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NATE Low-GWP study materials
NATE Low-GWP study resources

NATE Low-GWP practice questions

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Question 1Low GWP Refrigerant (LGWP)

Which property makes a refrigerant eligible for classification as a low-GWP refrigerant under the AIM Act technology transition framework?

  1. A GWP value below 150 with a B1 safety classification
  2. A GWP value below 750 with an A1 safety classification
  3. A GWP value below 2200 with zero ozone depletion potential
  4. A GWP value below 700 as listed in the AHRI standard or IPCC assessment Correct answer.

Explanation

The AIM Act technology transition rules use a GWP threshold of 700 for most refrigerant end-uses, referenced against the IPCC assessment values adopted in the rule. The threshold is defined by GWP alone, not by safety class or ODP. A refrigerant at GWP 750 or 2200 exceeds the low-GWP threshold regardless of its other properties.

Question 2Low GWP Refrigerant (LGWP)

A technician compares R-410A (GWP 2088) with R-454B (GWP 466). What is the approximate percentage reduction in GWP when R-454B replaces R-410A?

  1. About 22 percent
  2. About 78 percent Correct answer.
  3. About 96 percent
  4. About 45 percent

Explanation

The reduction is calculated as (2088 minus 466) divided by 2088, which equals roughly 0.777, or about 78 percent. This reflects the large gap between the high-GWP HFC blend and the lower-GWP HFO blend. Percentages near 22 or 45 percent understate the change and 96 percent overstates it.

Question 3Low GWP Refrigerant (LGWP)

Which refrigerant is commonly identified as a low-GWP replacement for R-134a in chillers and is classified A2L?

  1. R-513A
  2. R-1234ze Correct answer.
  3. R-407C
  4. R-404A

Explanation

R-1234ze is an HFO with a GWP of about 7 and an A2L safety classification, making it a common low-GWP choice for centrifugal chillers. R-513A is also low-GWP but is classified A1, not A2L. R-404A and R-407C are higher-GWP HFC blends.

Question 4Low GWP Refrigerant (LGWP)

Why do many low-GWP refrigerant alternatives carry an A2L safety classification?

  1. They are mildly flammable because of their HFO or hydrocarbon content Correct answer.
  2. They have higher toxicity than CFC refrigerants
  3. They operate only at sub-atmospheric pressure
  4. They contain nitrogen as a pressurizing agent

Explanation

A2L denotes lower flammability, and many low-GWP refrigerants achieve their reduced climate impact through HFOs or hydrocarbons that are mildly flammable. The classification reflects flammability, not added nitrogen or increased toxicity. Sub-atmospheric operation is a separate design characteristic.

Question 5Low GWP Refrigerant (LGWP)

What does the GWP value of a refrigerant represent?

  1. The mass of refrigerant released per year by a typical system
  2. The ozone depletion potential relative to CFC-11
  3. The energy efficiency ratio of the refrigerant in a standard cycle
  4. The relative climate impact of one kilogram compared with one kilogram of carbon dioxide over a defined time horizon Correct answer.

Explanation

GWP expresses the radiative forcing of a gas relative to carbon dioxide over a specified integration period, usually 100 years. It is a mass-based relative measure, not an annual leak rate. ODP and efficiency ratio are separate metrics.

Question 6Low GWP Refrigerant (LGWP)

A service technician is recovering refrigerant from a system charged with an A2L refrigerant. Which practice is required to manage the flammability risk?

  1. Increase the charge size beyond the nameplate limit
  2. Purge the system with oxygen before opening it
  3. Use recovery equipment rated for A2L refrigerants and eliminate ignition sources Correct answer.
  4. Vent the charge to the atmosphere before brazing

Explanation

A2L refrigerants require recovery equipment listed for flammable refrigerants and control of ignition sources during service. Purging with oxygen creates a serious fire and explosion hazard. Venting is prohibited and does not address flammability.

Question 7Low GWP Refrigerant (LGWP)

Which of the following is the primary regulatory driver for the transition to low-GWP refrigerants in the United States?

