus 60°F at atmospheric pressure, so liquid that contacts skin flash-boils and pulls heat out of the tissue almost instantly, freezing it. The injury is thermal, not chemical or electrical.

Question 29Refrigerant Properties, Safety, and Handling

Cylinders of R-410A are conventionally painted:

  1. Light green
  2. Rose (pink) Correct answer.
  3. White
  4. Light blue

Explanation

Refrigerant cylinder colors are a quick visual identifier, and R-410A cylinders are conventionally rose or pink. Light green is used for R-22, light blue for R-134a, and white for R-12, so color helps prevent misidentification.

Question 30Refrigerant Properties, Safety, and Handling

How should cylinders of R-410A be kept in a service van or shop?

  1. Laid flat in a rack so they cannot roll
  2. In any position if the valve cap is tight
  3. Upright and secured, away from heat Correct answer.
  4. In a sealed cabinet to keep valves dry

Explanation

Refrigerant cylinders should be stored upright, blocked or strapped so they cannot fall, with valve caps in place, and away from heat sources or direct sun. Heat raises cylinder pressure and can cause the relief device to discharge.

Question 31Refrigerant Properties, Safety, and Handling

Line sets, gauges, and components for R-410A must be rated for higher pressure than R-22 equipment because R-410A:

  1. carries oil that raises the head pressure
  2. has a wider glide than R-22 has
  3. has a higher molecular weight than R-22
  4. runs at 50 to 70 percent higher pressures Correct answer.

Explanation

At any given saturation temperature R-410A's pressure is roughly 50 to 70 percent higher than R-22's, so every pressure-containing part must be rated for that higher value. This is why approved R-410A manifolds and recovery equipment are required rather than R-22-rated gear.

Question 32Refrigerant Properties, Safety, and Handling

When pressure testing an R-410A system with dry nitrogen, the technician should:

  1. add a trace of oxygen to make leaks easier to find
  2. connect the regulator straight to the cylinder valve
  3. use full cylinder pressure to speed up the test
  4. use a regulator and stay below the low-side test limit Correct answer.

Explanation

Dry nitrogen is regulated down to a pressure below the system's low-side test limit so tubing and components are not overstressed. A regulator on the nitrogen cylinder is required because full cylinder pressure far exceeds system ratings.

Question 33Refrigerant Properties, Safety, and Handling

A technician recovering R-410A should never:

  1. put recovered R-410A into a cylinder that held R-22 Correct answer.
  2. recover into a cylinder that is sitting on a scale
  3. use a recovery cylinder that is already under vacuum
  4. recover liquid and vapor at the same time

Explanation

Mixing different refrigerants in one recovery cylinder creates a contaminated mixture that cannot be reclaimed and may no longer be safely used. Each recovery cylinder must be dedicated to a single refrigerant and labeled accordingly.

Question 34Refrigerant Properties, Safety, and Handling

Disposable refrigerant cylinders:

  1. can be used for recovery if marked DOT 4BA
  2. are legal to refill if the valve is replaced first
  3. must never be refilled or used for recovery Correct answer.
  4. may be refilled once by a certified technician

Explanation

Disposable cylinders are not designed or approved for refilling, and federal rules prohibit refilling them or using them to store recovered refrigerant. Recovery must go into a DOT-approved refillable recovery cylinder.

Question 35Refrigerant Properties, Safety, and Handling

An electronic leak detector used on R-410A equipment must be:

  1. capable of detecting chlorine in the sample
  2. set to its lowest sensitivity to avoid false alarms
  3. the heated-diode type used for CFCs and HCFCs
  4. rated and calibrated for HFC refrigerants Correct answer.

Explanation

HFCs contain no chlorine, so detectors must use a sensor designed for HFCs and be calibrated to the refrigerant being tested. Sensitivity should be set high enough to find small leaks, and the instrument should be checked against a known reference leak.

