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Chimney Fundamentals And Operation

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Title: Chimney Fundamentals And Operation


1
Chimney FundamentalsAnd Operation
  • The Art of Venting Flue Gases
  • Or
  • How Not To Kill Your Client

Presenter Earl Hicks
2
Objectives
  • Review New York WAP policy regarding venting
    systems
  • BPI Standards
  • Review combustion process
  • Define understand combustion air
  • How does a vent system work
  • Identify venting categories and materials
  • Using venting rules-of-thumb
  • Inspection of existing flues
  • Alternative venting methods

3
NYS WAP Policy
  • Ensure safe elimination of flue gases from the
    building

4
BPI StandardsBuilding Performance Institute
  • Any combustion appliance chimney/vent system that
    is in use must be visually evaluated for defects
  • A deteriorated chimney should be repaired or
    relined and causes corrected before reusing.

5
Principles Of Combustion
  • Three essential components for combustion
  • Fuel
  • Oxygen
  • Heat
  • Fuel Fossil fuels
  • Oxygen Air is 20.9 O2
  • Heat Pilot, spark, or igniter

6
Combustion Principles
7
The Chemical Reaction
  • CH4 4O2 heat CO2 2H2O heat
  • Complete combustion
  • Natural gas
  • 1 Cu Ft of CH4 10 Cu Ft of air for complete
    combustion
  • 11 Cu Ft of flue gases

8
Combustion Air
  • Must supply sufficient air for complete
    combustion when all appliances are in operation
    simultaneously.
  • Must determine whether CAZ is a confined or
    unconfined space per NFPA.
  • Tightening a dwelling too much may result in the
    need to bring in outside air for combustion
    regardless of NFPA classification.
  • Must follow established standards for bringing in
    combustion air.

9
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10
Confined / Unconfined
  • Confined Space
  • Not enough air in the combustion appliance zone
    to provide for complete combustion when all
    appliances are operating and the building is set
    in worst case criteria.
  • Unconfined Space
  • Enough air is present to provide for complete
    combustion when all combustion appliances are
    operating and the house is set for worst case
    criteria.

11
Standard 1/20 Rule
  • Measure the volume of the CAZ.
  • Add all input Btu ratings of appliance in the
    CAZ.
  • If dryer is in CAZ
  • Electric consider input rate of 100,000
  • Gas consider input rate of 125,000
  • Divide this total Btu by 20.
  • The resulting number is the Cu. Ft. separating
    confined from unconfined space.
  • Volume of CAZ below result confined space
  • Volume of CAZ above result unconfined space

12
Example
  • CAZ 10L X 14W X 8H
  • Appliances
  • Gas furnace 75,000 Btu input
  • Hot water heater 40,000 Btu input
  • Gas dryer - 125,000 Btu input

13
Solution
  • CAZ 10L X 14W X 8H
  • Volume 1120 Cu
  • Total appliance input Btu
  • 240,000 Btu
  • 1/20
  • 240,000 20 12,000 cu ft.
  • Actual volume is below 12,000 cu ft
  • CAZ is a confined space
  • Results Additional combustion air must be
    brought into the CAZ

14
Other Than Standard
  • IMPORTANT! The above standard is based on a
    known infiltration rate of less than .4 air
    changes per hour
  • When the ACH is known
  • For appliances other than fan-assisted, consult
    NFPA 54 8.3.2.2(1)
  • For fan-assisted appliances, consult NFPA 54
    8.3.2.2(2)

15
  • Table
  • 9.3.2.2(a)
  • Natural
  • Draft
  • Appliances

16
Table 9.3.2.2(b)Fan Assisted Appliances
17
Methods of Bringing In Combustion Air
  • Within the dwelling, from other zones
  • Ducted in horizontally from OD
  • Directly from OD above and or below

18
What is Draft
  • Negative pressure within a flue that pulls
    products of combustion out from the dwelling.

19
Factors That Affect Draft Pressure
  • Delta T, Indoors to Outdoors
  • Height of Vent
  • Interior Volume
  • Restrictions
  • Atmospheric Conditions
  • Pressure Imbalances in the CAZ

20
How Does A VentingSystem Work?
Air Flow
Combustion Gases
21
What is Considered Adequate Draft?
  • OD temp gt800F, gt-1 Pa or - .005WC
  • OD temp 300 800F, gt-2.5 Pa or -.01WC
  • OD temp below 300F, gt-5 Pa or -.02WC
  • (250 pascal 1W.C.)