  1. The Montreal Protocol's HCFC phase-out schedule
  2. The National Electrical Code's grounding requirements
  3. The AIM Act's technology transition and refrigerant management provisions Correct answer.
  4. The Clean Water Act's discharge permits

Explanation

The AIM Act authorizes EPA to phasedown HFC production and consumption and to set technology transition rules favoring low-GWP refrigerants. The Montreal Protocol HCFC phase-out addressed ozone depletion, not HFC GWP. Water and electrical codes do not govern refrigerant selection.

Question 8Low GWP Refrigerant (LGWP)

Which term describes the total CO2-equivalent emissions of a refrigerant over its full lifecycle, including production, use, and end-of-life?

  1. Ozone depletion potential
  2. Global warming potential
  3. Carbon intensity rating
  4. Total equivalent warming impact Correct answer.

Explanation

Total equivalent warming impact, or TEWI, combines direct refrigerant emissions with indirect emissions from energy consumption over the equipment lifecycle. GWP is only one input to that calculation. ODP and carbon intensity rating are different metrics.

Question 9Low GWP Refrigerant (LGWP)

A contractor must select a low-GWP refrigerant for a new commercial refrigeration rack. Which factor most directly limits the maximum charge permitted in an occupied space?

  1. The color of the service valves
  2. The compressor's displacement
  3. The refrigerant's ODP value
  4. The refrigerant's A2L flammability class and the room volume Correct answer.

Explanation

For A2L refrigerants, standards such as ASHRAE 15 and UL 60335-2-89 set charge limits based on flammability class and occupied space volume. ODP, compressor displacement, and valve color do not govern charge limits. The lower flammability limit drives the allowable concentration calculation.

Question 10Low GWP Refrigerant (LGWP)

Why is R-744 (carbon dioxide) considered a low-GWP refrigerant even though it is a greenhouse gas?

  1. It is destroyed by the atmosphere within one year
  2. Its GWP is defined as 1, so it is the reference baseline Correct answer.
  3. It is not regulated because it is naturally occurring
  4. It has zero ODP and is therefore exempt from GWP rules

Explanation

Carbon dioxide is the reference gas for GWP, assigned a value of 1, so any refrigerant with a GWP near 1 is effectively at the baseline. Its climate impact per kilogram is therefore minimal compared with HFCs. Natural occurrence and ODP do not by themselves establish low GWP.

Question 11Low GWP Refrigerant (LGWP)

A system using R-454B requires a leak detection system. What is the primary reason for this requirement?

  1. To measure the ozone depletion potential of the charge
  2. To detect the mildly flammable refrigerant before concentrations reach hazardous levels Correct answer.
  3. To confirm the refrigerant is not R-410A
  4. To verify the compressor oil level

Explanation

Leak detection for A2L refrigerants is intended to alarm before the concentration reaches a fraction of the lower flammability limit in an occupied space. It is a flammability safeguard, not an ODP measurement or oil-level check. Refrigerant identification is a separate procedure.

Question 12Low GWP Refrigerant (LGWP)

Which statement correctly distinguishes R-32 from R-410A in a low-GWP retrofit context?

  1. R-32 is a blend and R-410A is a single component
  2. R-32 is A1 and R-410A is A2L
  3. Both have identical GWP but different ODP
  4. R-32 has a lower GWP and is A2L, while R-410A is A1 and higher GWP Correct answer.

Explanation

R-32 is a single-component HFC with a GWP near 675 and an A2L classification, while R-410A is an A1 blend with a GWP near 2088. The safety class and GWP both differ. R-410A is a blend and R-32 is not.

Question 13Low GWP Refrigerant (LGWP)

In a supermarket using a transcritical CO2 booster system, why is the high-side pressure typically much higher than in an HFC system?

  1. CO2 requires a larger oil charge
  2. CO2 has a high ozone depletion potential
  3. CO2 cannot be compressed above 200 psig
  4. CO2 has a low critical temperature, so heat rejection occurs above the critical point Correct answer.

Explanation

CO2 has a critical temperature near 31 degrees Celsius, so in warm climates the system rejects heat in the supercritical region at pressures well above HFC condensing pressures. This is a thermodynamic property, not an ODP or oil issue. CO2 systems routinely operate above 200 psig.

Question 14Low GWP Refrigerant (LGWP)

A technician must braze a joint on a line set containing an A2L refrigerant. Which precaution is most important?

