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Gas A Level 2 > Level 1Review > Flashcards

Level 1Review Flashcards

1
Q

Describe the relationship between the % values of CO2 and O2 in the flue gas when you adjust the air shutter on a fan-assist burner during set-up?

A

The greater the amount of excess air, the higher the % of O2 and the lower the % of CO2

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2
Q

If three flue samples were taken, the first with 20% excess air, and the second with 32% excess air, and the third with 44% excess air which would contain the higher CO2 reading?

A

The sample with 20% excess air

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3
Q

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?

A

Both have the same air requirements, but propane has higher CO2

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4
Q

When performing an analysis of the products of combustion using natural gas, what percentages of carbon dioxide and oxygen you would expect to find if the excess air is set at 30%?

A

8.3% CO2, 5% O2

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5
Q

A gas appliance is firing at 5,400 Mbh on propane gas and condensing all water vapor to a liquid state. Calculate the capacity of water produced each hour in US Gallons

A

38 US Gallons

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6
Q

What is the formula for perfect (stoichiometric) combustion?

A

Fuel + O2 + N2 = CO2 + H2O + N2

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7
Q

What is the formula for complete combustion?

A

Fuel + O2 + N2 + Excess Air = CO2 + H2O + N2 + Excess Air

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8
Q

How does tertiary air control NOx emissions?

A

It slightly cools the flame

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9
Q

What can be done to control NOX emissions from a burner?

A

Inject steam around the flame

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10
Q

What can be used to control the combustion air for a burner system?

A

A Variable Frequency Drive or Electronically Commutated Motor

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11
Q

List three factors that can create CO in the products of combustion?

A

Running too much fuel, not enough combustion air or a failing draft inducer

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12
Q

What is the maximum air-free CO level allowed to be produced during combustion?

A

400 ppm

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13
Q

How many pounds of CO2 are produced per hour from a 54,784,000 BTUH fuel oil fired boiler?

A

8765 lbs

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14
Q

How many pounds of CO2 are produced per hour from a 7,312,000 BTUH natural gas fired boiler?

A

856 lbs

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15
Q

According to legislation, how much ppm sulfur content does heating oil need to be below?

A

500 ppm

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16
Q

What chemical compounds from combustion are collectively called SOX?

A

SO2 & SO3

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17
Q

What are two results when NO2 reacts with other pollutants?

A

Ozone and Acid Rain

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18
Q

What chemical compounds from combustion are collectively called NOX?

A

NO & NO2

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19
Q

What is the main reason for performing combustion analysis on gas fired equipment?

A

To ensure the equipment is operating in a safe and efficient manner.

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20
Q

How often should your combustion analyser be calibrated to ensure accurate test readings?

A

Once per year.

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21
Q

Where should the sampling probe take a sample from on a gas fired appliance?

A

Upstream of any draft control device or just downstream of a stack economizer.

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22
Q

What is the correct way to allow combustion analysis samples to be taken with plastic S636 systems?

A

Installing an access tee with a ½” tapped bushing as close as possible to the flue collar of the appliance where either a plastic or brass plug can be inserted.

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23
Q

What is a Peltier cooler used for in a combustion analyzer?

A

To drive out moisture from the sample

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24
Q

The gas cells in a combustion analyser are of what type?

A

Electrochemical

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25
Q

What can shorten the life span of the toxic sensors in a combustion analyser?

A

High gas concentrations or insufficient purging

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26
Q

What is the chemical formula for the Perfect combustion of Natural Gas?

A

1CO2 + 2H2O + 8N2

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27
Q

What is the chemical formula for the Perfect combustion of Propane?

A

3C02 + 4H2O + 20N2

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28
Q

What is added to the combustion process to produce Complete combustion?

A

Excess Air

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29
Q

What is the expected percentage range of O2 produced by a forced draft burner with CH4 as the fuel?

A

3% - 6%

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30
Q

What are four characteristics of Carbon Monoxide?

