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HVAC Excellence Master HP study materials
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HVAC Excellence Master HP practice questions

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Question 1HVACR Core Knowledge and Skills

A technician is brazing a copper line set and wants to prevent oxidation inside the tubing. What is the standard practice?

  1. Cap both ends of the tubing and braze quickly
  2. Increase the acetylene pressure to shorten heating time
  3. Flow dry nitrogen through the tubing during brazing Correct answer.
  4. Wet the inside of the joint with flux before heating

Explanation

A slow, low-pressure nitrogen purge displaces oxygen inside the tubing so copper oxide scale (soot) cannot form during brazing. Scale flakes can later migrate into the metering device, compressor, and filter-drier and cause restrictions or bearing damage.

Question 2HVACR Core Knowledge and Skills

Which instrument is used to measure the superheat of a refrigerant line?

  1. A megohmmeter
  2. A manometer
  3. A sling psychrometer
  4. A thermocouple clamp plus a refrigerant gauge manifold Correct answer.

Explanation

Superheat is the difference between the actual suction line temperature and the saturation temperature at suction pressure. You need both a temperature reading at the line and the corresponding pressure from a gauge manifold.

Question 3HVACR Core Knowledge and Skills

A heat pump in heating mode is running but delivering little warm air. The outdoor unit's reversing valve solenoid is de-energized, and the outdoor coil is heavily frosted while the defrost cycle never initiates. Which component is the most likely cause?

  1. The liquid-line filter-drier
  2. The defrost control board or its sensors Correct answer.
  3. The indoor blower capacitor
  4. The reversing valve solenoid coil

Explanation

Defrost initiation depends on the defrost control board reading coil and ambient sensors and then energizing the reversing valve and outdoor fan shutdown. A board or sensor failure leaves the coil frosted, blocking heat absorption and cutting capacity.

Question 4HVACR Core Knowledge and Skills

A manifold gauge set reads 60 psig suction and 250 psig discharge on an R-410A system with a 75°F indoor return. What does the suction pressure indicate about the evaporator saturation temperature?

  1. About 92°F, derived from the discharge pressure
  2. About 60°F, because psig equals saturation temperature
  3. About 20°F, since R-410A runs 40°F below ambient
  4. About 35°F, using the R-410A pressure-temperature chart Correct answer.

Explanation

Saturation temperature is found by looking up the measured pressure on the refrigerant's pressure-temperature chart. For R-410A, 60 psig corresponds to roughly 35°F saturation, which is a typical evaporator temperature for comfort cooling.

Question 5HVACR Core Knowledge and Skills

During a cooling call, a technician measures a 2°F temperature difference across the evaporator coil and a normal refrigerant charge. What is the most likely problem?

  1. Restricted liquid line
  2. Failed compressor valves
  3. Low indoor airflow Correct answer.
  4. Overcharge of refrigerant

Explanation

A low air temperature drop across the coil usually means too little air is passing through it, so the coil cannot transfer the expected heat. Common causes are a dirty filter, a slipping blower belt, or a blower running at the wrong speed.

Question 6HVACR Core Knowledge and Skills

What is the primary purpose of a crankcase heater on a compressor?

  1. To raise the condensing temperature during cold weather
  2. To keep oil in the crankcase warm so refrigerant does not migrate and dilute it Correct answer.
  3. To reduce the compressor's running current draw
  4. To warm the suction gas before it enters the compressor

Explanation

During the off cycle, refrigerant can condense and dissolve into the compressor oil, especially in cool ambient conditions. The crankcase heater keeps the oil warmer than the coldest part of the system so liquid refrigerant boils off and stays out of the oil.

Question 7HVACR Core Knowledge and Skills

A technician must recover refrigerant from a system before opening it for repair. Which statement about recovery is correct?

  1. Mixed refrigerants can be returned to the original system without concern
  2. Refrigerant may be vented if the system charge is under 5 pounds
  3. Recovery cylinders should be filled to 100 percent of their water capacity
  4. Recovered refrigerant must be stored in a DOT-approved recovery cylinder Correct answer.

