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HVAC Excellence AC practice questions

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Question 1Employment Ready

A technician is preparing to braze a refrigerant line set. Which safety precaution is most important before applying heat to the joint?

  1. Purge the system with nitrogen and ensure the area is ventilated Correct answer.
  2. Loosen all flare nuts to relieve pressure
  3. Fill the lines with compressed air to displace oil
  4. Increase system pressure to check for leaks

Explanation

Brazing heats copper and any residual oil or refrigerant, so the line must be purged with dry nitrogen and the area ventilated to prevent combustion or toxic decomposition products. Compressed air and refrigerant mixtures can be flammable or form acids, so they are never used for purging or pressure testing.

Question 2Employment Ready

Which personal protective equipment is required when working with refrigerant that can cause frostbite on skin contact?

  1. Ear plugs and a hard hat
  2. Safety glasses and insulated gloves Correct answer.
  3. Cotton work gloves only
  4. A dust mask and apron

Explanation

Liquid refrigerant boils at very low temperature and can freeze tissue instantly, so insulated gloves and eye protection are the minimum protection for handling refrigerant. Cotton gloves do not insulate and a dust mask offers no protection against cold burns or splashes.

Question 3Employment Ready

Under EPA Section 608 rules, a technician recovering refrigerant from a small appliance must use equipment certified to what recovery level?

  1. 80 percent recovery Correct answer.
  2. 90 percent recovery
  3. 95 percent recovery
  4. 100 percent recovery

Explanation

Small appliances and most systems manufactured before November 15, 1993 require recovery to 80 percent of the charge, while other categories have higher levels. The 90 and 95 percent levels apply to different equipment categories, not small appliances.

Question 4Employment Ready

A technician must dispose of a recovered refrigerant that is a CFC. Which statement describes the legal handling?

  1. It may be vented outdoors if the quantity is small
  2. It must be reclaimed or destroyed by an EPA-certified facility Correct answer.
  3. It may be burned in an open container on site
  4. It may be discharged into a drain with water

Explanation

The Clean Air Act prohibits venting ozone-depleting refrigerants, so recovered CFCs must be sent for reclamation or destruction by an EPA-certified facility. Venting, open burning, and draining all release the refrigerant to the atmosphere and violate the rule.

Question 5Employment Ready

What is the primary purpose of the Clean Air Act Section 608 certification for technicians who service refrigerants?

  1. To license technicians to install electrical panels
  2. To ensure technicians handle ozone-depleting refrigerants without releasing them Correct answer.
  3. To certify technicians to weld pressure vessels
  4. To permit technicians to sell refrigerant without a license

Explanation

Section 608 certification demonstrates that a technician understands how to handle refrigerants to minimize atmospheric release and comply with venting prohibitions. It does not cover electrical licensing, welding certification, or refrigerant sales authority.

Question 6Employment Ready

A technician is asked to identify hazards on a job site before starting work. This practice is best described as performing a:

  1. Refrigerant charge check
  2. Combustion analysis
  3. Load calculation
  4. Job hazard analysis Correct answer.

Explanation

A job hazard analysis identifies the tasks, hazards, and controls before work begins so that the crew can plan safe procedures. Load calculations, charge checks, and combustion analysis are technical measurements, not pre-task hazard planning.

Question 7Employment Ready

Which tool is required to safely measure the voltage present at a disconnect before servicing an air handler?

  1. A vacuum gauge
  2. A clamp-on ammeter only
  3. A refrigerant gauge manifold
  4. A CAT III or better rated digital multimeter Correct answer.

Explanation

Voltage measurements on distribution equipment require a meter rated for the available fault current and transient overvoltage, such as CAT III. Ammeters, manifolds, and vacuum gauges do not measure voltage and are not rated for that exposure.

Question 8Employment Ready

A technician must work on an electrical circuit that cannot be de-energized. Which practice best reduces the risk of shock?

  1. Work quickly to minimize exposure time
  2. Remove the equipment ground to prevent nuisance trips
  3. Bypass the disconnect to speed servicing
  4. Use insulated tools and stand on an insulating mat while keeping one hand free Correct answer.