A

Toxic, colourless, odourless and tasteless

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31
Q

What can cause too much draft in a venting system?

A

High stack temperatures

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32
Q

What percentage gain in efficiency is achieved by lowering stack temperature by 45⁰F?

A

Less than 1%

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33
Q

Calculate the net stack temperature if the ambient temperature is 72⁰F and the stack temperature is 420⁰F? Is this temperature within typically expected values?

A

348⁰F, Yes (330 - 500⁰F)

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34
Q

If the measure percent O2 reading is 4.1% and the measured NOx reading is 55 ppm, what would the NOx ppm be when corrected to standard?

A

58.58 ppm

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35
Q

If the measured CO reading is 38 ppm, and the measured %O2 reading is 4.2% what would the calculated air-free ppm reading be?

A

47.56 ppm

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36
Q

What is the power end of the Honeywell, Series 90 Modutrol used for?

A

It is used to drive linkages

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37
Q

What is the auxiliary end of the Honeywell, Series 90 Modutrol used for?

A

It is used to devices like auxiliary switches

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38
Q

In what orientation should motors with crankshafts be installed?

A

Horizontal

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39
Q

How is strain avoided on the motor and linkage of a fuel/air system?

A

The drive lever rotational start point is kept off of the shaft centerline

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40
Q

Fixed Stroke Actuators are available in what two opening ranges?

A

90⁰ or 160⁰

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41
Q

Adjustable stroke model actuators can be field adjusted between what range?

A

90⁰ - 160⁰

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42
Q

What controls the speed and the amount of rotation of the driven lever pivot point?

A

It is controlled by the starting position of both levers and the connection distance of the linkage to the lever pivot points

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43
Q

Placing the drive lever closer to the shaft centerline than the driven lever is placed will do what to the rotation of the driven lever?

A

It will be reduced

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44
Q

Placing the driven lever closer to the shaft centerline than the driver lever is placed will do what to the rotation of the driven lever?

A

It will be increased

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45
Q

How are precise changes made on the linkage for a fuel valve?

A

By adjusting the cam spring

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46
Q

The gas butterfly valve is used to control modulation and to stop gas flow?
TRUE / FALSE

A

FALSE, It is not used to stop gas flow

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47
Q

How can high and low fire be adjusted on a gas butterfly valve?

A

By using the stop screws

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48
Q

Where would you find information for making initial set up adjustments to linkages?

A

From the equipment manufacturer

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49
Q

What must be done while making any adjustments to linkages?

A

Combustion analysis must be performed

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50
Q

How do we balance safety and efficiency when adjusting our linkages with the use of a combustion analyzer?

A
  • Adding more oxygen reduces the chance of CO and increases safety
  • Reducing oxygen increases our efficiency but has the potential to increase CO thus being less safe.
  • Always prioritize safety
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51
Q

What advantage does a direct contact water heater have?

A

No loss out the stack, no lost condensation, no lost radiant heat.

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52
Q

Describe how an immersion burner works.

A

A submerged radiant tube heat exchanger is used to heat large volumes of liquid.

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53
Q

Describe how an indirect bath heater works.

A

It uses two separate, submerged heat exchangers to heat a fluid with one heat exchanger and transfer that heat from the fluid to the second heat exchanger.

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54
Q

What are three of the potential hazards of using a direct fired construction heater?

A
  • Being too close to combustibles can lead to a fire
  • The possibility of fire if used in a wood frame structure
  • There is the potential for dangerous levels of carbon monoxide
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55
Q

What is a curing oven used for?

A

Used to generate some form of chemical reactions once a temperature setpoint is reached by a particular substance.

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56
Q

What is a drying oven used for?

A

It is used to remove moisture from materials.

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57
Q

What is a baking oven used for?

A

It is used to remove moisture from materials and to generate some form of chemical reactions once a temperature setpoint is reached by a particular substance.

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58
Q

What is the purpose of a CO2 generator?

A

To produce carbon dioxide required by plants in commercial green houses.