Explanation

Recovered refrigerant is transferred into a recovery cylinder designed and marked for that service, and the cylinder is never filled above the safe fill limit. Venting refrigerant to the atmosphere is prohibited by federal regulation.

Question 8HVACR Core Knowledge and Skills

Which safety hazard is created by a refrigerant leak in a confined mechanical room with a low-lying ignition source?

  1. Increased humidity that damages controls
  2. Oxygen enrichment
  3. Reduced oxygen and possible ignition of flammable refrigerant blends Correct answer.
  4. Frozen condensate drain lines

Explanation

Refrigerant displaces air in a confined space, reducing oxygen available for breathing. Some newer refrigerant blends are classified as flammable, so a leak near an ignition source is a fire hazard.

Question 9HVACR Core Knowledge and Skills

A customer reports that a heat pump heats well but the auxiliary heat never comes on during a cold snap, leaving the space short of setpoint. What is the most likely cause?

  1. The reversing valve is stuck in cooling
  2. The outdoor thermostat or auxiliary heat lockout is set incorrectly Correct answer.
  3. The suction line is overcharged
  4. The indoor coil is oversized

Explanation

Auxiliary heat is staged by the thermostat and by an outdoor thermostat or control-board lockout that enables it only below a set outdoor temperature. If that setting is wrong or the sensor is failed open, the strip heat never energizes.

Question 10HVACR Core Knowledge and Skills

A technician is evacuating a system with a vacuum pump and a micron gauge. The gauge stalls at 1500 microns and rises quickly when the pump is valved off. What does this indicate?

  1. The system has reached a deep vacuum and is ready to charge
  2. There is a leak or moisture in the system Correct answer.
  3. The micron gauge is reading in inches of mercury
  4. The vacuum pump oil is brand new

Explanation

A vacuum that stalls well above the target and rises when isolated indicates air is entering or moisture is boiling off slowly. The technician should leak-check and repeat the evacuation, changing pump oil as needed.

Question 11HVACR Core Knowledge and Skills

What does a compressor's locked-rotor amps (LRA) rating represent?

  1. The current drawn by the condenser fan motor
  2. The current drawn at full-load running conditions
  3. The current at which the internal overload trips
  4. The maximum current the motor draws at the instant of start with the rotor stalled Correct answer.

Explanation

LRA is the inrush current when the rotor is not turning and full voltage is applied. It is a nameplate value used to check start components and to size circuit protection.

Question 12HVACR Core Knowledge and Skills

A PSC condenser fan motor hums but does not spin, and the technician measures full voltage at the motor terminals. Which test best isolates the fault?

  1. Verify the thermostat's fan setting
  2. Measure the capacitance of the run capacitor Correct answer.
  3. Measure the compressor winding resistance
  4. Check the refrigerant charge with gauges

Explanation

A PSC motor needs a good run capacitor to create the phase shift for starting and running torque. Measuring the capacitor with a meter set to microfarads quickly confirms whether it has failed open or drifted out of tolerance.

Question 13HVACR Core Knowledge and Skills

A technician measures 12°F subcooling on an R-410A system with a TXV, where the manufacturer specifies 8°F to 10°F. What does this suggest?

  1. A failed compressor
  2. Low indoor airflow
  3. Undercharge of refrigerant
  4. Overcharge or a restriction in the liquid line Correct answer.

Explanation

Subcooling above the target range means excess liquid refrigerant is stacking in the condenser, which points to overcharge or a liquid-line restriction. The technician should verify airflow and condenser cleanliness before adjusting charge.

Question 14HVACR Core Knowledge and Skills

Which practice protects a technician from electrical shock when servicing a rooftop unit's line-voltage compartment?

