Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the
question.
1)
1)
A Category IV furnace operates with a:
A)
High–temperature, negative–pressure vent.
B)
Low–temperature, positive–pressure vent.
C)
Low–temperature, negative–pressure vent.
D)
High–temperature, positive–pressure vent.
Answer:
B
A)
B)
C)
D)
2)
2)
What controls the amount of gas entering the burner?
A)
The gas valve
B)
The draft created by the gas flames
C)
The gas manifold pressure and the burner venturi size
D)
The burner orifice size
Answer:
D
A)
B)
C)
D)
3)
3)
Why are the 90 percent condensing furnaces unique?
A)
The venting material is rare, as it is no longer manufactured due to defects.
B)
The venting of this type of furnace is made of PVC and is easy to seal airtight.
C)
The flue gas is excessively hot and can cause fires if improperly used.
D)
The flue gas affects the venting material at a greater–than–normal rate.
Answer:
B
A)
B)
C)
D)
1
4)
4)
If the drain for a 90 percent efficient furnace and the drain for the air conditioning coil are run
with a common drain, the drain should be sized:
A)
To handle the combined condensate output of the air conditioner and the furnace.
B)
For the furnace drain, which is larger.
C)
For the air conditioning drain, which is larger.
D)
To match the cross–section area of the combined drains.
Answer:
C
A)
B)
C)
D)
5)
5)
How can a technician determine a major component failure on a mid–efficiency furnace?
A)
The technician can use the self–testing feature on the control box.
B)
The technician can send the control box to the manufacturer.
C)
The unit owner must accurately describe how the unit is operating to diagnose component
failure.
D)
The technician must examine each component to ensure it is operating properly.
Answer:
A
A)
B)
C)
D)
6)
6)
For what reason are Category II and Category III furnaces rare?
A)
The temperature of the system makes it hard to repair.
B)
These furnaces are no longer manufactured.
C)
These furnaces are not reliable and require more maintenance.
D)
The venting system is made of a material that is no longer available.
Answer:
D
A)
B)
C)
D)
2
7)
7)
What type of vent is used with 90 percent Category IV furnaces?
A)
Type B double–wall gas vent
B)
90 percent efficiency furnaces do not require a vent.
C)
Single–wall stainless steel
D)
PVC
Answer:
D
A)
B)
C)
D)
8)
8)
How does venting compare on 80 percent and 90 percent efficient heating units?
A)
80 percent units require outside air to be piped in for combustion and 90 percent do not.
B)
80 percent furnaces use type B vent and 90 percent furnaces use PVC pipe for venting
material.
C)
90 percent furnace vents are 10 percent larger in size than 80 percent furnace vents.
D)
80 percent furnaces use PVC vent and 90 percent furnaces use type B gas vent.
Answer:
B
A)
B)
C)
D)
9)
9)
What is required when installing a 90 percent furnace that is not required for an 80 percent
furnace?
A)
An oxygen line for the combustion gas afterburner
B)
An extra–large supply duct to handle the extra heat output
C)
A catalytic cell for the combustion gas catalytic converter
D)
A drain for the condensate from the recuperative coil
Answer:
D
A)
B)
C)
D)
3
10)
10)
Why are draft inducer fans necessary in today’s furnaces?
A)
To move the flue gases through the ductwork
B)
The flue gases cannot make their way through the new heat exchangers on their own.
C)
To move gas into the burner assembly
D)
To separate the flue gas from the heat through centrifugal force
Answer:
B
A)
B)
C)
D)
11)
11)
What type of burner do most modern furnaces use?
A)
B)
C)
D)
Answer:
C
A)
B)
C)
D)
12)
12)
When will installation technicians most likely install a horizontal furnace?
A)
When duct systems are set in concrete
B)
When the configuration may change
C)
When the ceilings are especially high
D)
When there is little floor space
Answer:
D
A)
B)
C)
D)
13)
13)
A furnace that is composed of a heat exchanger compartment and a blower compartment is
considered:
A)
An oil–fired boiler furnace.
B)
A radiant heat furnace.
C)
A gas–fired boiler furnace.
D)
A gas forced–warm–air furnace.
Answer:
D
A)
B)
C)
D)
4
14)
14)
How does a power burner differ from an atmospheric burner?
A)
Power burners are primarily for residential use.
B)
A power burner uses air forced into the combustion area by a fan.
C)
An atmospheric burner has a fan used to force air into combustion.
D)
Atmospheric burners are rarely used today.
Answer:
B
A)
B)
C)
D)
15)
15)
In all furnace cabinet configurations, the return air:
A)
Enters as combustion air, travels through the heat exchanger, and exits the fan end of the
furnace.
