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NATE Heat Pump ALL VERSIONS 2025 |
LATEST AND ACCURATE REAL EXAM
QUESTIONS WITH DETAILED ANSWERS |
VERIFIED FOR GUARANTEED PASS | LATEST
UPDATE
- When performing indoor air balancing tests, the thermostat should be set to: o A. Lowest fan speed o B. Cooling mode only o ✅ C. Bring on the indoor fan on mid-high speed o D. Heating mode Rationale: A mid-high fan speed allows for accurate air volume measurements during balancing.
- Most manufacturers recommend the thermostat wire should be: o A. 12 AWG o B. 14 AWG o ✅ C. 18 AWG o D. 20 AWG Rationale: 18 AWG is typically the smallest allowable size that meets voltage drop and safety standards.
- Voltage input to a compressor should be checked at the: o A. Thermostat o B. Line side of the contactor o ✅ C. Load side of the contactor o D. Breaker panel Rationale: Measuring at the load side confirms power is reaching the compressor.
- If 1st and 2nd stage are calling, the compressor runs, but not the electric heater in a heat pump: o A. Heater is defective o ✅ B. Second stage is open o C. Thermostat is in cool mode o D. Compressor is off Rationale: A break or fault in the second-stage circuit prevents the electric heat from energizing.
- After a compressor burnout, what should be done? o A. Recharge the system o ✅ B. Test the oil for acidity levels o C. Replace the contactor o D. Add more oil Rationale: Acid tests detect contamination from burnout, preventing further damage.
- The most accepted method to attach line sets to an AHU is: o A. Compression fittings o B. Flare connections o ✅ C. Brazing alloy D. Threaded joints Rationale: Brazing ensures strong, leak-free connections per manufacturer specs.
- Why are there more circuits in a HP outdoor coil than in an A/C coil? o A. Reduce energy use o ✅ B. Minimize pressure drop o C. Increase humidity D. Improve airflow Rationale: More circuits reduce refrigerant pressure drop, improving efficiency.
- What results from insufficient voltage or current to a solenoid? o A. Coil burn out o ✅ B. Vibration or chatter o C. Overheating D. Low suction Rationale: Low power causes unstable magnetic force, leading to solenoid chatter.
- To check for a grounded compressor, you should test for: o A. Voltage at the capacitor o ✅ B. Continuity from terminals to ground o C. Resistance between wires D. Amperage draw Rationale: Ground faults show continuity between windings and the compressor case.
- The coil of a potential relay is connected to: o A. Start and run terminals o ✅ B. Common and start terminals o C. Common and run terminals D. L1 and L Rationale: This allows the relay to sense motor startup conditions.
- C. Pump is faulty D. Oil is contaminated Rationale: A steady, immediate rise indicates a system leak.
- For refrigerant temperature accuracy on a large suction line (1 1/8" or more):
- A. Place TXV bulb at top of pipe
- ✅ B. Place TXV bulb at 4 or 8 o’clock position
- C. Place TXV bulb at bottom D. Clamp bulb to liquid line Rationale: 4 or 8 o'clock provides best contact and avoids oil pooling.
- Primary concern when bending soft copper is to:
- A. Avoid overheating
- ✅ B. Prevent reduction in cross-sectional area
- C. Prevent discoloration D. Create sharp bends Rationale: Flattened or kinked tubes restrict flow and reduce capacity.
- R-22 vapor line design aims to limit pressure drop to:
- A. 10 psi
- ✅ B. 6–7 psi or 6°F
- C. 2 psi D. 12 psi Rationale: Minimizing pressure drop preserves system efficiency and capacity.
- The primary purpose of flux when soldering is to:
- A. Join parts quickly
- ✅ B. Prevent oxidation
- C. Strengthen the joint D. Cool the pipe Rationale: Flux protects against oxidation for a clean, strong bond.
- Defrost runoff water from a heat pump must:
- A. Be recirculated
- ✅ B. Drain away from coil
- C. Freeze under the unit D. Flow into return duct Rationale: Standing water causes refreezing and restricts airflow.
- A component that reduces roof noise and seals against water for rooftop HP:
- A. Filter base
- B. Drain pan
- ✅ C. Curb gasket D. Flashing Rationale: Curb gaskets isolate vibrations and seal penetrations.
- When installing a heat pump coil on a fossil fuel furnace, you must:
- A. Insulate the furnace
- B. Install a TXV
- ✅ C. Prevent simultaneous heat pump and furnace operation D. Remove auxiliary heat Rationale: Simultaneous operation can damage components and waste energy.
