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Venting and Combustion Systems
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VENTING AND VENTING AND
COMBUSTION AIRCOMBUSTION AIRRoberts Mechanical Equipment Co.Roberts Mechanical Equipment Co.
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ANSI CATEGORIESANSI CATEGORIES
II
III
IV
ANSI Categories ANSI Categories
will tell you a great will tell you a great
deal about the deal about the
boiler and the boiler and the
application.application.
I
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Understand the TableUnderstand the Table
Left side indicates a Left side indicates a
negative pressure.negative pressure.
Right Side indicates Right Side indicates
a positive pressure.a positive pressure.II
III
IV
I
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Understand the TableUnderstand the Table
Top indicates nonTop indicates non--
condensing condensing
appliance (85% or appliance (85% or
less).less).
Bottom indicates Bottom indicates
condensing condensing
appliances (86% or appliances (86% or
more).more).
II
III
IV
I
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Examples (negative)Examples (negative)
Atmospheric Atmospheric
Some fan assistedSome fan assisted
Masonry Chimney Masonry Chimney
BB--Vent materialVent materialII
III
IV
I
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Examples (Positive)Examples (Positive)
Forced Draft Forced Draft
Side wall ventedSide wall vented
In line fan In line fan
UL Pressure stack or UL Pressure stack or
welded steelwelded steel
II
III
IV
I
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Condensing / NonCondensing / Non--CondensingCondensing
Effect of Inlet Water Temperature to Boiler EfficiencyEffect of Inlet Water Temperature to Boiler Efficiency
natural gas = 1050 Btu/ftnatural gas = 1050 Btu/ft
inlet water temperatureinlet water temperature
boile
r efficien
cy, %
boile
r efficien
cy, %
1801804040 1301308080
100100
8686
9494
condensing boilercondensing boiler nonnon--condensing boilercondensing boiler
dew pointdew point
8080
II
III
IV
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Lining A Masonry Lining A Masonry
Chimney (Cat. I)Chimney (Cat. I)
Atmospheric Atmospheric –– Clay Clay
Tile Liner Tile Liner
Fan Assisted Fan Assisted –– Clay Clay
Tile Liner (Interior) Tile Liner (Interior)
Metal Liner (Exterior)Metal Liner (Exterior)
Exception: Clay tile liner can
be used with exterior chimney
if an Atmospheric appliance is
connected to the same chimney
II
III
IV
I
Reference: ANSI Z223.1-2002 10.4.1
and 13.1.9, NFPA211 4-2.2
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Lining A Masonry Lining A Masonry
Chimney (Category III)Chimney (Category III)
Forced Draft Forced Draft –– Welded Welded
Steel, Pressure Stack, Steel, Pressure Stack,
or Inner Liner of or Inner Liner of
Pressure Rated StackPressure Rated Stack
II
III
IV
I
Reference: ANSI Z223.1-2002 10.4.1
and 13.1.9, NFPA211 4-2.2
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Lining A Masonry Lining A Masonry
Chimney (Category II)Chimney (Category II)
Fan AssistedFan Assisted––
(85%+ Combustion (85%+ Combustion
Efficiency) AL29Efficiency) AL29--4C4CII
III
IV
I
Reference: ANSI Z223.1-2002 10.4.1
and 13.1.9, NFPA211 4-2.2
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Lining A Masonry Lining A Masonry
Chimney (Category IV)Chimney (Category IV)
Fully Condensing Fully Condensing ––
AL29AL29--4C4C
II
III
IV
I
Reference: ANSI Z223.1-2002 10.4.1
and 13.1.9, NFPA211 4-2.2
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Safe Venting by CodeSafe Venting by Code
• Horizontal distances
• Large stack area
• Self venting connector rise
• Fan Min capacities
• Different type of appliances
• Existing masonry chimneys
• Location of draft inducer
National Fuel Gas Code
NFPA54 * IAS (A.G.A.) * ANSI Z 223.1
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Common ViolationsCommon Violations
10.6.1.4 The total horizontal
distance of a vent plus the
horizontal vent connector
serving draft hood-equipped
appliances shall not be greater
than 75 % of the vertical height
of the vent.
