Post on 08-Mar-2018
4/13/2010
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Ashrae Presentation April 2010Foil 1
CONDENSING BOILER TECHNOLOGY
Presented by:Ted SchmellingMulcahy CompanyManufactures rep of:Viessmann Manufacturing Co. (US) Inc.45 Access Rd.Warwick, RI
Ashrae Presentation April 2010Foil 2
What is condensing boiler TECHNOLOGYNon-condensing construction
Fin tube boiler Cast-iron sectional boiler
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Ashrae Presentation
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Natural gas CH4
Air
Oxygen
Nitrogen
Combustion
Nitrogen+
Nitrogen Oxides
Water vapor
Carbon Dioxide - CO2
�Light �Heat
NATURAL GAS COMBUSTION
Foil 3April 2010
Ashrae Presentation April 2010Foil 4
ENERGY CONTENT OF NATURAL GAS
SENSIBLE HEAT89.8%
Heat that can be measured or felt by a change in temperature
LATENT HEAT10.2%
Latent – Definition:Latin for “hidden”
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Ashrae Presentation April 2010Foil 5
Flue gas loss = 3 to 5 %
Boiler stand-by and jacket loss =3 to 5 %
Seasonal efficiency of conventional
Boilers=80%+
Fuel input = 100 %
Sensible heat =89.8%
Latent HeatHeat Loss = 10.2 %
Latent Heat10.2 %
CONVENTIONAL BOILER HEAT FLOW
Into mechanical room
Up chimneyUp chimney
Useful heat
Ashrae Presentation April 2010Foil 6
10% LATENT HEAT RECOVERY
WATER VAPOR LIQUID
Energy released
� Water vapor turns to liquid when it is reduced in temperature.
� Energy is released when vapor turns to liquid (Condenses)
132 F degrees
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Ashrae Presentation April 2010Foil 7
Boiler stand-byand jacket loss< 1%
Flue gas loss < 1 %Latent HeatHeat Loss < 2 %
Seasonal efficiency of conventional
boilers=82%+
Fuel input = 100 %
Sensible heat =89.8%
Latent Heat10.2 %
Seasonal efficiency
condensing
boilers= 96%+
CONDENSING BOILER HEAT FLOW
Ashrae Presentation April 2010Foil 8
Condensing boiler
Sensible heat
CondensationLatentheat
Total heatingvalue
Useableheat
Heatingsystem
MORE USABLE HEAT THROUGH CONDENSATION
What influences What influences the the raterateof of condensation?condensation?
100%
10.2%
Eff. From 85% to 98%
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Ashrae Presentation April 2010Foil 9
Heatingsystem
Emissions
FuelFuelBurnertype
Returnwater temp
Effective use of condensing
technology Pipinglayout
FACTORS INFLUENCING EFFECTIVENESS OF CONDENSING TECHNOLOGY
Combustionair
Ashrae Presentation April 2010Foil 10
Heatingsystem
Returnwater temp
Effective use of condensing
technology
FACTORS INFLUENCING EFFECTIVENESS OF CONDENSING TECHNOLOGY
Greatest Influence
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Ashrae Presentation April 2010Foil 11
Boiler return water temperature determines condensing operation
RETURN WATER TEMPERATURE
Less then 132F
Ashrae Presentation Nov 2005Foil 12
TYPICAL HYDRONIC WATER TEMPERATURE REQUIREMENTS:
High-temperature RFHunder wood sub-floor
Low temperature:è High mass radiant floor
ie: concrete floors 80 - 120 oFè Snowmelting systems 80 - 120 oF
High temperature:è Finned tube baseboard 140 - 190 oFè Air heat fancoils 140 - 180 oFè Pool/spa heat exchangers 160 - 180 oFè DHW production 150 - 190 oF
Medium temperature:è Cast iron radiators 100 - 140 oFè Low mass radiant floor
ie: wood joist floors 100 -150 oF
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Ashrae Presentation April 2010Foil 13
