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NATE Test

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Created by: Tg89

Question	Answer
Miscibility is the ability of the fluid to? Readily mix with other fluid Reacts with air and forms corrosion compounds Reacts with water and forms acidic compounds Reacts with water and air and burns	Readily mix with other fluid.
Most of the heat transfer from the heat exchanger is by which of the following?	convection
The heat energy change that is associated with a change in the phase (state) is?	Latent heat
_____ temperature is the temperature is the temperature below which moisture condense out of air? ______ Wet bulb Dry bulb Dew bulb	Dew bulb
True or false RTD which measure temperature have a positive temperature coefficient?	true
Heat transfer that takes place in liquids and gases in which of the following: Conduction None of the option is correct Radiation Convection
	Convection
1 horsepower = _________ watts: 3.41 3140 746 7460	746
True or false Mineral oils are not to be used with HFC alternate refrigerants:	True
In Psychrometric ________ indicates which of the following: Dew point temperature line? Lines that run diagonally from left to right across the chart Chart curved boundary X axis Y axis	Chart curved boundary
The downstream velocity of the sound wave between the points is greater than that of the same wave in a fluid at rest. This is due to: Hall effect Newton effect Doppler effect Acoustic effect	Doppler effect
In which of the following heat transfer will be in the form of waveform. Conduction All the options are correct Convection Radiation	Radiation
Dew point temperature is the temperature at which web bulb temperature is _________ the dry bulb temperature: Lesser than Greater than Equal to	Equal to
The temperature-resistance characteristic of a thermistor is _________ Linear Non linear	Non linear
Which of the following type of controllers are used in HVAC applications? PI I ID P	Pi
Gas valves operate at _____ voltage:	24v
When there is an increase in the heat load on the evaporator, the refrigerant will tend to evaporate at a _____ rate: Faster or Slower	Faster
The ________ of the manifold gauge set is used to charge, evacuate, add oil and recover refrigerant from a refrigeration and air conditioning system: Blue hose, Yellow hose or Red hose	Yellow hose
_______ use two special helical rotors that introduce suction vapors then compress them: Scroll Compressors, Reciprocating Compressors, All the options are correct or Screw Compressors	Screw Compressors
1 Watt = _____ Btu? 3140, 0.341, 341 or 3.41	3.41
Propane and Butane are _______ than air: Same weight, Heavier or Lighter	Heavier
Which of the following shall not be used near flammable material: Ultrasonic leak detector, Electronic leak detector, Halide leak detector or Sulfur leak detector	Halide leak detector
_______ is the temperature at which oil starts to produce a waxy substance that may interfere with the refrigeration system: Pour point Floc point Boiling point Dash point	Floc point
An oil separator is located in the _____: Liquid line Expansion line Suction line Discharge line	Discharge line
Higher the ambient temperatures, ____ will be the evacuation time of the refrigerants from the system: Higher Lesser	Lesser
Furnaces are placed into categories based upon: Total airflow in CFM Venting characteristics Btuh capacity range Gas valve type	Venting characteristics
A high pressure steam boiler operates at a pressure greater than ______ : 15 psig 20 psig 25 psig 5 psig	15psig
______ is the heat that is absorbed or extracted when a substance changes its state: Entropy Specific heat Latent heat Enthalpy	Latent heat
Sight glass is present at _____ in the refrigeration cycle Liquid line Suction line Expansion line Evaporation line	Liquid line
What will be the resistance in the circuit if the supply voltage is 30V and current flowing through the circuit is 5A: 6 ohms 1/6 ohms 3 ohms 1/3 ohms	6 ohms
Current in a closed circuit is limited by which of the following: Resistance Heat Temperature Voltage	Resistance
1 kilo watt = ______ Btu 0.003140 3140 341 3.41	3140
Dual voltage three phase motor has _____ number of terminals 9, 6, 12 Or 3	9
Which of the following gas is used for purging or pressurizing a refrigerant or air conditioning system: Air Oxygen All the options are correct or Nitrogen	Nitrogen
Which of the following is used to remove the trapped air from a low pressure system from the top of the condenser: Purge unit Compressor unit Recover unit Discharge unit	Purge unit
The tubes of the indoor evaporator coils are made of which of the following: Aluminum Copper Steel Brass	Copper
Turning the TXV valve stem in _______ direction increases super heat: Counter clockwise Clockwise	Clockwise
Which of the following compressor uses pistons, cylinders and valves to compress the refrigerant gas: Screw compressor Both Reciprocating and screw compressors None of the options are correct Reciprocating compressor	Reciprocating compressor