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59
Q

What is the typical temperature range of an industrial furnaces?

A

750 to 3,275 °F

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60
Q

What is the purpose of an exothermic generator?

A

To produce cover gasses as a non-oxidizing atmosphere for the heat treating of bright metals.

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61
Q

What is the purpose of an endothermic generator?

A

To provide a positive pressure in a heat-treating furnace, and a platform on which a carburizing or decarburizing environment can be formulated.

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62
Q

What is the purpose of tertiary air in the combustion process?

A

To add air to control emissions and flame shape

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63
Q

What type of heat transfer does an infrared burner utilize?

A

Direct radiation

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64
Q

What type of heat transfer does a low temperature indirect heating burner use?

A

It uses a fan to transport the heated air to the work

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65
Q

What type of heat transfer does a direct-fired burner use?

A

It uses a mix of radiation and hot gas convection

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66
Q

What type of heat transfer does a high temperature indirect-heated burner utilize?

A

Tubes or enclosed walls are heated and radiate heat to the work

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67
Q

A propane fired boiler has a low-fire input of 1,700,000 BTUH and a high-fire input of 22,100,000 BTUH. What is its turndown ratio?

A

13:1

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68
Q

What ratio of air/natural gas are most premix burners limited to for acceptable, normal operation?

A

10:1

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69
Q

What are three characteristics of a nozzle mix burner?

A
  • Its ability to operate over a wide range of air/gas ratios
  • To control the mixing of the gas and air without sacrificing clean combustion or flame stability
  • To allow the ability to vary the flame shape
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70
Q

What methods can be used to atomize oil in an oil fired burner?

A
  • Air atomizing
  • Pressure atomizing
  • Steam atomizing
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71
Q

How can the flame length of an oil-fired burner be modified?

A

Changing the oil nozzle spray angle

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72
Q

The main burner flame shall be proven at the furthest point(s) along its base from the source of ignition when the burner flame width is in excess of how many feet?

A

3 feet

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73
Q

From the combustion flow formula identify what each variable represents.

A

Q = flow rate (cubic feet per hour)
A = area of the orifice (square inches)
K = discharge coefficient of the orifice
∆P = pressure drop across the orifice (inches water column
Sg = specific gravity of the gas

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74
Q

What would be the most reliable source to find the specific gravity of natural gas?

A

From your natural gas utility

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75
Q

What is the purpose of an Orifice plate?

A

To measure a general approximation of flow rate

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76
Q

The higher the discharge coefficient of the orifice the less restriction there is to gas flow.
TRUE / FALSE

A

True

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77
Q

When using an Orifice plate what are three things that could skew the results?

A
  • The location of the pressure taps
  • The thickness of a square edge plate
  • If the appliance is operating in low fire
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78
Q

A direct fired make-up air unit is designed for temperatures ranging from -5⁰F to 75⁰F. At what outdoor temperature (within design parameters) will the velocity across the burners be the greatest?

A

75⁰F

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79
Q

A direct fired makeup air heater has the same function as an RTU.
TRUE / FALSE

A

FALSE

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80
Q

What is the main benefit of a DFMAH?

A

No efficiency lost to a heat exchange

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81
Q

Referring to the B149.1 under what conditions can a DFMAH be used?

A

A DFMAH shall not be installed unless it is necessary to exhaust air and replace it with preheated air

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82
Q

What must be proved before the DFMAH can start?

A

Any inlet or discharge air louvres must be proved open through an interlock with the control the exhaust system is operating

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83
Q

What is the purpose of makeup air?

A

To replace the air exhausted by large exhaust appliances which, when properly designed, installed and maintained ensure a neutral pressure in the building

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84
Q

When a DFMAH is used in a kitchen it must be interlocked with the kitchen exhaust fan so that neither fan can operate without the other operating?
TRUE / FALSE

A

TRUE

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85
Q

List three things that could affect the external static pressure placed on a DFMAH.

