NATE Heat Pump Exam

Typical slide-in packages of electric heating elements come in units of how many kilowatts each? A: 1 to 2 kw B: 3 to 6 kw C: 15 kw D: 25 kw

B: 3 to 6 kw

In the heating mode, ice can still collect on the outdoor coil even when the outside air temperature is above 40 degrees. Why? A: Because the outside air temperature of 40 degrees still has a dew point temperature below the freezing point B: Because the outdoor coil is vaporizing refrigerant at a temperature below 32 degrees C: Because the latent heat of the refrigerant is always below freezing D: The statement is an incorrect statement

B: Because the outdoor coil is vaporizing refrigerant at a temperature below 32 degrees

Solid state defrost control boards can be adjusted to: A: Program the thermostat from outside the house B: Change the frequency of defrosts C: Control the speed of the outdoor fan during defrost D: Control the speed of the indoor fan during defrost

B: Change the frequency of defrosts

The reversing valve has 4 pipe connections. One pipe connection is on one side of the valve and three pipe connections are on the opposite side. What is the single connection on the side opposite the three connections? A: Compressor suction connection B: Compressor discharge connection C: Outdoor coil connection D: Indoor coil connection

B: Compressor discharge connection

When a typical heat pump goes into defrost which of the following will occur? A: Compressor shuts off, reversing valve switches to cooling, defrost heaters energized and outdoor fan stops B: Compressor remains on, outdoor fan stops and auxiliary electric elements are energized C: Indoor and outdoor fans fun at higher speed, compressor remains on auxiliary and electric elements remain off D: Auxiliary electric elements operate at reduced voltage, compressor runs at half speed and outdoor fan shuts off

B: Compressor remains on, outdoor fan stops, and auxiliary electric elements are energized

Charging a heat pump with refrigerant is best accomplished in the _______ mode. A: Heating mode B: Cooling mode C: Defrost mode D: Emergency heating mode

B: Cooling mode

The coefficient of performance is determined by: A: Dividing the output btuh by the input btuh B: Dividing the input btuh by the output btuh C: Multiplying the input by the output D: Subtracting the output from the input

B: Dividing the input btuh by the output btuh The coefficient of performance or COP of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work required. Higher COPs equate to higher efficiency.

Terminal "G" on a heat pump thermostat is used for: A: Operating the reversing valve B: Operating the indoor fan motor C: Operating the compressor D: Operating the condenser fan motor

B: Operating the indoor fan motor

Which of the following compressors is most "liquid slug" tolerable? A: Reciprocating B: Scroll C: Compliant scroll D: Rotary

B: Scroll

SEER is an abbreviation for: A: Seasonal Energy Excellence Rating B: Seasonal Energy Efficiency Ratio C: Summer Energy Efficiency Ratio D: Special Efficiency Energy Rating

B: Seasonal Energy Efficiency Ratio

Two technicians are working on a heat pump system and are preparing to evacuate the system. Technician A says that in order to pull a good vacuum the reversing valve needs to be switched on and off during the evacuation so air and moisture are not trapped in the system. Technician B says technician A is incorrect and that the reversing valve will not switch with the system in a vacuum anyway. Who is correct? A: Technician A is correct B: Technician B is correct C: Both technicians A and B are correct D: Both technicians A and B are incorrect

B: Technician B is correct

A customer is concerned that during the heating season heavy ice builds up on one side of the concrete equipment pad and coil. The rest of the coil is clear of ice and the heat pump is meeting the heating needs of the house. What is most likely the cause of the problem? A: High winds on that side of the outdoor unit B: The outdoor unit is not level C: There is more refrigerant on that side of the coil D: A defrost problem exists

B: The outdoor unit is not level

Reading a voltage across the contacts of the outdoor thermostat means: A: The thermostat contacts are closed B: The thermostat contacts are open C: The thermostat contacts are stuck D: The thermostat contacts are working correctly

B: The thermostat contacts are open

A technician places a heat pump into the auxiliary electric heating mode with the compressor de-energized. He measures a temperature rise between the return and supply air of 40 degrees. The measured voltage at the electric elements is exactly 222 volts and the measured amperage of the heaters is 60 amps. Using the equation CFM = BTU divided by 1.08 x TD, what is the CFM of the system? A: 825 CFM B: 950 CFM C: 1055 CFM D: 1500 CFM

C: 1055 CFM 222 x 60 = 13,320watts 13,320 / 1000 = 13.32 Kw btuh = 13.32 x 3415 = 45,488 cfm =((45,488 / (1.08 x 40)) cfm = 45,488 / 43.2 = 1052.95

The United States Department of Energy has mandated that the minimum allowable SEER rating for a new residential air conditioning system installation is: A: 11 SEER B: 12 SEER C: 13 SEER D: 14 SEER

C: 13 SEER

A typical 3 ton split system residential heat pump would have auxiliary electric heating elements of about how many watts total? A: 4 kw B: 5 kw C: 15 to 20 kw D: 40 to 60 kw

C: 15 to 20 kw One ton of heat is 12,000 BTU's By dividing the total BTU's of the unit by 3.414 (watts to btu's conversion factor) we get the total Watts. 36,000 BTU/3.14 = 10,545 watts needed minimum or 3,515 watts per ton. To make sure enough heat is available for the defrost cycle and temperatures below the systems balance point, it is suggested that 5 to 7.5 Kw be installed per ton. This standard makes the 15 to 20 kw the correct answer.

