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NATE Heat Pump Install study materials
NATE Heat Pump Install study resources

NATE Heat Pump Install practice questions

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Question 1Heat Pump Fundamentals, Refrigerant Cycle, and System Components

In a vapor-compression heat pump operating in heating mode, which component rejects heat to the conditioned space?

  1. The compressor shell
  2. The indoor coil acting as condenser Correct answer.
  3. The expansion valve
  4. The outdoor coil acting as evaporator

Explanation

In heating mode the refrigerant cycle is reversed relative to cooling: the indoor coil becomes the condenser, where high-pressure hot gas condenses and gives up latent heat to the indoor air stream. The outdoor coil absorbs heat from outside air as the evaporator.

Question 2Heat Pump Fundamentals, Refrigerant Cycle, and System Components

A reversing valve on an air-source heat pump changes the direction of refrigerant flow primarily to:

  1. Bypass the accumulator
  2. Modulate compressor capacity
  3. Control defrost timing
  4. Swap the roles of the indoor and outdoor coils Correct answer.

Explanation

The four-way reversing valve redirects discharge and suction gas so the indoor and outdoor coils exchange condenser and evaporator functions, allowing one circuit to provide both heating and cooling. Capacity modulation and defrost control are handled by other devices.

Question 3Heat Pump Fundamentals, Refrigerant Cycle, and System Components

The primary purpose of the accumulator in a heat pump system is to:

  1. Prevent liquid refrigerant from reaching the compressor Correct answer.
  2. Dehumidify the supply air
  3. Store subcooled liquid for the expansion valve
  4. Increase discharge pressure

Explanation

The accumulator is located on the suction line and traps any liquid refrigerant that boils off before it can enter the compressor, protecting the compressor from slugging. It is not a liquid receiver for the liquid line.

Question 4Heat Pump Fundamentals, Refrigerant Cycle, and System Components

Which refrigerant state enters the compressor under normal operating conditions?

  1. Superheated vapor Correct answer.
  2. Subcooled liquid
  3. Saturated liquid-vapor mixture
  4. Supercritical fluid

Explanation

The compressor is designed to pump vapor, and a small amount of superheat ensures no liquid droplets enter the cylinders. Liquid entering the compressor can cause mechanical damage and oil dilution.

Question 5Heat Pump Fundamentals, Refrigerant Cycle, and System Components

The function of the metering device in a heat pump circuit is to:

  1. Raise refrigerant pressure before the condenser
  2. Reduce refrigerant pressure and regulate flow to the evaporator Correct answer.
  3. Provide superheat to the suction line
  4. Remove moisture from the refrigerant

Explanation

The metering device, such as a thermostatic expansion valve or fixed orifice, drops refrigerant pressure so it can evaporate at a low temperature and regulates the mass flow to match load. It does not raise pressure or dry the refrigerant.

Question 6Heat Pump Fundamentals, Refrigerant Cycle, and System Components

An air-source heat pump's rated heating capacity typically decreases as outdoor ambient temperature drops because:

  1. The reversing valve closes
  2. The evaporator's temperature difference and refrigerant mass flow decrease Correct answer.
  3. The condenser rejects more heat outdoors
  4. The compressor speed increases automatically

Explanation

As outdoor air cools, the evaporator absorbs less heat per pound of refrigerant and the reduced suction density lowers mass flow, so heating capacity falls. This is why balance-point calculations matter in cold climates.

Question 7Heat Pump Fundamentals, Refrigerant Cycle, and System Components

Which line in a heat pump piping diagram connects the outdoor unit's reversing valve to the indoor coil during the heating cycle?

  1. The suction line
  2. The liquid line
  3. The discharge line Correct answer.
  4. The defrost control line

Explanation

In heating mode the compressor discharge is routed through the reversing valve to the indoor coil, so the line carrying hot high-pressure gas indoors is the discharge line. The liquid line carries condensed liquid back out to the outdoor metering device.

Question 8Heat Pump Fundamentals, Refrigerant Cycle, and System Components

What is the primary reason heat pumps use a defrost cycle in heating mode?

