3

- i CHAPTER 3. MARKET AND TECHNOLOGY ASSESSMENT

TABLE OF CONTENTS

3.1 INTRODUCTION

................................ ................................ ................................ ........... 3

- 1
3.1.1 Product Definitions and Scope of Coverage

................................ ................................ .... 3

- 1
3.1.2 Test Procedure

................................ ................................ ................................ ................. 3

- 3
3.2 MARKET ASSESSMENT

................................ ................................ .............................. 3

- 4
3.2.1 Trade Association

................................ ................................ ................................ ............ 3

- 4
3.2.2 Manufacturers and Marke t Share

................................ ................................ ..................... 3

- 4
3.2.3 Potential Small Business Impacts

................................ ................................ .................... 3

- 6
3.2.4 Distribution Channels

................................ ................................ ................................ ...... 3

- 6
3.2.5 Regulatory Programs

................................ ................................ ................................ ....... 3

- 7
3.2.6 Non

- Regulatory Progra ms

................................ ................................ ............................... 3

- 9
3.2.7 Product Lifetime

................................ ................................ ................................ ............ 3

- 10
3.2.8 Market Performance Data

................................ ................................ .............................. 3

- 11
3.2.9 Efficiency Data

................................ ................................ ................................ .............. 3

- 11
3.2.10 Shipments

................................ ................................ ................................ ....................... 3

- 13
3.3 BOILE R TECHNOLOGY ASSESSMENT

................................ ................................ .. 3

- 15
3.3.1 Boiler and Heat Exchanger Characterization

................................ ................................ . 3

- 15
3.3.2 Technology Options that may Improve AFUE

................................ .............................. 3

- 18
3.3.3 Technologies That Do Not Increase AFUE or Standby

................................ ................. 3

- 22
3.3.4 Technology Options that Improve Standby Mode and Off Mode Energy Efficiency

... 3

- 22

LIST OF TABLES

Table 3.2.1 Residential Boiler Manufacturers

................................ ................................ ............. 3

- 5 Table 3.2.2 Current Federal Energy Conservation Standards Established by EISA

................... 3

- 8 Table 3.2.3 Canadian Energy Conservation Standards for Residential Boilers

.......................... 3

- 8 Table 3.2.4 SEDBUK Efficiency Bands

................................ ................................ ...................... 3

- 9 Table 3.2.5 ENERGY STAR Requirements for Qualifying Residential Boilers

........................ 3

- 9 Table 3.2.6 CEE Efficiency Tiers for Residential Gas Boilers

................................ .................. 3

- 10 Table 3.2.7 Number of Boiler Models Listed in DOE’s Residential Boiler database by Product

Class

................................ ................................ ................................ ................................ ........... 3

- 11 Table 3.2.8 Historical shipments data of hot wa ter and steam boilers reported from a SAIC report

................................ ................................ ................................ ................................ .................... 3

- 14 Table 3.2.9 Appliance Magazine Shipments

................................ ................................ ............. 3

- 14

LIST OF FIGURES

Figure 3.2.1 Replacement Distribution Channel

................................ ................................ .......... 3

- 7 Figure 3.2.2 New Construction Distribution Channel

................................ ................................ . 3

- 7 Figure 3.2.3 AFUE Ratings for Residential Hot Water Boilers in the DOE Database

.............. 3

- 123

- ii Figure 3.2.4 AFUE ratings for residential steam boilers in the DOE Database

........................ 3

- 13 Figure 3.2.5 Market Share of Shipments by Product Class (2003

- 2007)

................................ .. 3

- 14 Figure 3.3.1 Gas

- Fired Hot Water Boilers Heat Exchanger Materials in the DOE Database

... 3

- 17 Figure 3.3.2 Oil

- fired Hot Water Boiler Heat Exchanger Materials in the DOE Database.

...... 3

- 183

- 1 CHAPTER 3. MARKET AND TECHNOLOGY ASSESSMENT

3.1 INTRODUCTION

This chapter provides a profile of the residential boiler industry in the United States. The U.S. Department of Energy (DOE) developed the initial market and technology assessment presented in this chapter primarily from publicly available information. This assessment is helpful in identifying the major manufacturers and characteristics of products on the market, which form the basis of the downstream analyses

.