  1. Braze while the system is at full charge to keep oil flowing
  2. Use an open flame to verify the leak point
  3. Purge the line with nitrogen and remove or isolate the refrigerant charge Correct answer.
  4. Increase the acetylene pressure to speed the joint

Explanation

Brazing requires the charge to be removed or isolated and the line purged with nitrogen to prevent combustion of residual flammable refrigerant and oxidation inside the tubing. Higher acetylene pressure and brazing at full charge increase fire risk. An open flame must never be used to locate leaks.

Question 15Low GWP Refrigerant (LGWP)

Which refrigerant blend is designed as a drop-in replacement with reduced GWP for R-404A in commercial refrigeration and has a GWP near 1400?

  1. R-290
  2. R-1234yf
  3. R-717
  4. R-448A Correct answer.

Explanation

R-448A is an HFC/HFO blend with a GWP near 1400, substantially lower than R-404A's GWP near 3922, and is used as a retrofit option in commercial refrigeration. R-1234yf and R-290 have far lower GWPs and different applications, and R-717 is ammonia.

Question 16Low GWP Refrigerant (LGWP)

What is the primary purpose of the EPA's refrigerant management rule for HFCs?

  1. To ban all HFC refrigerants immediately
  2. To mandate the use of R-22 in new equipment
  3. To require leak repair, recordkeeping, and certified technicians for HFC systems above a charge threshold Correct answer.
  4. To set the electrical grounding requirements for condensers

Explanation

The refrigerant management rule extends leak repair and recordkeeping requirements to HFC systems above a charge threshold and requires certified technicians. It does not ban all HFCs immediately or mandate R-22. Grounding is governed by electrical codes.

Question 17Low GWP Refrigerant (LGWP)

Which property of R-290 (propane) makes it attractive as a low-GWP refrigerant despite its A3 classification?

  1. It is chemically identical to R-22
  2. Its GWP is near 3 and it has excellent thermodynamic efficiency Correct answer.
  3. Its GWP is near 2000 but it is nonflammable
  4. It has a high ODP that offsets its GWP

Explanation

R-290 has a GWP near 3 and favorable thermodynamic properties, which is why it is used in small sealed systems despite the A3 flammability classification. It has zero ODP and is not chemically identical to R-22. Its low GWP, not a high one, is the attraction.

Question 18Low GWP Refrigerant (LGWP)

A building owner wants to reduce TEWI without changing the refrigerant. Which measure most directly reduces the indirect portion of TEWI?

  1. Improving system energy efficiency and reducing run time Correct answer.
  2. Adding a second compressor of the same efficiency
  3. Increasing the refrigerant charge
  4. Shortening the maintenance interval for filters only

Explanation

The indirect portion of TEWI is driven by the energy consumed over the equipment life, so efficiency improvements and reduced run time lower it most directly. Increasing charge raises the direct portion, and adding an equally efficient compressor does not improve overall efficiency.

Question 19Low GWP Refrigerant (LGWP)

Which factor most affects the flammability risk of an A2L refrigerant in a occupied space?

  1. The compressor's nominal voltage
  2. The concentration reached relative to the lower flammability limit Correct answer.
  3. The color of the refrigerant cylinder
  4. The length of the liquid line

Explanation

Flammability risk depends on whether the concentration in air reaches the lower flammability limit, which is why charge limits and room volume matter. Cylinder color, voltage, and line length do not determine flammable concentration. Ventilation and charge size are the controlling variables.

Question 20Low GWP Refrigerant (LGWP)

Which statement best explains why HFO refrigerants such as R-1234yf have very low GWP values?

  1. They contain no fluorine atoms
  2. They are destroyed by the ozone layer
  3. They break down quickly in the atmosphere due to their carbon-fluorine double bond Correct answer.
  4. They are heavier than air and never reach the stratosphere

Explanation

HFOs contain a carbon-fluorine double bond that makes them reactive in the lower atmosphere, giving them short atmospheric lifetimes and very low GWP values. They do contain fluorine, and their low GWP results from rapid breakdown rather than from being destroyed by ozone.

Question 21Low GWP Refrigerant (LGWP)

When retrofitting an R-410A system to a lower-GWP A2L blend, which step is most critical before charging the new refrigerant?