Question 36Refrigerant Properties, Safety, and Handling

The most accurate way to charge an R-410A system is to:

  1. weigh in the charge shown on the nameplate Correct answer.
  2. charge until the suction line begins to frost
  3. set the manifold to the pressure on the gauge
  4. add vapor until the sight glass is clear

Explanation

Weighing the refrigerant with a scale and matching the nameplate charge is the most accurate method, especially for a blend whose composition must be preserved. Gauge pressure alone is affected by indoor and outdoor conditions and cannot confirm the charge.

Question 37Refrigerant Properties, Safety, and Handling

If liquid R-410A splashes into a technician's eye, the technician should:

  1. flush the eye with water and get medical help Correct answer.
  2. use a solvent eyewash to dissolve the oil
  3. apply a warm compress until the stinging stops
  4. rub the eye and keep working if vision seems normal

Explanation

Liquid refrigerant in the eye can freeze tissue and the oil mixed with it can irritate, so the eye must be flushed with water for at least 15 minutes and medical attention obtained. Rubbing the eye can worsen the injury.

Question 38Refrigerant Properties, Safety, and Handling

Under DOT rules, a typical refillable refrigerant recovery cylinder must be:

  1. retired after ten years regardless of condition
  2. requalified every time it is filled
  3. requalified only when the valve is replaced
  4. requalified (pressure tested) every five years Correct answer.

Explanation

Refillable refrigerant cylinders are DOT specification pressure vessels that must be requalified, typically by hydrostatic test, every five years. A cylinder without a current requalification date may not legally be filled or transported.

Question 39Refrigerant Properties, Safety, and Handling

A cylinder of R-410A is dropped and the valve stem is bent so the valve cannot be closed. The technician should:

  1. cap the valve and keep it in the van until empty
  2. straighten the stem with pliers and return it to service
  3. transfer the gas and discard the damaged cylinder
  4. isolate it, notify the supplier, and make no repair Correct answer.

Explanation

A damaged valve on a pressurized cylinder is a serious hazard, and field repair of cylinder valves is not permitted. The cylinder should be moved to a safe, isolated location if that can be done without risk, and the supplier should be contacted for handling instructions.

Question 40Refrigerant Properties, Safety, and Handling

A gauge reads 118 psig at the evaporator of an operating R-410A system. The saturated evaporator temperature is approximately:

  1. 40°F Correct answer.
  2. 75°F
  3. 22°F
  4. 60°F

Explanation

On an R-410A pressure-temperature chart, 118 psig corresponds to a saturation temperature of about 40°F. The technician converts the measured pressure to temperature using the chart, since the relationship is fixed for a given refrigerant.

Question 41Environmental Regulations and Compliance

Under Section 608 of the Clean Air Act, which statement accurately describes R-410A?

  1. It becomes an ozone depleter after it leaks.
  2. It is a Class I ozone-depleting substance.
  3. It is a Class II ozone-depleting substance.
  4. It has an ozone depletion potential of 0. Correct answer.

Explanation

R-410A is an HFC blend of R-32 and R-125 and contains no chlorine or bromine, so its ozone depletion potential is zero. Section 608's ozone-protection provisions target chlorine-bearing CFCs and HCFCs, while HFCs are regulated for their global warming impact instead.

Question 42Environmental Regulations and Compliance

R-410A belongs to which refrigerant family?

  1. Chlorofluorocarbon (CFC)
  2. Hydrochlorofluorocarbon (HCFC)
  3. Hydrofluorocarbon (HFC) Correct answer.
  4. Hydrocarbon (HC)

Explanation

R-410A is a 50/50 blend of R-32 and R-125, both of which are hydrofluorocarbons. It contains no chlorine, which is why it does not deplete stratospheric ozone but is still regulated as a greenhouse gas.

Question 43Environmental Regulations and Compliance

Which action is prohibited by EPA regulations when servicing an R-410A system?