Table 13.1 and 13.2 The total
horizontal length of the vent
plus the vent connector for a
single Category I appliance is:
100% of the height (vent 6 –
30 ft high); 30 ft (vent 31 – 50
ft high); 50% of the height
(vent 51 – 100 ft high)
(NFPA 54) Z223.1-2002
(Venting of Equipment)
Height
of
Vent
Not Greater than 75%
of the Vertical Height
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Common ViolationsCommon Violations
13.2.2 The maximum vent
connector horizontal length
shall be 18 in./in of
connector diameter.
13.2.4 The length of the
common vent manifold
shall not exceed 18 in./in.
of common vent diameter.
13.2.5 The horizontal
length of the common vent
offset shall not exceed 18
in./in. of common vent
diameter.
(NFPA 54) Z223.1-2002 13.2
(Sizing of Venting Systems)
Diameter
18 inches per inch
3" 4" 5" 6" 7" 8" 9" 10" 12" 14" 16" 18" 20" 22" 24"
4.5' 6' 7.5' 9' 10.5'12' 13.5'15' 18' 21' 24' 27' 30' 33' 36'
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Common ViolationsCommon Violations
(NFPA 54) Z223 Sizing Tables
1’ Min. (3”-10” diameter)
2’ Min. (12”- 18” diameter)
4’ Min. (20” and above)
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Common ViolationsCommon Violations
13.2.17 Where two or more
appliances are connected
to a vertical vent or
chimney, the flow area of
the largest section of
vertical or chimney shall
not exceed seven times the
smallest listed appliance
categorized vent areas,
flue collar area, or draft
hood outlet area unless
designed in accordance
with approved engineering
methods.
(NFPA 54) Z223.1-2002 13.2.17
(Sizing of Venting Systems)
Outlet Diameter
Not Greater than 7 Times
the Smallest Outlet Area
3" 4" 5" 6" 7" 8" 9" 10" 12" 14" 16"
7" 10" 12" 14" 18" 22" 22" 26" 30" 36" 42"
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Common ViolationsCommon Violations
10.10.4.2 Vent
connectors serving
Category I appliances
shall not be connected
into any portion of
mechanical draft
systems operating
under positive static
pressure, such as those
serving Category III or
Category IV appliances.
(NFPA 54) Z223.1-2002
10.10.4.2 (Venting of Equipment)
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Common ViolationsCommon Violations
10.5.4.3 Masonry
chimneys shall be built
and installed in
accordance with NFPA
211.
4-2.2 Masonry
chimneys shall be
lined….Cat II, III and IV
gas appliances - special
gas vents listed for
installation within
masonry chimneys.
(NFPA 54) Z223.1-2002 10.5.4.3
(NFPA 211) 4-2.2
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Common ViolationsCommon Violations
10.3.3 Forced draft systems
and all portions of induced draft
systems under positive pressure
during operation shall be
designed and installed so as to
prevent leakage of flue or vent
gases into a building.
10.3.4 Vent connectors serving
equipment vented by natural
draft shall not be connected into
any portion of mechanical draft
systems operating under
positive pressure.
(NFPA 54) Z223.1- 2002 10.3
(Mechanical Draft Systems)
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Resolving Codes using Resolving Codes using
Mechanical Draft SystemMechanical Draft System
503.6.9.3 Mechanical draft.
Chimney venting systems using
mechanical draft shall be sized
in accordance with approved
engineering methods.
10.5.3.1 Size of Chimneys.
Chimney venting systems using
mechanical draft shall be sized
in accordance with approved
engineering methods.
International Fuel Gas
Code - Section 503
(Venting of Equipment)
International Fuel Gas International Fuel Gas
CodeCode -- Section 503 Section 503
(Venting of Equipment)(Venting of Equipment)
Z223.1- 2002
Standard for Venting
of Equipment
Z223.1Z223.1-- 2002 2002
Standard for Venting Standard for Venting
of Equipmentof Equipment
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Mechanical Draft SystemMechanical Draft System
(Check List)(Check List)
�System should be UL listed (as
a designed system).
�System must Monitor proper
draft at all times.
�System must interlock, alarm
and lock out appliances.
�System must be supplied with
engineering (Acceptable
Engineering Method) specific to
installed appliances.
�System should modulate to
match today’s efficient
appliances.
�System performance should be
guaranteed.