Explanation

When energized work is unavoidable, insulated tools, an insulating mat, and the one-hand rule reduce the chance of current passing through the body. Speed, removing grounds, and bypassing disconnects increase the hazard rather than control it.

Question 9Employment Ready

A technician is using a ladder to access a rooftop unit. Which practice follows safe ladder use?

  1. Maintain three points of contact and face the ladder while climbing Correct answer.
  2. Lean the ladder against a flexible gutter
  3. Stand on the top cap to reach higher
  4. Carry tools in both hands while climbing

Explanation

Three points of contact and facing the ladder keep the body stable and centered during climbing. Carrying tools in both hands, leaning on a weak support, and standing on the top cap all increase the risk of a fall.

Question 10Employment Ready

Before entering a mechanical room to service a gas-fired furnace, a technician notices a strong odor of gas. What is the first action?

  1. Leave the area and shut off the gas supply from a safe location Correct answer.
  2. Open the flue damper and continue working
  3. Light a match to locate the leak
  4. Start the furnace to burn off the gas

Explanation

A gas odor indicates a potentially explosive atmosphere, so the area should be evacuated and the gas supply shut off remotely before any ignition source or work continues. Ignition sources and operating equipment must be avoided until the space is proven safe.

Question 11Employment Ready

A technician is brazing near a combustible wall. Which control best prevents a fire?

  1. Use a heat shield and keep a fire extinguisher within reach Correct answer.
  2. Open nearby windows to dilute the flame
  3. Work faster to reduce heat exposure
  4. Wet the wall once before starting

Explanation

A heat shield blocks radiant heat from the torch and a nearby extinguisher allows immediate response to a fire. Wetting the wall once or opening windows does not reliably prevent ignition of combustible materials.

Question 12Employment Ready

Which condition indicates that a recovery cylinder is overfilled and must be corrected before continuing?

  1. The cylinder valve is fully open
  2. The cylinder feels cool to the touch
  3. The cylinder has a recent hydrostatic test date
  4. The cylinder is filled to more than 80 percent of its capacity by weight Correct answer.

Explanation

Recovery cylinders must not be filled beyond 80 percent by weight to allow for liquid expansion and prevent hydrostatic rupture. A cool cylinder, an open valve, and a current test date are normal or acceptable conditions.

Question 13Employment Ready

A technician must lift a heavy compressor out of a rooftop unit. Which technique best reduces the risk of back injury?

  1. Lift quickly with arms extended
  2. Ask a helper to pull the compressor from above
  3. Use a mechanical lift and keep the load close to the body Correct answer.
  4. Bend at the waist and twist while lifting

Explanation

Mechanical lifting equipment and keeping the load close reduce the forces on the spine. Bending and twisting, lifting with extended arms, and pulling from above all increase spinal loading and the chance of injury.

Question 14Employment Ready

A technician is preparing to evacuate a system and must choose a vacuum pump. Which specification most directly affects how quickly the required vacuum can be reached?

  1. The pump's free-air displacement rating Correct answer.
  2. The brand of the vacuum gauge
  3. The color of the pump housing
  4. The length of the power cord

Explanation

Free-air displacement, often stated in cubic feet per minute, determines how much vapor the pump can move and therefore how quickly the target vacuum is reached. Housing color, cord length, and gauge brand do not determine pumping speed.

Question 15Employment Ready

During evacuation, a technician notices that the vacuum reading rises quickly after the pump is valved off. What does this most likely indicate?

  1. Moisture or a leak is present in the system Correct answer.
  2. The gauge is reading in the wrong units
  3. The system is properly dehydrated
  4. The pump is too large for the system

Explanation

A rapid rise in pressure after isolation indicates that something is entering the system, either through a leak or from moisture boiling off internal surfaces. A properly dehydrated, leak-free system holds vacuum for a sustained period.

Question 16Employment Ready

A technician is checking a nitrogen pressure test on a new line set. The gauge holds steady for the first hour and then drops slightly overnight. What is the most appropriate response?

  1. Investigate for a leak, since a drop indicates a loss of pressure Correct answer.
  2. Increase the pressure to stop the drop
  3. Assume the drop is normal and charge the system
  4. Add refrigerant and proceed with startup

Explanation

A pressure test must hold steady; a drop indicates a leak or a temperature-related change that must be explained before charging. Adding refrigerant or assuming the drop is normal can hide a leak and lead to premature failure.

