Exam (elaborations)
NATE Air Conditioning and Heat Pump Exam 2023
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NATE Air Conditioning and Heat Pump Exam 2023
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NATE Air Conditioning and Heat PumpWhich of the following factors affects a customers level of comfort? - Answer- 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. - Answer- +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. - Answer- +25%
The combined output of a heatpump and its auxiliary heat should not exceed the calculated heat loss of a home by more than ____%. - Answer- 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? - Answer- 3.2 kWh
The three processes that transfer heat energy are conduction, convection, and _________. - Answer- Radiation
Heat transfer that occurs when substances of different temperatures are in contact with each other is called _______. - Answer- conduction
What effect does raising the pressure in a sealed system have on refrigerant? - Answer-
The boiling point increases
What is the primary danger to people near an accidental refrigerant release or spill? - Answer- 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.; - Answer- 125 F, 80%
Boiling of the refrigerant occurs in which system component? - Answer- Evaporator Why is superheat necessary in a system that utilizes hermetic compressors - Answer- 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? - Answer- Suction pressure and discharge pressure both increase
What type of energy is transferred when work is done in the condenser? - Answer- Both
latent and sensible heat energy
What is the primary function performed by a thermal expansion valve? - Answer- It maintains the correct superheat in the suction vapor leaving the evaporator
Which component pumps refrigerant through the system and raises the vapor temperature? - Answer- compressor
How are hermetic compressor motors cooled? - Answer- With suction vapor drawn from
the evaporator
Heat pump compressors sometimes run hotter than compressors used in cooling-only units because heat pump compressors _____. - Answer- exhibit low refrigerant density at low suction pressures during the heating cycle
When is crankcase heat most needed? - Answer- When the compressor is off
Work done on the refrigerant in the condenser is transferred as ____. - Answer- 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? - Answer- 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? - Answer- 3.0 gpm per ton
What tool should be used to shorten a capillary tube? - Answer- A triangular or knife-
edge file
Which pressure in a TEV is opening pressure? - Answer- bulb pressure
What effect does a low refrigerant charge have on reversing valve operations? - Answer- It increases the chance that the reversing valve will not be able to transfer properly
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