A

Filters, Grilles, Ductwork

86
Q

When the DFMAH is in operation the burner is always firing?
TRUE / FALSE

A

FALSE

87
Q

What are the two modes of operation for a spray booth DFMAH?

A

Spray Mode, Bake Mode

88
Q

In a DFMAH what is adjusted to control air velocity?

A

Profile Other than make up air for a kitchen or spray booth list three other applications for DFMAH.
plates

89
Q

Other than make up air for a kitchen or spray booth list three other applications for DFMAH.

A

Shaft pressurization (stairwell or elevator), storage garage, mine shaft

90
Q

For refractory classification what would be considered a normal fusion temperature for the following refractories:

Normal Refractories
Super Refractories
High Temperature Refractories

A
  • Normal Refractories 1600⁰C
  • Super Refractories 2200⁰C
  • High Temperature Refractories 1900⁰C
91
Q

For refractory compounds and materials, what materials classification group do the following fall under:

Silica
Graphite
Lime

A
  • Silica Acid Materials
  • Graphite Neutral Materials
  • Lime Alkaline Materials
92
Q

Why do alkaline and acidic refractory material need to be kept apart on installation?

A

They react with each other under high temperature and form salt

93
Q

What is the main purpose of refractory material?

A

To contain the heat generated by the combustion process

94
Q

Properly selected, mixed and installed what percentage of fuel costs could refractory save.

A

5% - 7 %

95
Q

Broadly speaking, what are the two refractory types?

A

Shaped and Unshaped

96
Q

Refractory helps shape the burner flame in the combustion chamber?
TRUE / FALSE

A

TRUE

97
Q

What is the most important factor that affects the lifespan of refractory?

A

Refractory Dry-out

98
Q

What schedule must be followed for curing and dry-out of refractory?

A

Follow Manufacturer’s Instructions

99
Q

What can cause horizontal crack formation in refractory?

A

Thermal cycling, Stress accumulation, creep

100
Q

What four factors affect the flow of gas through a piping system?

A

Type of gas, diameter of pipe, length of pipe, pressure drop

101
Q

What factor determines which of the two formulas are used to develop the code tables?

A

System Pressure

102
Q

Pipe sizing tables in the B149.1 used to size low pressure piping systems make an allowance for a reasonable number of fittings. How is this accomplished?

A

By adding a hidden 20% to the displayed code zone lengths (as noted in the formula in the code book)

103
Q

Plastic pipe is approved for use in a liquid propane system.

TRUE / FALSE

A

FALSE (B149.1.20, 6.2.16)

104
Q

In what two ways can the volume of gas required for an appliance be determined?

A

The appliance rating plate, or the appliance manufacturer when the rating is not shown on the appliance (B149.1.20, 6.4.2)

105
Q

What shall not be done if piping or tubing is located in an area where a corrosive chemical is used?

A

It must not be concealed (B149.1.20, 6.7.3)

106
Q

In British Columbia, piping of NPS 2 ½” and over shall have welded pipe joints.

TRUE / FALSE

A

FALSE. BC Gas Safety Regulations - 2.3 Clause 6.9.2 of CSA B149.1-20 is repealed and the following substituted: 6.9.2 Piping of NPS 2-1/2 to 4 shall be either press-connect fittings certified to CSA 6.32(ANSI LC-4) or welded pipe joints. Piping greater than NPS 4 shall be welded pipe joints.

107
Q

If a gas piping system requires welding, who can perform this welding?

A

Welding of gas piping systems shall be performed in accordance with a procedure and by an operator registered under the applicable provincial or territorial legislation.

108
Q

When can piping or tubing enter a building below grade?

A

Only when permitted by the Authority Having Jurisdiction (good luck) (B149.1.20, 6.15.8)

109
Q

What are the three ways that piping or tubing can be identified by in a care, detention occupancy, commercial, industrial or assembly building?

