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COMPLETE: NATE Heat Pump Exam
(QUESTION WITH ANSWERS) LATEST
UPDATE 2024/
On an R-22 system, line diameters and lengths are typically specified for a vapor pressure drop that does not exceed what? 6 - 7PSI or 6F What is the primary purpose of using flux when soldering copper or brass parts? Prevent Oxidation The water that results from a defrost cycle of an air to air heat pump(runoff) must? Drain off and away from the outdoor coil. Why must the runoff be drained off and away from the outdoor coil? Excessive ice can build up on the bottom of the coil and can reduce capacity. What is the component that reduces sound transmission and prevents water leaks of a package heat pump installed on a roof? Curb Gasket
Why do you need to add a control for a heat pump indoor coil that is installed on a fossil fuel furnace? So the heat pump and furnace do not operate at the same time in normal heating. What happens when you energize a hermetic refrigeration compressor and the system is in a deep vacuum? Motor windings could become damaged. What needs to happen in order to consider an evacuation to be complete? System should be evacuated to a vacuum of 500 Microns or below. A system is supplied from the factory with charge for a 15 foot line set. The data plate shows the required system charge to be 5 pounds 10 ounces. The line set uses a 3/8 inch liquid line and is 25 feet long. The manufacturer's instruction sheet specifies 0.6 ounces of refrigerant to be added for each added foot of refrigerant line length. How much refrigerant is needed to completely charge the system? 6lbs Where are drive slips typically installed? On the shorter sides of rectangular duct. What is a necessary check to properly set a heat anticipator? Heating control circuit amperage draw.
When performing preventive maintenance on a heat pump what should the technician check and why? Outdoor fan. To be certain it runs freely with no binding. What is the effect of 170 volts supplied to a 208/230 volt compressor? Would cause the current to increase and the motor may trip on overload. On a service call for a cooling problem with a heat pump, your inspections find a liquid line that has condensation on it. What is most likely to cause this? Restriction in the liquid line. What is a reason for cool air complaints when a heat pump is operating in the heating cycle? Excessive supply air velocities. The following measurements are recorded on an operating heat pump system. The heat pump is operating with the compressor only with no auxiliary heat:
- Heat pump only supply air temperature 92°F
- Heat pump only return air temperature 70°F
- Outdoor temperature 54°F
- Supply air temp. /auxiliary heat ON 115°F
- Return air temp. /auxiliary heat ON 70°F
• CFM 1228
What is the heating capacity in BTUH? 29,177 BTU/H Inadequate heating can be caused by what? Dirty or clogged air filter. To minimize noise problems in residential duct systems, what is the range (recommended to maximum) of design air velocity in the rectangular main supply trunk? 700 to 900 fpm conditions while checking a packaged heat pump in cooling.
- The unit has a piston type metering device on both the indoor and outdoor coils.
- Outdoor temperature 75°F
- Superheat 55°F What is wrong with the system? Undercharged. What will you get when a capillary tube is overcharged?
A split system heat pump is using thermostatic expansion valves. The system performs properly in heating but in cooling the compressor pumps down. What could this mean? The power element of the indoor expansion valve has lost its charge. What condition can cause a reduction from design capacity in a heat pump? Undersized vapor line. What is the result of excessive liquid line length or lift? Flash gas. What symptom could a technician expect on a heat pump system in the cooling mode if the check valve is leaking internally? Flooding of the indoor coil. Voltage across a closed contact in a 24V control circuit could indicate what? Pitted or dirty contacts. What two checks typically made first on an electronic control? Proper input voltage and proper output voltage. In a low voltage circuit, what does a corroded wire-to-terminal connection acts like? An additional resistor.
How should you test the continuity of a fuse? Power off, fuse removed What is the first check made for most electrical troubleshooting? Voltage check of the supply line. 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 How do you find the total current? 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. What does this tell the technician? The capacitor charges and discharges. When should a technician test a hermetic compressor for a permanently open internal overload protector? While its cool.
Why is operating sound is a consideration in the location of a condensing unit? Because excessive noise could be disruptive to the customer A technician has determined a supply in a flexible duct system is leaking. What should be checked? All connections inner and outer layers. What is sensible heat ratio? sensible removed ÷ total heat removed Service site conditions are:
- House feels "drafty" in cooling
- 3½ ton split system
- High supply face velocities
- Ductwork is properly sized
- Total CFM 1400 What does this indicate? These readings indicate the system is operating normally but the supply registers are too restrictive
When a wet bulb reading is very close to the dry bulb reading from the same instrument, what does this indicate? Relative humidity is high. What measurements would be needed to properly evaluate a complaint of "drafty" operation with a heating system? System TD, Drop, and Static Pressure What kind of energy does the condenser remove from the refrigerant? Sensible heat and Latent heat Where does refrigerant boil? In the Evaporator. What is the common suction line on a heat pump connected to? The indoor coil and the compressor. What are the two generally used methods for changing capacity on demand in a heat pump? Two speed compressor. Two stage thermostat What are the three things that happen when a heat pump is cycled into the defrost mode? Reversing valve switches to cooling mode, Outdoor fan is shut off, and auxiliary heat is energized.