B)
Enters at the heat exchanger end and exits the fan housing end of the furnace.
C)
And combustion air enter the furnace through the same opening.
D)
Enters at the fan housing end and exits the heat exchanger end of the furnace.
Answer:
D
A)
B)
C)
D)
16)
16)
Which type of burner port should be used for maximum efficiency?
A)
B)
C)
D)
Answer:
A
A)
B)
C)
D)
17)
17)
Why do gas furnace efficiencies jump from 80 percent to 90 percent?
A)
By installing a recuperative coil ahead of the main heat exchanger.
B)
The physics of combustion make it impossible to produce an 85 percent efficient furnace.
C)
The blower used with 85 percent furnaces cannot be used for air conditioning.
D)
Federal regulations do not allow the production of mid–efficiency furnaces.
Answer:
A
A)
B)
C)
D)
5
18)
18)
What is the difference between a a 90 percent furnace with a sealed combustion system and a
typical 90 percent furnace?
A)
Sealed combustion units may use PVC pipe for venting material.
B)
Sealed combustion units require combustion air to be piped in from the outside.
C)
Sealed combustion units use household vented air for combustion.
D)
Sealed combustion units do not produce any combustion products.
Answer:
B
A)
B)
C)
D)
19)
19)
The different types of atmospheric gas burners include:
A)
Hyperbolic, hyperbaric, and atmospheric.
B)
Primary, secondary, condensing, and pulse.
C)
Inshot, drilled port, slotted, and ribbon.
D)
Serpentine, tubular, pulse, and modulating.
Answer:
C
A)
B)
C)
D)
20)
20)
The difference between 80 percent efficiency furnaces and 90 percent efficiency furnaces is that 90
percent efficiency furnaces:
A)
Use more combustion air per 1,000 BTU firing rate.
B)
Use more efficient air filters.
C)
Burn more gas to increase the heat exchanger temperatures.
D)
Have an extra recuperative heat exchanger that condenses water out of the flue gas.
Answer:
D
A)
B)
C)
D)
6
21)
21)
What did the removal of the pilot light, improvement of the heat exchanger, and addition of an
induced–draft blower do for the mid–efficiency furnace?
A)
It increased the cost of the unit by 20 percent.
B)
It improved the unit’s ease of repairs.
C)
It lowered the cost of the unit.
D)
It improved unit efficiency to 80 percent.
Answer:
D
A)
B)
C)
D)
22)
22)
A stainless steel coil that is built like a refrigeration coil and allows a high–efficiency unit to move
into the 90+ percent efficiency range is called:
A)
A recuperative coil.
B)
A serpentine coil heat exchanger.
C)
A hybrid coil recuperater.
D)
A serpentine coil heat recuperater.
Answer:
A
A)
B)
C)
D)
23)
23)
What is the purpose of the gas burner venturi?
A)
The venturi makes the flames swirl inside the combustion chamber to increase contact with
the heat exchanger and boost efficiency.
B)
The venturi mixes the gas and primary air by making them swirl as they pass through.
C)
The venturi ensures that only gas enters inside the burner while air is directed into the
combustion area.
D)
The venturi ensures that the proper amount of gas flows into the burner.
Answer:
B
A)
B)
C)
D)
7
24)
24)
How does the standing–pilot system provide a safety check for the continually lit pilot?
A)
The pilot flame is located on a runner leading to the burners.
B)
The pilot flame has no safety check.
C)
The pilot flame impinges on the thermocouple.
D)
The pilot runner impinges on the flame.
Answer:
C
A)
B)
C)
D)
25)
25)
Which of these technologies is NOT used in 80 percent furnaces?
A)
Flattening and serpentining heat exchangers
B)
Removing standing pilot lights
C)
Adding a condensing recuperative coil
D)
Adding induced draft combustion blowers
Answer:
C
A)
B)
C)
D)
26)
26)
Available furnace cabinet configurations include:
A)
Up–flow, down–flow, horizontal, lowboy, multiposition.
B)
Small, medium, and large.
C)
Flame–resistant, flameproof, and explosionproof.
D)
Vertical, horizontal, side–by–side, over–under, and wall mount.
Answer:
A
A)
B)
C)
D)
27)
27)
How did serpentine heat exchangers compare to older heat exchangers?
A)
The serpentine heat exchangers were made from plastic.
B)
The serpentine heat exchangers utilized a pressure switch.
C)
The serpentine heat exchangers required a heat–induced fan, causing negative pressure.
D)
The serpentine heat exchangers became straighter and longer.
