Class B Review Quiz Flashcards
State the chemical abbreviations for propane and natural gas.
Propane: C3H8, Natural Gas: CH4
State the ignition temperatures of propane and natural gas.
Propane: 920o to 1020oF, Natural Gas: 1100o to 1300oF
List the specific gravities for natural gas, propane vapour, and liquid propane.
Natural Gas: 0.6, Propane vapour: 1.5, Propane liquid: 0.51
What are the limits of flammability for natural gas and propane?
Natural Gas: 4 to 14%, Propane: 2.4 to 9.5%
What are the maximum flame temperatures that can be achieved with propane and with natural gas when mixed with air?
CH4:3500oF, C3H8: 3600oF
What are the boiling temperatures of propane and natural gas at sea level?
Propane: -44oF, Natural Gas: -258oF
What are the flame speeds of natural gas and propane?
25”/sec., 32”/sec. (tube method)
Define the term Btu.
British thermal unit. The amount of energy acquired or liberated when changing the temperature of 1 lb. of water 1oF
What is the energy content of 1 cubic foot of propane and 1 cubic foot of natural gas?
C3H8:2500 Btu/ft3, CH4:1000 Btu/ft3
List the products of complete combustion of natural gas and propane.
CO2 + H2O + N2
What are the expansion ratios from liquid to vapour for natural gas and propane?
CH4: 1:600, C3H8: 1:270
What are the percentages of nitrogen and oxygen found in air?
O2 = 20%, N2 = 80%
What is the air/gas ratio required to achieve complete combustion of natural gas and propane?
CH4: 10:1, C3H8: 25:1
What is the ratio of air to Btu content required to complete combustion of all hydrocarbon gases?
10ft3/1000Btu
How many Btu equal one kilowatt?
3413 Btu/Kw
Explain the term primary air, with reference to an atmospheric burner.
The air entrained and mixed prior to combustion
What is the term used to describe the additional air supplied to the combustion chamber of a gas appliance to ensure complete combustion?
Excess Air
What is the purpose of dilution air?
To reduce the velocity of the flue gasses
A gas appliance is considered to be high input when it exceeds what input?
400,000 Btu/hr., aka. 400MBH
What are the pressure limitations of a Class “B” license?
No pressure limitations however Safety Standards Act is limited to 700Kpa (100Psi)
pipe sizing
If the calorific value of a cubic meter of gas was 37,000 Btu.
What would the Btu content be per cu. ft?
What would the kW content be per cu. meter?
What would the kW content be per cu. ft?
Calculate the correction factor required when converting gas at 40 degrees F. to standard gas temperature conditions.
Calculate the correction factor required when converting gas under a pressure of
134.5 kPa absolute to standard gas pressure conditions.
100 cubic meters of gas is pressurized at 50 psig. Calculate the new volume if the gas is released to atmosphere at sea level.
a
A gas at sea level is contained under a pressure of 60 psig at 50 degrees F. Calculate the new pressure if the temperature is increased to 90 degrees F. Answer in psig.
Calculate the flow rate in Btuh and kW
Service pressure 60 psig
Inlet pressure to meter 5 psig
Manifold pressure 7” w.c
Test dial 5 Cu. Ft.
Time of 1 Revolution 1.5 Min.
Calorific Value of gas 1000 Btu/Cu. Ft.
Calculate the input under the following conditions.
Service pressure 50 psig
House line pressure 10 psig
Meter pressure 10 psig
Test dial 5 Cu. Ft.
1 Revolution 30 seconds
Ambient air temperature 700 F.
Gas temperature 500 F.
Local atmospheric pressure 14.73 psia.
Calorific value of gas 1000 Btu/Cu. Ft.
Calculate the time for 1 revolution of a 2 Cu. Ft. test dial.
Input 1,575,000 Btu/hr
Local atmospheric pressure 14.25 psia
Ambient air temperature 450 F.
Gas temperature 500 F.