Question 17Employment Ready

Which refrigerant is classified as A1 by ASHRAE Standard 34?

  1. R-123
  2. R-410A Correct answer.
  3. R-290 (propane)
  4. R-717 (ammonia)

Explanation

ASHRAE 34 assigns R-410A an A1 classification, meaning low toxicity and no flame propagation. Ammonia is B2L, R-123 is B1, and propane is A3, so those are not A1.

Question 18Employment Ready

A technician is selecting a replacement refrigerant and must consider the environmental impact of a leak. Which value expresses a refrigerant's contribution to global warming relative to carbon dioxide?

  1. Global warming potential Correct answer.
  2. Specific heat
  3. Critical temperature
  4. Ozone depletion potential

Explanation

Global warming potential compares the radiative forcing of a gas over a set horizon to that of carbon dioxide. Ozone depletion potential measures stratospheric ozone destruction, while critical temperature and specific heat are thermodynamic properties.

Question 19Employment Ready

A technician reads a Material Safety Data Sheet for a refrigerant. Which information is most useful for planning emergency response to a large release?

  1. The retail price of the cylinder
  2. The manufacturer's warranty terms
  3. The date the refrigerant was produced
  4. Exposure limits and required protective equipment Correct answer.

Explanation

Safety data sheets list exposure limits, health effects, and required protective equipment, which are the facts needed to plan emergency response. Price, warranty, and production date do not guide safe handling during a release.

Question 20Employment Ready

Which action is required before a technician disconnects refrigerant lines from a system?

  1. Recover the refrigerant to the required level Correct answer.
  2. Close the service valves and leave the charge in the lines
  3. Purge the system with compressed air
  4. Vent the charge to the atmosphere

Explanation

Refrigerant must be recovered to the required level before opening a circuit, since venting is prohibited and leaving the charge in disconnected lines risks a release. Compressed air must never be used to purge a refrigerant system.

Question 21Employment Ready

A technician is troubleshooting a system and must determine whether a compressor is energized. Which measurement is most direct?

  1. Temperature of the suction line
  2. Refrigerant pressure at the suction service valve
  3. Sound level of the compressor
  4. Voltage across the compressor contactor terminals Correct answer.

Explanation

Voltage at the contactor terminals directly shows whether power is being applied to the compressor circuit. Pressure, line temperature, and sound are indirect indicators that cannot confirm electrical energization.

Question 22Employment Ready

A technician finds that a capacitor reads significantly below its rated microfarad value. What is the most likely effect on the motor?

  1. The motor may fail to start or draw excessive current Correct answer.
  2. The motor will use less current
  3. The motor will run cooler than normal
  4. The motor speed will increase

Explanation

A weak capacitor reduces starting torque and can cause the motor to draw high current or fail to start, which may damage the winding. It does not improve cooling, increase speed, or reduce current draw.

Question 23Employment Ready

A technician is asked to verify that a unit is properly grounded before energizing it. Which test confirms the equipment grounding conductor is intact?

  1. Resistance across the run capacitor
  2. Voltage between line and neutral
  3. Current draw at the compressor
  4. Continuity between the equipment ground and the panel ground Correct answer.

Explanation

Continuity between the equipment grounding conductor and the panel ground confirms a low-impedance path back to the source. Line-to-neutral voltage, current draw, and capacitor resistance do not verify the grounding path.

Question 24Employment Ready

A technician must communicate a safety concern to a customer about a cracked heat exchanger. Which approach best protects both the customer and the technician?

  1. Ignore it if the unit still heats
  2. Repair it without informing the customer
  3. Quietly note it on the invoice without discussion
  4. Document the condition, explain the hazard, and recommend shutting down the unit Correct answer.

Explanation

A cracked heat exchanger can allow carbon monoxide into the living space, so the technician must document the finding, explain the hazard, and recommend shutdown until repair. Silent notes, unauthorized repairs, and ignoring the defect leave the customer exposed and create liability.

Question 25Employment Ready

A technician is training an apprentice on refrigerant cylinder handling. Which practice should the apprentice follow?