- Hermetic compressor motor windings under deep vacuum may:
- A. Overheat
- ✅ B. Be damaged if energized
- C. Run normally D. Short circuit Rationale: Lack of pressure reduces insulation, risking arc or burnout.
- To consider a system fully evacuated:
- A. Must hold 1000 microns for 1 min
- ✅ B. Vacuum of 500 microns or lower
- C. Equal suction/discharge pressure D. No refrigerant present Rationale: 500 microns indicates air and moisture removal.
- If a system with 15 ft lineset is factory-charged for 5 lb 10 oz and has 25 ft total, add:
- A. 4 oz
- ✅ B. 6 oz (10 extra ft × 0.6 oz/ft = 6 oz → total = 6 lb)
- C. 12 oz D. No need to add Rationale: Extra refrigerant compensates for added line volume.
- Drive slips are typically used on:
- A. Top of duct
- B. Long sides
- ✅ C. Short sides D. All corners Rationale: Drive slips secure short sides while S-cleats handle long sides.
- To properly set a heat anticipator:
- A. Use manufacturer default
- ✅ B. Measure control circuit amperage C. Set to 0.4 A D. Match thermostat voltage Rationale: Proper setting prevents short/long cycling.
- The temperature difference between HP coil and ambient is called:
- A. Ambient delta
- ✅ B. Coil TD
- Supplying 170V to a 208/230V compressor will:
- A. Make it run cooler
- ✅ B. Cause current increase and overload trip
- C. Have no effect
- D. Lower efficiency Rationale: Low voltage causes high current draw and overheating.
- Condensation on a liquid line during cooling usually indicates:
- A. Overcharge
- ✅ B. Restriction in the line
- C. Normal operation
- D. Low airflow Rationale: Liquid line restrictions cause flashing and condensation.
- Cool air complaints in heat mode on HP often stem from:
- A. Dirty coil
- ✅ B. Excessive supply air velocities
- C. Low refrigerant
- D. High humidity Rationale: High airflow velocity reduces perceived warmth at diffusers.
- Given: HP return = 70°F, supply = 92°F, AUX heat = 115°F, CFM = 1228. Heating capacity?
- A. 21,
- ✅ B. 29,
- C. 24,
- D. 31, Rationale: Capacity = 1.08 × CFM × ΔT → 1.08 × 1228 × 22 = 29,177 BTUh.
- Clogged air filters in a heat pump can lead to:
- A. More cooling
- ✅ B. Inadequate heating
- C. Overcooling
- D. High refrigerant flow Rationale: Blocked airflow reduces heating capacity.
- Recommended air velocity in main supply trunks (residential):
- A. 1000–1200 fpm
- ✅ B. 700–900 fpm
- C. 400–600 fpm
- D. 1300–1500 fpm Rationale: Keeps system quiet and efficient.
- With 15% return leak in 95°F ventilated attic on 2.5-ton system:
- ✅ B. Major performance issue due to hot air infiltration
- C. Can be ignored if filter is clean
- D. Ducts are oversized Rationale: Leaking hot attic air reduces cooling capacity.
- With piston metering, outdoor temp 75°F, superheat 55°F:
- A. Overcharge
- ✅ B. Low refrigerant charge
- C. Dirty coil
- D. Defective piston Rationale: High superheat typically indicates undercharge.
- Adding refrigerant to a system will:
- A. Decrease superheat
- ✅ B. Increase subcooling
- C. Lower static pressure
- D. Raise coil TD Rationale: More liquid refrigerant leads to higher subcooling.
- Overcharged capillary tube system results in:
- A. High superheat
- ✅ B. Low superheat and high subcooling
- C. High suction pressure
- D. Normal operation Rationale: Too much refrigerant floods evaporator, reduces superheat.
- Low charge effect on reversing valve:
- A. Makes valve stick open
- ✅ B. Reduces valve’s ability to switch
- C. Causes system to short cycle
- D. Increases coil TD Rationale: Low pressure impairs valve function.
- Compressor hums then trips internal overload at startup:
- A. Bad contactor
- ✅ B. Excessive pressure difference across compressor
- C. Low voltage
- D. Faulty relay Rationale: High pressure difference makes compressor stall.