This chapter consists of two sections: the market assessment and the technology assessment. The market assessment provides an overall picture of the market for the products concerned, including a scope of the products covered, product classes, industry structure, manufacturer market shares; regulatory and non

- regulatory efficiency improvement programs;
and m arket trends and quantities o f residential boilers sold. The technology assessment identifies

a n initial list of technology options for improving residential boiler efficiency to consider in the screening and engineering analys e s.

The information DOE gathers for the market and techn ology assessment serves as resource material for use throughout the rulemaking. DOE considers both quantitative and qualitative information from publicly available sources and interested parties.

3.1.1 Product Definitions and Scope of Coverage

Residential boil ers are heating devices that transfer heat from combustion gases to water
or from electric ity to water , which then provide heat to a home through a hot water or steam distribution system.

Residential boilers are defined in the Energy Policy and Conserv ation Act ( EPCA ) as a type of furnace. Specifically, the term “furnace” is defined as: “a product which utilizes only single

- phase electric current or direct current in conjunction with natural gas, propane, or home heating oil, and which

–

(A) is designed to be the principal heating source for the living space of a residence;

(B) is not contained within the same cabinet with a central air conditioner whose rated cooling capacity is above 65,000 Btu [British thermal units] per hour;

(C) is an electric central furn ace, electric boiler, forced

- air central furnace, gravity central furnace, or low pressure steam or hot water boiler; and

(D) has a heat input rate of less than 300,000 Btu per hour for electric boilers and low pressure steam or hot water boilers and les s than 225,000 Btu per hour for forced

- air central furnaces, gravity central furnaces, and electric central furnaces.”

(42 U.S.C. 6291(23))3

- 2 DOE has incorporated this definition into its regulations at 10 Code of Federal Regulations (CFR) 430.2. In addi tion, DOE has defined “electric boiler” and “low pressure
steam or hot water boiler” at 10 CFR 430.2 as follows:

Electric boiler means an electrically powered furnace designed to supply low pressure steam or hot water for space heating application. A low pressure steam boiler operates at or below 15 pounds per square inch gauge (psig) steam pressure; a hot water boiler operates at or below 160 psig water pressure and 250 °F water temperature.

Low pressure steam or hot water boiler means an electric, gas or oil burning furnace designed to supply low pressure steam or hot water for space heating application. A low pressure steam boiler operates at or below 15 pounds psig steam pressure; a hot water boiler operates at or below 160 psig water pressure and 25 0 °F water temperature.

Appendix N to Subpart B of 10 CFR Part 430 references the definitions section of the American Society of Heating, Refrigerating, and Air

- Conditioning Engineers (ASHRAE) 103

- 1993 (Method of Testing for Annual Fuel Utilization Effici ency of Residential Central Furnaces and Boilers)

, a which contains additional definitions of a boiler, many of which are similar to those listed above. Specifically, ASHRAE 103

- 1993 defines the following terms:

B oiler: a self

- contained fuel

- burning or electrically heated appliance for supplying low

pressure steam or hot water for space

- heating application.

Boiler, finned

- tube : a boiler whose heat exchanger consists of only finned

- tubes.

Boiler, low

- pressure steam or hot water : an electric, gas, or oil

- burning boiler designed to supply low

- pressure steam or hot water for space

- heating applications. A low

- pressure steam boiler operates at or below 15 psig steam pressure; a hot water boiler operates at or below 160 psig water pressure and 250°F water tem perature.

DOE has maintain ed the scope of coverage as defined by its current regulations for th e analysis of amended annual fuel utilization efficiency ( AFUE ) standards, which include s six product classes of boilers ( steam gas boilers

, hot water gas boi lers

, steam oil boilers

, hot water
oil boilers , steam electric boilers, and hot water electric boilers )

. DOE did not consider setting

new AFUE standards for electric boilers or separate standards for combination appliances for the reasons explained below.