Which of the following law states that the total pressure of a confined mixture of gases is the sum of pressures of each of the gases in the mixture: Dalton's law Boyle's law Charles's law Fleming's law	Dalton's law
True or False The larger the diameter of the center hose, higher will be evacuation time of the refrigerant from the system:	False
______ is the process in which solid turning directly into a vapor without going through the liquid phase: sublimation saturation subcooling superheating	sublimation
Which one of the following is known as the line that connects between the metering device and the evaporator: Inlet line Suction line Liquid line Discharge line	Inlet line
At 32°F, 1 lb of ice can be changed to 1 lb of water by adding ____ Btu 144 Btu 36 Btu 108 Btu 72 Btu	144 Btu
Which of the following circuit does not have multiple paths for current flow: parallel ac series dc	series
Relays and contactors are ____ control switches: pressure-activated temperature-activated electrically operated manually operated	electrically operated
In Fire tube boiler, which of the following pass through the tubes: either flue gases or hot water hot water flue gases	flue gases
True or False Modern high-efficiency burners use combustion blowers	True
Air handling equipment controls which of the following parameter: quality of air humidity temperature All the options are correct	All the options are correct
Curved boundary In Psychrometric chart indicates which of the following: Dry bulb temperature Latent heat Dew point temperature line Humidity ratio	Dew point temperature line
In water-tube boilers, pressures range from ______ : 50 to 500 psig 50 to 5000 psig 50 to 500,000 psig 50 to 50,000 psig	50 to 5000 psig
The heat energy change that is associated with a change in the phase (state) is: Sensible heat Latent heat Absolute heat Super heat	Latent heat
_____ is a combination of both sensible heat and latent heat: Enthalpy Entropy Resultant heat Absolute heat	Enthalpy
What will be typical range of the current sensor: 4-20 mA 0 - 5 mA 5 - 20 mA 0 - 10 mA	4-20 mA
Approximately _____ voltage is required for creating a spark on a spark ignition system: 150V 1500V 15000V 150000V	15000V
_____ is the air that is mixed with the fuel before the fuel reaches the burner: Primary air Secondary air Tertiary air None of the answers are correct	Primary air
Which one of the following in the refrigeration cycle changes the refrigerant from low pressure gas to high pressure gas: Evaporator Compressor Condenser Expansion device	Compressor
Which one of the following is used in systems for pressurizing the building: Exhaust or relief dampers Exhaust None of the above Relief dampers	Exhaust or relief dampers
True or false Heat transferred by radiation travels through space without heating the space	True
	Manometer
Disposable air filters should be changed atleast _______ times in a year: Twice Thrice Four times Once	Twice
Which of the fuels burns less efficiently than other: liquid fuels solid fuels gaseous fuels combustion efficiency will be same for all fuels	solid fuels
The reclaimed refrigerant must meet the standards of _________ before it can be resold: ARI 500 ARI 740 ARI 1000 ARI 700	ARI 700
For every 1000 feet above sea level,the capacity of a natural gas furnace is de-rated by _______ 1% 0.5% 4% 2%	4%
True or false If the surrounding air is colder than the skin temperature, the body gains heat:	False
Recovery cylinders are color coded with grey bottom and _______ top: Red Blue Yellow Green	Yellow
At _________ this superheated refrigerant vapor pressure and temperature is added: None of the options are correct Condenser Evaporator Compressor	Compressor
The power developed by the centrifugal pump is proportional to _________ its speed: Square Proportional to Cube Quadruple	Cube
According to ASME, safety valve of the boiler should be tested for every _____ days: 7 30 45 15	30
Flue gas temperatures at which the high-efficiency furnaces operate typically is: 100 and 275 degrees 250 and 450 degrees 450 and 675 degrees 180 and 360 degrees	100 and 275 degrees
In Psychrometric chart, ______ are used to measure dry-bulb temperatures: Diagonal lines Curved lines Horizontal lines Vertical lines	Horizontal lines
Low pressure steam boilers will have operating pressure less than: 5 psi 15 psi 25 psi 50 psi	15 psi
Locked Rotor Ampere (LRA) current of a motor will be typically ________ times the normal running current of the motor: 10 to 12 times 2 to 4 times 5 to 7 times 8 to 10 times	5 to 7 times
True or false A cooling thermostat closes on a temperature drops:	False
_______ is the cubic feet of the mixture per pound of dry air: Humidity ratio Specific volume Sensible heat ratio Enthalpy	Specific volume
Which of the following will never get energized during defrost mode in a heat pump: indoor fan crankcase heater outdoor fan reversing valve	outdoor fan
A ______ is used to control the flow of refrigerant in an air conditioning or refrigeration system: Pneumatic valve Switch Solenoid valve Fuse	Solenoid valve