  1. Confirm compatibility of the lubricant, seals, and expansion device with the new blend Correct answer.
  2. Increase the charge by 50 percent to compensate for the lower GWP
  3. Reuse the existing filter drier without inspection
  4. Remove the leak detection system to avoid nuisance alarms

Explanation

A retrofit requires verifying that the lubricant, elastomers, and metering device are compatible with the new blend, because the new refrigerant may have different solubility and pressure characteristics. Charge is set by weight per the nameplate, not by GWP. Leak detection must be retained or upgraded.

Question 22Low GWP Refrigerant (LGWP)

A technician calculates that a system with a 10 kg charge of a refrigerant with GWP 675 leaks 5 percent of its charge per year. What is the approximate annual CO2-equivalent leakage?

  1. About 68 kg CO2e
  2. About 33.8 kg CO2e
  3. About 338 kg CO2e Correct answer.
  4. About 6750 kg CO2e

Explanation

The leaked mass is 10 kg times 0.05, or 0.5 kg per year. Multiplying by the GWP of 675 gives about 338 kg CO2e per year. The other values result from omitting the leak fraction or misplacing the decimal.

Question 23Low GWP Refrigerant (LGWP)

A designer must choose between R-454B and R-32 for a packaged rooftop unit. Which combination of factors most strongly favors R-32 in this application?

  1. Lower GWP and single-component composition that simplifies charging and recycling Correct answer.
  2. Higher GWP and A1 classification
  3. Greater ozone depletion potential
  4. Higher toxicity classification

Explanation

R-32 has a GWP near 675 and is a single component, which simplifies charging, recycling, and fractionation concerns compared with a blend. It is A2L, not A1, and has zero ODP. Its toxicity classification is A, not B.

Question 24Low GWP Refrigerant (LGWP)

Why does the fractionation behavior of a zeotropic blend such as R-454B matter during a leak and recharge?

  1. The lubricant becomes corrosive at low temperatures
  2. The leaked vapor may have a different composition than the liquid, so the remaining charge composition can shift Correct answer.
  3. The blend separates into flammable and nonflammable layers that cannot be mixed
  4. The GWP of the blend increases with pressure

Explanation

Zeotropic blends have components with different volatilities, so a vapor leak can remove a disproportionate share of the more volatile component and shift the composition of the remaining charge. This is why proper charging by liquid and full recovery are important. The blend does not form unmixable layers, and GWP does not rise with pressure.

Question 25Low GWP Refrigerant (LGWP)

An engineer is evaluating a cascade system that uses CO2 in the low-temperature stage and a low-GWP HFO blend in the high-temperature stage. What is the main reason for this configuration?

  1. To increase the ODP of the system
  2. To eliminate the need for any compressor
  3. To allow the use of R-22 in the high stage
  4. To keep the CO2 stage below its critical point while limiting the total charge of flammable refrigerant Correct answer.

Explanation

A cascade arrangement lets the CO2 low stage operate in a range where it can condense against the high-stage refrigerant, avoiding transcritical operation, while the high-stage charge of flammable refrigerant is kept small. Cascade systems still require compressors in both stages. ODP is not increased, and R-22 is not a low-GWP choice.

Question 26Low GWP Refrigerant (LGWP)

Which value is used as the reference baseline for expressing a refrigerant's GWP under the IPCC AR4 reporting convention used by many low-GWP regulations?

  1. The GWP of methane, defined as 1
  2. The GWP of sulfur hexafluoride, defined as 1
  3. The GWP of carbon dioxide, defined as 1 Correct answer.
  4. The GWP of R-134a, defined as 1

Explanation

GWP is a relative metric in which carbon dioxide is the reference gas and is assigned a value of 1 over a stated time horizon. Every other refrigerant's GWP expresses how much radiative forcing it produces compared with the same mass of CO2. Reporting conventions specify which assessment report and time horizon were used, because values shift between AR4, AR5, and AR6.

Question 27Low GWP Refrigerant (LGWP)

A refrigerant is described as having a GWP of 150 under AR4. What does this number mean?