Answer:
C
A)
B)
C)
D)
8
28)
28)
What components are added to make a two–stage furnace?
A)
A two–stage gas valve, two draft proving switches, and a two–speed induced draft fan
B)
Electric heat strips and a second stage sequence
C)
A second heat exchanger and an electric vent gas damper
D)
An extra set of burners and an extra gas valve
Answer:
A
A)
B)
C)
D)
29)
29)
Some furnaces use two automatic shutoffs that are mechanically in series to provide additional
safety. What type of valves are these?
A)
Diaphragm valves
B)
Redundant valves
C)
Intermittent valves
D)
Direct–acting valves
Answer:
B
A)
B)
C)
D)
30)
30)
Hot–surface igniters are made of:
A)
Silicon carbide.
B)
Nickel–chrome wire.
C)
Carbon.
D)
Alnico–chromel wire.
Answer:
A
A)
B)
C)
D)
31)
31)
Hot–surface igniters typically operate on:
A)
B)
C)
D)
Answer:
A
A)
B)
C)
D)
9
32)
32)
The typical start up sequence for a hot surface ignition system is:
A)
Combustion blower energized, igniter energized and gas valve energized, flames sensed,
indoor blower energized after time delay.
B)
Combustion blower, indoor blower, igniter, and gas valve all energized simultaneously.
C)
Combustion blower prepurge, igniter energized after a delay, gas valve energized after a
delay, flames sensed, indoor blower energized after time delay.
D)
Gas valve and igniter energized, flames sensed, combustion blower and indoor blower
energized after time delay.
Answer:
C
A)
B)
C)
D)
33)
33)
Why do solenoid–type valves pose a problem for some types of burners?
A)
Solenoids open and close too quickly.
B)
Solenoids open and close too slowly.
C)
Solenoids create too much pressure when closing.
D)
Solenoids’ seal is not strong.
Answer:
A
A)
B)
C)
D)
34)
34)
How are transformers in the HVACR field rated?
A)
By primary power output
B)
By step–down capacity
C)
By secondary power output
D)
By induction ratio
Answer:
C
A)
B)
C)
D)
10
35)
35)
Two–stage furnaces require:
A)
A two–stage gas valve.
B)
A two–stage thermostat, a two–stage gas valve, a two–speed inducer fan, and two draft
pressure switches.
C)
Two draft pressure switches.
D)
A two–stage thermostat.
Answer:
B
A)
B)
C)
D)
36)
36)
In a traditional gas furnace with a standard combination gas valve, what controls the gas valve?
A)
The door switch
B)
The spark igniter
C)
The furnace ignition board
D)
The heating thermostat
Answer:
D
A)
B)
C)
D)
37)
37)
If pulsed DC current is not present in the flame rod, what is the effect on the gas valve in a direct
spark–ignition system?
A)
Pulsed DC current has no effect on the gas valve.
B)
The valve will open.
C)
The system will shut down.
D)
The valve will remain closed.
Answer:
D
A)
B)
C)
D)
38)
38)
Why do direct spark ignition furnaces and hot–surface ignition furnaces require redundant gas
valves?
A)
In case one fails to open, the other will.
B)
To modulate the gas pressure
C)
To open the valve slowly
D)
For safety since there is no pilot safety solenoid
Answer:
D
A)
B)
C)
D)
11
39)
39)
What is the purpose of a flame–proving device in a system with a standing pilot?
A)
It automatically resets the system when the pilot is relit.
B)
It relights the pilot if it goes out.
C)
It monitors the level of gas after a pilot goes out.
D)
It shuts off the gas flow in case the pilot goes out.
Answer:
D
A)
B)
C)
D)
40)
40)
When the room–temperature setting is reached, what components are opened?
A)
Heat anticipators
B)
Transformer relays
C)
Fan and blower contacts
D)
Thermostat and gas valve circuits
Answer:
D
A)
B)
C)
D)
41)
41)
How does the flame rod sense the flames in a flame rectification circuit?
A)
The resistance of the flame rod changes when heated by the flame.
B)
The flame rod expands from being heated, making a mechanical switch at its base.
C)
The flame changes the AC voltage to pulsed DC current.
D)
The flame rod is made of a semiconductor material that acts as a silicon controlled rectifier
when it is hot.
Answer:
C
A)
B)
C)
D)
42)
42)
What type of flame proving do direct spark ignition controls use?
A)
Thermocouple
B)
Warp switch
C)
Flame rectification
D)
Mercury–filled bulb
Answer:
C
A)
B)
C)
D)
12
43)
43)
What is a gas pilot light?
