Variable Speed Pumping
in Condensing Boiler
Systems
Get the Savings you paid for!
October 9, 2012
Presenters
 Brian Hammarsten, CEM – Trade Relations
Manager at Xcel Energy
 Peter Vinck – Senior Energy Efficiency Engineer
at Xcel Energy
 Russ Landry PE, LEED® AP - Senior Mechanical
Engineer at the Center for Energy and
Environment
Page 2
Overview
 Life Cycle Cost of Hot Water Systems
 Demand Side System Opportunities
 Transmission System Opportunities
 Supply Side System Opportunities
 Next Steps
Page 3
Component Life Cycle Cost
 Condensing Boiler
 1 MMBTU boiler purchase = approx $20,000
 Lifetime cost for the gas to operate boiler = $112,800
 Of the total cost of ownership, only 17% goes to the
purchase price of that boiler
 Circulator Pump
 5 hp pump costs = approx $2,000
 Lifetime cost for the energy to operate pump = $26,750
 Of the total cost of ownership, only 7.5% goes to the
purchase price of the pump
Page 4
Traditional Boiler LCC Example
Page 5
System LCC
 System LCC* – Condensing Boiler, 2-way valve to heat
exchangers, vfd on pump
 Total Equipment = $53,000
 1 MMBTU condensing boiler purchase = $20,000
 Valves & Piping modifications = $8,000
 Pump and Drive package = $5,000
 Labor and misc materials = $20,000
 Total Energy Costs = $202,650
 Lifetime cost for gas= $112,800
 Lifetime cost for pump = $26,750
 Lifetime cost for fans = $63,100
 Of the total cost of ownership, only 15% to 30% goes to the
purchase price of the initial equipment purchase
* This is a theoretical example
Page 6
Hot Water Systems
 Demand
 Space heating
 Domestic water
 Process
 Transmission (Piping, Pumps
& Valves)
 Pumps
 Piping
 Coils
 Supply Side




Page 7
Condensing boiler
Combustion air fan
Feed water pump
Controls
Demand Side Opportunity
 Demand side opportunity investigation
 Temp set points? In your process do you really need 190
degree water or will 175 work?
 Outside air temperature supply water reset temperature
 Domestic Hot Water heating in off season
Page 8
Outside air temp. vs supply water temp
Temperature resets can be a great opportunity you might be missing during the higher outside air
temperatures. Giving you lower losses due to over heating as well as lower return water helping
a condensing boiler.
Page 9
Demand Side (cont.) – Domestic Hot Water heating in
off season
 Boilers are left in operation to support domestic hot
water heat during summer.
 Consider separating the systems in order to increase
efficiency of domestic hot water year round.
 This would save on equipment life, energy costs,
redundancy, etc.
Page 10
Transmission Opportunity
 Reducing Pumping Costs
 Reduced System Flow Benefits
Page 11
Reducing Pumping Costs
 If you have anything in this list, you may have
some opportunity to reduce cost.
 Throttle valve-control system
 Bypass (recirculation) line normally open
 Multiple parallel pump system with same number of




Page 12
pumps always operating
Constant Pump operation in a batch environment or
frequent cycle batch operation in a continuous process
Cavitations noise (at pump or elsewhere in the system)
High system maintenance
Systems that have undergone change in function
Reduced System Flow Benefits
 Reduced transmission (pump) energy
 Improved efficiency of condensing boiler
 Reduced maintenance cost
Page 13
Supply Side Opportunity
Applying Condensing Boilers
 Big Savings Potential
 Unique “green” investment opportunity when
replacing boiler or building new building
 >15% ROI for some projects
 But… Savings Depend Heavily on Operating
Conditions
 New construction optimal design very different
from typical boiler system
 Retrofit situations must be carefully evaluated
Page 14
Efficiency Levels of Gas-Fired Hot Water
Boilers
Page 15
How Condensing Boilers get that
Efficiency “Boost”
 Water Vapor Generated by Burning Natural Gas is
Condensed
 Water vapor is natural product of burning natural gas
 About 12% of flue gas is water vapor, but….
 Condensing Energy ≈ 2,000°F of Vapor Temperature Drop
 Condensation Only Occurs at Low Water Temperatures
 Flue gas dewpoint ~130°F
 Efficiency keeps improving as temperature drops
Page 16
Getting The “Rated” Efficiency Boost Out
of Condensing Boilers (>90% Efficiency)
Page 17
Chart for Showing Moisture in Air Issues
 Curve at Top Shows When “Air”
Can’t Hold Any More Moisture
(aka dewpoint or saturated)
 Once at the Top,
Cooling More
Condenses Moisture
Out of Air
Page 18
Applying Condensing Boilers vs Furnaces
100%
Efficiency
95%
90%
85%
80%
75%
60°F
Page 19
80°F
100°F
120°F
140°F
160°F
Entering Water/Air Temperature
180°F
200°F
Applying Condensing Boilers vs Furnaces
100%
Efficiency
95%
90%
85%
80%
75%
60°F
Page 20
110°F
160°F
Entering Water/Air Temperature
Applying Condensing Boilers vs Furnaces
100%
Efficiency
95%
90%
85%
80%
75%
60°F
Page 21
80°F
100°F
120°F
140°F
160°F
Entering Water/Air Temperature
180°F
200°F
Three Rules for “Energy Value” of
Condensing Boiler System
1) Return Water Temperature!
2) Return Water Temperature!
3) Return Water Temperature!