Electronic air cleaners can operate with internal voltages as high as? 5000V What is the purpose of a cross break on the flat sides of metal ductwork? Increases rigidity and reduces vibration Whats the difference between a grille and a register? Register is equipped with a air volume control device, grille is not. What is the purpose of a thermostatic expansion valve (TXT, TEV)? Meter refrigerant flow to a coil to maintain superheater refrigerant leaving the coil What are Disc type temperature limit controls used for? Protect auxiliary heat elements from overheating. How are disc type temperature limit controls reset? By temperature. When the heat elements cool the switch resets. Where is the sensor of an outdoor ambient thermostat for a heat pump system typically installed? In the entering air stream to the outdoor coil.
A high pressure limit control is used for what? To shut down a compressor if condensing pressure becomes excessive Where is a high pressure limit control installed? Compressor discharge line. Where are low pressure limit controls installed? The suction line of a heat pump. What is the purposes of a low pressure limit control? Protect the compressor if suction pressure drops too low. To detect loss of charge. The timing specification of sequencers is often marked on the device using a code similar to what? H1-24 C45- 75 What is the specification for this sequencer code: H1-24 C45- 75 Contacts close 1-24 seconds after coil is energized and contacts open 45-75 seconds after coil is de- energized. What is the capability of electronic programmable room thermostat to reset the set point early so that the space temperature reaches a set temperature at a specific time called? Computed recovery
Heat pumps heat output (watts) divided by its total electrical input (watts) What is a benefit in using electronic air cleaner? Indoor Air Quality (IAQ) quality is improved. What is the thermal balance point of a dual fuel heat pump? Outdoor conditions at which the capacity of auxiliary heat alone matches the heating load. What is the minimum circuit amp listed on a units' data plate is used to determine? The max fuse or circuit breaker size. How are heat pumps particularly sized? Based on the cooling load. What is an effective method of reducing sound when AHU is located in a closet? Use Vibration isolators. When wiring a 20 amp FLA motor what is the minimum amp fuse or circuit breaker that should be used? 25amp How is the typical staging of a two stage HP system determined? Use the deviation of the t-stat setting to determine when to engage each stage.
What is the purpose of a sequencer in a HP with an AUX 20 kW electric heater? Energize one or two elements and the blower then energize the other elements in timed intervals. In a HP (heat pump) circuit what is used to by-pass refrigerant flow around the metering device? An open check valve. What is the most commonly used type of fan in residential systems? The forward curve centrifugal fan. When is condensation on vapor lines a concern?when the lines are routed inside a wall. When lines are routed inside a wall. In a single zone system; if a customer complains of feeling damp or sticky the cause could be what? Unconditioned air being pulled into the duct work through holes in the duct. When performing indoor air balancing tests how should the t-stat should be set? Should be set to bring on the indoor fan on mid-high speed. Most manufacturers recommend what size t-stat wire? The smallest most allowable, 18AWG (All Weather Gauge)
What is the purpose of an auto change over switch on a t-stat? To allow automatic change over between heating and cooling. What is the result of undersized duct work? High noise levels, high air quantity, and high static pressures. Where should the sensing bulb on a TXV be located to obtain an accurate refrigerant temperature on a horizontal suction line that is 1&1/8" or larger? Should be located at 4 or 8 o'clock position on the line. What factors affects a customer's level of comfort? Air movement Humidity Temperature What are the three processes that transfer heat energy? Conduction Convection Radiation Heat transfer that occurs when substances of different temperatures are in contact with each other is called?
Conduction What effect does raising the pressure in a sealed system have on refrigerant? The refrigerants boiling point increases. What is the primary danger to people near an accidental refrigerant release or spill? Suffocation caused by the heavier refrigerant displacing oxygen in the air. The maximum temperature at which refrigerant may be stored is__________ when the container is no more than ________% full 125F, 80% Why is superheat necessary in a system that utilizes hermetic compression? It ensures that dry vapor reaches the compressor so that mechanical damage does not occur When heat heat load on an evaporator increases, what is the effect on the system? Suction pressure and discharge pressure both increase What type of energy is transferred when work is done in the condenser? Both latent and sensible heat Which component pumps refrigerant through the system and raises the