  1. Store cylinders near a open flame for warmth
  2. Store cylinders upright and secured against tipping Correct answer.
  3. Lay cylinders on their side in a hot truck
  4. Remove valve caps to speed connection

Explanation

Cylinders should be stored upright and secured so they cannot fall or roll, and they must be kept away from heat sources. Laying them in a hot truck, storing near flame, and removing valve caps all increase the risk of damage or release.

Question 26Employment Ready

A technician arrives at a service call and the dispatcher has already collected the customer's complaint, model number, and site address. Which action best describes the technician's first step in the service call procedure?

  1. Energize the unit to see whether the complaint reproduces
  2. Begin recovering refrigerant before confirming the unit model
  3. Ask the customer to sign off on the repair invoice
  4. Review the work order and gather the tools and test instruments needed for the reported symptom Correct answer.

Explanation

A professional service call begins with reviewing the work order so the technician understands the reported symptom, equipment type, and site conditions before arriving. That review drives tool and instrument selection and lets the technician plan a safe, efficient diagnosis. Signing an invoice and recovering refrigerant are later steps that require a confirmed diagnosis and customer authorization.

Question 27Employment Ready

A technician is completing a work order and must record the refrigerant charge added to a residential split system. Which practice best reflects industry documentation standards?

  1. Record the amount added, the refrigerant type, and the reason for the addition on the work order Correct answer.
  2. Note only the date and the customer's signature
  3. Estimate the charge from the suction line temperature and write a range
  4. Leave the charge blank because the office tracks refrigerant separately

Explanation

Federal refrigerant management rules and good business practice require recording the type and quantity of refrigerant added, along with why it was needed. That record supports leak-rate tracking and later troubleshooting. Vague estimates or blank entries defeat both compliance and future service accuracy.

Question 28Employment Ready

A technician must calculate the total cooling load for a small office before recommending a replacement system. Which practice is most consistent with ACCA Manual J methodology?

  1. Size the system to match the ductwork already installed
  2. Base the load on the building's construction, windows, orientation, and local design conditions Correct answer.
  3. Size the equipment from the existing unit's nameplate capacity
  4. Use a rule of thumb of one ton per 400 square feet of floor area

Explanation

Manual J is a room-by-room load calculation that accounts for envelope construction, fenestration, orientation, internal gains, infiltration, and local design temperatures. Matching existing equipment or applying square-foot rules of thumb ignores those variables and commonly produces oversized systems. Duct capacity is a separate consideration addressed after the load is known.

Question 29Employment Ready

A technician is preparing to braze a joint on a refrigerant line and must select the correct filler metal and flux practice. Which combination is correct for a typical copper-to-copper joint?

  1. Phosphorus-copper alloy with no separate flux Correct answer.
  2. Silver solder with borax flux only
  3. Low-temperature 50/50 tin-lead solder with acid flux
  4. Lead-free plumbing solder with rosin flux

Explanation

Copper-to-copper joints in refrigeration piping are normally brazed with a phosphorus-bearing copper alloy, which self-fluxes the copper and produces a strong joint at brazing temperature. Adding a separate flux is unnecessary and can leave corrosive residue inside the system. Tin-lead solders and plumbing solders lack the strength and temperature rating required for refrigerant piping.

Question 30Employment Ready

A technician is measuring superheat on a fixed-orifice air conditioning system to verify the charge. Which condition indicates the system is overcharged?

  1. Superheat below the manufacturer's target range at the same indoor and outdoor conditions Correct answer.
  2. Superheat within the target range with a clear sight glass
  3. Superheat above the target range with a normal suction pressure
  4. Superheat fluctuating slightly as the indoor fan cycles

Explanation

On a fixed-orifice system, low superheat at the specified indoor and outdoor conditions signals too much liquid refrigerant reaching the compressor, which is the overcharge condition. Superheat must be compared against the manufacturer's target for the measured conditions. High superheat instead points to an undercharge or a restriction.

Question 31Employment Ready

A technician is checking subcooling on a TXV system and finds it well above the manufacturer's target. Which conclusion is best supported?