A

The entire piping or tubing system shall be painted yellow, The piping or tubing system shall be provided with yellow banding that has a minimum width of 1” and is marked at intervals not exceeding 20’, or the piping or tubing system shall be labelled “GAS” or “PROPANE” utilizing yellow label s or markings.

110
Q

Can a quick disconnect device be used instead of a manual shut off valve?

A

NO (B149.1.20, 6.18.7)

111
Q

What is the minimum diameter gauge allowed to be used for a pressure test on a gas piping system?

A

3 inch (B149.1 - 6.22.2 (b))

112
Q

Using good engineering practices, what type of fluid should be used to pressurize a piping systems 4 inches and larger that contain a combustible gas?

A

inert gas (B149.1 6.22.2)

113
Q

What is the minimum test pressure as per code requirements for 372’ of 8” NPS schedule 80 steel pipe (yellow jacket) installed underground operating at a gas pressure of 40 psig?

A

100 psig (B149.1

114
Q

When pressure testing a gas piping system, what is the maximum range the pressure gauge shall exceed the test pressure by?

A

at least by 15% but not more than 300% (B149.1 6.22.2 (b))

115
Q

What is the maximum diameter purge point opening when purging NPS 2”?

A

1/2 inch

116
Q

What is the maximum pipe size that can be purged using air or fuel gas as the purging agent if the length of the pipe is 45 feet?

A

2-1/2 inch (B149.1 Table 6.4)

117
Q

What is the recommended pressure used when purging with nitrogen?

A

0.5 or 14” w.c.

118
Q

What is the recommended purge velocity through the piping system?

A

200 ft/min

119
Q

What is the reason for purging at the correct velocity through a piping system?

A

completely scrubs the walls, no stratification, faster than flame speed

120
Q

Why is purging using an inert gas a requirement when exceeding the pipe lengths for the diameters given in Table 6.4 of the B149.1?

A

larger volumes of piping cannot withstand an internal explosion from a gas air mixture

121
Q

What does TOE stand for in a TOE nipple?

A

Thread One End

122
Q

During a nitrogen purge, what velocity must be maintained at the purge outlet?

A

200 ft/sec

123
Q

When purging outdoors, what is the minimum distance from a building intake allowed?

A

10 feet

124
Q

Identify the type of flame represented in the following images:

A

a. Figure 1 type A

125
Q

Identify the type of flame represented in the following images:

A

b. Figure 2 type C

126
Q

Identify the type of flame represented in the following images:

A

c. Figure 3 type E

127
Q

Identify the type of flame represented in the following images:

A

d. Figure 4 type F

128
Q

Identify the type of flame represented in the following images:

A

e. Figure 5 type H

129
Q

What style of burner is represented by the following images:

A

a. Gun burner

130
Q

What style of burner is represented by the following images:

A

b. Lance burner

131
Q

What style of burner is represented by the following images:

A

c. Cane burner

132
Q

What style of burner is represented by the following images:

A

d. Immersion burner

133
Q

In order to increase regulator accuracy, the pitot tube senses pressure at what point?

A

Lowest outlet pressure point

134
Q

Which regulator will have the least amount of droop under flow conditions?

A

A pilot operated regulator

135
Q

Critical flow in a regulator occurs when the velocity of the gas reaches what threshold?

A

Sonic Velocity

136
Q

What does a double-ported balance regulator use to sense downstream pressure?

A

A downstream sense line

137
Q

Where is the sense line connected on a proportional regulator?

A

To the top of the diaphragm

138
Q

When zero governor regulators are used for burners that are to be operated under positive or negative combustion chamber conditions, how can the combustion chamber pressure be counterbalanced?

A

Connecting a pressure reference line from the combustion chamber to the top diaphragm chamber of the zero governor

139
Q

What type of regulator is pictured below?

A

Double-ported balanced regulator

140
Q

In the above image what is the purpose of connecting the sense line?

A

To sense outlet pressure

141
Q

In the above image at what point is the sense line connected to the main supply piping?

A

Downstream to the top of the piping

142
Q

What type of regulator is pictured below?