  1. The indoor coil becomes too cold to heat the space
  2. Frost on the outdoor coil blocks airflow and reduces heat absorption Correct answer.
  3. Refrigerant pressure rises above the relief setting
  4. The compressor oil overheats

Explanation

When the outdoor coil surface falls below freezing, frost accumulates and insulates the coil, reducing airflow and heat transfer and lowering capacity. Defrost temporarily reverses the cycle or energizes heaters to melt the frost.

Question 9Heat Pump Fundamentals, Refrigerant Cycle, and System Components

A technician measures 12°F of superheat at the suction line of a heat pump in cooling mode with a TXV. Which condition is most likely?

  1. The compressor is unloading
  2. The evaporator is starved and capacity is reduced Correct answer.
  3. The condenser is rejecting excess heat
  4. The evaporator is flooded and liquid is returning to the compressor

Explanation

Excessive superheat indicates the evaporator is not being fed enough refrigerant, so the coil is starved and capacity drops. A TXV should normally maintain a modest superheat, typically in the range the manufacturer specifies.

Question 10Heat Pump Fundamentals, Refrigerant Cycle, and System Components

Subcooling measured at the liquid line leaving the condenser is used primarily to:

  1. Check the reversing valve position
  2. Confirm the evaporator is not starving
  3. Measure compressor amp draw
  4. Verify the condenser is fully condensing and the charge is adequate Correct answer.

Explanation

Subcooling indicates how far the liquid has been cooled below its condensing temperature, confirming the condenser is doing its job and helping verify charge on TXV systems. Low subcooling suggests undercharge or condenser problems.

Question 11Heat Pump Fundamentals, Refrigerant Cycle, and System Components

During heating, a heat pump's outdoor coil is iced over and the unit has been in defrost for several minutes. Which component typically energizes to prevent cold supply air during defrost?

  1. The outdoor fan motor
  2. The reversing valve solenoid
  3. Auxiliary electric resistance heaters Correct answer.
  4. The liquid line solenoid

Explanation

During defrost the system temporarily runs in cooling mode, so auxiliary heat is energized to temper the supply air and maintain comfort. The outdoor fan is usually stopped so coil temperature rises faster to melt frost.

Question 12Heat Pump Fundamentals, Refrigerant Cycle, and System Components

A heat pump in heating mode has high suction pressure and low superheat, with frost on the suction line at the compressor. What is the most likely cause?

  1. Overcharged system or excessive refrigerant flooding the evaporator Correct answer.
  2. Restricted liquid line filter-drier
  3. Undercharged system
  4. Failed outdoor fan motor

Explanation

High suction pressure combined with low superheat and frost at the compressor indicates liquid refrigerant is reaching the compressor, often from overcharge or a metering device feeding too much. This risks compressor damage and should be corrected promptly.

Question 13Heat Pump Fundamentals, Refrigerant Cycle, and System Components

Which statement correctly describes the relationship between balance point and supplemental heat for an air-source heat pump?

  1. The balance point is where the compressor shuts off permanently
  2. Supplemental heat replaces the compressor at all ambient temperatures
  3. Above the balance point, supplemental heat is required for normal operation
  4. Below the balance point, supplemental heat makes up the difference between capacity and building load Correct answer.

Explanation

The balance point is the outdoor temperature where heat pump capacity equals the building heat loss. Below it, the heat pump cannot meet the load alone, so supplemental heat stages on to cover the shortfall.

Question 14Heat Pump Fundamentals, Refrigerant Cycle, and System Components

A heat pump uses a fixed orifice metering device outdoors and a TXV indoors. During the heating cycle, which device meters refrigerant into the outdoor coil?

  1. The accumulator
  2. The indoor TXV
  3. The reversing valve
  4. The outdoor fixed orifice Correct answer.

Explanation

In heating mode the outdoor coil is the evaporator, so the outdoor metering device (the fixed orifice) controls refrigerant flow into it. The indoor TXV meters refrigerant into the indoor coil during cooling.

Question 15Heat Pump Fundamentals, Refrigerant Cycle, and System Components

Which condition best explains a heat pump that heats poorly in cold weather but cools normally in summer?