Combination appliances are used to provide both space heating and domestic hot water to a residence. These products are currently available on the market in various configurations. Manufacturers currently certify combination appliances by rating the efficiency of the unit when performing their primary function . DOE did not evaluate these products in th is analysis because DOE’s existing test procedure s are not capable of rating the space and water heating

a American Society of Heating Refrigerating and Air

- Conditi oning Engineers, American National Standards Institute (ANSI )/ASHRAE 103

- 1993 : Method of Testing for Annual Fuel Utilization Efficiency of Residential
Central Furnaces and Boilers (1993)

.3

- 3 performance of combination appliances and DOE h a s not yet adopted a test procedure to determine the energy effic iency of combination appliances in more than one operational mode

.

DOE has not include d electric boilers in th is analysis of amended AFUE standards. Electric boilers currently do not have a n AFUE requirement under 10 CFR 430.32(e)(2)(ii). Electric boilers typically utilize electric resistance coils as their heating elements and t he efficiency of these products already approaches 100 percent AFUE . Therefore, there are no options for increas ing the rated AFUE of this product, and the impact of setting AFUE energy conservation standards for these products would b e negligibl e. There are technologies that c an potentially improve the efficiency of electric boilers ( e.g. , heat pump technology), bu t such technologies are not captured by the AFUE metric. EPCA designated AFUE as the energy efficiency descriptor for residential boilers. ( 42 U.S.C. 6291(20) ) The AFUE metric , as measured by the DOE test method, assigns a value of 100 percent for electric boilers, and would not capture the impact of any technologies to improve efficiency

. However, DOE does intend to consider standby mode and off mode standards for electric boilers as described in the paragraph immediately below

.

This rulemaking will anal yze energy conservation standards for energy cons umption of
boilers operating in standby mode and off mode. S ection 310(3) of EISA 2007 amended EPCA to require that energy conservation standards published after July 1, 2010, address standby mode
and off m ode energy use (42 U.S.C. 6295(gg) (3) ), if justified by the criteria for adoption of standards in section 325(o) of EPCA (42 U.S.C. 6295(o)). Many residential boilers do not operate continuously. The AFUE metric accounts for fossil fuel consumption in st andby mode
and off mode but does not take electricity consumption into account in these modes

. DOE adopted a test method for determining standby mode and off mode energy consumption of residential boilers in a final rule published on October of 2010

. 75 FR 64621

. Accordingly, this rulemaking will consider the electrical consumption of boilers in standby mode and off mode, as required by EPCA.

3.1.2 Test P rocedure

The energy conservation standards for residential boilers are represented in terms of the
AFUE a s measured by the DOE test procedure. (42 U.S.C. 6295(F)(3)). The DOE test procedure for determining the AFUE of residential boilers is located at Appendix N to Subpart B of 10
CFR Part 430 and references ASHRAE Standard 103

- 1993 (Method of Testing for Ann ual Fuel Utilization Efficiency of Residential Central Furnaces and Boilers). AFUE is an annualized fuel efficiency metric that fully accounts for fuel consumption in active, standby, and off modes.

To satisfy the requirements of EPCA as amended by EISA

, as noted above DOE update d its test procedure for furnaces and boilers to establish a method for measuring the electrical energy use in standby mode and off mode for residential boilers in a final rule published on October 20, 2010

. 75 FR 64621

. These te st proc edure amendments were primarily based o n and incorporate by reference p rovisions of the International Electrotechnical Commission (IEC)
Standard 62301 ( Second Edition), ‘‘Household electrical app liances

— Measurement of standby

power. ”3

- 4 O n January 2 013 , DOE published a request for information (RFI) which initiated a rulemaking to consider modify ing the residential furnace and boiler AFUE test method. 78 FR
675 . Key proposed issues addressed in the RFI included whether to change of reference from
AS HRAE 103

- 1993 to ASHRAE 103

- 2007, as well as room temperature and humidity adjustment calculations. EPCA, as amended by EISA 2007, requires that DOE must review test procedures for all covered products at least once every 7 years. (42 U.S.C 6293(b)(1)(A)) Accordingly, DOE must complete this test procedure rulemaking no later than December 19, 2014 ( i.e., 7 years after the enactment of EISA 2007), which is before the expected completion of this standards rulemaking. DOE must base the analysis of amended st andards on the most recent version of its test procedures, and accordingly, DOE will use the amended test procedure in future rulemaking stages when considering product efficiencies, energy use, and efficiency improvements in its analyses.