A

Atmospheric regulator

143
Q

What type of regulator is pictured below?

A

Pilot operated regulator

144
Q

What would happen if the regulator shown below was installed backwards?

A

It will pass no flow

145
Q

What would happen if the above regulator was installed upside down?

A

It would provide lower downstream pressure

146
Q

When selecting a regulator for a gas piping system, what regulator inlet pressure should you assume there to be when the system is under no flow?

A

Static pressure (system setting)

147
Q

Referring to the image below, what must be done to create a proportioning regulator with the use of the regulator shown?

A

Cross-connect an impulse line from downstream of the combustion air control valve to the top of the regulator diaphragm

148
Q

When an impulse line is used for a proportional regulator system, what is the minimum pipe diameter the line should be installed from the shaft of the combustion air control valve?

A

5 Pipe diameters

149
Q

When an impulse line is used for a proportional regulator system, what is the minimum pipe diameter the line should be installed from any pipe tee or elbow (change in direction)?

A

3 Pipe diameters

150
Q

If it is absolutely necessary to locate the connection of an impulse line less than the recommended pipe diameters downstream of the combustion air control valve, how should the hole be drilled in the pipe?

A

Parallel to the to the shaft of the valve on the side of the pipe

151
Q

How should a cross-connection impulse line from the combustion air to the regulator be installed?

A

With no dips in the line to avoid trapping water and pitched towards the combustion air line

152
Q

Referring to the figure above, what is the purpose of the limiting orifice?

A

It limits gas flow to the maximum burner rate

153
Q

Referring to the figure above, how is low fire adjusted and set?

A

By adjusting the spring in the regulator

154
Q

Referring to the figure above, what can be done to correct the regulator action affected from variable combustion chamber pressures or any combustion chamber pressures higher or lower than the room pressure adjacent to the regulator?

A

An impulse line can be cross-connected from the combustion chamber to the air/gas ratio regulator

155
Q

For nozzle mix burners, when is a cross-connected impulse line from the regulator’s vent to the main combustion air line required?

A

When the minimum gas inlet pressure exceeds the maximum air pressure by 3.5 or more inches water column

156
Q

If the minimum gas pressure at the proportional regulator inlet is not more than the maximum air pressure at high fire, what can be done to compensate for this?

A

Install a two-pipe bleeder and set it so the maximum impulse pressure is 4 iwc less than the gas inlet pressure

157
Q

When is an overpressure protection device required by code?

A

When the inlet pressure to a main pressure regulator exceeds the pressure rating of any downstream component or accessory

158
Q

What method of overpressure protection will interrupt flow of gas in the event of an over pressurization?

A

Automatic shut-off system

159
Q

Which type of over pressure protection system must be manually reset after it has been activated?

A

Automatic shut-off

160
Q

Referring to the figure below, this is an example of which type of over-pressure protection?

A

Pressure relief

161
Q

Referring to the figure below, if the main diaphragm ruptures, what is the likely result?

A

The relief valve will provide reduced flow rates

162
Q

Referring to the figure below, what method of overpressure protection is represented?

A

Upstream monitor system

163
Q

Referring to the figure below, how can we easily change which regulator is the worker and which is the monitor?

A

Switch the set points on the regulators

164
Q

A separate line relief valve shall be installed where in relationship to the regulator?

A

As close as possible downstream from the regulator

165
Q

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

A

Units with draft control require dilution air

166
Q

An atmospheric gas appliance has an input of 390 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?

A

9”

167
Q

A furnace room complies with code clause 8.2.1. (a) or (b). It contains a 260 Mbh furnace without draft control and a 120 Mbh hot water heater with a draft hood.

Size the combustion air duct based on a length of 21’

A

7”

168
Q

A boiler room contains the following five pieces of equipment:

  • one 3500 Mbh boiler with draft control
  • two 450 Mbh hot water heaters with draft hoods
  • two 750 Mbh duct heaters without draft control.