Which of the following element is used to increase the power factor of a circuit: All the options are correct Resistor Capacitor Inductor	Capacitor
Which of the following motors are more rugged and can handle more load: Sleeve bearing type motors Or Ball bearing type motors	Ball bearing type motors
True or false Square cut or butt joints are not permitted on corners of ductboard sections:	True
Which of the following motor is best suited for speed control applications: Induction motor Synchronous motors DC shunt motors Reluctance motor	DC shunt motors
A suction line accumulator is used for which of the following purpose: All the options are correct Store liquid refrigerant during the off cycle Prevent liquid refrigerant from entering compressor Store liquid refrigerant during the off cycle	Prevent liquid refrigerant from entering compressor
Which of the following is not available in heat pump: compressor crankcase heater suction line accumulator reversing valve low pressure sensing switch	low pressure sensing switch
The speed of 4 pole motor is about ______ rpm: 2400 3600 1200 1800	1800
A thermostatic expansion valve modulates to maintain suction _____: superheat pressure temperature volume	superheat
An amperage is the measurement of which of the following: Voltage Current Electric charge Power	Voltage
The efficiency of a boiler increases as the heating surface of the boiler ______ : increases decreases	increases
Which of the following motors are more rugged and can handle more load: Sleeve bearing type motors Ball bearing type motors	Ball bearing type motors
Excessive pressure drop in liquid lines will result in which of the following: Both the options are correct Partial vaporization Flashing	Both the options are correct
Fuse is used for which of the following protection: Overload Short circuit Open circuit Unbalance	Short circuit
With increase in evaporator load, the liquid refrigerant evaporates at _____ rate: Faster Slower	Faster
The minimum Annual Fuel Utilization Efficiency (AFUE) available is set by federal law for most furnace types at _______ : 60% 86% 78% 95%	78%
True of false The wetback fire tube boiler has more heating surface compared to dryback fire tube boiler:	True
Higher the suction pressure, the greater the efficiency of the _______: Condenser All the options are correct Compressor Evaporator	Compressor
As the number of poles in a motor increases, the speed of the motor _______: Increases Remains same Decreases	Decreases
Suction pressure at the ________ is governed by the design of the evaporator: Condenser Compressor	Compressor
The refrigerant holding capacity of the accumulator is based on an average conditions of ______ percent fill under running conditions: 50% 75% 80% 65%	65%
______ of a fan is the total pressure diminished by the fan velocity pressure: Velocity pressure Static pressure Dynamic pressure Total pressure	Static pressure
True of false A filter drier is located in the Liquid line at the outlet of the condenser:	True
Which of the following compressors have pulsations: Screw Compressors Reciprocal Compressors Centrifugal Compressors All the options are correct	Reciprocal Compressors
When a system is circulating an excessive amount of oil, the oil indicator may become saturated. This results in the indicator to appear in _______ color Red Brown Orange Yellow	Brown
Which of the following gas shall not be used to pressurize a refrigeration system: Both the options are correct Oxygen Acetylene	Both the options are correct
________ compressors operate most efficiently with a high molecular weight, high specific volume refrigerant: Scroll Centrifugal Reciprocating	Centrifugal
The horsepower required for any fan or blower varies directly as the ______ of the speed: Square directly proportional Cube 4 times	Cube
To minimize the possibility of freeze-up or corrosion, the maximum safe limits of moisture in Refrigerant R-22 is: 15 ppm 60 ppm 30 ppm 45 ppm	60 ppm
_______ Heat that can be measured or felt Internal heat External heat Sensible heat Latent heat	Sensible heat
True or false Discharge Bypass Valves (DBV) responds to the change in downstream or suction pressure:	True
Heat pumps operating cost is much _____ compared to electrical heating: lower higher	Lower
True or false Purging refers to the release of air or noncondensable gases from the system:	True
True or false Centrifugal compressors are constant speed machines:	True
True or false In boiler safety valves can be used to vent:	False
A _______ uses a piston moving inside a cylinder to compress the refrigerant: Scroll Compressor Reciprocation Compressor Screw Compressor Centrifugal Compressor	Reciprocation Compressor
Induction motor always operated with ______ power factor: Unity Lagging Leading	Lagging
Smoke chamber should be constructed so that slopes at ______ angle from the smoke shaft to the flue opening: 75 degrees 30 degrees 45 degrees 60 degrees	45 degrees
One MBH is equivalent to ______ BTU’s per hour 12,400 1,000 746 5,400	1,000