3.2 MARKET ASSESSM ENT

The following market assessment identifies manufacturer trade associations, domestic
and internation al manufacturers of residential boilers , and regulatory and non

- regulatory programs. The market assessment also describes the cost structure for the re sidential boiler industry and summarizes relevant market performance data.

3.2.1 Trade Association

The Air

- Conditioning, Heating, and Refrigeration Institute (AHRI) is a national tra de
association of manufacturers of residential, commercial and industrial appl iances and equipment

, including residential boilers . AHRI was established in January of 2008 when the Air

Conditioning and Refrigeration Institute (ARI) merged with the Gas appliance Manufacturers Association (GAMA). AHRI develops and publishes technical s tandards for residential and commercial air conditioning, heating, and refrigeration equipment using rating criteria and procedures for mea suring and certifying product performance. AHRI maintains the Directory of
Certified Product Performance that lists a ll products that have been certified for performance by

AHRI

. AHRI maintains a certified performance directory for residential boilers

. DOE used the
data in th e AHRI certification directory for residential boilers in its market assessment.

3.2.2 Manufacture r s and Market Share

DOE constructed a database of residential boilers based on its review of the AHRI directory of certified performance for residential boilers 1

, manufacturers’ websites and product catalogs , the ENERGY STAR listing of qualified residentia l boilers 2 , the California Energy Commission (CEC) appliance efficiency database 3 , and the DOE certification and compliance
management system 4 (CCMS) database to create a comprehensive database of residential boilers
available on the market. DOE examined t his database to identify residential boiler
manufacturers. DOE does not have empirical data on the market shares of particular
manufacturers of residential boilers. However, i n Table 3.2

. 1

, DOE divided manufacturers into “major” a nd “other” based on DOE research and discussions with manufacturers. “Major”3

- 5 manufacturers are estimated to have a market share of at least 15 percent, and the rest of the
manufacturers are considered as “other”.

Table 3.2

. 1 Residential Boiler Manufacturers

Company Parent Name (if applicable) Market

Lochinvar Corporation A.O. Smith Water Products Company Other

Crown Boiler Company Burnham Major
Burnham Commercial Burnham Hydronics (US Boiler Company, In c) New York Boiler Company,

Inc. Argo ECR International Major ECR International, LTD

- Olsen Division Oneida Royal
Dunkirk Boilers Pennco, Inc. Utica Boilers, Inc. Ultimate Engineering Hydrotherm Division of
Mestek Mestek Other

S mith Cast Iron Boilers Embassy Industries Inc
RBI Water Heater Division of Mestek, Inc. Raypak, Inc. Paloma Industries Other
Weil

- McLain SPX Corporation Major
Williamson

- Thermoflo
Bosch Bosch Other
Buderus

Viessmann Viessmann
Manufactu ring Company Other

LAARS Heating Systems Bradford White Other

Axeman

- Anderson Axeman

- Anderson Other

Boyertown Furnace Company Boyertown Furnace Company Other

Columbia Boiler Company of

Pottstown Columbia Boiler Company Other

Navien Kyung Dong Network Co, Ltd. Other

EFM EFM Other3

- 6 Thermo

- Dynamics Boiler Company Thermo

- Dynamics Boiler Company Other

Camus Hydronics Camus Hydronics Other Energy Kinetics Ener gy Kinetics Other

NY Thermal (NTI) Dennison Holdings
Ltd. Other

Triangle Tube ACV International

NV Other

SIME North America SIME Other

Heat Transfer Products, Inc Heat Transfer Products, Inc Other

PB Heat LLC Peerless Boilers Other Slant/Fin Corporation Slant/Fin Corporation Other
Thermolec Thermolec Other

Allied Engineering Company E

- Z

- Rect

M anufacturing Ltd. Other

Pensotti Pensotti Other

3.2.3 Potential Small Business Impacts

DOE also takes into consideration the impact of amended energy conservation standards
on small businesses. SBA lists small business size standards for industries as they a re described in North American Industry Classification System (NAICS). For residential boilers, the size standard is matched to NAICS code 333414, Heating Equipment (except Warm Air Furnaces) Manufacturing. The number of employees in a small business is co mbined with the total employees of the parent company; it does not represent the division manufacturing residential
boilers. At thi s time, DOE has identified 7 small businesses in the residential boiler market that
fall under the Small Business Administra tion (SBA)’s definition as having 500 employees or
fewer. 13 CFR part 121. DOE studies the potential impacts on these small businesses in detail during the Manufacturer Impact Analysis in the NOPR phase.