Calculate the required free area of the combustion air duct.

A

436 in2

169
Q

The following gas appliances are installed in a mechanical room:

  • one 1400 Mbh steam boiler with a barometric damper
  • one 550 Mbh hot water heater with draft hood
  • two 600 Mbh direct fired make-up air units

Select a square 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 67% free area).

A

18” x 18” (314.507 in2)

170
Q

The air supply to a 20,000 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?

A

600,000 ft3 (30 ft3 for every 1,000 btu/h)

171
Q

A 2,752 Mbh forced draft natural gas boiler is operating in a mechanical room, excess air set at 40%. What is the required free area for the combustion air duct?

A

92 in2

172
Q

A structure is equipped with a boiler rated at 5,300 MBH and a hot water tank rated at 400,000 Btu/h. Both pieces of equipment are equipped with draft controls and the air supply is ducted from outdoors. What is the size of the free ventilation air opening?

A

47.9 in2

173
Q

A structure is equipped with a boiler rated at 750 kW and a barometric draft control. What is the free area of the combustion air supply opening in mm?

A

162,750 mm2

174
Q

A structure is equipped with appliances rated at 1,900 MBH. None of the appliances is equipped with draft control devices and the air supply is ducted from outdoors. What is the free area of the ventilation air opening?

A

10 in2

175
Q

A structure has a mechanical room into which air must be ducted from outdoors. It contains the following appliances:

  • One boiler rated at 3,000 MBH, equipped with a barometric damper
  • Two duct heaters without draft controls rated at 950,000 Btu/h each
  • Two hot water tanks rated at 250,000 Btu/h each. Both tanks are equipped with draft hoods

What is the free area of the combustion air supply opening?

A

385 in2

176
Q

A structure has a mechanical room into which air must be ducted from outdoors. It contains the following appliances:

  • One boiler with no draft control rated at 500 kW
  • One boiler with draft control rated at 4,000 MBH
  • One duct heater with no draft control rated at 125 kW
  • One hot water heater with a draft hood rated at 800,000 Btu/h

What is the free area of the combustion air supply opening?

A

485.37 in2

177
Q

A mechanical room is equipped with gas appliances with a total input of 3,200 Mbh. All appliances are equipped with draft control devices. The louvre specified for the combustion air opening has a free area of 70%. What is the size of the opening required to fit the louvre?

A

428.58 in2

178
Q

What is the minimum opening size on a screen used on a combustion air-supply opening?

A

1/4”

179
Q

On a combustion air louvre with dampers the dampers must be controlled in what way?

A

Automatically

180
Q

What interlock is required for an automatically adjustable combustion air louvre?

A

Normally Open contact interlocked with burner control

181
Q

What two fan styles are commonly used for mechanical air supply systems?

A

Axial and Centrifugal

182
Q

When air is provided by mechanical means what type of switch must be used?

A

The code does not specify the type. Air proving switch (sail or differential)

183
Q

What three factors would lead you to want to pre heat combustion air?

A

Prevent the freezing of pipes, prevent thermal shock of the boiler, maintain appliance efficiency

184
Q

What do ICI Appliance manufacturers do for high altitude installations? (above 4500 feet)

A

Increase blower motor horse power

185
Q

What is the relationship between static pressure and air flow?

A

As static pressure goes up air flow goes down

186
Q

What three factors have the greatest affect the static pressure in ducting?

A

Cross sectional area, length, number of fittings

187
Q

What is the static pressure ranges of the following combustion supply-air ducting systems?

a. Low Pressure:

b. Medium Pressure:

c. High Pressure:

A

a. less that 3” w.c.
b. 3” to 6” w.c.
c. 6” to 10” w.c.

188
Q

Referring to the figure below, what type of actuator is used to drive the vent damper?

A

Linear

189
Q

Referring to the figure below, what type of actuator is used to drive the vent damper?

A

Rotary

190
Q

When an automatic flue damper used on an appliance equipped with direct-spark ignition falls fully open upon loss of driving medium, the fuel supply to the appliance needs to be shut off.