22
Most Common Poor Draft Factors Found in the Field
  • Return air leaks in the basement
  • Long horizontal vent connectors
  • Blocked vents
  • Deteriorated flue
  • Bird nests
  • Outside masonry flues with fan assisted heating
    appliances
  • Fireplaces with no outside combustion air and
    without front enclosures.
  • Overly tight houses

23
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24
Venting Categories
25
Venting Categories
  • NFPA 54 and 58 criteria
  • Standardized
  • Category I
  • Negative pressure, non-condensing
  • Category II
  • Negative Pressure, condensing
  • No longer produced
  • Category III
  • Positive pressure, non-condensing
  • Category IV
  • Positive pressure, condensing

26
Non-Condensing
Condensing
27
Category I
  • What we normally think of when we think chimney
  • Negative pressure sucks products of combustion
    from the appliance breech and deposits them
    outdoors

28
Category II
  • No longer manufactured
  • Negative pressure vent with combustion gases at
    or below the dew point
  • Heavy gases at the dew point are not buoyant
    enough to vent with a negative pressure flue

29
Category III
  • Direct sidewall vented without additional
    apparatus.
  • Positive pressure requires joints in flue
    material to be sealed
  • Because these 80 appliance flue gases are close
    to the dew point, and the vent material is single
    wall, corrosion resistant materials must be used
  • Drains are typically incorporated to remove flue
    condensation before it enters the heat exchanger

30
Category III
  • Has been used to solve installation problems
    where no appropriate flue is available
  • Positive pressure requires joints in flue
    material to be sealed

31
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32
Category IV
  • Positive pressure condensing appliances, joints
    must be sealed
  • 90 AFUE
  • Appliances are designed to dispose of flue
    condensate as well as condensate formed within
    the secondary heat exchanger
  • May be able to sidewall vent at reduced distances
    to openings in the building than NFPA suggests
  • Sealed combustion
  • Combustion air intake in same pressure plane

33
Category I Vent MaterialsFound With Older
Heating Appliances
  • Single wall galvanized pipe, 26 gauge
  • Only as a connector on 70 AFUE and lower gas
    appliances and all oil appliances
  • Connector for oil appliances
  • Masonry
  • Vitreous clay liner
  • Oil appliances
  • Transite
  • Rated as single wall
  • Asbestos
  • Does not meet any venting requirements

34
Category I Vent Materialscont.
  • B Vent double wall
  • Galvanized steel outside, aluminum inner pipe
  • Rated only for gas appliances
  • Used as a vent connector for all 78 and 80 AFUE
    appliances
  • May not be run outside of the building
  • Used as a liner in an existing flue chase

35
Category I Vent Materialscont.
  • Flexible liner
  • Aluminum gas appliances
  • Stainless Steel gas and oil appliances
  • Used to retrofit existing flue passages to meet
    code or a specific application
  • L Vent double wall
  • Inner and outer pipes are stainless steel
  • Oil appliances
  • All Fuel, double wall insulated
  • Oil
  • Solid Fuels

36
Category III Flue Materials
  • Aluminum
  • No longer recommended because of corrosion
    problems
  • Stainless Steel
  • Use type specified by manufacturers to reduce
    corrosion issues
  • High temperature plastic
  • Was the most common material specified by
    manufacturers
  • Have been involved in recall
  • Manufacturer specific installation protocol
  • Sealed joints, High temperature sealant
  • Hanger spacing
  • Pitch back to appliance ¼ per Ft.

37
Category IV Flue Materials
  • PVC
  • Low cost
  • Sealed joints
  • Must be provided with adequate hanging support
  • Pitch back to appliance ¼ per Ft.
  • CPVC
  • Higher operating temperatures than PVC
  • Follow manufacturer instructions
  • Manufacturer specific
  • Sealed Joints

38
Water In The Flue
  • Water is a byproduct of combustion
  • Key for category I appliances is to maintain
    water in a gaseous state within the flue so that
    it exits to the outdoors.
  • Category IV appliances are engineered to remove
    liquid water from within the secondary heat
    exchanger and flue.