  1. Working only with one hand in the panel
  2. Locking out and tagging out the disconnect and verifying with a meter Correct answer.
  3. Wearing cotton gloves and standing on a dry roof
  4. Relying on the unit's internal contactor to open

Explanation

Lockout/tagout with a verified voltage check is the only reliable way to ensure the circuit is de-energized. Personal protective equipment and one-hand technique reduce exposure but do not remove the hazard.

Question 15HVACR Core Knowledge and Skills

A technician is checking a gas furnace's heat exchanger for cracks. Which method is acceptable?

  1. Spraying soap bubbles on the burners
  2. Measuring the flue-gas temperature only
  3. Visual inspection with a mirror and flashlight plus a combustion analyzer Correct answer.
  4. Checking the manifold pressure only

Explanation

Cracks are often hidden, so a visual inspection with a mirror is combined with combustion analysis to detect carbon monoxide or dilution-air changes. Any confirmed breach requires shutting down the furnace and replacing the exchanger.

Question 16HVACR Core Knowledge and Skills

Which refrigerant is classified as A2L under ASHRAE Standard 34?

  1. R-32 Correct answer.
  2. R-134a
  3. R-22
  4. R-410A

Explanation

R-32 is mildly flammable and is classified A2L. R-22, R-410A, and R-134a are A1 refrigerants with no flame propagation at standard conditions.

Question 17HVACR Core Knowledge and Skills

A technician is installing a new line set and must size the suction line. Which consequence results from selecting a suction line that is too small?

  1. Higher suction pressure at the compressor
  2. Increased subcooling at the condenser
  3. Excessive pressure drop and reduced capacity Correct answer.
  4. Lower compressor current draw

Explanation

An undersized suction line creates excessive pressure drop, which lowers the pressure at the compressor and reduces mass flow and capacity. The refrigerant also gains extra superheat, which can overheat the compressor.

Question 18HVACR Core Knowledge and Skills

A technician finds that a heat pump's outdoor coil is clean but the unit ices up in heating mode within minutes. Which condition most likely explains this?

  1. A failed outdoor fan capacitor
  2. Low refrigerant charge or a restricted indoor metering device Correct answer.
  3. A thermostat set to continuous fan
  4. A dirty indoor air filter

Explanation

Low charge or a restriction lowers suction pressure and temperature, so the outdoor coil drops below freezing and frosts quickly even with good airflow. Normal defrost should still initiate, but rapid icing points to a system-side problem.

Question 19HVACR Core Knowledge and Skills

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

  1. To store liquid refrigerant and prevent it from reaching the compressor Correct answer.
  2. To filter acid and moisture from the refrigerant
  3. To increase the condensing temperature
  4. To meter refrigerant into the evaporator

Explanation

The accumulator is located on the suction line and traps any liquid refrigerant that returns from the evaporator, allowing it to boil off before reaching the compressor. This protects the compressor from slugging and oil dilution.

Question 20HVACR Core Knowledge and Skills

A technician measures 0 volts between R and Y at the thermostat with the thermostat calling for cooling. What is the most likely cause?

  1. The transformer is open or the low-voltage circuit is broken Correct answer.
  2. The condenser fan is defective
  3. The compressor is shorted to ground
  4. The refrigerant charge is low

Explanation

The thermostat receives 24 volts from the transformer on R and switches it to Y to start cooling. No voltage at Y during a call means the control circuit is open somewhere, such as a blown transformer, open safety switch, or broken wire.

Question 21HVACR Core Knowledge and Skills

A technician is charging a system with a fixed-orifice metering device on a hot day. Which method is appropriate?

  1. Charge until the suction pressure equals the outdoor temperature
  2. Charge to the superheat target Correct answer.
  3. Charge until the sight glass is clear
  4. Charge to the subcooling target

Explanation

Fixed-orifice systems are charged by superheat because the orifice cannot adjust to load changes. TXV systems are typically charged by subcooling, since the valve maintains superheat.

Question 22HVACR Core Knowledge and Skills

A technician is testing a compressor's windings and finds infinite resistance between the common terminal and ground. What does this indicate?

