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Sheet Metal 4th Year > Commercial HVAC > Flashcards

Commercial HVAC Flashcards

1
Q

What is the relationship between straight duct and hoods or elbow fittings?

A

Both hoods and elbows should be 2 gauges heavier than straight pipe.

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2
Q

Can dash stops ever be removed, overrided or modified?

A

No

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3
Q

What is the average face velocity at which air is drawn through the face to the hood exhaust?

A

60-100 fpm

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4
Q

What must always be provided for a local exhaust system?

A

A make up air unit

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5
Q

The key to designing an industrial exhaust system is?

A

Speed

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6
Q

What type of ducts are recommended for industrial exhaust systems?

A

Smooth and round

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7
Q

Before it enters the fan, how many diameters should duct be straight for?

A

At least 2 diameters

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8
Q

What is the biggest resistance on an exhaust system?

A

The filter

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9
Q

What 2 types of fans are used in an industrial exhaust system?

A

Axial-propeller

Centrifugal-draws air into the centre of the fan and exhausts it at 90 degrees.

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10
Q

Straight blade fans move?

Curved blade fans move?

A

Material

Air

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11
Q

Exhaust stacks should be located how far away from a buildings fresh air intake?

A

50’

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12
Q

How far from a roof line should exhaust stacks be located?

A

10’

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13
Q

Air velocity should be how many fpm out of an exhaust stack?

A

3000 fpm

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14
Q

Where should clean out or access doors be provided on an industrial exhaust system?

A

Near elbows or close to any other change in direction of the duct

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15
Q

What is the face velocity for hazardous materials?

A

50 fpm

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16
Q

How does a variable air volume hood maintain constant face velocity?

A

By slowing down or speeding up the air

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17
Q

Three types of workplace ventilation are:

A

Indoor air quality ventilation
Dilution ventilation
Local exhaust ventilation

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18
Q

Velocity is measured in?

A

FPM feet per minute

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19
Q

Volume is measured in?

A

CFM cubic feet per minute

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20
Q

What is the formula to find CFM?

A

CFM=FPM x area

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21
Q

Hoods located 4” from a source will require how many times the amount of CFM to provide the same degree of capture as a hood located 2” from the source?

A

4x

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22
Q

What 2 factors need to be considered when sizing a fan to ensure it can overcome resistance in the exhaust system?

A

Appropriate size and type

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23
Q

For velocities of 2500 fpm or less, how many diameters of straight on fan discharge should there be?

A

2.5 D

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24
Q

Duct hangers and supports should be of sufficient capacity to carry the weight of the system if what?

A

If half of the system is filled with material

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25
Q

What are explosion doors used for?

A

To provide instantaneous pressure discharge

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26
Q

How far should a hanger be from a joint?

A

At least 2 duct diameters

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27
Q

What is the minimum distance in inches that a draw band joint should be?

A

4” minimum

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28
Q

Why are expansion joints used?

A

To provide stress relief and absorb movement during extreme temperatures

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29
Q

A blast gate or slide damper is used for what?

A

When a positive seal is desired and to close off or isolate parts of a system when they are not in use

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30
Q

Name 3 types of longitudinal seams?

A

Groove seam
Butt weld seam
Spiral seam

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31
Q

Which seam can be used for all five duct classes?

A

Butt weld seam

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32
Q

Screws or rivets should be 6” maximum Center to Center?

A

True

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33
Q

How many inches of lap should there be on commercial pipe?

A

2”

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34
Q

Class 1 only and 2 gauges heavier than chart values describe what?

A

Aluminum duct

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35
Q

Elbows should have a centreline radius of what?

A

No less than twice but preferably 2.5 times the pipe diameter

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36
Q

All branches should enter the main duct at what angle?

A

Not to exceed 45 with 30 degrees being preferred

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37
Q

Branches should be installed in what orientation?

A

On their side or on the top

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38
Q

For transitions, every 1 unit of change requires how many units in length?

A

5

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39
Q

For fan outlets, what can be provided if an elbow inlet is necessary?

A

An inlet box or turning vanes

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40
Q

When designing an industrial exhaust system, if pipe size falls between 2 numbers you should go with the bigger size?

A

No, to maintain velocity revert to the smaller pipe size

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41
Q

When sizing a blow pipe system, is it possible to not include certain types of machines?

A

Yes, if the machine is seldomly used it is not included in sizing.

Eg. floor sweep

42
Q

What type of duct is used for class 5?

A

Plastic or stainless as the application consists of corrosives such as acid

43
Q

If a stack extends more than 10’ above a roof, what may be required?

A

A guy wire set which may be 3 wires minimum

44
Q

What is the result of exhausting large amounts of air without a proper make up air unit provided?

A

Carbon monoxide

45
Q

What built up in a duct can increase the risk of flash fire or explosion?

A

Static electricity

46
Q

What can be used to avoid static buildup in a system?

A

Aluminum or copper ground wire

47
Q

What is the purpose of a well designed industrial exhaust system?

A

Eliminate undesirable contaminants where protection of workers health is required

48
Q

Why do some industrial exhaust systems require special piping or duct work?

A

There may be the possibility of corrosion or abrasion

49
Q

What 4 provisions must be considered when designing/installing industrial exhaust duct?

A

Cleaning
Maintenance
Fire protection
Drainage

50
Q

What is the maximum face velocity when exhausting toxic fumes?

