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Variable Speed Pumping in Condensing Boiler Systems Get the Savings you paid for! October 9, 2012.

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Presentation on theme: "Variable Speed Pumping in Condensing Boiler Systems Get the Savings you paid for! October 9, 2012."— Presentation transcript:

1 Variable Speed Pumping in Condensing Boiler Systems Get the Savings you paid for!
October 9, 2012

2 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

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

4 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

5 Traditional Boiler LCC Example
Page 5

6 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

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

8 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

9 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

10 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.

11 Transmission Opportunity
Reducing Pumping Costs Reduced System Flow Benefits

12 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

13 Reduced System Flow Benefits
Reduced transmission (pump) energy Improved efficiency of condensing boiler Reduced maintenance cost

14 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

15 Efficiency Levels of Gas-Fired Hot Water Boilers

16 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

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

18 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

19 Applying Condensing Boilers vs Furnaces

20 Applying Condensing Boilers vs Furnaces

21 Applying Condensing Boilers vs Furnaces

22 Three Rules for “Energy Value” of Condensing Boiler System
Return Water Temperature!

23 Getting Heat Into a Space in a Building: “Typical” Central System
Gas, Coal or Oil 3,500 – 4,000F Boiler ~350 to 400F Avg Boiler Water 170F Radiators Air Handler/VAV Mix Mixed or Cooled Air Page 23

24 Central System Designed for Condensing Boiler
Gas at 3,500F Boiler Boiler Water 160F Average + Air Handler/VAV Radiators Radiant Floor Heated Air Mix Mixed or Cooled Air Page 24

25 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

26 System Piping: Driving Return Water Temperature Down
Typical Flow Low Flow Avoid 3-way/4-way Valves on Main Line Reduced Flow Brings Down Return Temperature If Mixed Boilers – Cold Water & Max Load to Condensing

27 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

28 Outdoor Reset Lowers Water Temperature
As the heating load goes down, less temperature difference is needed to drive the heat flow. Boiler Water 150F Average Space 75F

29 Combined Outdoor Reset & VSD

30 Getting The “Rated” Efficiency Boost Out of Condensing Boilers (>90% Efficiency)
Page 30

31 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 Boiler >130°F

32 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

33 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 of Hi-Rise

34 Key for Condensing Boiler Efficiency: Driving Return Water Temperature Down
Space Heating Elements System Piping System Control—Pump System Control—Temperature Service Hot Water

35 In Conclusion.... Condensing Boilers Can Be a Great, Green Investment
Success Depends on Different Approach by All 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

36 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.

37 Questions?

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

39 Condensing Boiler Sensitivity to Excess Air
Controlling Excess Air Even More Important Excess air reduces concentration of water vapor Dewpoint decreases

40 Traditional Factor of Burner “Excess Air” Is Even More Critical

41 Condensing Boiler Comparison to Direct- Fired Heater
Page 41

42 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


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