DOE has identified the following small business ma nufacturers of residential boilers :

• Axeman Anderson

• Thermo

- Dynamics Boiler Company

• Energy Kinetics

• ECR International

• Heat Transfer Products, Inc.

• Peerless Boiler

• Slant/Fin Boiler

3.2.4 Distribution Channels3

- 7 Two distribution channel s represent the majority of t he HVAC market. In the replacement market the original equipment manufacturer ( OEM ) assembles the system and sells
it to a wholesaler ; the wholesaler sells the unit to a contractor (also known as a dealer); and the
contractor sells the unit to the final co nsumer and performs the installation. In the replacement market, the final consumer is usually the homeowner, as illustrated in Figure 3.2

. 1 , and is very influential in product selection. Replacements "in kind" (replacing a unit w ith a similar or identical product) are common, although premium products are also commonly sold in this
market. In the new construction distribution channel, the manufacturer sells to the equipment wholesaler, who in turn sells to the mechanical contracto r, who in turn sells it to the general
contractor then to the consumer.

Figure 3.2

. 1 Replacement Distribution Channel

Figure 3.2

. 2 New Construction Distr ibution Channel

3.2.5 Regulatory Programs

The following section details current regulatory programs mandating energy conservation
standards for residential boilers. Section 3.2.5.1 discusses current Federal energy cons erva tion

sta ndards. Section 3.2.5.2 review s Canadian energy conservation stan dards that may impact the companies servicing the North American market.

3.2.5.1 Current Federal Energy Conservation Standards

Part A of Title III of EPCA addresses the energy conservation standard s for consumer products other than automobiles, which include residential boilers. (42 U.S.C. 6291

- 6309) The current Federal standards prescribed by EPCA , shown in Table 3.2

. 2

, have applied since September

, 1, 2012

. Manufacturer Wholesaler Mechanical Contractor Consumer

Manufacturer Wholesaler Mechanical Contractor General Contractor Consumer3

- 8 Table 3.2

. 2 Current Federal Energy Conservation Standards Established by EISA

Product Class Minimum Annual Fuel Utilization Efficiency Design Requirements

Gas Hot Water 82% No Constant Burning Pilot,
Automatic Means for A djusting Water Temperature

Gas Steam 80% No Constant Burning Pilot
Oil Hot Water 84% Automatic Means for Adjusting Temperature
Oil Steam 82% None
Electric Hot Water None Automatic Means for Adjusting Temperature
Electric Steam None None

3.2.5.2 Canadian Ene rgy Conservation Standards

The Natural Resources Canada (NRCan) Office of Energy Efficiency regulation mandates minimum energy conservation standards for residential boiler s that apply to imports and interprovincial trade. The standards for boilers are ex pressed as minimum annual fuel utilization energies (AFUEs), rated according to the Canadian test standard CAN/CSA P.2

- 2007
entitled Testing method for measuring annual fuel utilization efficiency of residential gas

- fired furnaces and boilers; ( CSA P.2 ). The Canadian boiler standards are shown in Table 3.2

. 3 . The
AFUE standard b ecame effective in September 1, 2010 and the prescriptive requirements became effective on September 1, 2012 5

.

Table 3.2

. 3 Canadian Energy Conservation Standards for Residential Boilers Boiler Type Minimum AFUE Prescriptive Requirements
Gas Hot Water 82% No constant burning pilot; Automatic means for adjusting
water temperature
Gas Steam 80% No constant burni ng pilot
Oil Hot Water 84% Automatic means for adjusting
water temperature
Oil Steam 82% N one Electric Hot Water N one Automatic means for adjusting
water temperature

3.2.5.3 United Kingdom Energy Conservation Standards

Part L1 of the Building Regulations cod e in the United Kingdom requires that all gas

fired boilers installed in England or Wales after April 1, 2005, and all oil fired boilers installed after April 1, 2007 must be a condensing boiler. These boilers must be rated A or B on the
Seasonal Efficien cy of Domestic Boilers in the UK (SEDBUK) scale 6