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Vent Category ReviewVent Category Review
CategoryCategory CharacteristicCharacteristic TypeType DraftDraft VentVent
II
IIII
IIIIII
IVIV
Non-
Condensing
Negative
pressure
Natural draft
appliance and
fan assisted
< 86 % efficient
Draft hood:
Negative
Fan-assist: - 0.02
to - 0.08
B-Vent
Condensing
Negative pressure
Fan assisted
appliance
> 86 % efficient
Fan-assist:
- 0.02 to -
0.08
AL29-4C
Non-Condensing
Positive pressure
Forced draft /
Direct Vent
< 86 % efficient
Positive
Forced Draft
(Pressure
stack) Direct
Vent (AL29)
Condensing
Positive pressure
Fan assisted/
Pulse
Positive AL29-4C
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Combustion AirCombustion Air
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Combustion AirCombustion Air
CodeCode
8.3.3.2 One Permanent Opening Method: One permanent
opening, commencing within 12 in. of the top of the
enclosure, shall be provided. The opening shall
directly communicate with the outdoors or shall
communicate through a vertical or horizontal duct to
the outdoors or spaces that freely communicate with
the outdoors and shall have a minimum free area of
the following:
1 in.²/3000 Btu of the total input rating of all equipment
located in the enclosure, and not less than the sum
of the areas of all vent connectors in the space.
8.3.3.2 One Permanent Opening Method: One permanent 8.3.3.2 One Permanent Opening Method: One permanent
opening, commencing within 12 in. of the top of the opening, commencing within 12 in. of the top of the
enclosure, shall be provided. The opening shall enclosure, shall be provided. The opening shall
directly communicate with the outdoors or shall directly communicate with the outdoors or shall
communicate through a vertical or horizontal duct to communicate through a vertical or horizontal duct to
the outdoors or spaces that freely communicate with the outdoors or spaces that freely communicate with
the outdoors and shall have a minimum free area of the outdoors and shall have a minimum free area of
the following:the following:
1 in.1 in.²²/3000 Btu of the total input rating of all equipment /3000 Btu of the total input rating of all equipment
located in the enclosure, and not less than the sum located in the enclosure, and not less than the sum
of the areas of all vent connectors in the space.of the areas of all vent connectors in the space.
Z223.1Z223.1--2002 8.3.3 Outdoor Combustion Air2002 8.3.3 Outdoor Combustion Air.
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Sizing Combustion Air Sizing Combustion Air
Louvers (Gravity)Louvers (Gravity)
Louver(s) Sizing:
1 sq.in./4000 Btu per louver1 sq.in./4000 Btu per louver
4000 MBH = 1000 in24000 MBH = 1000 in2
of of freefree area per louver.area per louver.
Typical louver has 30-60%
free area.
Depending on louver design Depending on louver design
actual louver size will be:actual louver size will be:
Using 45% free area Using 45% free area
louverslouvers
= Two 5= Two 5’’ x 4x 4’’
louverslouvers
2000
MBH
2000
MBH
Tip: Check with the Louver Manufacturer for accurate Tip: Check with the Louver Manufacturer for accurate ‘‘free free
spacespace’’ than watch equal products in the submittals.than watch equal products in the submittals.
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Combustion Code Combustion Code
Summery.Summery.
NFPA 54
gas
NFPA 31
oil
BOCA
all
SBCCI
gas & oil
SBCCI
solid
Minimum No. openings required 2 2 2 2 2
Outdoor opening, sq. in./Btuh 1/4000 1/4000 1/4000 1/4000 2/1000
Vertical ducts, sq. in./Btuh 1/4000 1/4000 1/4000 1/4000 -
Horizontal ducts, sq. in./Btuh 1/2000 1/2000 1/2000 1/2000 -
Ducts same as opening yes yes - yes -
Minimum duct dimension, inches 3 3 3 3 3
Louver & grill free area opening opening - - opening
Free area allowance, wood* 20-25% 20-25% 25% - -
Free area allowance, metal* 60-75% 60-75% 75% - -
Damper interlocked yes yes yes - -
*use manufacturer's free area rating when available.
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Below Grade Mechanical Below Grade Mechanical
RoomsRooms
�Total fuel input rate of all
fuel-burning devices located
in the boiler room
considered.
�The Btu rate per hour of all
boilers at maximum burning
rate, plus other devices such
as water heaters, are used to
size air openings.
�Outside air openings sizing
must be done based on its
free area. (Protective mesh
must be no smaller than 0.25
inch to minimize dirt build-up
or obstruction.