  1. The refrigerant can reduce a system's energy use by 150 percent
  2. One kilogram of the refrigerant destroys 150 times more ozone than CFC-11
  3. One kilogram of the refrigerant has the same 100-year climate impact as 150 kilograms of CO2 Correct answer.
  4. The refrigerant boils at 150 degrees below zero on the Celsius scale

Explanation

GWP compares the integrated radiative forcing of a unit mass of a gas with the same mass of CO2 over a chosen horizon, commonly 100 years. A value of 150 therefore means each kilogram released is equivalent to 150 kilograms of CO2. GWP says nothing about ozone depletion, boiling point, or efficiency.

Question 28Low GWP Refrigerant (LGWP)

Which pairing of refrigerant and classification is correct for a low-GWP refrigerant widely used in new light commercial equipment?

  1. R-454B, classified A2L Correct answer.
  2. R-410A, classified A1 with a GWP near 200
  3. R-404A, classified A1 with a GWP near 675
  4. R-22, classified A2L with a GWP near 1

Explanation

R-454B is an A2L blend with a GWP around 466 under AR4 and is used in new packaged and split equipment. Its mildly flammable classification drives charge limits and mitigation requirements. The other pairings misstate either the safety class or the approximate GWP.

Question 29Low GWP Refrigerant (LGWP)

Under ASHRAE Standard 34, what does the '2L' portion of an A2L classification indicate?

  1. Lower flammability and low burning velocity compared with A2 and A3 refrigerants Correct answer.
  2. Lower toxicity than A1 refrigerants in occupied spaces
  3. Lower GWP than 150 under the AR4 convention
  4. Lower operating pressure than A1 refrigerants

Explanation

The 2L subclass was created for refrigerants that are flammable but burn slowly, with a maximum burning velocity at or below 10 cm/s. This lower burning velocity is what allows larger charge limits than A3 refrigerants in occupied spaces. Toxicity, GWP, and pressure are not part of the 2L designation.

Question 30Low GWP Refrigerant (LGWP)

Which refrigerant has a GWP of 1 by definition and is therefore excluded from HFC phase-down accounting?

  1. R-452B
  2. R-32
  3. R-1234yf
  4. R-744 (carbon dioxide) Correct answer.

Explanation

Carbon dioxide is the reference gas for GWP and is assigned a value of 1, and it is not an HFC or HFO controlled by the HFC phase-down schedule. R-744 is therefore attractive for low-GWP systems despite high operating pressures. The other substances are fluorinated refrigerants with GWPs above 1 and are counted under HFC controls.

Question 31Low GWP Refrigerant (LGWP)

Which document or program is the primary source of approved refrigerant substitutes and their use conditions in the United States?

  1. EPA's Significant New Alternatives Policy substitute list under Section 612 Correct answer.
  2. ASHRAE Standard 15 equipment room ventilation tables
  3. The Montreal Protocol Article 5 country schedule
  4. AHRI Standard 700 refrigerant purity specifications

Explanation

The SNAP program evaluates and lists acceptable refrigerant substitutes along with any use conditions, such as charge limits or required mitigation. Technicians and designers check the SNAP list to confirm a refrigerant is legal for a given end use. The other documents address ventilation, purity, or international phase-out timing rather than substitute approval.

Question 32Low GWP Refrigerant (LGWP)

Why must a technician use a recovery machine rated for A2L refrigerants when servicing a low-GWP blend?

  1. Recovery is unnecessary because A2L refrigerants have no GWP
  2. Only recovery equipment built before 2010 can process blends
  3. The equipment must be evaluated for use with flammable refrigerants to control ignition risk Correct answer.
  4. A2L refrigerants cannot be recovered and must be vented

Explanation

Recovery equipment used with flammable refrigerants must be listed or evaluated for that service so that motors, switches, and connections do not become ignition sources. Standard recovery practice still applies, including recovery rather than venting. A2L refrigerants have nonzero GWP and are regulated.

Question 33Low GWP Refrigerant (LGWP)

Which leak-detection approach is generally acceptable for finding a small leak in a system charged with an A2L refrigerant?

  1. An open flame halide torch
  2. A pressure gauge reading taken while the system is off
  3. An electronic leak detector rated for the refrigerant's flammability class Correct answer.
  4. A soap bubble test performed only after venting the charge

Explanation

Electronic detectors must be rated for the refrigerant and its safety group so that the sensor responds correctly and the instrument is safe to use around a flammable gas. Halide torches are prohibited with flammable refrigerants because they introduce an ignition source. Bubble testing is useful but should not require venting the charge.