.3

- 9 Table 3.2

. 4 SEDBUK Efficiency Bands Efficiency Band SEDBUK

A 90% and above

B 86%

- 90%

C 82%

- 96%

D 78%

- 82%

E 74%

- 78%

F 70%

- 74%

G Below 70%

3.2.6 Non

- Regula tory Programs

DOE identified non

- regulatory programs aimed at improving the energy efficiency of
residential boilers . Two such programs are based on voluntary efficiency targets for residential
boilers : the ENERGY STAR program and the Consortium for Energ y Efficiency (CEE)
initiative.

3.2.6.1 ENERGY STAR

ENERGY STAR is a voluntary labeling program conducted by the U.S. Environmental Protection Agency (EPA) and DOE that identifies and promotes energy

- efficient products. To qualify, a product must usually exceed F ederal minimum standards by a specified amount, or if

no F ederal standard exists, it must meet minimum efficiency levels set by the program and/or exhibit selected energy saving features. ENERGY STAR maintains minimum energy efficiency specifications for v arious products, including residential boilers

. The current ENERGY STAR
levels are shown in Table 3.2

. 5 which t ook effect in April 1, 2002 . E PA is currently in the process of reviewing the ENERGY STAR efficiency level for resident ial boilers.

Table 3.2

. 5 ENERGY STAR Requirements for Qualifying Residential Boilers

Product AFUE Rating

Residential Boiler 85

3.2.6.2 Consortium for Energy Efficiency

The Consortium for Energy Efficiency (CEE) i s a coalition of energy efficiency programs in the U.S. and Canada, including state energy efficiency offices, energy efficiency advocacy groups, and utilities, engaged in establishing common goals and methods for promoting energy efficiency across a broad range of products. The CEE High Efficiency Residential Gas Heating Initiative promotes the use of high

- efficiency gas residential boilers. CEE identifies two tiers of efficiency levels for residential boilers listed in Table 3.2

. 6 7

.3

- 10 Table 3.2

. 6 CEE Efficiency Tiers f or Residential Gas Boilers

Tier AFUE Rating

Tier 1 85

Tier 2 90

3.2.6.3 Consumer Rebate Program

In addition to the Federal and State tax credits available for purchasers of residential boilers, many States and local utility companies offer rebates for higher efficiency boilers, typically for existing homes and retrofits only. DOE maintains a database for such rebates, called
the Database of State Incentives for Renewables & Efficiency (DSIRE) 8 , in addition to
information on other state , local, utility, and federal incentives and policies that promote renewable energy and energy efficiency. For more information on individual rebate programs, please visit the DSIRE website at www.dsireusa.org

3.2.6.4 Federal Tax Credits

Until December 31, 2010 , a Federal tax credit provides consumers with a $150 credit towards their Federal income tax if they purchase qualifying residential boilers. To qualify for
the Federal tax credit a hot water bo iler should have an AFUE of 95 or greater 9

.

3.2.7 Product Lifetime

The lifetime of residential boilers can vary significantly depending on how often the system is used (which is dependent upon the climate of the region where the product is installed
and the personal preferences of the consumer) and how regularly it is maintained and serviced.

DOE reviewed available literature to determine the appropriate lifetime for residential
boilers. Generally, most sources estimate the lifetimes of residential boilers to be in the 15 to 25

year range. Appliance Magazine publishes an Annual Portrait of the U.S. Appliance Industry in which it estimates low, high, and average lifetimes for a range of home appliances, including

gas

- fired boilers, based on input from applian ce experts and many additional sources. Appliance Magazine estimates the typical service li fetime range of a gas boiler is from 17 to 24 years

. 10

DOE’s methodology for determining the lifetime of the products under analysis are described in detail in ap pendix 8

- F. Using a combination or RECS data and shipment history, DOE estimated that the median lifetime for all residential boilers is 22 years.