  1. A failed reversing valve or defrost control affecting heating operation Correct answer.
  2. A failed indoor blower motor
  3. Low refrigerant charge
  4. A restricted liquid line filter-drier

Explanation

Normal cooling but poor heating points to a component used only in heating, such as the reversing valve, defrost control, or outdoor metering device. A charge or airflow problem would typically degrade both modes.

Question 16Heat Pump Fundamentals, Refrigerant Cycle, and System Components

The suction line on a heat pump should be insulated primarily to:

  1. Prevent frost on the liquid line
  2. Increase refrigerant pressure
  3. Reduce compressor amp draw
  4. Prevent heat gain and condensation on the cold vapor line Correct answer.

Explanation

Insulating the suction line limits heat pickup that would reduce capacity and prevents condensation or frost on the cold line. Pressure, amp draw, and liquid line frost are not controlled by suction line insulation.

Question 17Heat Pump Fundamentals, Refrigerant Cycle, and System Components

Which sequence correctly describes the refrigerant cycle in a heat pump operating in heating mode?

  1. Compressor → reversing valve → indoor coil → outdoor metering device → outdoor coil → accumulator → compressor Correct answer.
  2. Compressor → reversing valve → outdoor coil → outdoor metering device → indoor coil → compressor
  3. Compressor → indoor coil → indoor metering device → outdoor coil → accumulator → compressor
  4. Compressor → outdoor coil → indoor metering device → indoor coil → reversing valve → compressor

Explanation

In heating, discharge gas goes through the reversing valve to the indoor condenser, then liquid passes through the outdoor metering device into the outdoor evaporator, and vapor returns through the accumulator to the compressor. This sequence matches the reversed flow of a heating cycle.

Question 18Heat Pump Fundamentals, Refrigerant Cycle, and System Components

A technician reads 0°F superheat at the evaporator outlet on a fixed-orifice heat pump in cooling mode. What does this indicate?

  1. The charge is low
  2. The condenser is restricted
  3. The compressor is short-cycling
  4. The evaporator may be flooded and liquid could reach the compressor Correct answer.

Explanation

Zero superheat means saturated vapor or liquid is leaving the evaporator, so liquid may be returning to the compressor. The cause could be overcharge, high indoor load, or an oversized orifice, and it should be investigated to protect the compressor.

Question 19Heat Pump Fundamentals, Refrigerant Cycle, and System Components

Why is the outdoor coil of a heat pump typically larger than the indoor coil?

  1. To reduce the refrigerant charge
  2. To absorb enough heat from outdoor air at low temperatures and handle defrost Correct answer.
  3. To increase discharge pressure
  4. To avoid the need for a reversing valve

Explanation

The outdoor coil must extract heat from cold ambient air in heating mode, so it needs more surface area to achieve adequate heat transfer. This also helps manage frost and defrost cycles.

Question 20Heat Pump Fundamentals, Refrigerant Cycle, and System Components

A heat pump's compressor runs but the indoor fan does not, and the high-pressure switch trips during heating. Which is the most likely cause?

  1. Failed reversing valve solenoid
  2. Outdoor fan failure
  3. Low refrigerant charge
  4. Indoor blower failure reducing airflow across the condenser Correct answer.

Explanation

Without indoor airflow, the indoor condenser cannot reject heat, so discharge pressure rises until the high-pressure switch opens. The blower must be restored before the system can operate safely.

Question 21Heat Pump Fundamentals, Refrigerant Cycle, and System Components

Which component in a heat pump system protects the compressor by opening on excessively high discharge pressure?

  1. Low-pressure switch
  2. Suction line accumulator
  3. Defrost thermostat
  4. High-pressure switch Correct answer.

Explanation

The high-pressure switch is a safety control that opens the compressor circuit when discharge pressure exceeds a set limit, preventing damage. The low-pressure switch protects against loss of charge or low suction pressure.

Question 22Heat Pump Fundamentals, Refrigerant Cycle, and System Components

A heat pump in heating mode shows low suction pressure, high superheat, and a frosted outdoor coil that defrosts normally. Which is the most likely explanation?

  1. Failed reversing valve
  2. Failed indoor blower
  3. Low refrigerant charge Correct answer.
  4. Overcharge

Explanation

Low suction pressure with high superheat and normal defrost behavior suggests the system is undercharged, so the evaporator is starved. Overcharge would raise suction pressure and lower superheat.