In any case, the compressor's discharge line temperature should not exceed what temperature? A: 175 degrees F B: 200 degrees F C: 225 degrees F D: 350 degrees F

C: 225 degrees F

A heat pump operating normally in the heating mode would be expected to have a supply air temperature in the range of: A: 70 to 80 degrees B: 80 to 90 degrees C: 85 to 105 degrees D: 100 to 130 degrees

C: 85 to 105 degrees

A heat pump is operating in the heating mode. The lower the outside air temperature, the: A: More efficient the heat pump becomes B: Higher the SEER rating C: Higher the compression ratio D: Lower the balance point

C: Higher the compression ratio

Which of the following components is exclusive to the heat pump? A: Condenser B: Oil separator C: Reversing valve D: Accumulator

C: Reversing valve

Typical residential split system heat pumps operate on how many voltages? A: One B: Two C: Three D: Four

C: Three

Heat is present in winter outdoor air until the outside air ambient temperature reaches a low temperature of: A: 0 degrees F B: 32 degrees F C: 273 degrees F D: -459 degrees F

D: -459 degrees F Technically this is true, but not practical. A heat pump is doing good to continue to work below 10 deg F unless specifically designed for lower temperatures.

A heat pump operating in the cooling mode would be expected to have a return-to-supply air temperature differential in the range of: A: 5 to 6 degrees B: 5 to 8 degrees C: 8 to 12 degrees D: 18 to 22 degrees

D: 18 to 22 degrees

Which of the following airflow rates is the most reasonable for a heat pump system operating in the heating cycle? A: 200 cfm per ton B: 300 cfm per ton C: 400 cfm per ton D: 450 cfm per ton

D: 450 cfm per ton

Auxiliary electric heat is necessary because: A: It provides heat for the home during defrosts B: It provides heat for the home in the event of a heat pump failure C: It provides heat for the home if the heat pump is unable to meet the demand for heat D: All of the above

D: All of the above

What function does a Ranco E15 control serve? A: It is a common, combination time and temperature defrost control B: It is a mechanical defrost timer with a builtin thermostatic control C: It is a defrost control that checks outdoor coil for frost buildup every 30, 45 or 90 minutes D: All of the above are correct

D: All of the above are correct This control is all but obsolete

Compressor crankcase heaters are used to: A: Help decrease refrigerant migration B: Reduce the potential of liquid flood-back C: Reduce the potential of flooded starts D: Both a and c are correct

D: Both a and c are correct

What may happen if the body of a reversing valve is slightly dented? A: Nothing, as they are made to be very durable B: The internal slide may stick C: The valve may make noises from the gas trying to pass through partially open ports D: Both b and c are correct

D: Both b and c are correct

When a heat pump is operating in the cooling mode, the suction line at the compressor should feel _____ and when operating in the heating mode the same suction line should feel _____. A: Cool, hot B: Hot, cool C: Hot, hot D: Cool, cool

D: Cool, cool

Which of the following is not a type of heat pump? A: Ground to air B: Air to air C: Water to air D: Direct coupled

D: Direct coupled

Which of the following is an incorrect term for the solenoid valve that switches the heat pump between the heating and cooling modes? A: Changeover valve B: Reversing valve C: Four-way valve D: Discharge operator valve

D: Discharge operator valve

A heat pump defrosts even when there is no ice on the outside coil. Which of the following is most likely the problem? A: The defrost time clock is set for too short a cycle B: The outdoor coil is dirty and the system uses a pressure differential type of defrost initiation C: The sensing bulb of the defrost control is mounted too close to the bottom of the outdoor coil D: Each of these could cause the problem

D: Each of these could cause the problem

The heat pump utilizes: A: Two filter-driers with check valves B: One bi-flow filter-drier C: A single mono-flow filter-drier in the liquid line D: Some use the bi-flow filter-drier and others use two filter-driers with check valves

D: Some use the bi-flow- filter-drier and others use two filter-driers with check valves

The correct way to size a heat pump is to perform both heating and cooling load calculations and select the heat pump size by: A: Adding the heating load and cooling loads B: Subtracting the smaller load from the larger load C: Using the heating load to size the system D: Using the cooling load to size the system

