1

Question 0

A good description of how a bi-metal fan switch operates the blower motor on a gas furnace is:

Answer 0

Temperature on - temperature off

Question 1

A gas furnace is to be installed in a garage. The national standards require that the burners and ignition sources must be located ….. From the floor.

Answer 1

18 inches

Question 2

Redundant gas valves used on gas furnaces will shut down if gas pressure exceeds?

Answer 2

13.5 in. W.C.

Question 3

Burning one cubic foot of liquefied petroleum gas completely will produce approximately…. BTUs

Answer 3

2000-2500

Question 4

LP gas has a specific gravity of:

Answer 4

1.5-2.0

Question 5

What is the purpose of a spoiler screw located on a burner, or adjustable-shutters?

Answer 5

Mix primary air and gas

Question 6

Furnace limit switches are wired in series with the:

Answer 6

Gas valve

Question 7

A tech is using an extension ladder to work on a roof top unit. The top of ladder should extend how much beyond the support joint.

Answer 7

3 feet

Question 8

A technician determines that a natural gas furnace has a defective heat exchanger. The technician should:

Answer 8

Inform the homeowner, turn the thermostat off, turn the gas to the furnace off.

Question 9

A natural gas (standing pilot) furnace usually requires….gas pressure at the manifold and burners.

Answer 9

3.5 in. W.C.

Question 10

The vent system for a condensing furnace is classified as…. by the national field gas code.

Answer 10

Category 4

Question 11

Type B vent pipe must be kept at least….from combustible materials.

Answer 11

One inch

Question 12

All condensing furnaces manufactured after 1992 must have a AFUE rating of at least:

Answer 12

90%

Question 13

You have installed a category 4 two-type vent system that terminates through the roof of the residence. The elbow for the combustion air intake, above the roof, should:

Answer 13

Point down

Question 14

The reason heating thermostats have anticipators is to?

Answer 14

Reduce overshoot

Question 15

The typical flue gas temperature of a category 3 furnace is:

Answer 15

280F- 300F

Question 16

The proper chemical name for natural gas is?

Answer 16

Methane

Question 17

Burning one cubic foot of natural gas will produce approximately….BTUs.

Answer 17

900-1100

Question 18

A furnace nameplate specifies a temperature rise of 40 to 70 degrees. Temperature measurements indicate a rise of 80 degrees. The most appropriate action is to:

Answer 18

Increase fan speed

Question 19

A BTU is the amount of heat required to raise the temperature of one pound water:

Answer 19

One degree Fahrenheit

Question 20

Natural gas piping must be sized to prevent excessive pressure drops. The national fuel gas code maximum pressure drop allowance is approximately:

Answer 20

.35 in. W.C.

Question 21

Gas piping must be installed with a pitch of:

Answer 21

1/4” per 15’ run.

Question 22

Pipe joint compound should be applied to:

Answer 22

Male threads less two end threads

Question 23

A technician is installing a copper elbow on LP gas line; what type of solder is recommended:

Answer 23

95/5 solder

Question 24

To burn one cubic foot of Natural Fas completely, at least.... of combustion air must be available.

Answer 24

15 cu ft.

Question 25

The ignition temperature of Natural Has is?

Answer 25

1000-1200F

Question 26

Air that is mixed with Natural Gas in the burner is called:

Answer 26

Primary air

Question 27

A Natural Gas furnace is operating properly. How many cubic feet of flue gas are needed for every one cu. ft. burned?

Answer 27

20 cu. ft

Question 28

The purpose of a flue baffle is:

Answer 28

Increase heat exchange.

Question 29

The LP gas pressure supplied to the gas valve should be:

Answer 29

11-13 in. W.C.

Question 30

An installed gas furnace should have a minimum of....inches for service access.

Answer 30

30 inches

Question 31

What would cause the temperature limit safety to shut off the burner?

Answer 31

Fan motor failure

Question 32

The cut off plate is a component of the:

Answer 32

Blower housing.

Question 33

A "spud" or burner orfice does what?

Answer 33

Meters gas to the burner

Question 34

A good thermocouple should read approximately .....on a D.C. meter.

Answer 34

18 millivolts

Question 35

Liquefied petroleum, ( LP) gases are:

Answer 35

Propane and butane

Question 36

Fan tine/temperature delay switches are used to:

Answer 36

Allow the vent to create proper draft and allow the heat exchanger to warm up

Question 37

What instrument would a technician use to calculate return airflow to a furnace?