  1. The windings are shorted together
  2. The winding insulation is intact with no ground fault Correct answer.
  3. The run capacitor is shorted
  4. The internal overload is open

Explanation

Infinite resistance to ground means no path exists from the windings to the compressor shell, so the insulation is holding. A grounded compressor would show measurable or near-zero resistance to ground.

Question 23HVACR Core Knowledge and Skills

A technician is performing a heat-load estimate and must account for infiltration. Which factor most directly increases infiltration load?

  1. A tighter building envelope with weatherstripping
  2. Higher indoor relative humidity
  3. A higher indoor thermostat setpoint
  4. A large pressure difference across the envelope Correct answer.

Explanation

Infiltration is driven by pressure differences from wind, stack effect, and mechanical exhaust. A larger pressure difference pushes more outdoor air through cracks and openings, increasing the sensible and latent load.

Question 24HVACR Core Knowledge and Skills

What is the correct procedure when a technician finds a refrigerant cylinder with a damaged valve and an expired hydrostatic test date?

  1. Vent the contents and discard the cylinder
  2. Return the cylinder to a qualified reclaimer or cylinder requalifier Correct answer.
  3. Fill the cylinder to 90 percent and continue use
  4. Use the cylinder only for recovery of the same refrigerant

Explanation

A damaged valve or an out-of-date test makes the cylinder unsafe and noncompliant. It must be taken out of service and sent to a qualified requalifier or reclaimer for proper handling.

Question 25HVACR Core Knowledge and Skills

A technician is diagnosing a system with a thermostatic expansion valve. The valve is stuck closed. What symptoms are expected?

  1. Low suction pressure and high superheat Correct answer.
  2. Normal suction pressure and low subcooling
  3. High discharge pressure and low superheat
  4. High suction pressure and low superheat

Explanation

A TXV stuck closed starves the evaporator, so suction pressure falls and the refrigerant leaving the coil is far above saturation, producing high superheat. Frost may form near the valve outlet.

Question 26HVACR Core Knowledge and Skills

A technician reads a system's low-side pressure with a gauge manifold and converts it to saturation temperature using a pressure-temperature chart. What does that saturation temperature represent for the refrigerant in the evaporator?

  1. The dew point of the indoor air passing over the coil
  2. The temperature of the superheated vapor leaving the coil
  3. The temperature at which liquid and vapor coexist at that pressure Correct answer.
  4. The temperature of the liquid line entering the metering device

Explanation

Saturation temperature is the temperature at which a refrigerant changes phase at a given pressure, with liquid and vapor present together. Technicians use it to compare against actual line temperature when calculating superheat or subcooling.

Question 27HVACR Core Knowledge and Skills

A split system has a suction line that is sweating and cold while the suction pressure is below normal and superheat is high. Which condition is most consistent with these readings?

  1. Restriction in the liquid line or metering device Correct answer.
  2. Thermostat set to fan-only mode
  3. Failed condenser fan motor
  4. Overcharge of refrigerant in the system

Explanation

High superheat with low suction pressure points to insufficient refrigerant reaching the evaporator, typical of a restriction or a starved coil. A sweating suction line alone does not rule this out because the coil is still partly active.

Question 28HVACR Core Knowledge and Skills

When brazing copper refrigerant lines, which practice protects the internal surfaces from oxidation that can later clog metering devices?

  1. Flowing dry nitrogen through the tubing during brazing Correct answer.
  2. Wrapping the joint with wet rags
  3. Cooling the joint quickly with water after brazing
  4. Increasing the acetylene flow for a hotter flame

Explanation

A slow flow of dry nitrogen displaces oxygen inside the tubing so copper oxide scale does not form during brazing. Scale flakes can migrate and block small orifices such as TXV ports and filter screens.

Question 29HVACR Core Knowledge and Skills

A technician is preparing to leak-test a newly assembled R-410A system. Which method is appropriate for locating leaks before evacuation?