A

False

191
Q

What type of tubing is used to connect a differential pressure transducer used to control a damper actuator to the flue stack probe?

A

Silicon

192
Q

What is the typical maximum distance a differential pressure transducer used to control a damper actuator should be connected to the flue stack probe?

A

6 feet

193
Q

Referring to the figure below, What should distance ‘A’ be to improve accuracy?

A

3 times the vent diameter

194
Q

If a CO sensor is used in a boiler room, how high above the floor should the sensor be mounted?

A

4 to 6 feet

195
Q

When CO sensors are installed in an 28,250 ft2 boiler room, a total of how many sensors are required?

A

4

196
Q

What would be the calculated theoretical draft developed by a stack 55 feet in height with an average temperature of 310°F, and the ambient temperature is 70°F?

A

0.246” w.c.

197
Q

A boiler is firing natural gas at 4,000 Mbh with 30% excess air. What would be the calculated the volume in cubic feet per minute of flue gases leaving the flue outlet if the temperature is 450°F, and the outside air temperature is 70°F?

A

1603 cfm

198
Q

A natural gas boiler is firing at 3 million Btu/h with 40% excess air. The ambient air temperature is 66°F and the stack temperature is 410°F. What would be the calculated velocity of the flue gas if the boiler is equipped with a 16-inch diameter stack?

A

889 fpm

199
Q

If a stack has a velocity of 1000 fpm, what would be the calculated draft produced?

A

0.06 w.c.

200
Q

A boiler equipped with a power burner is firing at 11 million Btu/h with 35% excess air. The combustion air duct is sized to meet the Gas Code requirements. What would be the calculated velocity through the combustion air duct if the boiler is operating at full input, the ambient air temperature is 70°F, and the stack temperature is 460°F?

A

972 fpm

201
Q

You are called on to commission an installation of a 4,750,000 Btu/h natural gas boiler.

  • Excess air set at 30%
  • Stack diameter 18 inch
  • Combustion chamber and heat exchanger pass volume 188 ft3
  • Gross stack temperature 485 deg. F
  • Ambient temperature 76 deg. F

Based on this information what is the expected draft in the stack?

A

0.0762” w.c.

202
Q

What factors would achieve the highest draft in a chimney?

A

Tall chimney, hot combustion products, hot ambient (outside) air

203
Q

A mechanical draft produced by a device upstream from the combustion zone of an appliance is a definition of what type of draft?

A

Forced draft

204
Q

A mechanical draft produced by a device downstream from the combustion zone of an appliance is the definition of what type of draft?

A

Induced draft

205
Q

What reading would the draft pressure gauge indicate when measuring in the combustion chamber of a gas fired appliance using a force draft burner?

A

Positive pressure

206
Q

What reading would the draft pressure gauge indicate when measuring in the combustion chamber of a gas fired appliance using a fan-assisted burner?

A

Non-positive pressure (Negative over-fire pressure)

207
Q

What does a balanced draft system incorporate?

A

A forced draft burner and an induced draft fan

208
Q

What type of draft control does a gas-fired appliance incorporate when using a forced draft burner?

A

Internal damper

209
Q

Why is the draft reduced when using flue gas recirculation to control NOx?

A

Lower flame temperatures

210
Q

Why is the draft reduced when using a scrubber (air pre-heater)?

A

Heat is removed from the flue gases

211
Q

Referring to the figure below, to maintain a draft of 0.08” w.c. at E what will the draft pressure need to be across the damper B?
The draft at A should be 0.6’ w.c. and the draft losses through the appliance are as follows:

  • C = 0.12” w.c.
  • D = 0.11” w.c.
  • Elbow = 0.05” w.c. each
A

Across damper B = 0.19 “w.c.
- calculation: 0.6 – (0.08 + 0.12 + 0.11 + 0.10) = 0.19

Gas A Level 2 (8 decks)

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