Are Boiler Stacks Exhausting? - Cleaver

Are Boiler Stacks Exhausting?
Common Problems and Causes of Improperly
Designed Stack and Breeching Assemblies
Presented by Steve Connor
April 24, 2013
Common
Problems With
Improperly
Designed
Boiler Exhaust
Systems
The Most Common Problems
• Efficiency loss
• Boiler damage
• Increased boiler
maintenance
• Damaged breeching &
stacks
• Production downtime
• Increased operating costs
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The Most Common Problems
• Efficiency loss
• Boiler damage
• Increased boiler
maintenance
• Damaged breeching &
stacks
• Production downtime
• Increased operating costs
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Efficiency Loss, Boiler Damage, Increased Maintenance
Remember, the boiler consumes
4 times its original cost in fuel
EVERY year!
Efficiency Loss, Boiler Damage, Increased Maintenance
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Boiler Damage
Repair
Vent outlet
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Vent Outlet
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The Most Common Problems
• Efficiency loss
• Boiler damage
• Increased boiler
maintenance
• Damaged breeching &
stacks
• Production downtime
• Increased operating costs
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Damaged Breeching & Stacks
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Increased Maintenance & Downtown
Pilot Failure
Poor Combustion
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Increased Operating Cost
Causes of the Major Problems
• Poor design
• Undersized for the
duty
• Boilers added
• Too much
resistance
• Environmental
variances
• External conditions
• Wrong material
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Poor Design; Boiler Room Air
Two (2) openings, either side of room;
Below 7 feet
Required conditions
• No obstruction over openings besides screen
or louvers
• No exhaust fan
• Minimum opening is 1 square foot of area
• Formula: Area (sq. ft.) = CFM/FPM
Rule of thumb Calculation
•
•
•
•
•
•
•
Comb. Air - Max. BHP x 8 CFM/BHP
Vent. Air - Max. BHP x 2 CFM/BHP
Total = 10 CFM/Max BHP
Divided by Velocity:
(7) foot high ceiling – 250 FPM
> (7) feet – 500 FPM
Ducted air to boiler – 1000 FPM
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Poor Breeching Design
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Poor design
Boiler added
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Causes of the Major Problems
• Poor design
• Undersized for the
duty
• Boilers added
• Too much
resistance
• Environmental
variances
• External conditions
• Wrong material
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Environmental Variances & External Conditions
Caps?
Down Drafts?
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Causes of the Major Problems
• Poor design
• Undersized for the
duty
• Boilers added
• Too much
resistance
• Environmental
variances
• External conditions
• Wrong material
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Boiler Categorization
Category I
A boiler which operates with a non-positive
vent static pressure and with a vent gas
temperature that avoids excessive
condensate production in the vent.
(B-Vent, Type A)
Category II
A boiler which operates with a non-positive
vent static pressure and with a vent gas
temperature that may cause excessive
condensate production in the vent.
(Type BH)
Category III
A boiler which operates with a positive vent
pressure and with a vent gas temperature
that avoids excessive condensate
production in the vent.
(Type BH)
Category IV
A boiler which operates with a positive vent
pressure and with a vent gas temperature
that may cause excessive condensate
production in the vent.
(Type BH)
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Today’s Main Focus
Category III
A boiler which operates with a positive vent
pressure and with a vent gas temperature
that avoids excessive condensate
production in the vent.
(Type BH)
Category IV
A boiler which operates with a positive vent
pressure and with a vent gas temperature
that may cause excessive condensate
production in the vent.
(Type BH)
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Condensing, Near Condensing & Non-condensing
Category III
Category IV
Category IV
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UL Certification
UL 1738 (USA) / ULC S-636 (CAN)
•
Intended to be connected directly to the flue outlet of the Category
II, III and IV gas burning appliances, as defined by the National Flue
Gas Code, ANSI Z223.1/NFPA 54 with maximum continuous flue
gas temperature not exceeding 550ºF with a maximum rated
positive pressure of 15 inches W.C.
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UL Certification
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Materials Of Construction
Installation-Ready Exhaust Systems
Structural
• Stainless steel (301/304 / 316 / 316L
• Aluminized steel (Type 430)
Insulation 1” or 2”
• Air
• Mineral fiber (wool)
• Ceramic fiber
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Considering the Design Variables
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The Variables
Draft
calculation
based on
criteria
such as:
Local codes
Flue gas velocity
Type of fuel
Seasons
(summer vs. winter)
Flue gas temperature
Seismic & Wind loads
Appliance category
Stack and breeching
diameter, height, length
Altitude
Flow restriction: tees, elbows,
wyes, dampers, reducers
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Induced Draft Fan
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Chimney Liner
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UL Certification
UL 1777 (USA) / ULC S-635 (CAN)
Chimney Liners
•
Intended to be installed in masonry chimneys used to vent gas or oil
fuel fired residential type and building heating appliances where the
maximum continuous flue gas temperature produced does not
exceed 570ºF
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Scenarios of Two
Typical Problems
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Scenario One:
New Construction
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Scenario Two
Boiler Replacement
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Summary
• Exhaust systems are an integral part of the entire
boiler system, seriously influencing its proper
operation.
• Improper exhausting can increase fuel, maintenance
and downtime costs. These are significant
contributors to total operating costs within the
facility.
• Important that the proper amount of ventilation air is
present to support and sustain combustion.
• One must understand the variables before laying out
a stack and breeching system.
• Proper material selection based on the Category
representing interior pressure and condensing/noncondensing conditions is critical.
• Stack and breeching designs vary, and one must be
aware of those systems which not only provide the
solution for the conditions, but installation savings
as well.
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Contacts for additional Information:
Chuck Zinda
Product Manager
czinda@cleaverbrooks.com
(414) 577-2734
cleaverbrooks.com/exhaustsolutions
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