39
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40
  • 93(lbs) 10 gallons
  • Million Btu 100,000 Btu _at_ 10 Hrs run time
  • 10 Hr run time for natural gas 10 gallons of
    water that must be removed from the flue.

41
70 AFUE Gas Furnace Overview
  • 21 Cu Ft flue gases for every 1 Cu Ft of natural
    gas burned
  • Draft diverter mixes the extra 10 Cu Ft of air
    with the flue gases before entering the flue
  • Reduced efficiency means more heat going up the
    chimney, hot flue gases (4500 6000F)
  • Dilution gases reduce the relative humidity and
    increases the dew point

42
Draft Hood Appliances
  • 1 Cu Ft CH4 10 Cu Ft air 10 Cu Ft of dilution
    air mixed at draft hood
  • 21 Cu Ft of flue gases up chimney under maximized
    conditions
  • Draft hood
  • aids in minimizing fluctuation of draft
  • Prevents backdraft from affecting burner

Spill Switch
43
78 80 AFUE Furnace Venting Overview
  • Draft induced fan does not force flue gasses into
    the vent.
  • A category I flue of adequate design must be used
  • More heat in the building and less up the chimney
    yields a colder chimney
  • Cycle time is longer than older furnaces to
    adequately warm the flue and keep moisture in a
    gaseous state.

44
TO WARM UP A CHIMNEY
  • If firing rate 100,000 Btu/hr and SSE 75,
    then 75,000 Btu/hr go to the distribution system
    and 25,000 Btu/hr go through the vent.If the
    burner on-cycle is 12 minutes (.2 hrs), then
    during one cycle the vent receives
    .2 hr x 25,000 Btu/hr 5,000 Btu/cycle
    MASONRY CHIMNEYA masonry
    chimney (block or brick tile liner) requires
    about 4570 Btu/.ft. to go from 0o to 120o. So,
    on a very cold day, about one foot of chimney
    will be warmed in one burner cycle 5,000
    Btu/cycle _at_4,570Btu/ft 1 ft/cycle
    TYPE B-VENT CHIMNEYA 6" B-vent
    chimney requires about 90 Btu/.ft. to go from 0o
    to 120o. So,5,000 Btu/cycle _at_ 90Btu/ft 55
    ft/cycle

45
After Weatherization with aNew Furnace
  • If firing rate 75,000 Btu/hr and SSE 82, then
    61,500 Btu/hr go to the distribution system and
    13,500 Btu/hr go through the vent.
  • If the burner on-cycle is 6 minutes (.1hrs), then
    during one cycle the vent receives
  • .1hr x 13,500 Btu/hr 1,350 Btu/cycle
  • EXISTING MASONRY CHIMNEY
  • About four inches of the existing masonry chimney
    will be warmed during one burner cycle
  • 1,350 Btu/cycle _at_ 4,570Btu/ft .3 ft/cycle
  • TYPE B-VENT CHIMNEY
  • During each burner on cycle, enough heat to warm
    15feet of B vent goes into the chimney
  • 1,350 Btu/cycle _at_ 90Btu/ft 15 ft/cycle

46
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47
Draft Induced Category I Venting Guidelines
  • No exterior masonry chimneys without a properly
    sized metal liner.
  • Flex or B
  • No interior masonry chimneys over 2 stories
  • No transite chimneys
  • No unlined masonry chimneys
  • No masonry chimneys unless common vented with a
    draft hood type appliance without a vent damper

48
Draft Induced Category I Venting Guidelines
(cont.)
  • Must have double wall B vent connector
  • Furnace must be properly sized
  • Furnace must be set up correctly
  • Temperature rise
  • Gas input
  • Heat anticipator or cycle rate set _at_ 3 cycles per
    hour
  • Vent sizing should be in accordance with tables
    supplied with the furnace or NFPA
  • When sidewall venting a power vent kit must be
    used unless the manufacturer specifies otherwise.