IMPACT OF SYSTEM TEMPERATURES ON CONDENSATIONExample 3: Supply/return temperature:
104/86oF
1559
1050
541
032
-523
-1014
-155
oCoF
Outside temperature
104oF
86oF
Dewpoint temperature (natural gas 132oF)
Condensation rangeCondensation range
20
30
40
50
Sys
tem
wa
ter
tem
per
atu
re
68
86
104
122
60
70
140
158
oCoF
2068
Radiant floor
Ashrae Presentation April 2010Foil 14
IMPACT OF SYSTEM TEMPERATURES ON CONDENSATIONExample 1: Supply/return temperature:
180/160oF
1559
1050
541
032
-523
-1014
-155
oCoF
Condensation rangeCondensation range
Dewpoint temp 132oF
180oF
160oF
25.5oF
20
Sys
tem
wa
ter
tem
per
atu
re
68
3086
40104
50122
60140
70158
oCoF
80176
90194
Outside temperature
2068
Fin tube
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Ashrae Presentation April 2010Foil 15
ASHRAE weather data for Boston, MA
CONDENSING / NON CONDENSING RATIOS
yste
m w
ate
r te
mp
era
ture
75% Condensing
25% Non-condensing
Condensation Condensation rangerange
72
86
104
122
140
158
176oF
+68 +54 +41 +28 +14 0 -13 oF
Supply180oF
Return160oF
Design temperature
Boston: +7oF
Dewpoint temp135
Ashrae weather data, hours of occurrence: Sept -May
1497 hr24.3%
627 hr10% 11 hrs
0.2%
124 hrs2%
1675 hr27%
2258 hr36.5%
Ashrae Presentation April 2010Foil 16
IMPACT OF SYSTEM TEMPERATURES ON CONDENSATIONExample 2: Supply/return temperature:
160/140oF
1559
1050
541
032
-523
-1014
-155
oCoF
160oF
140oFDewpoint temp 132oF
Condensation range
11.3oF
20
Sys
tem
wa
ter
tem
per
atu
re
68
3086
40104
50122
60140
70158
oCoF
80176
90194
Outside temperature
2068
�Hydro-Air�Radiators
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Ashrae Presentation April 2010Foil 17
ASHRAE weather data for Boston, MA
CONDENSING / NON CONDENSING RATIO
97% Condensing
3% Non-condensing
Condensation rangeCondensation range
72
86
104
122
140
158
176oF
+68 +54 +41 +28 +14 0 -13
Sys
tem
wa
ter
tem
per
atu
re
oF
Supply160oF
Return140oF
Design temperature
Boston: +7oF
1497 hr24.3%
627 hr10% 11 hrs
0.2%
124 hrs2%
Dewpoint temp135
2258 hr36.5%
1675 hr27%
Ashrae weather data, hours of occurrence: Sept -May
Ashrae Presentation April 2010Foil 18
SYSTEM WATER TEMPERATURE DROP
Typical system 20oF Temperature drop
180oF
160oF
What about a higher temperature drop?30oF……40oF?
150oF
Benefits to this?
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Ashrae Presentation
Low-Temp technology
Evolution of the heat exchanger
Low-Temp heating elementThese can work very effectively at low water temper atures, as low as 90 F
Ashrae Presentation April 2010Foil 20
Air flowAir flow
Air flowAir flow
180OF
160OF
140OF
120OF
Same BTU’s Same BTU’s delivereddelivered
TRUE SYSTEM EFFICIENCY System Components
Fan coil sizing
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Ashrae Presentation April 2010Foil 21
Effective use of condensing
technology
Pipinglayout
FACTORS INFLUENCING EFFECTIVENESS OF CONDENSING TECHNOLOGY
Ashrae Presentation April 2010Foil 22
USE OF MIXING VALVES WITH CONDENSING BOILERS
3-way mixing valve
No boiler return water temperature elevation
CORRECT
4-way mixing valve
Boiler return water temperature elevation
INCORRECT
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Ashrae Presentation April 2010Foil 23
INJECTION PUMPING WITH CONDENSING BOILERS
INCORRECT
Ashrae Presentation April 2010Foil 24
High temp system
Lowtempsystem
CONDENSING BOILERS IN HIGH FLOW SYSTEMS
Hydraulic system decoupling
How many have heard of this before?
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Ashrae Presentation
COMMERCIAL LOW LOSS HEADER
Main Return
Main Supply
RADIANT FLOOR HYDRO AIR
1
OUTDOORSENSOR
SNOW MELT
HEATEXCHANGER
EXPANSIONTANK
FLOOR MOUNTED LOW LOSS HEADER
DEKAMATIK-M1
EXPANSIONTANK
DEKAMATIK-M2
Custom Control
M
Benefits of LLH:�Hydraulic separation�Protects boiler from debris�Air removal�Optimum boiler operation
For use with all commercial boilers
Foil 25April 2010
Ashrae Presentation
Low loss header
Principle of operation:T1 – Boiler supply temperature
T2 – Boiler return temperature
T3 – System supply temperature
T4 – System return temperature
Vprimary – Boiler circuit flow rate
Vsecondary – Heating circuit flow rate
Qprimary – Heat supplied by boiler
Qsecondary – Heat consumed by system
Vprimary < Vsecondary
T1 > T3T2 = T4Qprimary = Qsecondary
Vprimary Vsecondary
T1
T2
T3
T4
What is going to happen here?Temp Sensor needed
: ..: : .::::
. :.::.
.:
Debris can fall out
Air Bleed
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Ashrae Presentation
• Vp < Vs
• T1 > T3
• T2 =T4
T1 T3
T2 T4
Vp Vs
LOW LOSS HEADERSPrinciple of operation
Boiler supply 100 GPM
Boiler supply 100 GPM
System supply 125 GPM
System return 125 GPM
Bypass flow 25 GPM
Ashrae Presentation
COMMERCIAL LOW LOSS HEADERS
Maximum system flow rate
Model 400/200 – 250 gpmModel 400/400 – 528 gpm
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Ashrae Presentation
LOW LOSS HEADERFrom small to very big
Back to Piping
Foil 29April 2010
Ashrae Presentation April 2010Foil 30
COMBINATION OF BOILERS
LAG BOILER LEAD BOILER
System Return
System Supply
Condensing boilerNon-Condensing boiler
Boiler
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Ashrae Presentation April 2010Foil 31
MULTIPLE FUNCTION, MULTIPLE TEMPERATURE SYSTEM
3 way mixing valve
Boiler
System water fill
M M
M
Unique Germany piping and mixing system
Series ConnectionHot
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Ashrae Presentation April 2010Foil 32
FuelFuelBurnertype
Effective use of condensing
technology
FACTORS INFLUENCING EFFECTIVENESS OF CONDENSING TECHNOLOGY
Combustionair
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Ashrae Presentation
98%
EF
FIC
IEN
T
….can reach efficiencies of 98% - and more…..
MARKETING AND REALITY
Foil 33April 2010
Ashrae Presentation
…pending return watertemperature, can reach efficiencies of98% - and more.
April 2010Foil 34
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Ashrae Presentation
85% 85% 85%
April 2010Foil 35
Ashrae Presentation April 2010Foil 36
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Ashrae Presentation
EFFICIENCYWhat does it all mean??What does it all mean??
• Combustion Efficiency
• Cycle Efficiency or turn down
• AFUE (Seasonal Efficiency)
• Thermal Efficiency
• System Efficiency
• Manufactures claimed Efficiency
April 2010Foil 37
Ashrae PresentationFoil 38
Fuel Input
Air Input
Tair
CO2%Tflue gas
Boiler Boiler
Constant load
180oF
80oF
ANSI Z21.13 / CSA 4.9-2000
Heat exchanger
Condensate measured for condensing boilers test
∆T=100°F
COMBUSTION EFFICIENCYTesting for non-condensing gas commercial boilers
April 2010
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Ashrae Presentation
CYCLE EFFICIENCY
Cycle Efficiency = Total useful heat output (Btu/h) of boiler over a period of time
Energy content of fuel (Btu/h) over same time perio d
Cyc
le E
ffici
ency
%
Run Fraction %
90
35
80
25
65
15
55
45
0
5
One Cycle
Steady State Steady State Efficiency = 90%Efficiency = 90%
0 1009040 8030 7020 605010
Time required to reach Steady State depends on appliance
April 2010Foil 39
Ashrae Presentation
AFUE EFFICIENCYAnnual Fuel Utilization Efficiency
Seasonal efficiency test for boilers up to 300,000 Btu/h
HeatHeatExchangerExchanger
Hot Water out
Cold Water in
Constant Load140 F
120 F
Vent Damper
Boiler Boiler
Fuel Input
Heated SpaceHeated Space
One cool down cycle evaluated
JacketLosses
Measured in test:CO2, O2%, Tgas , Troom
April 2010Foil 40
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Ashrae Presentation
BoilerBoilerHeat Heat
ExchangerExchanger
Thermal efficiency:Thermal efficiency:The ratio of the amount heat absorbed by the water to The ratio of the amount heat absorbed by the water to the higher heating value (HHV) in the fuel burnedthe higher heating value (HHV) in the fuel burned
Hot water outHot water out
Cool water inCool water in
Total fuel burnedTotal fuel burned
Thermal efficiency is sometimes confused with combustion efficiency
THERMAL EFFICIENCY TESTING
April 2010Foil 41
Ashrae Presentation
Condensate measured for condensing boilers test
Heat Exchanger
Constant Load
∆T=100°FBTS-2000
180oF
80oF
COMBUSTION EFFICIENCY TESTINGFor condensing gas commercial boilers >300 MBH
Boiler
Air Input
Fuel Input
………………
April 2010Foil 42
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Ashrae Presentation
CONDENSING BOILER EFFICIENCY
Measured rate of condensate (Boiler only!)
Heat gain from condensate = 8783 Btu / usg of conde nsate2320 Btu / ltr of condensate
[ Boiler input btu/hr (metered gas flow) x
Combustion eff. (measured) + Heat gain from
condensate (btu/hr)
Formula:
]Efficiency of condensing boiler (%) =
Boiler input btu/hr
BoilerCombustion efficiency from flue gas analysis
TOTAL HEAT OUTPUT OF CONDENSING BOILER
SENSIBLE HEAT CAPTURED
LATENT HEAT CAPTURED= +
………
April 2010Foil 43
Ashrae Presentation
Boiler efficiency (%)
=1,008,000 btu/hr
[ 1,008,000 btu/hr x 0.89 ] + [ 4.68 usg x 8783 btu/hr/gal ]
897,120 btu/hr + 41,104 btu/hr
1,008,000 btu/hr = = 93.1%
Boiler
Flue gas analysis:� Comb. Eff.=89%� Flue gas temp. = 118 oF
Condensate rate:� 4.68 gal/hr (60 g/KWh)
� CT3-89� Low fire rate:
1,008 MBH / 295 KWh
� Return water temp. – 113 oF
� Altitude – 2091’
CONDENSING BOILER EFFICIENCYSample project: Community College, Alberta
………
April 2010Foil 44
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Ashrae Presentation
HIGH EFFICIENCY BOILERSUnder what conditions??Under what conditions??
• Burner Efficiency (C02%) or excess air
– Sealed combustion?
– Turn down ratio?
• System water temperatures (return water)
• Boiler Controls
• Boiler Construction and Materials
April 2010Foil 45
Ashrae Presentation April 2010Foil 46
Higher CO2
=Higher Dew point=More Condensation
Dew
po
int w
ater
vap
or
77
86
95
104
113
122
131
140
oF oC
25
30
35
40
45
50
55
60
CO2 in Vol %2 3 4 5 6 7 8 9 10 11 12
Natural Gas (95% CH4)
CO2% of flue gas influences dew point temperature
WATER VAPOR DEW POINT
Lower CO2
=Lower Dew point=Less Condensation
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Ashrae Presentation April 2010Foil 47
DEW POINT AND ALTITUDE
120
122
124
126
128130
132
134
136
138140
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
Altitude – Feet above sea level
Dew
Po
int T
emp
erat
ure
Dew Point of Natural Gas Based on 1000 btu/ft3, 50% RH and 60oF Room Air
Fo Co
60
50
52.2
54.4
56.6
58.8
53.3
55.5
57.7
51.1
Ashrae Presentation April 2010Foil 48
CONDENSING BOILER TECHNOLOGY
What influences the CO 2% ?
THE BURNER!
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Ashrae Presentation
PERFECT (STOICHIOMETRIC) COMBUSTION
Each fuel has an Maximum CO 2 % ifStoichiometric Combustion is achieved:
�Natural gas : 11.9% CO2
�Propane gas : 13.7% CO2
When theoretical perfect air/fuel mixtures are applied, Stoichiometric Combustion is achieved.
Eg: 10 parts air to 1 part Natural gas,25 parts air to 1 part Propane.
April 2010Foil 49
Ashrae Presentation April 2010Foil 50
THEORETICAL PERFECT NATURAL GAS COMBUSTION OR STOICHIOMETRIC
1 part gas
9.7 parts air by volume
Excess air0%
The CO2 = 11.9%The CO = 0 ppm
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Ashrae Presentation
SAFE AND EFFICIENT COMBUSTION
Acceptable range of CO 2%:
�Natural gas: 9.1 – 10 % CO 2
�Propane gas: 10.7 – 11.1% CO 2
Acceptable values for safe and efficient combustion:
Excess Air: 17 - 30%Oxygen: 3 – 5%
April 2010Foil 51
Ashrae Presentation April 2010Foil 52
REAL WORLD NATURAL GAS COMBUSTION WITH GOOD BURNER TECHNOLOGY
1 part gas
9.7 parts air
Excess air20 to 25%
What can cause the amount of excess air to change after start-up?
The CO2 = 9.5 to 10%The CO = 0 to 20 ppm
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Ashrae Presentation
COMBUSTION ANALYSIS RESULTS
Boilers with good burner technology should be able to get very low CO!
New power fired boilers
April 2010Foil 53
Ashrae Presentation April 2010Foil 54
NATURAL GAS COMBUSTION
Power-fired burner technology
GasAir
25% Excess Air 9.5% CO2
4% O2
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Ashrae Presentation April 2010Foil 55
� Combustion with minimal excess air
�CO2: 9.5 to 10%
�Excess air: 20 – 25%
� Fully modulating input
� Precise calibration thru entire firing range (Linkage-less control)
� O2 trim
� Low NOx and CO emissions
BURNER REQUIREMENTS FOR CONDENSING BOILERS
Ashrae Presentation
Combustion air temperatures
Air temperature correction chart from an Analyzer Company
INLET AIR TEMPERATURECO2%
April 2010Foil 56
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Ashrae Presentation
0
87
84
85
86
90
89
88
92
91
93
100
95
94
96
98
97
99
100604030 50 8070 90
Partial Load in %
Boi
ler e
ffici
ency
in %
SUPPLY / RETURN at 100% Load (Design Conditions):
104oF/86oF40oC/30oC
140oF/120oF60oC/49oC
167oF/140oF75oC/60oC
194oF/158oF90oC/70oC
BOILER EFFICIENCY
April 2010Foil 57
Ashrae Presentation April 2010Foil 58
CONDENSING BOILER TECHNOLOGY
Construction requirements of condensing boiler technology
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Ashrae Presentation April 2010Foil 59
PHYSICAL REQUIREMENTS OF THE HEAT EXCHANGER SURFACES
Best material for condensing boilers: � Single wall� Highly conductive� Smooth surface
BoilerWater122oF
Heat Flow
158oF
194oF
131oF
122oF
Condensateformation
Dew PointNatural gas
Flue Gas
Ashrae Presentation
PYSICAL REQUIREMENTS OF THE FLUE GASAND CONDENSATE PASSAGE WAYS
Boi
ler W
ater
Boi
ler W
ater
Flue gas
Con
dens
ate
Con
dens
ate
Flue gas
Flue gas and condensate must flow in the same direction (parallel flow)
CORRECT INCORRECT April 2010Foil 60
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Ashrae Presentation April 2010Foil 61
Condensing boiler requirements:
� Counterflow principle for flue gas and boiler water – optimal heat transfer
� Parallel flow direction for flue gas and condensate – uniform flow with self-cleaning effect of heat transfer surfaces
Condensing boiler
Hot Flue gas
Flue gas
HR
HR
HS
Normalheating boiler
HS
HR
CONDENSING BOILER CONSTRUCTION
Ashrae Presentation April 2010Foil 62
Why is material construction of the boiler heat exchanger so important?
HEAT EXCHANGER CONSTRUCTION
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Ashrae Presentation April 2010Foil 63
Oil Gas
Flue gas condensate
Typical householdsewage
pH-ValueBasicAcidic
0 1 2 3 4 5 6 7 8 9 10 11 12
0 1 2 3 4 5 6 7 8 9 10 11 12
AmmoniaLakewater
Tapwater
Distilledwater
(neutral)
Clean rainwater
Rainwater
Vinegar
Lemonjuice
Battery acidGastric acid
pH VALUES OF VARIOUS FLUIDS
Ashrae Presentation April 2010Foil 64
� Highly corrosion resistant
� High strength with thin wall thickness
� Formable
� Long term reliability
MATERIAL REQUIREMENTS FOR CONDENSING BOILERS