  1. The system is likely undercharged and needs refrigerant added
  2. The condenser may be restricted or the system overcharged, so liquid is backing up Correct answer.
  3. The TXV is hunting and the reading should be ignored
  4. The compressor is short-cycling on the low-pressure control

Explanation

High subcooling means liquid refrigerant is stacking in the condenser, which can result from an overcharge, a condenser airflow restriction, or a liquid-line restriction. The technician should inspect the condenser coil and airflow before adjusting charge. Low subcooling, by contrast, typically indicates undercharge.

Question 32Employment Ready

A technician is diagnosing a PSC blower motor that hums but does not start. Which component should be tested first?

  1. The compressor contactor coil
  2. The thermostat's anticipator setting
  3. The run capacitor's microfarad rating Correct answer.
  4. The condensate float switch

Explanation

A humming PSC motor that will not start commonly has a failed run capacitor, so the capacitor should be checked against its rated microfarad value with a meter. A capacitor that reads far below rating cannot provide the phase shift needed for starting torque. The other listed components do not affect blower motor starting.

Question 33Employment Ready

A technician is troubleshooting a heat pump that heats poorly in cold weather while the outdoor unit runs continuously. Which measurement set best isolates whether the reversing valve or the defrost system is at fault?

  1. Thermostat setpoint versus room temperature
  2. Suction and liquid line temperatures at the outdoor unit during a forced defrost cycle Correct answer.
  3. Compressor amp draw at the disconnect
  4. Supply and return air temperatures only

Explanation

Forcing a defrost cycle and observing line temperatures shows whether the reversing valve shifts and whether the outdoor coil clears, separating valve faults from defrost control faults. Air temperature readings alone cannot distinguish the two causes. Amp draw and thermostat setpoint comparisons do not reveal valve position or defrost operation.

Question 34Employment Ready

A technician is installing a condensate drain for an air handler located in an attic. Which practice best protects the building from water damage?

  1. Install a primary drain with a trap and a secondary drain or float switch that shuts the unit down Correct answer.
  2. Slope the drain upward to the roof penetration
  3. Route the drain to the nearest wall cavity
  4. Omit the trap because the unit has a positive-pressure coil

Explanation

Attic air handlers require a trapped primary drain plus a secondary drain or float switch that stops the unit if the primary clogs. That redundancy prevents overflow into the ceiling structure. Draining into wall cavities, upward slope, or omitting the trap all invite water damage or drain failure.

Question 35Employment Ready

A technician is checking a gas furnace and finds the burners light but the blower does not start until the limit switch opens. Which component is the most likely cause?

  1. The fan-and-limit control or blower relay Correct answer.
  2. The flame sensor
  3. The igniter
  4. The gas valve regulator

Explanation

When the blower starts only after the high-limit opens, the fan-on function of the fan-and-limit control or the blower relay is not initiating at the proper temperature. The limit is acting as a backup safety, which indicates a fan control problem rather than a flame problem. Flame sensor, gas valve, and igniter faults affect ignition, not blower timing.

Question 36Employment Ready

A technician is preparing to install a replacement compressor and must follow good evacuation practice. Which step is required before charging?

  1. Triple evacuate with nitrogen sweeps and confirm the vacuum holds with the pump valved off Correct answer.
  2. Charge the system by weight before evacuation
  3. Flush the system with liquid refrigerant
  4. Pull a vacuum for ten minutes and charge immediately

Explanation

Triple evacuation with dry nitrogen sweeps removes moisture and non-condensables, and a standing vacuum test confirms the system is leak-free and dry before charging. A brief vacuum pull or charging before evacuation leaves moisture and air in the system, which leads to acid formation and premature failure. Refrigerant should never be used to flush a system.

Question 37Employment Ready

A technician must determine the airflow of a system using a duct traverse with a thermal anemometer. Which procedure produces the most reliable result?

  1. Read at the point of highest velocity
  2. Average readings from a grid of traverse points across the duct cross-section Correct answer.
  3. Take a single reading at the center of the duct
  4. Measure at the return grille only

Explanation

Velocity is not uniform across a duct, so a traverse averages readings from a grid of points to approximate the true average velocity. A single center reading or the highest velocity point overstates airflow. Multiplying the average velocity by the duct cross-sectional area yields the volumetric flow.