Page 22
Getting Heat Into a Space in a Building:
“Typical” Central System
Gas, Coal or Oil
3,500 – 4,000F
Boiler
180°F
~350 to
400F
Avg Boiler Water 170F
100°F
80°F
60°F
40°F
20°F
0°F
-20°F
Page 23
Page 23
Mixed or
Cooled Air
Mix
120°F
Radiators
140°F
Air Handler/VAV
160°F
Central System Designed for Condensing Boiler
Gas at 3,500F
Boiler
180°F
+
Boiler Water 160F Average
80°F
60°F
40°F
20°F
0°F
-20°F
Page 24
Mixed or
Cooled Air
Heated Air
Mix
100°F
Air Handler/VAV
120°F
Radiant
Floor
140°F
Radiators
160°F
Carrying Heat from One Place to Another
 Heat Carried by Water or Air
 Depends on temperature change (TD or T)
 Depends on water or air flow rate
Page 25
System Piping: Driving Return Water
Temperature Down
100%
Boiler Efficiency
95%
90%
85%
Typical Flow
80%
75%
80°F
Low Flow
100°F
120°F
140°F
160°F
180°F
En terin g Water T emperatu re
 Avoid 3-way/4-way Valves on Main Line
 Reduced Flow Brings Down Return Temperature
Page 26
 If Mixed Boilers – Cold Water & Max Load to Condensing
System & Load Affects on Condensing
Boiler Efficiency “Boost”
 Lower Flow (e.g. Pump VSD & 2-way Valves)
 Pump Energy Savings
 Low Return Water Temperature = Condensing Boiler
Efficiency Improvement
 If low delta, may be good opportunity in any system
 Outdoor Reset Control
 Reduces Load from Overheating & Pipe Heat Loss
 Lower Return Water Temperature = Condensing Boiler
Efficiency Improvement
 If high temperatures in mild weather, may be good
opportunity in any system
Page 27
Outdoor Reset Lowers Water Temperature
As the heating load goes down, less temperature difference is needed to drive the heat flow.
180°F
160°F
Boiler Water 150F Average
140°F
120°F
100°F
80°F
Space 75F
60°F
40°F
20°F
0°F
-20°F
Page 28
Combined Outdoor Reset & VSD
Page 29
Getting The “Rated” Efficiency Boost Out
of Condensing Boilers (>90% Efficiency)
Page 30
Service Hot Water: Driving Return Water
Temperature Down
 Traditional Coil-In Tank Requires High Boiler
Temperatures
 Efficiency > Traditional Water Heaters
 Efficiency Sacrificed with Condensing Equipment
>130°F
130°F
Boiler
Page 31
Key Design & Application Considerations:
Preventing Problems
 Product-Specific Issues
 Small water passages in old cast iron system
 Pressure drop compatibility with system
 Flow rate compatibility (short-cycling)
 Control coordination
 Dual temperature inlets
 General Load & System Issues
 Ability to provide adequate heat w/low return temperatures
 Ability to reduce flow rate w/out branch balance problems
 2-way valves on loads to replace 3-way valves
Page 32
Key Design & Application Considerations:
Preventing Problems (cont.)
 Venting Considerations
 Design & Installation Details to Deal with Condensate
 Sidewall Venting Can Cause Moisture Problems With
Large Boilers
 Orphaned Water Heater
 Vent Cost Key Factor @Bottom of Hi-Rise
Page 33
Key for Condensing Boiler Efficiency:
Driving Return Water Temperature Down
 Space Heating Elements
 System Piping
 System Control—Pump
 System Control—Temperature
 Service Hot Water
100%
Boiler Efficiency
95%
90%
85%
80%
75%
80°F
100°F
120°F
140°F
Entering Water Temperature
Page 34
160°F
180°F
In Conclusion....
 Condensing Boilers Can Be a Great, Green Investment
 Success Depends on Different Approach by All
 Minimize return water temperature!
 Minimize return water temperature!
 Minimize return water temperature!
 High Efficiency Boiler Information
 Air-Conditioning, Heating, and Refrigeration
Institute (www.ahrinet.org)
 EnergyStar.gov
 California Energy Commission web site
 Consortium for Energy Efficiency
www.cee1.org/gas/gs-blrs/gs-blrs-main.php3
www.cee1.org/gas/gs-blrs/Boiler_assess.pdf
Page 35
Utility “Key”
 Utilities offer rebates to customers to help pay for the
identification, energy savings quantification, and for the
changes once implemented.
 Check with your electric and gas utility to see what rebates the offer
 There are several here today
 Programs to look for:
 Study (investigation process) – Heating System Optimization, C/I Turn
Key, Audits
 Tune ups – Boiler Tune ups, Steam Trap Leak Study, Recommissioning
 Prescriptive Measures – O2, Stack Dampers, pipe insulation, new boilers,
VFDs, Motors
 Custom – Insulation of valves, rebates for industrial process heating
systems, most demand side measures, piping modifications, adjust temp
set points.
Page 36
Questions?
Page 37
Bonus Slides
 The following slides are bonus material that was
cut from the final, live presentation due to time
constraints.
Page 38
Condensing Boiler Sensitivity to Excess Air
 Controlling Excess Air Even More Important
 Excess air reduces concentration of water vapor
 Dewpoint decreases
Page 39
Traditional Factor of Burner “Excess Air”
Is Even More Critical
Page 40
Condensing Boiler Comparison to DirectFired Heater
Direct-Fired Heater
Page 41
Chart for Showing Moisture in Air Issues
 Moisture is Much More Diluted
in Direct-Fired Heater
 It Reaches a Lower Temperature,
but Never Condenses
(THANKFULLY!)
Direct Fired Heater
Page 42