- 40VA transformer with 24V secondary – max current draw:
- A. 2.0 amps
- ✅ B. 1.7 amps
- C. 1.2 amps
A split system heat pump is using thermostatic expansion valves. The system performs properly in heating but in cooling the compressor pumps down... - ANSWER Which could mean the main power element of the indoor expansion valve has lost its charge Conditions that can cause a reduction from design capacity in a heat pump are an... - ANSWER Undersized vapor line A symptom that a technician would expect on a heat pump system in the cooling mode if the check valve is leaking internally is... - ANSWER Flooding of the indoor coil A voltage reading across a closed contact in a 24V control circuit indicates... - ANSWER Pitted or dirty contacts The first two checks typically made on an electronic check are... - ANSWER Presence of proper input signals and proper output signals In a low voltage circuit, a corroded wire-to-terminal connection acts in the circuit like... - ANSWER An additional resistor The continuity of a fuse should be tested by... - ANSWER Checking resistance with the power off The first check made for most electrical troubleshooting is... - ANSWER Voltage check of the supply line To properly check an energized compressor circuit... - ANSWER The technician should use a VOM set for volts The following conditions exist in a circuit that supplies power to three parallel loads
- One load is resistive
- One load is capacitive
- One load is inductive - ANSWER The total current in the circuit when operating will be the sum of the currents through each load The technician is using an analog multimeter to check a run capacitor. With the meter set to ohms, the needle swings toward zero and then slowly rises toward infinity... - ANSWER This tells the technician that the capacitor charges and discharges If the technician believes that a hermetic compressor has a permanently open internal protector... - ANSWER The technician should test the compressor while it is cool A control string is defined as two or more switch contacts connected in a circuit, or set of circuits, to control a load. In order to troubleshoot a load controlled by a control string... - ANSWER The technician must first check for proper voltage applied across the load The technician suspects that an outdoor thermostat used to bring on auxiliary heat may out of calibration. The thermostat is a CLOSE ON FALL type that is adjustable. One method for checking the thermostat calibration is to... - ANSWER Manually rotate the shaft until the thermostat until the thermostat closes and then compare the dial setting to an accurate outdoor temp. reading plus 10F When changing out the evaporator coil the installer mjust be certain to... - ANSWER Plumb the cabinet so its sides are vertical The recommended maximum external static pressure used for heating and cooling equipment with blowers for 5 ton of cooling or less is... - ANSWER 0.1 inWC When a balancing check of a newly installed duct system the... - ANSWER Dampers should be open completely in all rooms Operating sound is a consideration in the location of a condensing unit because... - ANSWER Excessive noise could be disruptive to the customer
The three things that happen when a heat pump is cycled into the defrost mode are... - ANSWER Reversing valve switches to cooling mode, Outdoor fan turns off, and Auxiliary heat is energized An extended plenum duct system is a... - ANSWER Single trunk extending in one or two directions with many branch ducts The effect on supply airflow when static pressure on the return is reduced is... - ANSWER Airflow will be increased The voltage most often used to power the outdoor unit in a residential system is... - ANSWER 240V single phase Residential control or low voltage wiring normally is... - ANSWER Shredded wired If you increased suction pressure on a reciprocating compressor... - ANSWER The capacity would increase The refrigerants typically used in residential and light commercial pumps... - ANSWER Have a storage life of an indefinite length of time A restricted drier can cause... - ANSWER A lower than normal suction pressure The blower motor type generally used on air handling equipment with capacities of 4000cfm or greater is... - ANSWER A belt driven 3 phase Electronic air cleaners can operate with internal voltages as high as... - ANSWER 5000V A "cross-break" made on all flat sides of any rectangular section of metal duct will... - ANSWER Increase rigidity and reduce vibration
The terms grille and register are often used interchangeably. There is a difference between these components. The primary difference between a grille and a register is... - ANSWER A register is equipped with an air volume control device, while a grille is not Thermostatic expansion valves meter refrigerant flow to a coil to... - ANSWER Maintain superheated refrigerant leaving the coil Some electromechanical type thermostats require connections to Both the hot side and Common side Of the low voltage transformer... - ANSWER Because the display lights must be powered using both sides of the line Disc type temperature limit controls, used to protect auxiliary heat elements from overheating are... - ANSWER Always auto reset by temperature A disc-type, close-on-rise pressure control is being used as a loss-of-charge limit control on the liquid line of a heat pump. The control must sense a specified pressure within 15 seconds of a compressor start for the compressor to continue operation. If the cut-in setting of the control drifts lower... - ANSWER The system is less likely to shut down as a result of a small leak The sensor of an outdoor ambient thermostat for a heat pump system is typically installed in the... - ANSWER Entering airstream to the outdoor coil A high pressure limit control, used to shut down a compressor if condensing pressure becomes excessive is... - ANSWER Typically installed to sense compressor discharge line pressure Low pressure limit controls are often placed in the suction line of a heat pump for two purposes. They are to... - ANSWER Protect the compressor if suction pressure drops, and to detect a loss of charge