Calorific value of gas 1050 Btu/Cu. Ft.
Meter pressure 10 psig
Three appliances are firing at 75,000 Btu/hr each; the time for 1 revolution of a 2 Cu. Ft. Test dial is 32 seconds when all of the appliances are operating. Is the total input correct? (Meter pressure is 7” WC.)
A 4th appliance is added, rated at 27 kW. The time for 1 revolution is now 24 seconds. Is the input correct? Is it over fired or under fired?
The clocked input of an appliance is 2,000,000 Btuh. The test dial is 5 Cu. Ft. The local atmospheric pressure is 13.9 psia and the gas temperature is 200 F.
How many seconds will it take to complete 1 revolution of the test dial?
Calorific value of gas 1000 BTU/CF
Meter pressure is 20 psig
Calculate the input
Meter pressure 34 kpa
Local atmospheric pressure 97.3 kpa
Gas temperature 3 degrees C.
Test dial 0.5 Cubic Meters
Time for one revolution 31 seconds
Calorific value of gas 10.35 KW/Cu. M
When dealing with the combustion of hydrocarbon gases why is stoichiometric combustion of fuel and air not a viable option for most burners?
This will produce an unacceptable luminous flame
Burners are not capable of perfectly mixing air and fuel
This type of combustion produces unacceptable flue gas components
Stoichiometric combustion is unstable and unsuitable for heating applications
Burners are not capable of perfectly mixing air and fuel
Why is it important to add excess air to the combustion chamber?
To provide cooling for the heat exchanger
To ensure that perfect combustion occurs
To provide an adequate amount of dilution air
To ensure complete combustion occurs
To ensure complete combustion occurs
What is the ideal combustion ratio air-to-fuel ratio for natural gas?
20 ft3 to 1 ft3
25 ft3 to 1000 Btu
10 ft3 to 1000 Btu
2 ft3 to 100 Btu
10 ft3 to 1000 Btu
What is a colourless, odourless, tasteless, and potentially lethal by-product of incomplete combustion?
Oxygen
Carbon monoxide
Nitrogen
Aldehydes
Carbon monoxide
What is a colourless, acrid smelling toxic by-product of incomplete combustion?
Oxygen
Carbon monoxide
Nitrogen
Aldehydes
Aldehydes
What can be another cause of incomplete combustion other than insufficient air?
Flame temperature dropping below 1,200°F
Poor fuel to heat exchanger ratio
Combustion chamber too large
Too much humidity in the air
Flame temperature dropping below 1,200°F
At what point on the venting system should an analysis of the flue products be taken?
downstream of the draft control device
downstream of the flue collar
upstream of the draft control device
upstream of the fan assist burner
upstream of the draft control device
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 percentage of CO2 in the flue products?
Natural gas has higher air requirements and lower CO2
Propane has higher air requirements and higher CO2
Both have the same air requirements, but natural gas has higher CO2
Both have the same air requirements, but propane has higher CO2
Both have the same air requirements, but propane has higher CO2
How much excess air is added to the combustion process to achieve the ultimate percentage of CO2?
1/3 volume of combustion air
2/3 volume of combustion air
50% of combustion air
none is required
none is required
What percentage of excess air will produce equal percentages of O2 and CO2 in the flue products?
25%
33%
50%
100%
50%
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?
lack of combustion air
lack of excess air
excessive dirt on fan blades
cracked heat exchanger
cracked heat exchanger
If a gas hot water tank was 100% efficient, what would the temperature of the flue products be?
same as ambient
100°F above ambient temperature
100°F below ambient temperature
minimum 127°F to maintain draft
same as ambient
A gas appliance is firing at 1000 Mbh on natural gas. Calculate the volume of CO2 produced each hour.
100 ft3
1,000 ft3
2,000 ft3
10,000 ft3
1,000 ft3
A gas appliance is firing at 3,000 Mbh on propane. Calculate the volume of CO2 produced each hour.