Answer 37

Meg get

Question 38

A furnace with a hot surface igniter will not light. Before changing the igniter the technician should:

Answer 38

Check voltage to the igniter

Question 39

A technician starts a standing pilot furnace and notices on main ignition the flames "roll out". The technician suspects:

Answer 39

A faulty vent

Question 40

A technician servicing an LP gas furnace notices a tag stating it was converted from natural gas. He finds large amounts of soot in the heat exchanger. What could be the cause of this soot?

Answer 40

Orifice, (spud) too large.

Question 41

A customer tells a technician that his six mont old furnace stops heating before the residence is warm. This happens only on very cold nights. The technician lights the furnace, and tries to adjust the gas valve, but the flames do not change. He suspects:

Answer 41

A defective gas regulator.

Question 42

A standing pilot furnace had a bi-metal fan control. What are the factory settings?

Answer 42

Fan on 125F / Fan off 80F / Limit cut out 200F

Question 43

Type B vent pipe is constructed with an inner pipe and outer pipe. The inner pipe is made of what?

Answer 43

Aluminum

Question 44

On a dedicated vent system, a fire stop support is located:

Answer 44

Where it passes through a ceiling

Question 45

When venting Category 1 furnaces, it is sometimes necessary to increase the vent pipe size. The proper location to adapt to the larger vent is:

Answer 45

At the furnace connection

Question 46

You are installing 1/2" and 3/4" black iron pipe to a natural gas furnace. What is the approximate number of threads to cut?

Answer 46

8-10

Question 47

The proper name of the tool used to clean the inside of steel pipe is a?

Answer 47

Reamer

Question 48

Clevis, ring, and single hook are types of :

Answer 48

Hangers to support gas piping

Question 49

The proper name of the tool used to cut the threads of a steel pipe is a:

Answer 49

Die

Question 50

You are installing two sections of a rectangular sheet metal duct to the main supply line. What connectors are used to secure sections of the trunk line?

Answer 50

A connectors and drive clips.

Question 51

Metal ductwork tends to transmit noise and fan vibrations to conditioned spaces in residential installations. What type of connectors are specified to control this?

Answer 51

Flex connectors

Question 52

Duct wrap is used to insulate round metal ducts. What is the approximate R- value for "one inch" of this insulation?

Answer 52

R=4.0

Question 53

A category 1 natural gas furnace has a typical air temperature rise of:

Answer 53

40F-70F

Question 54

A technician connects the electrical circuit to an 80,000 BTU gas furnace with a 3-ton cooling system. The fan motor is rated 1/3 HP @ 120 VAC. What size conductor would normally be used? (Copper conductors)

Answer 54

12-14 AWG

Question 55

A GFCI circuit breaker detects:

Answer 55

Current leaks to ground

Question 56

A homeowner complained that his furnace makes a loud bang upon ignition. The technician decides to check the gas pressure and finds 3.2 in. W.C. at the manifold. The technician should:

Answer 56

Check the supply gas pressure

Question 57

The proper instrument for measuring carbon dioxide is a:

Answer 57

Combustion analyzer

Question 58

If voltage is applied across two speed terminals on a fan motor, the motor will:

Answer 58

Short out

Question 59

The maximum static pressure on a typical gas furnace blower system is:

Answer 59

.7 - .9 in. W.C.

Question 60

Induced draft furnaces have a vent safety switch that should open at?

Answer 60

100F

Question 61

Thermostat wire comes in two standard gauges:

Answer 61

22 and 20 AWG

Question 62

A technician solders a spade connector to a wire. What type of solder should he use?

Answer 62

Rosin core

Question 63

The anticipator is wired in series with the?

Answer 63

Gas valve

Question 64

To change the speed of a belt driven blower, the technician should:

Answer 64

Adjust motor pulley

Question 65

How much current does a typical flame sensor produce?

Answer 65

1-30 microamps

Question 66

A typical vent stack temperature on a category 1 furnace is?

Answer 66

350F-450F

Question 67

A customer complains that a 2 year old gas furnace will not light. The technician determines that the furnace locks out while attempting to light. He reads 19 VAC at the gas valve and concludes

Answer 67

The transformer could be faulty.

Question 68

The pilot assembly orifice of a spark ignition furnace is completely clogged. The technician should:

Answer 68

Replace it

Question 69

Carbon monoxide is dangerous. What percentage of CO is acceptable in a sample of the flue gas?