  1. Recovering the charge into a DOT-approved cylinder
  2. Venting refrigerant to the atmosphere during a repair Correct answer.
  3. Returning recovered refrigerant to an EPA-certified reclaimer
  4. Recycling the refrigerant on site and reusing it

Explanation

Knowingly venting HFC refrigerants such as R-410A to the atmosphere is prohibited under Section 608. Refrigerant must be recovered before a system is opened and before an appliance is disposed of.

Question 44Environmental Regulations and Compliance

Which federal law gives EPA the authority to regulate refrigerant recovery, certification, and venting?

  1. The Resource Conservation and Recovery Act
  2. The Safe Drinking Water Act
  3. The Clean Air Act Correct answer.
  4. The Toxic Substances Control Act

Explanation

Title VI of the Clean Air Act, the Stratospheric Ozone Protection provisions, contains Section 608. That section sets the rules for technician certification, refrigerant recovery, leak repair, and the venting prohibition.

Question 45Environmental Regulations and Compliance

A technician is scheduled to service a residential split system that holds 8 pounds of R-410A. Which EPA certification does the technician need?

  1. Type III, because R-410A operates at high pressure
  2. No certification, because the system holds less than 20 pounds
  3. Type I, because the system holds less than 10 pounds
  4. Type II or Universal Correct answer.

Explanation

Small appliances are hermetically sealed, factory-charged units holding 5 pounds or less of refrigerant. A split system holding 8 pounds exceeds that limit and is a high-pressure appliance, so Type II or Universal certification is required.

Question 46Environmental Regulations and Compliance

An appliance with a full charge of 100 pounds of R-410A has had 12 pounds added over the last 12 months. What is the annual leak rate and what does it require?

  1. 6 percent; no action is required
  2. 120 percent; the appliance must be retired
  3. 12 percent; the leak must be repaired Correct answer.
  4. 10 percent; no action is required

Explanation

Leak rate equals refrigerant added over 12 months divided by the full charge, so 12 divided by 100 gives 12 percent. The trigger rate for comfort cooling is 10 percent, so the appliance exceeds the trigger and the leak must be repaired within 30 days.

Question 47Environmental Regulations and Compliance

After an appliance containing 50 or more pounds of R-410A is found to exceed its trigger leak rate, how long does the owner have to complete the repairs?

  1. 10 days
  2. 7 days
  3. 30 days Correct answer.
  4. 90 days

Explanation

The leak repair rule requires the owner or operator to complete repairs within 30 days of discovering that the appliance exceeded its trigger rate, unless the owner instead develops a retrofit or retirement plan.

Question 48Environmental Regulations and Compliance

After a leak repair on an appliance subject to the Section 608 leak repair requirements, when must the initial verification test be performed?

  1. No later than 10 days after the repair is completed Correct answer.
  2. No later than 30 days after the repair is completed
  3. Only if the appliance begins leaking again
  4. Within 24 hours of the repair

Explanation

The rule requires an initial verification test as soon as practicable and no later than 10 days after the repair is completed. A follow-up verification test is also required afterward to confirm the repair is holding.

Question 49Environmental Regulations and Compliance

How long must a technician or appliance owner keep records of refrigerant recovered, added, and disposed of?

  1. Five years
  2. Two years
  3. Three years Correct answer.
  4. One year

Explanation

The recordkeeping provisions of 40 CFR 82.166 require service, recovery, and disposal records to be retained for at least three years. Records must be made available to EPA on request.

Question 50Environmental Regulations and Compliance

Recovered R-410A may be sold for use in a different customer's appliance only after it has been:

  1. Recycled by the technician who recovered it
  2. Filtered through a recovery unit equipped with driers
  3. Stored in a non-refillable cylinder
  4. Reclaimed to AHRI Standard 700 Correct answer.

Explanation

Refrigerant that leaves a job site for use in another appliance must be reclaimed by an EPA-certified reclaimer to AHRI 700 purity. Recycling only cleans refrigerant for reuse in the same appliance or one owned by the same person.