Question 38Employment Ready

A technician is asked to verify that a newly installed duct system meets the design static pressure. Where should the total external static pressure be measured?

  1. Between the return plenum and the supply plenum, outside the cabinet Correct answer.
  2. At the filter slot alone
  3. At the farthest supply register
  4. Across the blower only, with both probes inside the cabinet

Explanation

Total external static pressure is measured across the air handler from the return plenum to the supply plenum, with probes located outside the cabinet so internal component losses are not double-counted. Comparing the result to the blower performance table confirms whether the duct system is within design. Register or filter-slot readings alone do not represent total external static pressure.

Question 39Employment Ready

A technician is explaining to a homeowner why a new high-efficiency furnace needs a two-pipe combustion air system. Which explanation is most accurate?

  1. It draws outdoor air for combustion and vents flue gases separately, keeping combustion isolated from indoor air Correct answer.
  2. It allows the furnace to vent through a chimney without a liner
  3. It uses indoor air for combustion to improve efficiency
  4. It eliminates the need for a condensate drain

Explanation

A two-pipe system uses one pipe to bring outdoor combustion air to the burner and a second to carry flue products outside, so the appliance does not consume conditioned indoor air. This arrangement suits high-efficiency condensing furnaces installed in tight buildings. It does not remove the need for a condensate drain, which condensing furnaces require.

Question 40Employment Ready

A technician must determine whether a compressor is drawing locked-rotor current or running normally. Which measurement approach is most appropriate?

  1. Clamp the common wire and compare the reading with the nameplate rated load amps and locked-rotor amps Correct answer.
  2. Measure voltage at the thermostat terminals
  3. Read the suction line temperature
  4. Check the capacitor with an ohmmeter while the unit runs

Explanation

Clamping the compressor common wire gives the actual current, which can be compared with nameplate rated load amps and locked-rotor amps to classify the condition. A reading near locked-rotor amps with the compressor not turning indicates a locked rotor. Thermostat voltage, capacitor resistance, and line temperature do not directly classify compressor current.

Question 41Specialty Certifications

A technician is preparing to braze a copper-to-copper joint on a refrigeration line. Which filler metal and flux combination is appropriate for this joint?

  1. Silvaloy 15 with white paste flux Correct answer.
  2. Silvaloy 15 with black paste flux
  3. 50/50 tin-lead solder with rosin flux
  4. 95/5 tin-antimony solder with acid flux

Explanation

Silver-phosphorus brazing alloys (such as 15% silver) are self-fluxing on copper-to-copper joints, so a white paste flux is used only as a precaution or not at all. Black flux is required when brazing copper to brass or copper to steel with silver alloys. Soft solders are not acceptable for refrigerant-containing joints in modern practice.

Question 42Specialty Certifications

During a system evacuation, a technician observes that the micron gauge reading stalls at about 1,500 microns and will not drop further. What is the most likely cause?

  1. The system has a leak or trapped moisture that is boiling off slowly Correct answer.
  2. The micron gauge is reading in absolute pressure and needs calibration
  3. The vacuum pump oil is contaminated with moisture
  4. The compressor is running and masking the vacuum

Explanation

A vacuum that stalls well above the target (typically 500 microns) usually indicates either a leak or moisture/air that continues to vaporize and load the pump. A contaminated pump oil degrades ultimate vacuum but the classic stall pattern points to system-side contamination. The proper response is a standing vacuum test and, if needed, a triple evacuation with dry nitrogen sweeps.

Question 43Specialty Certifications

What is the primary purpose of a liquid-line filter drier in a refrigeration system?

  1. To separate oil from refrigerant vapor before the compressor
  2. To store excess refrigerant during low-load operation
  3. To remove moisture and particulate contamination from the refrigerant Correct answer.
  4. To reduce refrigerant flow to the evaporator

Explanation

A liquid-line filter drier uses a desiccant and filter media to trap moisture, acid, and particulate matter before the refrigerant reaches the metering device. This protects the expansion valve and compressor from contamination and ice formation. Oil separation and refrigerant storage are handled by other components.