Question 34Low GWP Refrigerant (LGWP)

A technician is charging an A2L blend into a system in a small mechanical room. Which practice best reduces ignition risk during the procedure?

  1. Charge as a liquid into the high side after evacuating and confirming no ignition sources are present Correct answer.
  2. Warm the cylinder with an open flame to speed transfer
  3. Purge the lines with air before opening the system
  4. Charge as vapor into the low side while the room's gas furnace is running

Explanation

Charging liquid into the high side after evacuation is standard for blends and avoids fractionation, and eliminating ignition sources during charging is essential with a flammable refrigerant. Air purging creates a flammable or reactive mixture and is never acceptable. Open flames near a refrigerant cylinder are prohibited.

Question 35Low GWP Refrigerant (LGWP)

A zeotropic low-GWP blend leaks from a system and is later recharged without recovering the remaining charge. What is the main consequence?

  1. The refrigerant's GWP drops to zero once it has leaked
  2. The remaining liquid has a shifted composition, so the system charge may not match design performance Correct answer.
  3. The blend separates permanently into two immiscible liquids
  4. The lubricant becomes non-conductive and must be replaced

Explanation

Zeotropic blends change composition when they leak because components leave at different rates, so the liquid left behind is richer in the less volatile components. Topping off without full recovery leaves an unknown mixture and unpredictable performance. The correct practice is to recover, evacuate, and recharge with virgin refrigerant.

Question 36Low GWP Refrigerant (LGWP)

A designer is comparing R-454B and R-32 for a new packaged unit. Which statement about their composition is accurate?

  1. R-454B is a blend of R-32 and R-1234yf, while R-32 is a single-component refrigerant Correct answer.
  2. Both are pure HFOs with identical composition
  3. Both are azeotropic blends of R-32 and R-125
  4. R-454B is a single component, while R-32 is a ternary blend

Explanation

R-454B is a zeotropic blend of roughly 69 percent R-32 and 31 percent R-1234yf, whereas R-32 is a single-compound HFC. This difference means R-454B has glide and fractionation behavior while R-32 does not. Both are A2L, but their composition and handling differ.

Question 37Low GWP Refrigerant (LGWP)

Why does a transcritical CO2 booster system require high-strength piping and components compared with an HFC system?

  1. The system operates above the critical pressure of CO2, so the high side sees very high pressures Correct answer.
  2. CO2 reacts with copper tubing and must be piped in steel only
  3. CO2 systems use a flammable refrigerant requiring heavier walls
  4. The low side operates in a vacuum at all ambient conditions

Explanation

Above about 31 degrees Celsius ambient, a transcritical CO2 system runs above the critical pressure of roughly 7.4 MPa, so the high side is exposed to pressures far above typical HFC condensing pressures. Components and piping must be rated for that pressure. Copper is widely used in CO2 systems, and CO2 is nonflammable.

Question 38Low GWP Refrigerant (LGWP)

A technician must identify the correct cylinder for an A2L refrigerant before charging. Which marking should be present?

  1. A label stating the refrigerant is nonflammable and exempt from transport rules
  2. Only the refrigerant number, because safety markings are optional
  3. The refrigerant number and safety group, with a DOT classification reflecting the flammable gas hazard Correct answer.
  4. An ozone depletion warning label required for all HFCs

Explanation

Refrigerant cylinders must be identified by refrigerant number and carry transport markings that reflect the hazard class, which for A2L refrigerants includes a flammable gas classification. Correct identification prevents cross-charging and ensures the cylinder is handled under the right rules. HFCs do not carry ozone depletion labels because their ODP is zero.

Question 39Low GWP Refrigerant (LGWP)

What is the effect of refrigerant glide on the evaporator of a system using a zeotropic low-GWP blend?