Answer 69

.04%

Question 70

A technician starts up a 15 year old natural gas furnace. The main burner lights and after 60 seconds the blower fan comes on, but the blower flames wave in one corner. The technician suspects:

Answer 70

A faulty heat exchanger

Question 71

A technician starts a spark type ignition furnace. The main burners light, but the spark igniter continues to spark. After 60 seconds, the blower fan comes on and the burner goes out. The technician suspects:

Answer 71

A faulty ignition board

Question 72

A gas furnace has an induced draft fan. What switch must operate properly before ignition sequence?

Answer 72

Differential air pressure

Question 73

A technician reads 0 Ohms between the common and low speed wires on a 120 VAC furnace motor. From this the technician determines that the winding is:

Answer 73

Shorted

Question 74

On his ohmmeter a technician reads infinity between the high and low speed wires on a 120 VAC furnace motor. What does this indicate?

Answer 74

Open

Question 75

The "bonnet capacity" of a furnace is:

Answer 75

Furnace input BTUs

Question 76

At what altitude does a gas furnace need to have adjustments made to operated properly?

Answer 76

2000 feet

Question 77

Failure to wire a replacement low voltage transformer in an electronic ignition furnace, based on it's noted polarity, will:

Answer 77

Cause flame rectification problems

Question 78

A spark ignitor operates at?

Answer 78

10,000 VAC and higher

Question 79

What type of metallic conduit is recommended for indoor use only?

Answer 79

EMT

Question 80

A furnace nameplate specifies a temperature rise of 40 to 70 degrees. Temperature measurements indicate a rise of 80 degrees. The most appropriate action is to:

Answer 80

Increase fan speed.

Question 81

A dedicated vent system:

Answer 81

Is the only vent for an appliance.

Question 82

A yellow flame indicates:

Answer 82

Incomplete combustion is occurring. Soot may be created, which further hampers burner operation. Lack of primary air is the main cause.

Question 83

A lifting flame indicates:

Answer 83

The gas velocity is faster than the speed at which the gas can burn.

Question 84

Flashback indicates:

Answer 84

The gas is flowing slower than the speed at which burn is occurring.

Question 85

A floating flame indicates:

Answer 85

Incomplete combustion is occurring. Soot may be created, which further hampers burner operation. Lack of primary air is the main cause.

Question 86

Fan speed should be set by:

Answer 86

The temperature rise called for on the data plate.

Question 87

Gas flow to a natural gas furnace can be checked:

Answer 87

Using the gas meter installed at the site

Question 88

It the exact amount of air is supplied and perfect combustion occurs, in a natural gas furnace, a specific percentage of CO2 content will be present in the flue gases. What percentage will be present?

Answer 88

11.7% to 12.2%

Question 89

When an LP unit is properly installed and operating normally, the CO2 content of the exhaust gases:

Answer 89

11% to 12%

Question 90

While evaluating a gas valve that failed to open, the technician determined that; the gas valve knob in the proper position - the thermostat was calling for heat - the valve is an electric ignition type- continuity of the main gas valve coil was good - and proper voltage was present at the main gas valve coil terminal(s). What action should be taken?

Answer 90

Replace the gas valve

Question 91

In a house with central return system and seven supplies located in rooms with interior doors, what outcomes are likely when the interior doors ate closed and the air handler is turned on?

Answer 91

The static pressure that the HVAC fan gas to run against is increased resulting in less air through the air handler. The main body of the house experiences negative pressure. The rooms behind the closed interior door become positively pressurized.

Question 92

The formula (x=sensible heat btu/h/ 1.08 xTD) is used to calculate what?

Answer 92

CFM

Question 93

The most common burner used in induced draft furnaces is:

Answer 93

inshot

Question 94

A technician wraps a thermostat wire ten times around his clamp-on ammeter and measures 5.5 amps between R and W terminals on the thermostat sub-base. He should set the heat anticipator to:

Answer 94

.50

Question 95

A gas valve with 100% shut-mean:

Answer 95

gas to the pilot burner is shut-off

Question 96

A gas furnace has an electronic control board. How is the fan cycled during heating?

Answer 96

Time

Question 97

A primary cause of burner "flashback" is:

Answer 97

low manifold pressure

Question 98

A technician needs to run thermostat wire 75 feet. To avoid a voltage drop the technician should use:

Answer 98

#20 AWG