Question 23Heat Pump Fundamentals, Refrigerant Cycle, and System Components

Which statement about heat pump auxiliary heat versus emergency heat is accurate?

  1. Both terms describe the same resistance heater stage
  2. Auxiliary heat only operates in cooling mode
  3. Emergency heat supplements the compressor while auxiliary locks it out
  4. Auxiliary heat supplements the compressor, while emergency heat locks out the compressor Correct answer.

Explanation

Auxiliary heat stages on to assist the compressor when capacity is insufficient, whereas emergency heat mode disables the compressor and relies solely on resistance heat. Emergency heat is used when the compressor is locked out or failed.

Question 24Heat Pump Fundamentals, Refrigerant Cycle, and System Components

A technician is commissioning a heat pump and must verify the reversing valve shifts fully. Which observation best confirms proper valve operation in heating mode?

  1. Equal temperatures on both sides of the valve
  2. Hot gas temperature at the indoor coil and a temperature difference across the valve consistent with the manufacturer's specification Correct answer.
  3. Suction pressure equal to discharge pressure
  4. The outdoor fan runs continuously

Explanation

A properly shifted reversing valve routes hot discharge gas to the indoor coil, producing a measurable temperature difference across the valve and warm indoor coil. Equal temperatures or equalized pressures indicate the valve is not shifting.

Question 25Heat Pump Fundamentals, Refrigerant Cycle, and System Components

A dual-fuel heat pump system uses a fossil-fuel furnace as backup. Which control strategy is typically used to switch between the heat pump and the furnace?

  1. A pressure switch that senses furnace gas pressure
  2. A balance-point or outdoor thermostat that locks out the heat pump below a set ambient temperature Correct answer.
  3. A float switch in the condensate drain
  4. A fixed timer that alternates the two systems hourly

Explanation

Dual-fuel systems switch to the furnace when outdoor temperature falls below a balance point where the heat pump becomes uneconomical or unable to meet load. The changeover is set by an outdoor thermostat or a control board with a balance-point setting.

Question 26Heat Pump Fundamentals, Refrigerant Cycle, and System Components

A heat pump system is being commissioned, and the technician must identify the component that reverses refrigerant flow so the outdoor coil can act as the evaporator in heating mode. Which component performs this function?

  1. The defrost control board, which periodically switches the unit into cooling to melt outdoor coil frost
  2. The accumulator, which stores excess liquid refrigerant and returns it to the compressor suction
  3. The check valve at the outdoor metering device, which bypasses the orifice during the heating cycle
  4. The reversing valve, which redirects discharge and suction gas between the indoor and outdoor coils Correct answer.

Explanation

The reversing valve is a four-way valve whose solenoid pilot shifts the sliding piston, swapping which coil receives hot discharge gas and which returns suction gas. In heating mode it routes discharge gas to the indoor coil and makes the outdoor coil the evaporator. Defrost controls and check valves change operating states but do not reverse refrigerant flow direction.

Question 27Site Survey, Load Calculation, and Equipment Selection

During a site survey for a new heat pump, which measurement is most important for sizing the outdoor unit's heating capacity?

  1. The length of the driveway to the equipment pad
  2. The amperage rating of the existing electric water heater
  3. The design heat loss of the conditioned space at the winter design temperature Correct answer.
  4. The total square footage of the unconditioned garage

Explanation

Heating capacity must meet the building's design heat loss calculated at the local winter design temperature. This load figure, not ancillary measurements, drives equipment selection so the system can hold setpoint on the coldest expected day.

Question 28Site Survey, Load Calculation, and Equipment Selection

A Manual J load calculation for a residence shows a sensible heat gain of 24,000 Btu/h and a latent gain of 6,000 Btu/h. What is the total cooling load used for equipment selection?

  1. 36,000 Btu/h
  2. 30,000 Btu/h Correct answer.
  3. 24,000 Btu/h
  4. 18,000 Btu/h

Explanation

Total cooling load is the sum of sensible and latent gains, so 24,000 plus 6,000 equals 30,000 Btu/h. Equipment selection uses the total load, while the sensible heat ratio helps verify the coil's dehumidification performance.