  1. Pressurizing with oxygen and listening for hiss
  2. Pressurizing with dry nitrogen and using an electronic leak detector Correct answer.
  3. Pressurizing with acetylene and using a soap bubble solution
  4. Pulling a deep vacuum and watching the micron gauge alone

Explanation

Dry nitrogen is the standard inert pressurizing gas for leak testing; an electronic detector or soap bubbles then locate the leak point. Oxygen and acetylene are dangerous with refrigeration oils and must never be used for this purpose.

Question 30HVACR Core Knowledge and Skills

A technician finds that a compressor's run capacitor is bulging and reads open on a capacitance meter. Which symptom would this most directly explain?

  1. Compressor has correct winding resistance but infinite resistance to ground
  2. Compressor trips on internal overload shortly after start Correct answer.
  3. Compressor runs but produces no cooling and draws low current
  4. Compressor starts and runs normally with high suction pressure

Explanation

A failed run capacitor reduces starting and running torque, so the compressor draws high current and trips its overload. Replacing the capacitor with the correct microfarad rating restores normal operation.

Question 31HVACR Core Knowledge and Skills

A technician is calculating airflow using the sensible heat equation. Which set of measurements is required to determine sensible BTUH delivered by an air stream?

  1. Refrigerant pressure, superheat, and subcooling
  2. Static pressure, fan RPM, and motor horsepower
  3. CFM, temperature rise, and the 1.08 constant Correct answer.
  4. CFM, wet-bulb depression, and the 4.5 constant

Explanation

Sensible heat in an air stream is found from CFM times the temperature difference times 1.08 for standard air. This allows the technician to verify delivered capacity against the equipment rating.

Question 32HVACR Core Knowledge and Skills

A technician is preparing to braze a joint near a service valve. Which precaution best protects the valve's internal seals from heat damage?

  1. Increasing the nitrogen purge pressure to 50 psig
  2. Opening the valve fully before heating
  3. Wrapping the valve body with a wet rag and directing the flame away Correct answer.
  4. Applying flux to the valve threads

Explanation

Heat travels through copper quickly, so wet rags or heat-sink paste plus flame direction protect elastomeric seals. Excess heat can destroy seats and seals, causing a leak after the repair.

Question 33HVACR Core Knowledge and Skills

A technician must verify that a heat pump's reversing valve shifts correctly. Which observation confirms the valve has changed position after the solenoid is energized?

  1. Suction pressure rises while discharge pressure falls Correct answer.
  2. The compressor's current draw drops to zero
  3. The indoor blower speed increases
  4. The outdoor fan motor reverses rotation

Explanation

When the reversing valve shifts, the roles of the indoor and outdoor coils swap, so suction and discharge pressures move in the expected direction for the new mode. Confirming the pressure change verifies the valve actually stroked.

Question 34HVACR Core Knowledge and Skills

A technician is measuring external static pressure on an air handler. Where should the readings be taken to determine total external static pressure?

  1. At the compressor service ports
  2. At the thermostat wire terminals
  3. In the return duct before the blower and in the supply duct after the unit Correct answer.
  4. Across the evaporator coil only

Explanation

Total external static pressure is the sum of the return-side and supply-side readings taken outside the cabinet. This value is compared with the blower performance table to estimate airflow.

Question 35HVACR Core Knowledge and Skills

A technician is checking a PSC blower motor that does not run. Voltage is present across the motor terminals, but the motor hums and does not rotate. Which test is most appropriate next?

  1. Measure the refrigerant superheat
  2. Verify the compressor contactor coil resistance
  3. Measure the capacitance of the run capacitor and compare with its rating Correct answer.
  4. Check the thermostat's anticipation resistor

Explanation

A PSC motor needs a good run capacitor to produce starting torque; a failed capacitor produces the hum-without-rotation symptom. Testing capacitance against the nameplate value isolates the cause.

Question 36HVACR Core Knowledge and Skills

A technician is brazing new copper tubing and notices that the tubing has been stored outdoors with open ends. Which step should be taken before assembly?