A)
An LED that indicates the burner activity
B)
The first portion of the main burner that remains on at all times
C)
A small flame that is used to light the main burners
D)
A light that allows the technician to see inside the furnace
Answer:
C
A)
B)
C)
D)
44)
44)
Hot–surface ignition units:
A)
Are standard ignition systems.
B)
Substantially increase an electric bill.
C)
Operate for only a few minutes per day.
D)
Are powered by 220 V.
Answer:
C
A)
B)
C)
D)
45)
45)
Why might a technician need to install a larger transformer in a heating system?
A)
If output from the system is decreasing.
B)
If the furnace wire size is incorrect.
C)
If accessories are added to an existing furnace.
D)
If the technician is performing regular maintenance.
Answer:
C
A)
B)
C)
D)
46)
46)
The operation of modern induced–draft equipment is normally controlled by:
A)
An elaborate system of mechanical switches and sensors.
B)
A simple control system with very few controls.
C)
Manually operated valves, levers, and shutters.
D)
An electronic board.
Answer:
D
A)
B)
C)
D)
13
47)
47)
What does the furnace board do on most modern furnaces?
A)
It monitors furnace safety.
B)
It controls the flame’s ignition sequence.
C)
It controls the ignition, safety, and blower operation.
D)
It cycles the indoor blower motor.
Answer:
C
A)
B)
C)
D)
48)
48)
The main limit switch shuts the gas valve down when:
A)
The blower motor overheats.
B)
The house temperature reaches 80°F.
C)
The heat exchanger area becomes overheated.
D)
The monthly BTU limit has been reached.
Answer:
C
A)
B)
C)
D)
49)
49)
Combination gas valves used on standing pilot furnaces combine:
A)
Gas heating control, fan operation, and air conditioning sequencing.
B)
Pilot safety, fan control, and gas pressure regulation.
C)
Pressure regulation, automatic gas control, and pilot safety.
D)
The transformer, gas valve, and fan relay.
Answer:
C
A)
B)
C)
D)
50)
50)
What is an intermittent pilot ignition system?
A)
The gas pilot light works correctly only some of the time.
B)
A pilot light that operates only when the thermostat is not calling for heat
C)
A pulsing LED that indicates the burner activity
D)
The gas pilot is ignited with each call for heat and shuts off at the end of the call.
Answer:
D
A)
B)
C)
D)
14
51)
51)
What is the purpose of the limit switch?
A)
It improves efficiency by limiting furnace run time.
B)
It prevents overheating by interrupting the circuit to the gas valve.
C)
It limits the indoor blower fan speed to supply a regulated supply of warm air.
D)
It improves efficiency by limiting the supply air temperature.
Answer:
B
A)
B)
C)
D)
52)
52)
What does a roll–out switch do?
A)
It allows the combustion components to be rolled out of the combustion chamber.
B)
It shuts off the gas valve if flames are sensed outside the combustion area.
C)
It ensures proper clearance between the furnace and nearby walls.
D)
It checks to make sure the blower has not rolled out of position on the unit.
Answer:
B
A)
B)
C)
D)
53)
53)
Why should the heating element of a hot–surface igniter NOT be touched when installing a
replacement igniter?
A)
Your hands will be in the way of the mounting screws, making it impossible to install.
B)
The igniter comes already charged and will deliver a painful shock.
C)
The igniter will burn out where you touched it.
D)
The igniter is very hot and will cause severe burns.
Answer:
C
A)
B)
C)
D)
54)
54)
As a safety measure, when starting an LP gas furnace, you should position yourself:
A)
In any position so long as you are not touching the furnace.
B)
Directly in front of the burners in order to observe the lighting sequence.
C)
Off to the side and off the ground.
D)
Off to the side and low to the ground.
Answer:
C
A)
B)
C)
D)
15
55)
55)
What should the net stack temperature be on a category I gas furnace?
A)
150°F to 325°F
B)
500°F to 675°F
C)
350°F to 475°F
D)
200°F and higher
Answer:
C
A)
B)
C)
D)
56)
56)
What effect do volatile liquids stored near the furnace have on its performance?
A)
They damage vent work.
B)
They corrode furnace components.
C)
They help to create carbon monoxide.
D)
They can produce flammable vapors.
Answer:
D
A)
B)
C)
D)
57)
57)
Furnace gas manifold pressure is measured in:
A)
Psia.
B)
Inches water column.
C)
Psig.
D)
Inches mercury column.
Answer:
B
A)
B)
C)
D)
58)
58)
What type of gas production is a definite indication of incomplete combustion?
