Variable Speed Pumping in Condensing Boiler Systems Get the Savings you paid for!

October 9, 2012

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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

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Overview

 Life Cycle Cost of Hot Water Systems  Demand Side System Opportunities  Transmission System Opportunities  Supply Side System Opportunities  Next Steps

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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

Traditional Boiler LCC Example

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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% purchase price of the initial equipment purchase goes to the * This is a theoretical example

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Hot Water Systems

   Demand  Space heating  Domestic water  Process Transmission (Piping, Pumps & Valves)   Pumps Piping  Coils Supply Side    Condensing boiler Combustion air fan Feed water pump  Controls

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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

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.

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.

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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 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 Page 12

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

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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)

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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

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100% 95% 90% 85% 80% 75% 60°F 80°F 100°F 120°F 140°F 160°F Entering Water/Air Temperature 180°F 200°F

Applying Condensing Boilers vs Furnaces

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100% 95% 90% 85% 80% 75% 60°F 110°F 160°F Entering Water/Air Temperature

Applying Condensing Boilers vs Furnaces

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100% 95% 90% 85% 80% 75% 60°F 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) 2) 3) Return Water Temperature!

Return Water Temperature!

Return Water Temperature!

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120°F 100°F 80°F 60°F 40°F 20°F 0°F -20°F Page 23 Page 23 180°F

Getting Heat Into a Space in a Building: “Typical” Central System

Gas, Coal or Oil 3,500 – 4,000  F Avg Boiler Water 170  F Boiler ~350 to 400  F 160°F 140°F Mixed or Cooled Air

Central System Designed for Condensing Boiler

Gas at 3,500  F Boiler 180°F 160°F 140°F 120°F 100°F 80°F 60°F 40°F 20°F 0°F -20°F Boiler Water 160  F Average Mixed or Cooled Air

+

Heated Air

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% 95% 90%

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85%

Typical Flow

80%

Low Flow

75% 80°F 100°F 120°F 140°F En terin g Water T emperatu re 160°F 180°F

 Avoid 3-way/4-way Valves on Main Line  Reduced Flow Brings Down Return Temperature  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 140°F 120°F 100°F 80°F Space 75  F 60°F 40°F 20°F 0°F -20°F Boiler Water 150  F Average Page 28

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Combined Outdoor Reset & VSD

Getting The “Rated” Efficiency Boost Out of Condensing Boilers (>90% Efficiency)

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% 95% 90% 85% 80% 75% 80°F 100°F 120°F 140°F Entering Water Temperature 160°F

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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!

  High Efficiency Boiler Information  Minimize return water temperature!

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

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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.

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Questions?

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Bonus Slides

 The following slides are bonus material that was cut from the final, live presentation due to time constraints.

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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

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Condensing Boiler Comparison to Direct Fired Heater

Direct-Fired Heater

Chart for Showing Moisture in Air Issues

 Moisture is Much More Diluted in Direct-Fired Heater  It Reaches a Lower Temperature, but Never Condenses (T HANKFULLY !) Direct Fired Heater Page 42