Question 44Specialty Certifications

A technician measures a superheat of 2°F at the evaporator outlet of a TXV-controlled system with a design superheat of 10°F. What does this indicate?

  1. The TXV is underfeeding refrigerant to the evaporator
  2. The evaporator airflow is excessive
  3. The system charge is low
  4. The TXV is overfeeding refrigerant to the evaporator Correct answer.

Explanation

Superheat is the temperature of refrigerant vapor above its saturation temperature, and a TXV modulates to maintain a set superheat. A reading far below design superheat means the valve is passing too much refrigerant, risking liquid floodback to the compressor. Low charge or a restricted valve would produce high superheat, not low.

Question 45Specialty Certifications

A technician is recovering refrigerant from a system that contains R-410A. Which recovery cylinder should be used?

  1. A DOT-approved cylinder rated for R-410A with a gray body and yellow top Correct answer.
  2. A disposable refrigerant drum
  3. An unmarked steel cylinder rated to 240 psig
  4. Any cylinder that previously held R-12

Explanation

Recovery cylinders must be DOT-approved, in hydrostatic test, and dedicated to the refrigerant being recovered to prevent mixing. R-410A cylinders are typically gray with a yellow top and are rated for the higher pressures of the blend. Mixing refrigerants or using unrated cylinders creates a serious safety and legal violation.

Question 46Specialty Certifications

What is the required EPA Section 608 evacuation level for a system using R-410A that was manufactured after November 15, 1993, when the system is not a small appliance?

  1. 15 inches of mercury
  2. 0 inches of mercury
  3. 10 inches of mercury Correct answer.
  4. 20 inches of mercury

Explanation

EPA regulations require evacuation to 10 inches of mercury vacuum for systems containing ozone-depleting refrigerants or their substitutes, except for very high-pressure systems or small appliances. R-410A falls under the standard 10 inHg requirement for typical systems. Higher vacuums are required for systems with certain components or for very high-pressure refrigerants in some cases.

Question 47Specialty Certifications

A technician is checking a compressor and finds the suction pressure is low and the discharge pressure is high. Which condition best explains this?

  1. An overcharged system with a restricted condenser Correct answer.
  2. A worn compressor valve
  3. A restricted suction line
  4. A restricted liquid line

Explanation

High discharge pressure with low suction pressure suggests the compressor is working against a restricted condenser while starved for suction gas. An overcharge combined with a restricted condenser produces exactly this pattern. Restricted liquid or suction lines and worn valves produce different symptom sets.

Question 48Specialty Certifications

What is the function of the accumulator in a heat pump or refrigeration system?

  1. To prevent liquid refrigerant from reaching the compressor Correct answer.
  2. To increase the subcooling of the liquid line
  3. To store liquid refrigerant for the heating cycle
  4. To regulate the flow of refrigerant to the evaporator

Explanation

An accumulator is installed on the suction line to trap any liquid refrigerant that leaves the evaporator and allow it to vaporize before entering the compressor. This protects the compressor from slugging and oil dilution. It does not store liquid for the heating cycle or regulate evaporator flow.

Question 49Specialty Certifications

A technician is brazing refrigerant lines and must flow dry nitrogen through the tubing during the process. Why is this done?

  1. To cool the joint so the filler does not melt
  2. To purge moisture from the system
  3. To prevent oxidation and scale formation inside the tubing Correct answer.
  4. To increase the pressure inside the line for leak testing

Explanation

Flowing dry nitrogen displaces oxygen inside the tubing during brazing, preventing the formation of copper oxide scale that can later clog the metering device, filter drier, or compressor. A low flow rate is used, and the line is typically capped or vented to atmosphere. Nitrogen does not cool the joint or purge moisture.

Question 50Specialty Certifications

What is the primary safety concern when working with R-410A compared with R-22?

  1. R-410A is toxic and requires a respirator
  2. R-410A operates at significantly higher pressures Correct answer.
  3. R-410A depletes the ozone layer
  4. R-410A is flammable at room temperature

Explanation

R-410A is a near-azeotropic blend with a much higher saturation pressure than R-22, so gauges, hoses, recovery equipment, and components must be rated for the higher pressures. It is not flammable at room temperature, has low toxicity, and is an HFC with zero ozone depletion potential.