Question 29Site Survey, Load Calculation, and Equipment Selection

When performing a room-by-room survey, which construction detail has the greatest effect on the calculated infiltration load?

  1. The measured air leakage characteristics and tightness of the building envelope Correct answer.
  2. The color of the interior wall paint
  3. The brand of the thermostat
  4. The number of electrical receptacles per room

Explanation

Infiltration load depends on how much air leaks through the envelope, which is estimated from construction tightness, window and door quality, and sealing details. Paint color, thermostat brand, and receptacle count do not change air leakage.

Question 30Site Survey, Load Calculation, and Equipment Selection

A site survey reveals the existing duct system runs through an unconditioned attic. How should this affect equipment selection?

  1. Account for duct losses and gains so delivered capacity meets the room loads Correct answer.
  2. Select the smallest available unit to limit duct heat gain
  3. Reduce the selected capacity because attic ducts add free cooling
  4. Ignore duct location because ducts never affect capacity

Explanation

Ducts in an unconditioned attic lose heating capacity and gain heat in cooling, so the equipment and duct design must offset those losses to deliver the required room loads. Ignoring duct location leads to undersized delivered capacity and comfort complaints.

Question 31Site Survey, Load Calculation, and Equipment Selection

Which value is required to correctly size a heat pump for a cold-climate installation where capacity must be checked at the design temperature?

  1. The manufacturer's rated capacity at the local winter design temperature Correct answer.
  2. The summer sensible heat ratio alone
  3. The nominal tonnage printed on the condensing unit only
  4. The static pressure rating of the indoor blower

Explanation

Heat pump heating capacity drops as outdoor temperature falls, so selection must compare rated capacity at the actual winter design temperature against the design heat loss. Nominal tonnage and summer-only data do not confirm cold-weather performance.

Question 32Site Survey, Load Calculation, and Equipment Selection

During the survey, a technician measures the windows and finds large west-facing glazing without shading. This finding most directly affects which part of the load calculation?

  1. The garage ventilation requirement
  2. The domestic hot water load
  3. The winter infiltration rate
  4. The summer solar gain through fenestration Correct answer.

Explanation

West-facing unshaded glass receives strong afternoon solar radiation, which adds a significant sensible cooling load in summer. Fenestration orientation and shading are recorded specifically to capture this solar gain.

Question 33Site Survey, Load Calculation, and Equipment Selection

A homeowner wants a heat pump sized to the exact calculated load with no margin. Why is matching capacity closely to the load generally preferred over gross oversizing?

  1. Oversizing always improves dehumidification
  2. Oversizing lowers the electrical service requirement
  3. Oversizing increases cycling and can reduce moisture removal and efficiency Correct answer.
  4. Oversizing eliminates the need for a load calculation

Explanation

An oversized unit short-cycles, which reduces runtime needed for latent removal and can hurt part-load efficiency and humidity control. Close matching, using manufacturer performance data, supports better comfort and efficiency.

Question 34Site Survey, Load Calculation, and Equipment Selection

Which document should a technician reference to confirm the allowable clearances around a new outdoor heat pump unit during the site survey?

  1. The refrigerant piping schematic from a different brand
  2. The manufacturer's installation manual for the specific model Correct answer.
  3. The homeowner's utility bill history
  4. The local building permit application form

Explanation

Clearance requirements are model-specific and are published in the manufacturer's installation manual, which governs airflow and service access. Other brands' schematics or unrelated paperwork cannot establish the required clearances.

Question 35Site Survey, Load Calculation, and Equipment Selection

A survey finds the electrical panel is rated 100 A and the existing service load is near capacity. What is the most appropriate action before selecting a heat pump?

  1. Perform a service load calculation and plan for any required electrical upgrade Correct answer.
  2. Install a larger breaker than the panel rating
  3. Assume the heat pump draws no additional load
  4. Disconnect the range to free capacity without evaluation

Explanation

A service load calculation determines whether the existing panel can support the added heat pump load or whether an upgrade is needed. Installing an oversized breaker or making assumptions violates electrical code and safety.