D: Using the cooling load to size the system

Heat pumps often employ which of the following accessories? A: An accumulator B: Evaporator pressure regulator C: Electronic suction throttling valve D: Crankcase pressure regulator

A: An accumulator

Which of the following actions will result in a decrease in volumetric efficiency? A: An increase in head pressure B: A decrease in head pressure C: An increase in suction pressure D: Both a and c

A: An increase in head pressure This is the ratio of the actual delivered gas volume to the swept volume or total displacement of the cylinder. The actual volume of gas inducted inside the cylinder for compression is less than the theoretical calculated volume because of the clearance volume. When the gas is compressed, and is delivered by the discharge valve, not all the gas is discharged since some volume of the gas remains inside the clearance volume at high discharge pressure. When the piston starts moving downwards, the suction valve does not opens immediately because of this high pressure gas. As the piston moves downwards the pressure of the gas in the clearance volume starts reducing due to expansion. Only when the pressure of this gas reaches to certain minimum level, the suction valve opens. Thus the portion of the suction stroke of the piston goes unused and during this certain volume of the refrigerant is not sucked. This reduces the volume of the refrigerant that can be sucked by the cylinder or the compressor. Read more: http://www.brighthub.com/engineering/mechanical/articles/51998.aspx?p=2#ixzz14iyB2WTb

Why are reversing valves pilot operated? A: Because pilot operated valves use the differential pressure to operate the valve ports instead of having a solenoid valve working against the head pressure B: Because that is just the way they are made C: Pilot operated valves are quiet D: Heat pump reversing valves are NOT pilot operated!

A: Because pilot operated valves use the differential pressure to operate the valve ports instead of having a solenoid valve working against the head pressure

The reversing valve has 4 pipe connections. One pipe connection is on one side of the valve and three pipe connections are on the opposite side. What is the center connection on the side with three pipe connections? A: Compressor suction connection B: Compressor discharge connection C: Outdoor coil connection D: Indoor coil connection

A: Compressor suction connection

During the heat pump's cooling cycle, the outdoor coil is utilized as a _________ while the indoor coil is utilized as a____________. A: Condenser, evaporator B: Evaporator, condenser C: Compressor, accumulator D: Accumulator, condenser

A: Condenser, evaporator

A thermistor is an: A: Electronic temperature sensor that changes its resistance with changes in temperature B: Electronic pressure sensor that changes its resistance with changes in pressure C: Electromechanical thermostat used to terminate the defrost cycle when outdoor coil is clear of ice and frost D: None of these is correct

A: Electronic temperature sensor that changes its resistance with changes in temperature

Heat pumps can provide both heating in the winter and cooling in the summer. In which mode is the heat pump more efficient? A: Heating mode B: Cooling mode C: Defrost mode D: Emergency heating mode

A: Heating mode

The outdoor coil on a heat pump is defrosted using: A: Hot gas B: Electric heaters C: Off cycle defrost D: Straight time defrost

A: Hot gas

Which of the following can prevent the reversing valve from changing positions? A: Low refrigerant charge B: Overcharge of refrigerant C: Air in the system D: Low indoor airflow due to a dirty air filter

A: Low refrigerant charge

The supply air temperature on a normally operating heat pump is: A: Lower than that of a gas heating system B: Higher than that of a gas heating system C: About the same as that of a gas heating system D: Heat pumps do not use supply air

A: Lower than that of a gas heating system

Terminal "O" on a heat pump thermostat is used for: A: Operating the reversing valve B: Operating the indoor fan motor C: Operating the compressor D: Operating the condenser fan motor

A: Operating the reversing valve

High SEER rated heat pumps are those that employ: A: Scroll compressors and over-sized coils B: Reciprocating compressors and over-sized coils C: Scroll compressors and accumulators D: Reciprocating compressors and accumulators

A: Scroll compressors and over-sized coils

During the defrost cycle the outdoor fan motor is: A: Shut down B: Operated at a reduced speed C: Stepped up to its highest speed D: Allowed to run at its normal speed

A: Shut down

The "balance point" of a heat pump is: A: The lowest temperature at which the heat pump can meet the heating requirement for the structure B: The lowest temperature at which the heat pump can operate C: The temperature at which the heat pump has the highest efficiency D: The point at which the heating and cooling loads meet

A: The lowest temperature at which the heat pump can meet the heating requirement for the structure

Which of the following metering devices can improve the operating efficiency of a heat pump? A: Thermostatic expansion valve B: Automatic expansion valve C: Fixed orifice D: Capillary tube

A: Thermostatic expansion valve

The best location for the outdoor section of an air to air heat pump is: A: Where it gets the winter sun B: Where it is sheltered from the sun's radiation C: Where it never snows D: Under the shelter of a porch

A: Where it gets the winter sun