  1. Rinse the tubing with water and allow it to air dry
  2. Coat the inside of the tubing with refrigerant oil
  3. Cap or plug the tubing and purge with dry nitrogen before brazing Correct answer.
  4. Blow the tubing out with compressed air from a shop compressor

Explanation

Open tubing can collect moisture, dirt, and debris that later contaminate the system. Capping the ends and purging with dry nitrogen during brazing keeps the internal surfaces clean and dry.

Question 37HVACR Core Knowledge and Skills

A technician is checking a system with a thermostatic expansion valve and finds frost forming at the valve outlet while superheat is very high. Which condition best fits these symptoms?

  1. The valve is overfeeding refrigerant
  2. The valve is restricted or the inlet screen is plugged Correct answer.
  3. The condenser is overcharged
  4. The compressor valves are leaking

Explanation

A restriction at the valve or its inlet screen starves the evaporator, producing high superheat and localized frost at the restriction. The pressure drop across the restriction causes the low temperature.

Question 38HVACR Core Knowledge and Skills

A technician is measuring superheat on a system with a fixed-orifice metering device. Which condition indicates the charge may be low?

  1. Superheat below the manufacturer's target range
  2. Superheat above the manufacturer's target range Correct answer.
  3. Suction pressure above the target range
  4. Subcooling above the target range

Explanation

With a fixed orifice, superheat is the primary charging indicator; high superheat signals insufficient refrigerant in the evaporator. The technician adds charge in small increments until superheat falls within the target range.

Question 39HVACR Core Knowledge and Skills

A technician is diagnosing a heat pump that runs but delivers little heat in heating mode. The outdoor coil is heavily frosted and the defrost cycle never initiates. Which component should be checked first?

  1. The reversing valve solenoid coil
  2. The indoor blower capacitor
  3. The compressor start relay
  4. The defrost control board and its sensors Correct answer.

Explanation

If the coil ices and defrost never starts, the defrost control or its temperature and pressure sensors are the likely cause. The control decides when to initiate defrost based on those inputs.

Question 40HVACR Core Knowledge and Skills

A technician is working on an electrical panel and must verify that a circuit is de-energized before touching conductors. Which practice is correct?

  1. Assume the circuit is off if the unit is not running
  2. Rely on the disconnect switch position alone
  3. Touch the conductors with an insulated screwdriver to check for arcing
  4. Test the conductors with a known-good meter and confirm zero voltage Correct answer.

Explanation

Always verify zero voltage with a meter that has been checked on a known live source before and after the test. Switch position and equipment status are not reliable proof of de-energization.

Question 41HVACR Core Knowledge and Skills

A technician is using a recovery machine to recover refrigerant from a system. Which practice complies with typical EPA requirements for recovery?

  1. Recovering refrigerant into an unmarked container
  2. Releasing refrigerant into the atmosphere if the system is being replaced
  3. Recovering only the vapor and venting the liquid
  4. Recovering refrigerant to the required vacuum level for the appliance type Correct answer.

Explanation

Recovery must continue until the appliance reaches the vacuum level specified for its type under EPA regulations. Recovered refrigerant must be stored in properly labeled, DOT-approved containers.

Question 42HVACR Core Knowledge and Skills

A technician is diagnosing a compressor that trips the breaker immediately at startup. Which test sequence is most appropriate?

  1. Check winding resistance and insulation to ground before replacing parts Correct answer.
  2. Adjust the thermostat and retest
  3. Add refrigerant and retest
  4. Replace the contactor and retest

Explanation

An immediate breaker trip suggests a shorted compressor or wiring fault, so winding and insulation tests come first. Replacing parts before testing risks damage and wasted cost.

Question 43HVACR Core Knowledge and Skills

A technician is sizing a replacement liquid-line filter drier for a system. Which consideration is most important?