A)
B)
C)
D)
Answer:
B
A)
B)
C)
D)
16
59)
How much time should it take the ½ ft3 to turn per revolution if a furnace is using 142.8 ft/hr3 of
gas?
59)
A)
52.4 seconds per revolution
B)
25.2 seconds per revolution
C)
50.4 seconds per revolution
D)
12.6 seconds per revolution
Answer:
D
A)
B)
C)
D)
60)
60)
The normal oxygen and carbon dioxide percentages in the flue gas of a properly operating gas
furnace are approximately:
A)
B)
C)
D)
Answer:
C
A)
B)
C)
D)
61)
61)
What type of vent is designed specifically for category I gas appliances?
A)
Single–wall, galvanized metal vent
B)
PVC vent
C)
Type B vent
D)
Type L vent
Answer:
C
A)
B)
C)
D)
62)
62)
What effect does slowing down the blower speed have on a heating unit?
A)
It does not affect the unit temperature.
B)
It causes return–air temperature to increase.
C)
It decreases the air temperature rise.
D)
It increases the air temperature rise.
Answer:
D
A)
B)
C)
D)
17
63)
63)
A technician measures a return air temperature at the furnace of 70°F and a supply air
temperature of 180°F on a furnace whose temperature rise is rated at 40 to 60°F. The technician
should:
A)
Leave it alone; it is working great.
B)
Increase the airflow to reduce the temperature rise.
C)
Decrease the airflow to reduce the temperature rise.
D)
Increase the gas manifold pressure to reduce the temperature rise.
Answer:
B
A)
B)
C)
D)
64)
64)
Which is mixed with fuel in the burner prior to combustion?
A)
Superheated air
B)
Primary air
C)
Propane
D)
Oxygen
Answer:
B
A)
B)
C)
D)
65)
65)
What is the net stack temperature?
A)
Stack temperature – ambient temperature = net stack temperature
B)
Stack temperature + ambient temperature = net stack temperature
C)
Supply air temperature + ambient temperature = net stack temperature
D)
Supply air temperature – ambient temperature = net stack temperature
Answer:
A
A)
B)
C)
D)
18
66)
66)
How is a gas meter used to check gas furnace input?
A)
The gas level is checked before and after firing the furnace, and the firing rate is calculated
based on the heating value of the gas and the amount of gas used.
B)
The meter is zeroed, the furnace is operated, and the meter is sent to the furnace
manufacturer for analysis.
C)
The firing rate indicator on the gas meter calculates the firing rate based on gas
consumption.
D)
The number of times the gas dial rotates in a minute and the gas heating capacity are used
to calculate the firing rate.
Answer:
D
A)
B)
C)
D)
67)
67)
What is a vent connector?
A)
Vent connector is simply another name for vent.
B)
The vent connector is the pipe running from the furnace to the vent.
C)
The vent connector is the collar on the gas appliance where the vent pipe connects.
D)
A vent connector is used to join two pieces of vent pipe.
Answer:
B
A)
B)
C)
D)
68)
68)
How is using propane different from using natural gas?
A)
Propane is harder to measure than natural gas.
B)
Propane requires a self–contained tank.
C)
Natural gas requires a self–contained tank.
D)
Appliances that use natural gas cannot use propane.
Answer:
B
A)
B)
C)
D)
19
69)
69)
How do technicians increase the blower speed in a belt–driven motor?
A)
They decrease pulley spread.
B)
They loosen belt tension.
C)
They tighten belt tension.
D)
They increase the pulley spread.
Answer:
A
A)
B)
C)
D)
70)
70)
Which of the following is TRUE of piping tables?
A)
The length of piping helps to find cubic foot capacity.
B)
The cubic foot capacity can help to determine length.
C)
The table is only accurate for heating systems.
D)
The table uses pipe width to determine cubic foot capacity.
Answer:
A
A)
B)
C)
D)
71)
71)
Where do you measure the supply air temperature when checking furnace temperature rise?
A)
In a small hole drilled in the vent
B)
As close to the furnace outlet as possible
C)
At the supply registers in the house
D)
Preferably in a duct after the air has left the supply plenum
Answer:
D
A)
B)
C)
D)
72)
72)
Why did the development of 80 percent efficient furnaces using draft–inducer fans present a
problem for venting tables?
A)
The inducer fan cooled the air, and a smaller vent was required to prevent condensation.
B)
The fan heated the air too much for standard venting.
C)
The use of natural–draft and draft–induced furnaces had little impact on venting tables.
D)
The draft–inducer fans required the use of a larger vent.
Answer:
A
A)
B)
C)
D)
20