1,200 ft3
3,000 ft3
3,600 ft3
4,800 ft3
3,600 ft3
A gas appliance is firing at 5,000 Mbh on propane gas and condensing all water vapor to a liquid state. Calculate the volume of water produced each hour (expansion ratio vapor to liquid is 1700:1).
30 Imperial gallons
60 Imperial gallons
90 Imperial gallons
120 Imperial gallons
30 Imperial gallons
If a 2,350 Mbh forced draft burner was firing on natural gas with 23% excess air, what would be the expected percent of O2 when taking a combustion analysis?
2.3%
3.5%
4.1 %
5%
4.1 %
If a 2,350 Mbh forced draft burner was firing on natural gas with 23% excess air, what would be the expected percent of CO2 when taking a combustion analysis?
8.85 %
9.2%
10.4 %
13%
8.85 %
What is absolute zero equal to in:
Degrees F?
Degrees C?
Degrees F: -460 F, Degrees C: -273 F
Convert 30 degrees Fahrenheit to Celsius
30 – 32 / 1.8 = -1.1 C
Convert 30 degrees Celsius to Fahrenheit
30 X 1.8 + 32 = 86 F
Define sensible heat
Heat that can be measured
Define latent heat
Heat energy required or liberated during a change of state
State the number of BTU’s required to change 1 lb. of 32oF ice to 32oF water.
144 BTU
State the number of BTU’s required to change 1 lb. of 212oF water to 212oF steam
970.4 BTU
State the specific heat of water
1
State the specific heat of steam
0.48 (ice: 0.53)
What is the formula to find the efficiency of a gas fired appliance?
Output/Input
Why do air requirements differ for appliances with and without draft control?
All units require air to be supplied at a ratio of 30:1
Units with draft control require more combustion air
Units with no draft control require more excess air
Units with draft control require dilution air
Units with draft control require dilution air
In theory, which gas appliance will require more air per hour to operate?
1000 Mbh appliance with a draft hood and atmospheric burner
500 kW appliance operating on 50% excess air and no draft control device
1000 Mbh power burner using 30% excess air and a barometric damper
2200 Mbh power burner using 25% excess air and no draft control
1000 Mbh appliance with a draft hood and atmospheric burner
An atmospheric gas appliance has an input of 350 Mbh and is equipped with a draft hood. It is to be installed in a building that complies with code clause 8.2.1. A or B. What size duct is required to provide air to this appliance?
6 inch
7 inch
8 inch
9 inch
8 inch
A furnace room complies with code clause 8.2.1. (a) or (b). It contains a 200 Mbh furnace without draft control and a 100 Mbh hot water heater with a draft hood. Size the combustion air duct based on a length of 30’.
6 inch
7 inch
8 inch
9 inch
7 Inch
A boiler room contains the following five pieces of equipment:
one 2500 Mbh boiler with draft control
two 350 Mbh hot water heaters with draft hoods
two 650 Mbh duct heaters without draft control.
Calculate the required free area of the combustion air duct.
43 in2
300 in2
321 in2
343 in2
343 in2
The following gas appliances are installed in a mechanical room:
one 1200 Mbh steam boiler with a barometric damper
one 350 Mbh hot water heater with draft hood
two 500 Mbh direct fired make-up air units
Select a grill for the combustion air opening in the boiler room wall that will meet the minimum requirements of the B149.1 gas code (grills rated at 60% free area).
10” ´ 12”
10” ´ 14”
15” ´ 20”
20” ´ 20”
15” ´ 20”
The air supply to a 30,000 Mbh boiler, using a force draft burner, is provided by mechanical means through a horizontal duct 42 feet in length. What is the quantity of air required to be supplied to the boiler?
1 ft3 for each 1,000 Btu/h
10 ft3 for each 1,000 Btu/h
15 ft3 for each 1,000 Btu/h
30 ft3 for each 1,000 Btu/h
30 ft3 for each 1,000 Btu/h