  1. The evaporator pressure stays constant while the temperature drops to absolute zero
  2. The boiling temperature changes as the blend composition shifts across the coil Correct answer.
  3. Glide eliminates the need for a thermostatic expansion valve
  4. The refrigerant condenses at a single fixed temperature regardless of composition

Explanation

Glide is the temperature difference between the bubble point and dew point of a zeotropic blend at a given pressure. As the blend boils in the evaporator, the more volatile component leaves first, so the boiling temperature rises across the coil. Designers account for glide when setting superheat and selecting components.

Question 40Low GWP Refrigerant (LGWP)

A facility must comply with refrigerant management requirements for an HFC blend. Which record-keeping element is typically required for appliances above the applicable charge threshold?

  1. A copy of the building's fire sprinkler inspection
  2. An annual efficiency rating from the equipment manufacturer
  3. A daily log of outdoor ambient temperature
  4. Documentation of refrigerant purchases, additions, and recovery during service Correct answer.

Explanation

Refrigerant management rules require owners and operators to track refrigerant quantities, including purchases, additions, and recovery, so that leak rates can be calculated and repairs verified. These records support leak-rate compliance and disposal documentation. Ambient logs, sprinkler records, and efficiency ratings are unrelated.

Question 41Low GWP Refrigerant (LGWP)

An owner wants to lower the climate impact of an existing R-410A rooftop unit without replacing it. Which action most directly reduces the refrigerant's contribution to TEWI?

  1. Repairing leaks promptly and verifying the charge to minimize refrigerant loss Correct answer.
  2. Increasing the refrigerant charge to improve part-load capacity
  3. Switching the thermostat fan setting to continuous operation
  4. Adding a second compressor to the circuit

Explanation

The direct refrigerant portion of TEWI depends on how much refrigerant escapes over the equipment's life, so leak repair and charge verification reduce it most directly. Increasing charge or adding components can raise refrigerant quantity without addressing leakage. Fan settings affect energy use, not refrigerant emissions.

Question 42Low GWP Refrigerant (LGWP)

Which statement correctly describes the relationship between ODP and GWP for low-GWP HFO refrigerants such as R-1234ze?

  1. They have high ODP but low GWP
  2. They have zero ODP and a GWP well below 1 under AR4 Correct answer.
  3. They have ODP and GWP values equal to those of R-12
  4. They have zero GWP but significant ODP

Explanation

HFOs contain a carbon-carbon double bond that makes them short-lived in the atmosphere, so their 100-year GWP is very small, often below 1. They contain no chlorine or bromine and therefore have zero ODP. ODP and GWP are independent metrics.

Question 43Low GWP Refrigerant (LGWP)

A technician is preparing to evacuate a system that will be charged with an A2L blend. Which step is most important before starting the vacuum pump?

  1. Set the recovery unit to vent to the room
  2. Open the refrigerant cylinder to purge air from the manifold
  3. Disconnect the vacuum gauge to speed evacuation
  4. Confirm the pump and hoses are rated for the refrigerant and that no ignition sources are nearby Correct answer.

Explanation

Evacuation equipment and hoses must be compatible with the refrigerant, and the work area must be free of ignition sources when a flammable refrigerant is present. Opening a cylinder or venting refrigerant defeats the purpose of evacuation and is unsafe. Gauges must remain connected to verify the vacuum level.

Question 44Low GWP Refrigerant (LGWP)

Which factor most strongly determines the allowable charge of an A2L refrigerant in an occupied space under safety standards?

  1. The room volume and the refrigerant's lower flammability limit Correct answer.
  2. The age of the compressor
  3. The refrigerant's boiling point at sea level
  4. The color of the equipment cabinet

Explanation

Allowable charge is based on the refrigerant's flammability characteristics, especially its lower flammability limit, combined with the volume of the occupied space and ventilation. These inputs determine the maximum concentration that could occur after a leak. Cabinet color, boiling point, and compressor age do not enter the calculation.

Question 45Low GWP Refrigerant (LGWP)

A technician recovers a low-GWP blend and must prepare it for reuse. Which practice supports the refrigerant's suitability for reclamation?

  1. Recover into a dedicated, properly evacuated cylinder and record the refrigerant identity and quantity Correct answer.
  2. Mix recovered refrigerant from different systems into one cylinder
  3. Recover liquid and vapor together without labeling the cylinder
  4. Store the recovered refrigerant in an unmarked container

Explanation

Reclamation requires refrigerant of known identity and composition, so recovered gas must go into a dedicated, evacuated, labeled cylinder with documentation of the source and quantity. Mixing refrigerants makes reclamation impossible and may render the batch waste. Unmarked containers are a compliance and safety violation.