  1. Using a suction-line drier on the liquid line
  2. Selecting a drier based only on physical dimensions
  3. Selecting a drier rated for the system's refrigerant and capacity Correct answer.
  4. Choosing the largest drier available regardless of capacity

Explanation

A filter drier must be rated for the refrigerant type and system tonnage to avoid excessive pressure drop and to provide adequate moisture removal. Correct selection protects the metering device and compressor.

Question 44HVACR Core Knowledge and Skills

A technician is checking a system's subcooling and finds it is below the manufacturer's target with normal superheat. Which condition is most likely?

  1. The system is overcharged
  2. The system is undercharged Correct answer.
  3. The blower is set too slow
  4. The evaporator coil is restricted

Explanation

Low subcooling with normal superheat indicates insufficient liquid refrigerant in the condenser, consistent with undercharge. The technician should locate any leak and add charge to the target subcooling.

Question 45HVACR Core Knowledge and Skills

A technician is installing a condensate drain for an air handler. Which practice helps prevent water damage and nuisance trips?

  1. Running the drain uphill to save space
  2. Sealing the drain line completely with no vent
  3. Installing a trap and sloping the drain downward to the discharge point Correct answer.
  4. Connecting the drain directly to a sanitary sewer without a trap

Explanation

A properly trapped drain sloped downward allows condensate to flow away and prevents air from being drawn through the drain. This protects the cabinet and prevents water damage.

Question 46HVACR Core Knowledge and Skills

A technician is diagnosing a heat pump that heats poorly and has a very low suction pressure in heating mode with a normal-looking outdoor coil. Which condition is most likely?

  1. Low refrigerant charge or a restriction in the outdoor metering device Correct answer.
  2. Failed indoor blower capacitor
  3. Defective reversing valve solenoid coil
  4. Thermostat set to emergency heat

Explanation

In heating mode the outdoor coil is the evaporator, so low suction pressure with poor heating points to low charge or a restricted outdoor metering device. The technician should verify charge and check the outdoor piston or TXV.

Question 47HVACR Core Knowledge and Skills

A technician is confirming proper airflow across an evaporator coil. Which measurement set best supports an airflow estimate when a manufacturer's blower table is available?

  1. Static pressure readings and blower speed tap Correct answer.
  2. Condensate pH and drain rate
  3. Compressor current and voltage
  4. Refrigerant superheat and subcooling

Explanation

Manufacturer blower tables correlate external static pressure and speed tap with delivered CFM. Comparing measured static pressure with the table gives a reliable airflow estimate.

Question 48HVACR Core Knowledge and Skills

A technician is checking a gas furnace's venting after replacing the inducer motor. Which condition indicates the venting is acceptable?

  1. The vent connector is disconnected at the chimney
  2. The inducer runs continuously after the call ends
  3. Combustion products are drafted out with no spillage at the draft hood Correct answer.
  4. Visible flue gas is spilling into the room

Explanation

Proper draft means combustion products leave the appliance and vent safely with no spillage at the draft hood. Spillage indicates a venting or draft problem that must be corrected.

Question 49HVACR Core Knowledge and Skills

A technician is comparing a heat pump's rated capacity with actual delivered capacity. Which measurement combination best supports a capacity check in heating mode?

  1. Outdoor ambient temperature and fan RPM
  2. Airflow and the temperature rise across the indoor coil Correct answer.
  3. Compressor current and voltage only
  4. Refrigerant pressure and superheat only

Explanation

Delivered heating capacity can be estimated from airflow and the temperature rise across the indoor coil using the sensible heat equation. Comparing that result with the rating verifies performance.

Question 50HVACR Core Knowledge and Skills

A technician is preparing to replace a compressor. Which step is required before opening the refrigerant circuit?

  1. Vent the refrigerant to relieve pressure
  2. Recover refrigerant to the required vacuum level Correct answer.
  3. Add refrigerant to increase pressure
  4. Run the compressor to pump down the system

Explanation

Refrigerant must be recovered to the required vacuum level before the circuit is opened. This protects the environment and complies with refrigerant handling regulations.