Question 36Site Survey, Load Calculation, and Equipment Selection

Which factor most influences the selection between a single-zone and a multi-zone heat pump system during the survey?

  1. The number of independently controlled conditioned areas with differing loads Correct answer.
  2. The age of the homeowner's refrigerator
  3. The color of the outdoor unit cabinet
  4. The length of the thermostat wire

Explanation

Multi-zone systems are chosen when multiple areas need independent temperature control or have significantly different load profiles. Cabinet color, wire length, and appliance age do not determine zoning needs.

Question 37Site Survey, Load Calculation, and Equipment Selection

A survey measures 1,800 square feet of conditioned floor area in a climate with a design heat loss of 30 Btu/h per square foot. Which approximate heating load should guide preliminary equipment selection?

  1. 18,000 Btu/h
  2. 54,000 Btu/h Correct answer.
  3. 1,800 Btu/h
  4. 30,000 Btu/h

Explanation

Multiplying 1,800 square feet by 30 Btu/h per square foot yields 54,000 Btu/h. This rough check is only a preliminary estimate; a full room-by-room load calculation should confirm the final selection.

Question 38Site Survey, Load Calculation, and Equipment Selection

During the survey, a technician notes the outdoor unit will be placed where snow accumulation is likely. Why does this matter for equipment selection and placement?

  1. Snow has no effect on heat pump operation
  2. Snow blockage can reduce airflow and capacity, so elevation and clearance must be planned Correct answer.
  3. Snow improves heat transfer and should be encouraged
  4. Snow requires selecting a smaller unit

Explanation

Snow can block the coil and fan, reducing airflow and heating capacity, so units are often elevated above expected snow depth with proper clearances. Placement planning protects performance during winter operation.

Question 39Site Survey, Load Calculation, and Equipment Selection

Which measurement from the site survey is needed to verify that the selected air handler can deliver the required airflow?

  1. The external static pressure of the duct system Correct answer.
  2. The water heater's tank size
  3. The outdoor unit's paint finish
  4. The exterior wall thickness

Explanation

External static pressure, combined with the manufacturer's blower performance table, confirms whether the air handler can deliver design airflow against the actual duct resistance. Wall thickness, paint, and water heater size do not affect airflow capability.

Question 40Site Survey, Load Calculation, and Equipment Selection

A load calculation for a home shows a very low sensible heat ratio. What does this indicate about equipment selection?

  1. The home has a large latent load relative to sensible load, so moisture removal capacity matters Correct answer.
  2. The heating load is zero
  3. The home needs no cooling capacity
  4. The home has no latent load

Explanation

A low sensible heat ratio means latent load is a large share of the total, so the selected equipment must remove moisture effectively at part-load conditions. Selection should consider coil performance and controls that support dehumidification.

Question 41Site Survey, Load Calculation, and Equipment Selection

When surveying a home for a ductless mini-split installation, which factor most affects indoor head placement?

  1. The color of the ceiling
  2. The length of the condensate drain only
  3. The brand of the outdoor unit
  4. The supply air throw pattern and obstructions to air distribution Correct answer.

Explanation

Indoor head placement must ensure supply air reaches the occupied space without being blocked by furniture, beams, or walls. Throw pattern and obstructions determine comfort and are assessed during the survey.

Question 42Site Survey, Load Calculation, and Equipment Selection

A survey reveals the home has a sealed, tightly constructed envelope with mechanical ventilation. How does this affect the infiltration portion of the load calculation?

  1. Ventilation loads are never part of the calculation
  2. Infiltration should be assumed very high regardless of construction
  3. Infiltration must be ignored entirely
  4. Infiltration is reduced, but ventilation load from the mechanical system must be included Correct answer.

Explanation

Tight construction reduces uncontrolled infiltration, but deliberate mechanical ventilation introduces outdoor air that adds a sensible and latent load. The calculation must reflect both the reduced infiltration and the added ventilation load.

Question 43Site Survey, Load Calculation, and Equipment Selection

Which survey finding would most likely require selecting a heat pump with enhanced low-ambient heating performance?

  1. A home with many interior doors
  2. A mild climate with a winter design temperature rarely below freezing
  3. A home with a large attic fan
  4. A cold climate with a winter design temperature well below freezing Correct answer.