According to fire protection codes, fire dampers should be used in Any air duct the passes through walls or... - ANSWER Partitions of a light commercial installation When the capacity of a heat pump in heating, measured in Btu's, is the same at the heat loss of a structure... - ANSWER The system is sad to have reached its balance point Electronic air cleaners... - ANSWER DO NOT remove odors A packaged heat pump must be... - ANSWER Mounted on a slab if its location is at grade level Whenever possible, the slab should be... - ANSWER Located away from the structure to minimize noise A suction line accumulator should be used in a residential heat pump only when recommended by the manufacturer... - ANSWER If long refrigerant lines increase system charge over recommended maximum charge The measurement of a heat pumps efficiency is often stated using its 'Coefficient of Performance' or COP. The COP of a heat pump is the... - ANSWER Heat pumps heat output in watts/ Total electrical input in watts A benefit in using electronic air cleaner is... - ANSWER Indoor air quality(IAQ) is improved The purpose of calculating the heat loss at a outside design temperature is to... - ANSWER Select appropriate equipment based on Btu output The thermal balance point of a dual fuel heat pump is... - ANSWER The outdoor conditions at which the capacity of auxiliary heat alone matches the heating load
The minimum circuit amp listed on a units' data plate is used to... - ANSWER Determine the max fuse or circuit breaker size heat pumps are particularly sized based on... - ANSWER The cooling load The effective method of reducing sound when AHU is located in a closet is to... - ANSWER Use vibration isolators When wiring a 20 amp FLA motor, the minimum amp fuse or circuit breaker... - ANSWER Should be 25 The typical staging of a two stage heat pump system uses the... - ANSWER Deviation of the t-stat setting to determine when to engage each stage The purpose of a sequencer in a heat pump with an AUX 20 kW electric heater is to... - ANSWER Energize one or two elements and the blower then energize the other elements in timed intervals In a heat pump circuit, an open check valve is used to... - ANSWER By-pass refrigerant flow around the metering device The forward curve centrifugal fan is the... - ANSWER Most commonly used type in residential systems In a reversing valve... - ANSWER The single pipe is connected to the compressor discharge What is the purpose of the reversing valve on an air-to-air heat pump: - Ans - It changes the flow of the refrigerant, making the indoor coil the condenser during the winter months On a reversing-valve solenoid, what is connected to the top tube: - Ans - the compressor discharge line
What position must the reversing valve be in during the defrost cycle: - Ans - the cooling mode When a heat pump switches into the defrost cycle, it must: - Ans - remain in defrost until the outdoor coil has reached a predetermined temperature A defrost termination thermostat is commonly located: - Ans - on the outdoor coil, and opens at 55° F What type of system uses a temperature and a pressure sensor to control the defrost cycle: - Ans - a pressure-initiation-temperature-termination defrost system A pressure switch, used on the defrost cycle of a heat pump, commonly closes at a preset pressure difference of: - Ans - .5" to .65" WC Temperature split refers to: - Ans - the temperature difference between the air entering a coil and the temperature of the coil The outdoor ambient thermostat is commonly used to: - Ans - energize the auxiliary strip heaters during the second stage of heating A hold-back thermostat is used to: - Ans - keep the system energized during a defrost cycle, when the room thermostat is satisfied A discharge temperature thermostat is used: - Ans - on air-to-air heat pump systems that use fossil fuel When sizing a heat pump, it must initially be sized for: - Ans - the cooling load
When sizing for the auxiliary heat for a heat pump system, the auxiliary heat must: - Ans - be capable of handling the entire heat load of the structure Auxiliary strip heaters are: - Ans - located at the indoor unit downstream from the indoor coil What controls the auxiliary strip heaters in a heat pump system: - Ans - the second stage of a two-stage thermostat What is the purpose of the de-ice coil on an air-to-air heat pump: - Ans - It prevents the formation of ice on the lower section of the outdoor coil The coefficient of performance (COP) is: - Ans - a heat pump's rating in the heating cycle, comparing the heat output by the electrical input When installing a heat pump system, the unit should always be located as close to the indoor unit as possible because: - Ans - during the heating cycle a longer vapor line will cause the system to operate less efficiently When installing an outdoor coil, it must: - Ans - never be placed under the overhang of the building What are common supply-air static pressures for a heat pump duct system: - Ans - .15" WC What is a common temperature rise over the indoor coil of a heat pump during the heating cycle: - Ans - 35° F When installing an indoor unit, a clearance that is commonly required for service accessibility is:
