BOILERS AND EFFICIENCY
Gary Archer
Vice President of Sales
JW Stevens Co.
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BOILERS AND EFFICIENCY
TYPES OF BOILERS – STEAM
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Water tube, Fire tube, Cast Iron
Fuels – gas, oil, combination
Typical Efficiencies – 78-84%
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HOW DO YOU INCREASE EFFICIENCY
ON STEAM BOILERS?
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Burner/controls upgrades as discussed
earlier
ECONOMIZERS!!!!
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ECONOMIZERS
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ECONOMIZERS
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Take flue gases from the boiler to pre-heat water
that can be used for potable use if you have a large
need for domestic hot water. (i.e. Hospital, Food
Processing )
OR
Use the hot water (260 degrees) to be used as
boiler feed water. (Typical feed water temperatures
are 160-225)
Increases boiler efficiency by 3% or more and
usually have less than an 18 months payback
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BOILERS AND EFFICIENCY
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TYPES OF BOILERS - HOTWATER
Water tube, Fire tube, Cast Iron
Fuels – gas, oil, combination
Typical Efficiencies – 78-84%
MODULAR BOILERS!!!!
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MODULAR BOILERS
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MODULAR BOILERS
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Gas Only – Natural or Propane
Small Footprint
Low mass/light weight design
Non-Condensing and Condensing
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What is a Non Condensing -vs- a Condensing Boiler?
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Non – Condensing Boilers
These style boilers run in the 85-86% efficiency range regardless of
return water temperatures.
Vessel design must allow for continuous operation @ >130 F return
water temperature.
Heat transfer (fireside) surfaces do not consist of materials
resistant to acidic condensate and corrosive elements. They are
typically made of copper
Less expensive than condensing boilers
Typical Applications are Standard building heat and/or indirect DHW.
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Condensing Boilers
To achieve maximum efficiency a hydronic boiler must fully condense.
 This means the return water temperature back to the boiler must be
below 130F. This allows for the flue gas temperature to drop below its
dew point. This causes the water vapor in the flue gases to condense
or change phase from a gas to liquid therefore giving off more energy
Vessel design must be such that the flue gases are cooled down as
low as possible.
Heat transfer surfaces [fireside] must consist of materials resistant to
acidic condensate and corrosive elements, typically stainless steel.
Condensing boiler efficiencies can run as high as 99%.
Typical Applications are radiant floor heating, snow melt, heat pump,
hybrid heating systems
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Condensing
Boiler Efficiency
%
99
98
Relative
Boiler Load
96
94
Non condensing
92
20%
50%
75%
100%
90
88
86
84
68
20
80
100
120
63
4
2
Return
0 flow temperature °F
140
160
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Modular Boilers – Hybrid System
What Is a Hybrid System???
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Hydronic Boilers – Hybrid System
Hybrid Systems Utilize Both Non-Condensing And Fully Condensing
Boilers.
The Condensing Boilers Run In The Warmer Or “Shoulder” Months
(i.e. October, November, March, April) while the Non Condensing
Boilers Run In The Coldest Of Months.
Building management systems can control the enabling or disabling
of the two different type of boilers or most boiler manufacturer’s have
their own stand alone controls that can achieve the same results.
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Condensing
Boiler Efficiency
%
99
98
Relative
Boiler Load
96
94
Non condensing
92
20%
50%
75%
100%
90
88
86
84
68
20
80
100
120
63
4
2
Return
0 flow temperature °F
140
160
58
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Hydronic Boilers – Hybrid System
In conclusion about Hybrid systems,
Use the boilers that condense and get up to 99%
efficient when the outside air temperature is milder and
supply water temperature to the fin-tube radiation in the
occupied space can be lower
Use the non-condensing boilers in the coldest months
when you need high temperature water to keep the
occupied spaces warm. This will achieve maximum
seasonal efficiency.
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JW Stevens Co
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Stop by our booth to see a case study on a
DVD loop to see an example of a hybrid
system we did last year with Oswego CSD.
They will earn well over $100,000.00 in
National Grid Incentive Dollars
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