49
New Category I Venting Rules-Of-Thumb
  • Use B vent as connector from the appliance to
    the flue
  • Reduce heat loss in the connector
  • Pitch connector down toward appliance ¼ per Ft.
  • Warm air rises
  • Maximum horizontal distance (Table 13.2.2)
  • 1 ½ times the diameter of the connector in feet
  • 4 connector 6 maximum horizontal distance

50
Rule-Of-Thumb Continued
  • Follow NFPA 54 sizing charts
  • Never used unlined masonry flue
  • Dont use outside masonry flue
  • Never use Transite
  • If you take the heating appliance out of the flue
    and leave the water heater in, you are
    responsible to ensure the water heater will vent
    properly
  • Line the flue

51
Oil Appliance Venting
  • NFPA 31 sizing guidelines
  • Masonry
  • Type L
  • stainless steel
  • All fuel

52
What We Should See In The Field
Outside Masonry
L Vent
53
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54
Why The Fuss About Venting Fan Assisted Gas
Appliances?
  • 11 Cu Ft flue gas for every 1 Cu Ft natural gas
    (Vs. 21 Cu Ft for 70 AFUE)
  • Lower flue gas temperatures, (3500F)
  • No dilution air (no draft hood) so gases are
    close to the dew point
  • Water must stay in gaseous state to be removed
    from the building
  • KEEP FLUE GAS AS WARM AS POSSIBLE

55
Tools Equipment Used for Vent Inspection
Sizing
  • Tape measure
  • Flashlight
  • Mirror
  • Combustion Analyzer
  • Pressure Probe
  • Temperature Probe
  • Boroscope
  • Digital Cameral
  • NFPA manual
  • 54, Natural Gas
  • 58, LP Gas
  • 31, Oil
  • 211, Solid Fuels

56
Safety Inspection of the Venting System
  • Inside visual inspection
  • General Safety Inspection
  • Vent connections
  • Internal flue inspection
  • Outside visual inspection
  • CAZ Test

57
Flue Safety
Combustible?
  • Clearance to combustibles
  • 6 single wall pipe, gas
  • 9 single wall pipe, oil
  • 1 B vent, gas
  • Single wall connectors must not pass through
    walls.
  • Spill switches
  • Flue blockage
  • Condition of flue materials
  • Draft under worst case conditions

1 Clearance?
Fire stop?
58
Vent Connections
Corrosion
Pitch
59
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60
Inspecting An Existing Application
  • Remove vent connector
  • Inspect with mirror light
  • Is the vent straight or is there an offset
  • Is there a liner present
  • Are tiles cracked allowing flue gas to escape
  • Blockage
  • Examine termination from outside
  • Cap
  • Condition of flue

61

An appliance that produces soot is a cause for
concern. Auditor should call for clean and
service.
62
Evidence of backdrafting
63
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64
Unsafe vent
65
Check the chimney for accumulated debris.
66
Oil-fired boiler before cleaning plugged with
soot after several years without service.
67
Same boiler after cleaning
68
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69
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70
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71
Termination Failure
72
B-vent exposed to the outdoors not properly
supported
  • Does not meet code (13.2.20)
  • Sizing tables 13.6 through 13.10 are not to be
    used for B vent exposed to the outdoors below
    the roofline.

73
Draft assisted furnace, or only water heater left
in flue?
Condensation bleed through
74
Condensation Damage
75
CAZ Test
  • Place building in winter mode
  • Place all combustion appliances in pilot mode, or
    turn off
  • Energize all exhaust fans
  • Measure pressure difference between CAZ in
    relation to outdoors
  • Open and close interior doors until the worst
    case draft condition is reached
  • Must have draft to continue
  • OD temp gt800F, gt-1 Pa or - .005WC
  • OD temp 300 800F, gt-2.5 Pa or -.01WC
  • OD temp below 300F, gt-5 Pa or -.02WC

76
Vent Dampers
  • Used to reduce off cycle losses
  • Motorized
  • End switch safety
  • Thermal

Spill Switch
77
Thermal Vent Damper
Bimetal petals warp open when heated
78
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79
Vent Terminations
  • Follow manufacturer instructions
  • Use NFPA guidelines if manufacturer instructions
    are not available

80
Category I Chimney termination
  • A chimney shall extend at least 3 ft. above the
    highest point where it passes through a roof of a
    building and at least 2 ft. higher than any
    portion of a building within a horizontal
    distance of 10 ft.