A

60-125 fpm

51
Q

What is another name for an auxiliary air fume hood?

A

Makeup air fume hood

52
Q

What is incorporated to maintain a desired face velocity on a variable air volume fume hood?

A

A closed loop control system

53
Q

What is the basic principle on how dilution ventilation works?

A

Blow clean air in and exhaust dirty air out

54
Q

List 5 basic components in a local exhaust ventilation system?

A 
Hood
Duct
Air cleaning device
Fan
Exhaust stack
55
Q

What type of pressure is found in a local exhaust ventilation duct?

A

Slightly negative pressure

56
Q

What occurs if face velocity in a hood exceeds 125 fpm on a capturing hood?

A

Turbulence

57
Q

What is a blast gate also known as?

A

Slide damper

58
Q

When is plastic or PVC duct used on an industrial exhaust system?

A

For corrosive or toxic fumes are to be conveyed

59
Q

What is the best practice regarding centreline radius and number of gores on elbows used for an industrial exhaust system?

A

Centreline of 2.5 and 7 gores

60
Q

What can be added to maintain velocity in a constant volume exhaust system in a building that has a variable air volume ventilation system?

A

Bypass dampers

61
Q

What can be installed to reduce energy consumption in a building that employs a large amount of exhaust systems?

A

Heat recovery system

62
Q

What is the recommended face velocity for a hood under normal conditions?

A

100 fpm

63
Q

What is the function of a kitchen canopy or hood?

A

Capture plume of heated air that is rising

64
Q

What are two main categories of commercial kitchen exhaust hoods?

A

Type I

Type II

65
Q

What are Type I hoods designed to handle?

A

Heat and grease laden effluents

66
Q

What are the two broad categories of Type I hoods?

A

Standard and Listed

67
Q

What does a Type I hood capture that a Type II does not?

A

Grease

68
Q

What are two basic styles of hoods?

A

Canopy and non-canopy

69
Q

List 4 types of canopy hoods?

A

Island
Wall
Corner
Slotted

70
Q

List two types of non-canopy hoods?

A

Back shelf

Eyebrow

71
Q

List 4 items that could be part of the grease removal system?

A

Filters
Baffles
Air washers
UV technology

72
Q

What 4 codes must a grease removal system meet when installed?

A

Alberta building code
NFPA
Manufacturers specs
Authority having jurisdiction

73
Q

What is installed to suppress a flare up prior to having heat damage in a grease removal system?

A

Fire suppression system

74
Q

In what orientation should commercial kitchen exhaust ducts be installed?

A

Vertically

75
Q

What is the minimum air velocity through commercial kitchen exhaust ducts be according to the NFPA?

A

500 fpm or 152.4 m/minute

76
Q

How much make up air is required in a commercial kitchen?

A

100%

77
Q

What is a control interlock panel used for in a commercial kitchen?

A

To ensure that when the exhaust fan is on, the make up air unit is also on and vice versa

78
Q

How much overhang must a commercial kitchen canopy have in regards to the cooking equipment?

A

At least 6” per exposed side

79
Q

What gauge of mild steel can be used in the construction and installation of a commercial kitchen canopy?

Stainless steel?

A

18 gauge mild steel

20 gauge stainless

80
Q

At what length on a commercial kitchen exhaust canopy is it desirable to have two take offs on top for discharge?

A

When the canopy exceeds 10’

81
Q

What gauge of mild steel can be used in the construction of commercial kitchen exhaust duct?

Stainless steel?

A

16 gauge mild steel

18 gauge stainless

82
Q

Where shall access doors, for the purpose of cleaning and inspection, be installed on commercial kitchen exhaust duct?

A

Side or top

83
Q

How much extra weight needs to be accounted for in commercial kitchen exhaust duct if the cross sectional area exceeds 24”?

A

800 lbs

84
Q

How much clearance must a commercial kitchen exhaust duct have to combustibles?

A

18”

85
Q

How far away from adjacent buildings, air intakes or property lines must a commercial kitchen exhaust duct terminate outside?

A

10’

86
Q

How far from a roof surface must the outlet for a fan discharge be?

A

40”

87
Q

What is the maximum storage capacity of the grease collector?

A

1 US gallon

88
Q

What type of force extracts grease through a baffle tape grease filter?

A

Centrifugal force

89
Q

What is the optimum operating velocity of air through a baffle type grease filter?

A

150-300 fpm

90
Q

What takes precedence over original drawings and specs?

A

Addenda and revisions

91
Q

What is the purpose of a spec?

A

To describe the work to be done

92
Q

What is the purpose of a schedule?

A

To provide information on what goes where

93
Q

What is a change to a blueprint called?

A

A revision

94
Q

What is a change to a specification called?

A

An addenda

95
Q

What should always be read before starting a job?

A

The mechanical general notes

96
Q

What point are all elevations derived from?

A

The datum point

97
Q

What are changes to drawings referred to as?

A

As builds

98
Q

What does BIM stand for and what does it include?

A

It stands for building information management and includes all of the information used to construct a building

99
Q

What must carefully be studied when compiling a job takeoff?

A

The plans and specifications

100
Q

What is ACTS?

A

The Alberta construction tendering system

101
Q

What does a bid bond guarantee?

A

If the contractor is the low bidder that they will honor the bid

Sheet Metal 4th Year (5 decks)

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