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Direct Connect Direct Connect
Combustion AirCombustion Air
�Best with Fan
Assisted
Appliances.
�Roof or Single side.
�Careful combining
Combustion air
intakes.
�Watch Horizontal
lengths (fitting
equal 10’).
�FREEZE
PROTECTION
Tip:Tip: Freeze protection should be proven damper
system operating in the specific boiler sequence.
Allows combining inlet also prevent freezing
without power.
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Combustion AirCombustion Air
CodeCode
8.3.6 Mechanical Combustion Air Supply. Where all combustion
air is provided by a mechanical air supply system, the
combustion air shall be supplied from outdoors at the
minimum rate of 0.35 ft³/min per 1000 Btu/hr for all
appliances located within the space.
8.3.6.1 Where exhaust fans are installed, additional air shall be
provided to replace the exhausted air.
8.3.6.2 Each of the appliances served shall be interlocked to the
mechanical air supply system to prevent main burner
operation where the mechanical air supply system is not in
operation.
8.3.6 Mechanical Combustion Air Supply. Where all combustion 8.3.6 Mechanical Combustion Air Supply. Where all combustion
air is provided by a mechanical air supply system, the air is provided by a mechanical air supply system, the
combustion air shall be supplied from outdoors at the combustion air shall be supplied from outdoors at the
minimum rate of 0.35 ftminimum rate of 0.35 ft³³/min per 1000 Btu/hr for all /min per 1000 Btu/hr for all
appliances located within the space.appliances located within the space.
8.3.6.1 Where exhaust fans are installed, additional air shall b8.3.6.1 Where exhaust fans are installed, additional air shall be e
provided to replace the exhausted air.provided to replace the exhausted air.
8.3.6.2 Each of the appliances served shall be interlocked to th8.3.6.2 Each of the appliances served shall be interlocked to the e
mechanical air supply system to prevent main burner mechanical air supply system to prevent main burner
operation where the mechanical air supply system is not in operation where the mechanical air supply system is not in
operation.operation.
Z223.1Z223.1--20022002
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Mechanical Mechanical
Combustion AirCombustion Air
� Guaranteed to
provide proper
combustion air.
� Small opening /
more aesthetic.
� Solves Code
Issues
Tip:Tip: Multiple water heaters or boilers running
high efficiency firing rates warrant a modulating
combustion air system.
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Sizing Mechanical Sizing Mechanical
Combustion AirCombustion Air
Louver Sizing:
Engineered using ASHRAE
Chimney Design
Equation.
Flue Gas Volume corrected
for temperature = 1,400
cfm of combustion air
1400 cfm/500 fpm = 2.8 ft2 of
louver free area
Using a 45% free area louver
= One 3’ x 2’ louver
Tip:Tip: Be sure to consider any mechanical exhaust in the boiler.
Fan must keep up with all ventilation as well.
2000
MBH
2000
MBH
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The Barometric DamperThe Barometric Damper
NORMAL OPERATION
Barometric Damper is weighted
to open and ‘break’ draft by
mixing a % of room air.
The chimney is drawing at a
specific rate, but now draws
from the water heater/boiler
and room.
Typical draft for negative
commercial appliances is -.02
to -.08.
Tip:Tip: Use a barometric damper on stacks over 25’ or 30’ as
long as the appliance is category I or II (negative).
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The Barometric DamperThe Barometric Damper
NEGATIVE MECH ROOM:
� Room goes negative.
� Barometric is pulled into the
room.
� The barometric becomes a
source of make up air for
the room.
� Problem is, this make up air
is deadly.
Tip:Tip: Pay close attention to the combustion air in a room.
Look for sources of problems such as old leaky returns.
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Thank You!Thank You!
More Information / Additional Training:
Roberts Mechanical Equipment
P: 216-587-0005
F: 216-587-0008
Or visit our industry leading web site at:
www.robertsmech.com
More Information / Additional Training:More Information / Additional Training:
Roberts Mechanical EquipmentRoberts Mechanical Equipment
P: 216P: 216--587587--00050005
F: 216F: 216--587587--00080008
Or visit our industry leading web site at:Or visit our industry leading web site at:
www.robertsmech.comwww.robertsmech.comWritten by/Property of: Grant RobertsWritten by/Property of: Grant Roberts
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