NATE Air Conditioning and Heat Pump with 100% correct answers

Which of the following factors affects a customers level of comfort? All of the above A cooling load calculation estimates the sensible heat gain of the structure. The cooling-only system should be within _____% of this calculated value. +15% The maximum sensible cooling capacity of a heat pump should be within ______% of the calculated sensible heat gain of a structure with a large heating load. +25% The combined output of a heatpump and its auxiliary heat should not exceed the calculated heat loss of a home by more than ____%. 15% What amount of auxiliary electronic heat is needed when the output of a heat pump on a design day equals 18,800 Btuh and the heat loss of a home is 29,700 Btuh? 3.2 kWh The three processes that transfer heat energy are conduction, convection, and _________. 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 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 ______ F when the container is no more than ____% full of liquid by volume.; 125 F, 80% Boiling of the refrigerant occurs in which system component? Evaporator Why is superheat necessary in a system that utilizes hermetic compressors It ensures that dry vapor reaches the compressor so that mechanical damage does not occur When the 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 energy What is the primary function performed by a thermal expansion valve? It maintains the correct superheat in the suction vapor leaving the evaporator Which component pumps refrigerant through the system and raises the vapor temperature? compressor How are hermetic compressor motors cooled? With suction vapor drawn from the evaporator Heat pump compressors sometimes run hotter than compressors used in cooling-only units because heat pump compressors _____. exhibit low refrigerant density at low suction pressures during the heating cycle When is crankcase heat most needed? When the compressor is off Work done on the refrigerant in the condenser is transferred as ____. Both sensible and latent heat Why are more circuits needed in the outdoor coils used in heat pumps than in the condenser coils used in cooling-only units? To keep the pressure drop across the outdoor coil low What is they typical water flow rate per ton of cooling for water-source heat pumps operating in closed loop systems? 3.0 gpm per ton What tool should be used to shorten a capillary tube? A triangular or knife-edge file Which pressure in a TEV is opening pressure? bulb pressure What effect does a low refrigerant charge have on reversing valve operations? It increases the chance that the reversing valve will not be able to transfer properly When adding a heat pump to an existing fossil-fuel furnace, an installer must do all of the following except ______. Make sure that the new number of fins per inch of the new coils equals that of the replaced coils What is the purpose of a receiver? It store liquid refrigerant What is the typical storage life of modern refrigerants? Modern refrigerants have an indefinite storage life Which of the following should be used to leak-test refrigerant tubing? Dry Nitrogen Of the motors commonly used in HVACR systems, which type has the lowest starting torque? Shaded-pole motor What is the typical phase angle for a split-phase motor? 30 What determines the staging of a two-speed compressor in a heat pump application? Deviation from setpoint of the thermostat The NEC approves a _____ dual-element time-delay fuse as overcurrent protection for a 20 A motor. 60-A Voltage supplied to a motor may vary from the rated voltage by _____%. +10%,-10% What is one of the most Important reasons for using electronic controls in HVACR systems? they make decisions based on many inputs Hard-start kits are often needed on ______. reciprocating compressors used with TEVs A 24-V transformer with a 40-VA rating can operate safely with a current of _____. 1.67 A Some electromechanical thermostats must be connected to both sides of the transformer in order to power the _______. display lights on the subbase A cooling anticipator in the control circuits is connected in _____ with the _____ switch of the thermostat. parallel, cooling According to Ohm's Law, what will happen if the voltage to a heater element is increased by 10%? The current draw will increase by 10% When air flow through an electric heater is not sufficient, the technician will observe ______. Heater elements glowing red or orange Which of the following combination of measurements indicates an open heater element? Voltage to the heater with no current draw through the heater elements Which of the following functions occur when a heat pump goes into a defrost cycle? The auxiliary heat comes on, the outdoor fan stops running, and the reversing valve switches to the cooling mode What internal voltage is likely to be measured in an electronic air cleaner? 5,000 V What precaution must you take when installing a dual-fuel split system? The control system must not allow the heat pump and furnace to operate at the same time during a normal heating cycle What problem is likely to occur if a proper trap is not used on the condensate drain for a draw-through unit? condensate water will not drain properly and will back up above the primary drain. Which of the following issues affects the decision to use a running trap on a condensate line at the evaporator coil? Running traps do not allow for the proper drainage of condensate water The auxiliary drain line from an overflow pan must _____. Be terminated at some conspicuous location so that an overflow is readily noticed Which of the following statements about a packaged unit installation is true? The pad used to support a package heat pump should not make contact with the building Which of the following brazing materials is acceptable for use on refrigerant piping? Brazing alloy with an approved flux What type of flame is recommended for brazing refrigerant piping? Neutral flame Why must you exercise special care when you bend soft-drawn refrigerant tubing? Any distortion of the tubing diameter creates a restriction to refrigerant flow that reduces system capacity the evacuation of a refrigerant circuit is considered complete when a vacuum of _____ can be maintained. 500 microns or less As the length of electrical wire increases, its resistance _____ while the temperature is maintained at a constant level Increases What is the thermal balance point of a heat pump system? The outdoor air temperature at which the output of the heat pump equal the heat loss of the home What voltage is measured between any two legs of the three hot legs in a delta-connected 240-V three-phase distribution panel? 240 V Which of the following statements about the installation of an electronic air cleaner (EAC) is true? An EAC should be wired so that it operates only when the on/off switch is in the "on" position and the supply air blower is operating What is the indoor air flow for an electric furnace when the supply air temperature is 98 degrees F, the return air temperature is 70 degrees F, the voltage being supplied to the furnace is 220 V, and the current draw of the furnace is 47 A? 1,170 cfm Which of the following statements about understanding wiring diagrams is Not true? Schematics are always shown with the circuits energized Some types of loads may be connected in series. Which of the following are loads that must not be connected in series? motors Which of the following electrical components is a power-passing device? Fan Switch In wiring diagrams, solid heavy lines usually indicate ______. Factory-installed line-voltage wiring In wiring diagrams, dashed or dotted lines usually indicate ______. Field-installed wiring All safety switches must be _____ connected in series with the control switch Refer to figures 6-13 and 6-14 to determine which of the following statements about the circuit shown is true. The crankcase heater is energized when the contactor contacts are open Refer to Figure 6-15 to determine which of the following statements about the circuit shown is true. The crankcase heater is energized whenever voltage is supplied to L1 and L2