Question 46Low GWP Refrigerant (LGWP)

An engineer compares the direct emissions of two systems over 15 years. System A holds 8 kg of a refrigerant with GWP 675, and System B holds 8 kg of a refrigerant with GWP 2,088. Assuming both leak 3 percent of charge per year, what is the approximate difference in direct CO2-equivalent emissions?

  1. About 5,090 kg CO2e more for System B Correct answer.
  2. About 340 kg CO2e more for System B
  3. About 16,700 kg CO2e more for System B
  4. About 1,130 kg CO2e more for System B

Explanation

Annual leakage is 0.24 kg for each system. Over 15 years, System A emits 3.6 kg times 675, or about 2,430 kg CO2e, while System B emits 3.6 kg times 2,088, or about 7,517 kg CO2e. The difference is roughly 5,090 kg CO2e, so the higher-GWP refrigerant dominates the direct impact.

Question 47Low GWP Refrigerant (LGWP)

A supermarket considers replacing an R-404A rack with a system using R-448A. Which outcome is expected if charge size and leak rate stay the same?

  1. Direct emissions fall to zero because R-448A is an HFO
  2. Direct emissions rise because R-448A has a higher GWP than R-404A
  3. Direct CO2-equivalent emissions fall substantially because R-448A has a much lower GWP than R-404A Correct answer.
  4. Direct emissions are unchanged because both refrigerants are A1

Explanation

R-404A has a GWP near 3,922, while R-448A is around 1,387, so the same mass leaked produces far fewer CO2-equivalent emissions. The safety class and blend status do not determine the direct emissions. R-448A still contains HFCs, so emissions are reduced but not eliminated.

Question 48Low GWP Refrigerant (LGWP)

A technician finds that a system charged with a zeotropic blend has a liquid-line temperature that does not match the expected bubble point. Which explanation is most consistent with fractionation?

  1. The refrigerant has converted entirely into an azeotrope
  2. The lubricant has changed the refrigerant's GWP
  3. A previous leak removed lighter components, so the remaining blend has a different composition Correct answer.
  4. The system pressure has dropped below absolute zero

Explanation

When a zeotropic blend leaks as a vapor, the more volatile components escape preferentially, leaving a liquid with a shifted composition and a different bubble point. This is why a system that lost charge must be fully recovered and recharged rather than topped off. Blends do not convert into azeotropes, and absolute zero is not attainable.

Question 49Low GWP Refrigerant (LGWP)

A designer evaluates a cascade system using CO2 in the low-temperature stage and an HFO blend in the high-temperature stage. Which statement best explains the climate benefit?

  1. CO2 has a negative GWP that offsets the HFO blend's emissions
  2. The cascade arrangement eliminates all refrigerant leakage
  3. The HFO blend has a GWP higher than R-404A, which is offset by CO2
  4. CO2 has a GWP of 1 and the HFO blend has a low GWP, so direct emissions from both stages are small Correct answer.

Explanation

Both stages use refrigerants with low direct climate impact: CO2 is the GWP reference at 1, and HFO blends have GWPs far below the HFCs they replace. Cascade designs also improve efficiency by matching each refrigerant to its temperature range. No arrangement eliminates leakage entirely, and CO2 does not have a negative GWP.

Question 50Low GWP Refrigerant (LGWP)

A building owner asks why a low-GWP refrigerant alone may not reduce total climate impact. Which explanation is most accurate?

  1. Refrigerant GWP is measured only at the moment of manufacture
  2. Direct emissions are excluded from TEWI calculations
  3. Low-GWP refrigerants always increase energy use by a fixed percentage
  4. Indirect emissions from energy use can outweigh the direct refrigerant emissions over the equipment life Correct answer.

Explanation

TEWI combines direct refrigerant emissions with indirect emissions from the energy consumed over the equipment's life. In efficient or heavily used systems, the indirect portion can dominate, so refrigerant choice must be paired with good efficiency and leak control. Low-GWP fluids do not inherently impose a fixed efficiency penalty.