81
Sealed Combustion Category IV
82
Concentric Vent Category IV
83
Alternative Venting
84
Look for conditions that may affect health or
safety of the occupants, the weatherization crew,
and YOU. Dangerous vent, fire hazards, CO, fuel
leaks, etc. Complete a Health and Safety Warning
form if necessary.
85
Scary, home-made distribution system
86
REALLY scary homemade vent connector
87
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88
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89
Sizing Category I Vents
  • Use the appropriate NFPA manual
  • 54 for Natural gas
  • 58 for LP
  • for Oil
  • 211 for Solid fuels
  • Find the appropriate chart
  • One or more appliances?
  • B Vent or masonry?
  • B Connector or single wall?

90
Using NFPA Sizing Charts
  • Height of flue
  • From top of tallest appliance to the top of the
    flue termination
  • Increasing the height increases the draw
  • Horizontal distance to flue
  • Used with single appliance application
  • Increased horizontal run decreases draw
  • Vertical connector height
  • From the appliance breech to the point where flue
    gases combine
  • Used with multiple appliances
  • Elbows Charts are listed with up to (2) 900
    elbows in the vent

91
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92
Problem 1
  • Single draft assisted appliance
  • 50,000 BTU input rate
  • Total chimney height 17
  • Lateral distance 3
  • B vent and connector

93
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94
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95
Problem 2
  • 2 category I appliances
  • 50,000 BTU fan assisted furnace
  • Connector rise 2
  • 30,000 BTU water heater
  • Connector rise 3
  • B vent with B connectors
  • Chimney height 18

96
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97
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98
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99
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100
Flexible Flue Liner
  • Follow manufacturer sizing tables
  • Use NFPA sizing tables, but reduce capacity by
    20
  • The masonry or original flue is used as a chase
    for the liner
  • If a liner is installed, the remaining space
    around the liner can not be used to vent other
    appliances.
  • More than one liner may be installed in the
    masonry chase

101
Other Liner Materials
  • B vent may be used as a liner
  • Drop down an inadequate or improperly sized flue
  • Original flue must be straight.
  • SS flexible liner

102
Review
  • The height of a chimney is identified as
  • If the chimney height falls between two columns
    in the NFPA chart, do you round up or down?
  • For a single category I appliance installation,
    if the lateral distance falls between two value
    on the chart, do you round up or down?
  • Can you use NFPA charts to size a flexible
    chimney liner?
  • What is one advantage of using a flexible liner
    over B vent?

103
Vent Free Heaters
  • NYS WAP Policy
  • Operational Requirements
  • Oxygen Depletion Sensor

104
NYS WAP Policy
  • WAP funds cannot be used to purchase or install
    any type of unvented or ventless combustion
    appliance including but not limited to unvented
    kerosene space heaters, unvented natural gas
    space heaters, unvented propane space heaters,
    unvented gas fireplaces, and unvented gas
    fireplace logs.

105
IAQ / Health Safety Tests
  • Unvented Space Heaters Educate the client about
    the potential danger of CO and fire from unvented
    space heaters. Explain that significant amounts
    of combustion products including water vapor and
    CO2 are produced.

106
Combustion Air
  • Must supply combustion air while operating
  • Open window while operating
  • Tucson instructions require defining the space as
    confined / unconfined
  • Products of combustion remain in the conditioned
    space
  • Must provide some measure of safety for oxygen
    depletion

107
Fresh Air Requirements Tucson Heater
108
Oxygen Depletion Sensor
109
If You Take Away Nothing Else
  • KEEP THE WATER IN A GASEOUS STATE WHILE IN THE
    FLUE
  • Use Bvent connectors on any new category I gas
    appliance installation
  • Most masonry chimneys will need a liner
  • Never leave a water heater in a flue alone
    without ensuring it will vent
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