Line B Combustion

Question 1

When dealing with the combustion of hydro carbon gases, why is stoichiometric combustion of fuel and air not a viable option for most burners?

1) This will produce an unacceptable luminous flame

2) Burners are not capable of perfectly mixing air and fuel

3) This type of combustion produces unacceptable flue gas components

4) Stoichiometric combustion is unstable and unsuitable for heating applications

Answer 1

2) Burners are not capable of perfectly mixing air and fuel

Question 2

It is important to add excess air to the combustion chamber to:

1) Provide cooling for the heat exchanger

2) To ensure perfect combustion occurs

3) To provide an adequate amount of dilution air

4) To ensure complete combustion occurs

Answer 2

4) To ensure complete combustion occurs

Question 3

Which of the air to fuel ratios shown below is for natural gas?

1) 20 ft3 to 1 ft3

2) 20 ft3 to 100 Btu’s

3) 10 ft3 to 1000 Btu’s

4) 2 ft3 to 100 Btu’s

Answer 3

3) 10 ft3 to 1000 Btu’s

Question 4

Why do air requirements differ for appliances with and without draft control?

1) All units require air to be supplied at a ratio of 30:1

2) Units with draft control require more combustion air

3) Units with no draft control require more excess air

4) Units with draft control require dilution air

Answer 4

4) Units with draft control require dilution air

Question 5

In theory, which gas appliance will require more air per hour to operate?

1) 1000 MBH appliance with a draft hood and atmospheric burner

2) 500 kW appliance operating on 50% excess air and no draft control device

3) 1000 MBH power burner using 30% excess air and a barometric damper

4) 2200 MBH power burner using 25% excess air and no draft control

Answer 5

1) 1000 MBH appliance with a draft hood and atmospheric burner

Question 6

At what point on the venting system should an analysis of the flue products be taken?

1) Downstream of the draft control device

2) Downstream of the flue collar

3) Upstream of the draft control device

4) Upstream of the fan assist burner

Answer 6

3) Upstream of the draft control device

Question 7

If a natural gas appliance and a propane appliance were firing at the same rate and under the same conditions, which would have the greater air requirements and which would have the greater % of CO2 in the flue products?

1) Natural gas has higher air requirements and lower CO2

2) Propane has higher air requirements and higher CO2

3) Both have the same air requirements but natural gas has a higher CO2

4) Both have the same air requirements but propane has a higher CO2

Answer 7

4) Both have the same air requirements but propane has a higher CO2

Question 8

How much excess air is added to the combustion process in order to achieve the ultimate percentage of CO2?

1) 1/3 the volume of combustion air

2) 2/3 the volume of combustion air

3) 50% of combustion air

4) None is required

Answer 8

4) None is required

Question 9

What percentage of excess air will produce equal percentages of O2 and CO2 in the flue products?

1) 25%

2) 33%

3) 50%

4) 100%

Answer 9

3) 50%

Question 10

Analyzing the flue products after servicing a burner shows acceptable levels of CO2 and O2 but unacceptable levels of CO. What type of circumstances could cause this to happen?

1) Lack of combustion air

2) Lack of excess air

3) Excessive dirt on fan blades

4) Poor mixing ability of burner system

Answer 10

4) Poor mixing ability of burner system

Question 11

If a gas hot water tank was 100% efficient, what would the temperature of the flue products be?

1) Same as ambient

2) 100°F above ambient temperature

3) 100°F below ambient temperature

4) Minimum 127°F to maintain draft

Answer 11

1) Same as ambient

Question 12

A gas appliance is firing at 1000 Mbh on natural gas. Calculate the volume of CO2
produced each hour.

1) 100 CFH

2) 1000 CFH

3) 2000 CFH

4) 10000CFH

Answer 12

2) 1000 CFH

Question 13

A gas appliance is firing at 3000 Mbh on propane. Calculate the volume of CO2 produced each hour.

1) 1200 CFH

2) 3000 CFH

3) 3600 CFH

4) 4800 CFH

Answer 13

3) 3600 CFH

Question 14

A gas appliance is firing at 5000 Mbh on propane gas and condensing all water vapour to a liquid state. Calculate the volume of water produced each hour (note: the expansion ratio for water from liquid to vapour is 1700:1).

1) 30 imperial gallons

2) 60 imperial gallons

3) 90 imperial gallons

4) 120 imperial gallons

Answer 14

1) 30 imperial gallons

Question 15

The theoretical perfect combustion of natural gas requires an air/gas ratio of:

1) 10:1

2) 15:1

3) 25:1

4) 30:1

Answer 15

1) 10:1

Question 16

The complete combustion of propane in air (include 50% excess air) requires an air/gas ratio of:

1) 10:1

2) 15:1

3) 25:1

4) 37:1

Answer 16

4) 37:1

Question 17

A furnace operating at the rated input on propane is converted to natural gas. The total air requirements for the furnace will:

1) Increase by 5%

2) Increase by 10%

3) Decrease by 15%

4) Remain the same

Answer 17

4) Remain the same

Question 18

The ultimate percentage of CO2 in the flue products of natural gas is:

1) 8%

2) 12%

3) 15%

4) 20%

Answer 18

2) 12%

Question 19

Some flue gas analyzers can test for combustibles. Which of the following could not be detected?

1) Carbon

2) Hydrogen

3) Carbon monoxide

4) Carbon dioxide

Answer 19

4) Carbon dioxide

Question 20

The difference between the flue stack temperature and the room temperature is called the:

1) Net stack temperature

2) Ambient temperature

3) Gross stack temperature

4) Critical temperature

Answer 20

1) Net stack temperature

Question 21

A fan assist burner operating at its rated input is producing flue gas with 8.6% CO2. In order to increase the CO2 level you must:

1) Increase the air supply

2) Decrease the air supply

3) Increase the fuel supply

4) Decrease the fuel supply

Answer 21

2) Decrease the air supply

Question 22

A fan assist burner operating at its rated input is producing flue gas with 10% oxygen content. The efficiency of the appliance could be increased by:

1) Increasing the air supply

2) Decreasing the air supply

3) Decreasing the CO2 content

4) Decreasing the fuel supply

Answer 22

2) Decreasing the air supply