variable speed pumping in condensing boiler systems

Variable Speed Pumpingin Condensing BoilerSystems

Get the Savings you paid for!

October 9, 2012

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

Presenters

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

Overview

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

Component Life Cycle Cost

Traditional Boiler LCC Example

Page 5

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

System LCC

Demand Space heating Domestic water Process

Transmission (Piping, Pumps & Valves) Pumps Piping Coils

Supply Side Condensing boiler Combustion air fan Feed water pump Controls

Hot Water Systems

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

Demand Side Opportunity

Outside air temp. vs supply water tempTemperature 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

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.

Demand Side (cont.) – Domestic Hot Water heating in off season

Reducing Pumping Costs

Reduced System Flow Benefits

Transmission Opportunity

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

Reducing Pumping Costs

Reduced transmission (pump) energy

Improved efficiency of condensing boiler

Reduced maintenance cost

Reduced System Flow Benefits

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

Supply Side Opportunity Applying Condensing Boilers

Efficiency Levels of Gas-Fired Hot Water Boilers

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

How Condensing Boilers get that Efficiency “Boost”

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

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

75%

80%

85%

90%

95%

100%

60°F 80°F 100°F 120°F 140°F 160°F 180°F 200°F

Entering Water/Air Temperature

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Applying Condensing Boilers vs Furnaces


75%

80%

85%

90%

95%

100%

60°F 110°F 160°F

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75%

80%

85%

90%

95%

100%

60°F 80°F 100°F 120°F 140°F 160°F 180°F 200°F


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Three Rules for “Energy Value” of Condensing Boiler System

1) Return Water Temperature!2) Return Water Temperature!3) Return Water Temperature!

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

-20°F

0°F

20°F

40°F

60°F

80°F

100°F

120°F

140°F

160°F

180°F

Gas, Coal or Oil3,500 – 4,000F

Avg Boiler Water 170FBoiler

Radi

ator

s

Air H

andl

er/V

AV

Mixed or Cooled Air

Mi x

~350 to 400F

Page 23

Central System Designed for Condensing Boiler

-20°F

0°F

20°F

40°F

60°F

80°F

100°F

120°F

140°F

160°F

180°F

Gas at 3,500F

Boiler Water 160F Average

BoilerRa

diat

ors

Heated Air

Mixed or Cooled Air

M ix

Radi

ant

Fl

oor

+

Air

Han

dler

/VAV

Page 24

Heat Carried by Water or Air Depends on temperature change (TD or T) Depends on water or air flow rate

Carrying Heat from One Place to Another

75%

80%

85%

90%

95%

100%

80°F 100°F 120°F 140°F 160°F 180°F

Entering Water Temperature

Bo

ile

r E

ffic

ien

cy

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

Bo

ile

r E

ffici

en

cy

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

System & Load Affects on Condensing Boiler Efficiency “Boost”

Outdoor Reset Lowers Water Temperature

As the heating load goes down, less temperature difference is needed to drive the heat flow.

-20°F

0°F

20°F

40°F

60°F

80°F

100°F

120°F

140°F

160°F

180°F

Boiler Water 150F Average

Space 75F

Combined Outdoor Reset & VSD

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

Page 30

Traditional Coil-In Tank Requires High Boiler Temperatures Efficiency > Traditional Water Heaters Efficiency Sacrificed with Condensing Equipment

Service Hot Water: Driving Return Water Temperature Down

130°F

Boiler

>130°F

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

Key Design & Application Considerations: Preventing Problems

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

Key Design & Application Considerations: Preventing Problems (cont.)

Space Heating Elements System Piping System Control—Pump System Control—Temperature Service Hot Water

Key for Condensing Boiler Efficiency: Driving Return Water Temperature Down

75%

80%

85%

90%

95%

100%

80°F 100°F 120°F 140°F 160°F 180°F

Entering Water Temperature

Bo

iler

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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.php3www.cee1.org/gas/gs-blrs/Boiler_assess.pdf

In Conclusion....

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.

Utility “Key”

Questions?

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

Bonus Slides

Controlling Excess Air Even More Important Excess air reduces concentration of water vapor Dewpoint decreases

Condensing Boiler Sensitivity to Excess Air

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

Condensing Boiler Comparison to Direct-Fired Heater

Page 41

Direct-Fired Heater

Chart for Showing Moisture in Air Issues

Moisture is Much More Dilutedin Direct-Fired Heater

It Reaches a Lower Temperature, but Never Condenses(THANKFULLY!)

Direct Fired Heater

variable speed pumping in condensing boiler systems

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