Explanation

In a cold climate, the design heat loss is high and outdoor temperatures are low, so standard capacity may not meet the load. Enhanced low-ambient performance or cold-climate-rated equipment helps maintain capacity.

Question 44Site Survey, Load Calculation, and Equipment Selection

During the survey, a technician records the orientation and area of all fenestration. What is the primary purpose of this data in equipment selection?

  1. To size the condensate pump
  2. To select the thermostat model
  3. To determine the refrigerant line length
  4. To calculate solar gain and conductive losses through windows and doors Correct answer.

Explanation

Fenestration data drives both conductive losses and solar gain, which are significant parts of the heating and cooling loads. These loads then feed into the equipment selection process.

Question 45Site Survey, Load Calculation, and Equipment Selection

A homeowner asks whether the new heat pump should be sized to the largest room's load or the whole-house load. What is the correct basis for equipment selection?

  1. The whole-house block load, with room-by-room data used for distribution design Correct answer.
  2. The largest single room's load
  3. The smallest room's load
  4. The outdoor unit's nominal tonnage alone

Explanation

Equipment is selected on the whole-house block load, while room-by-room calculations guide duct and distribution design. Sizing to one room or to nominal tonnage alone can misapply capacity.

Question 46Site Survey, Load Calculation, and Equipment Selection

Which combination of survey data is essential to select a heat pump that will satisfy both heating and cooling design conditions?

  1. Only the summer latent load
  2. Only the outdoor unit footprint
  3. Winter design heat loss and summer design total cooling load Correct answer.
  4. Only the winter design temperature

Explanation

A heat pump must meet both the winter design heat loss and the summer design total cooling load, so both calculations are required for proper selection. Using only one season's data can leave the system undersized in the other mode.

Question 47Site Survey, Load Calculation, and Equipment Selection

A survey shows the proposed outdoor unit location is within the required clearance of a dryer vent. What is the appropriate action?

  1. Seal the dryer vent permanently
  2. Relocate the unit or vent to maintain manufacturer clearances and avoid coil fouling Correct answer.
  3. Reduce the clearance because dryer vents are harmless
  4. Proceed because lint improves coil performance

Explanation

Dryer exhaust carries lint and moisture that can foul the coil and reduce performance, so the installation must maintain manufacturer clearances or relocate components. Sealing the vent or reducing clearance creates safety and performance problems.

Question 48Site Survey, Load Calculation, and Equipment Selection

Which survey practice best supports accurate equipment selection for a home with an addition that has different construction than the original structure?

  1. Ignore the addition because it is newer
  2. Calculate loads separately for each distinct construction area, then combine them Correct answer.
  3. Treat the entire home as one uniform construction type
  4. Size the equipment to the addition alone

Explanation

Areas with different insulation, fenestration, and tightness have different load characteristics, so they should be calculated separately and combined into the block load. Treating the home as uniform or ignoring the addition produces inaccurate results.

Question 49Electrical Power, Controls, and Low-Voltage Wiring

A heat pump's outdoor unit nameplate lists a compressor rated 208/230 V single-phase. The building supply measures 208 V. Which contactor coil rating should be selected for reliable compressor control?

  1. A 460 V three-phase coil
  2. A 208/230 V dual-rated coil Correct answer.
  3. A 24 V coil fed from a separate transformer
  4. A 120 V coil tapped from one leg

Explanation

Dual-voltage contactor coils are designed to pull in reliably anywhere in the 208–230 V band, which matches the nameplate range of the compressor. Selecting a coil outside the supplied voltage risks chatter, welded contacts, or coil burnout.

Question 50Electrical Power, Controls, and Low-Voltage Wiring

During a heat pump startup, the technician measures 0 VAC across the low-voltage transformer's secondary terminals while the primary reads 240 VAC. What is the most likely cause?

  1. Open secondary winding Correct answer.
  2. Defective reversing valve solenoid
  3. Low refrigerant charge
  4. Shorted thermostat wire

Explanation

If the primary is energized and the secondary reads zero, the transformer secondary winding is open or the internal fuse has opened. A shorted thermostat wire would typically blow a fuse but would not normally read 0 V across a healthy secondary.