DOE interviewed several manufactures to gather information regarding the lifetime of
residential boilers. Many manufacturers stated that the design and efficiency level of the boiler impacted its expected lifetime. During manufacturer interviews conducted for the initial analysis, s everal m anufacture r s stated that high er efficiency condensing boilers , made o f
stainless steel or cast aluminum often have shorter lifetimes than lower efficiency cast iron
boilers. Manufact urers pointed to the warranties offered on both types of heat exchanger s to substantiate their claims

. However, these manufacturers also genera lly noted that condensing3

- 11 residential boilers have only been available a relatively short time, so estimating the lifetime is
difficult.

3.2.8 Market Performance Data

As explained previously, DOE examined several sources to compile a comprehensive
database o f residential boilers available on the market today. This database contain s information such as manufacturer name, model number, input capacity, efficiency , and other physical and performance characteristics . DOE only examined products that meet EPCA’s de finition of a
residential boiler (see section 3.1 in this chapter). Table 3.2

. 7 shows the number of the models in
the DOE database for each product class. As Table 3.2

. 7 indic ates, the majority of residential
boilers on the market are gas

- fired hot water boilers.

Table 3.2

. 7 Number of Boiler Models Listed in DOE’s Residential Boiler database by
Product Class

Product Class Number of Models as of September 2013

Gas

- Steam 83

Gas

- Hot Water 653

Oil

- Steam 93

Oil

- Hot Water 5 0 1

3.2.9 Efficiency Data

DOE characterized the distribution of boiler efficiencies currently available to consumers by separating the active models listed in the DO E database into their respective product classes (section 3.1 ) and p l acing the models into bins based on their efficiency

. The efficiency ratings

were rounded to the nearest whole percentage as specified in 10 CFR 430.23 ( n )( 2 ) and separated
into bin s in sizes of 1 percent AFUE ( i.e.

, 83.7 is in the 8 4 AFUE bin). DOE then count ed the number of models in each efficiency bin to examine the distribution of product efficiency

.3

- 12 Figure 3.2

. 3 AFUE R atings for R esidential H ot W ater B oilers in the DOE Database

As shown in Figure 3.2

. 3

, hot water boiler models generally fall into one of two ranges

–

non

- condensing ( i.e.

, 82 to 8 6 percent AFUE) or condensing ( i.e

. , at or above 90 percent AFUE). The efficiency distribution of the boilers varies based upon the fuel type used. This is because of
the chemical makeup of the fuel combustion byproducts

. Gaseous fuels such as natural gas and

propane have a higher hydrogen content which causes more water vapor to be formed during
combustion. This results in lower efficiencies in non

- condensing gas boilers. M ost non

condensing boilers are concentrated at 82 percent AFUE for ga s fired hot water boilers and 85 percent AFUE fo r oil fired hot water boilers. M ost condensing boilers are at either 90 or 95 percent AFUE b for gas

- fired hot water boilers

.

The majority of oil boilers on the market are non

- condensing ( i.e. , less than 90 percent AFUE) , however t here are a small number of oil

- fired condensing boiler models and most are at
90 and 91 percent AFUE. Condensing oil boilers are less common due in part to the high sulfur content of heating oil which can cause additional maintenance and corrosion issues. New limits
on maximum sulfur content of heating oil in the Northeast may reduce these issues. Using low

sulfur heating oil with boiler systems can not only reduce the emission of particulate matter, but also allow for the use of a secondary condensing heat exchanger.

b The high number of 90% AFUE ratings may be due in part to a recent rerating initiative for AHRI member
manufacturers to addres s inflated ratings caused by an error in the DOE test procedure which impacted condensing boilers with two stage or modulating input rates. AHRI has lowered the stated AFUE ratings of certain boilers to 90% for its member companies until a revised rating has been determined with the corrected test procedure. 0 20 40 60 80 100 120 140 160

82 83 84 85 86 87 88 89 90 91 92 93 94 95 96Number of Models

AFUE, % Oil

Gas3

- 13 Figu re 3.2

. 4 AFUE ratings for residential steam boilers in the DOE Database

As shown in Figure 3.2

. 4 residential steam boilers have efficiencies ranging from 80 percent AFUE up to 86 pe rcent AFUE. As with hot water boilers, t he efficiency of the boilers varies based upon the fuel type used. There are no higher level efficiencies in steam boilers.

3.2.10 Shipments

To prepare an estimate of the national impact of energy conservation standard s for
residential boilers , DOE needed to estimate annual residential boiler shipments. For this stage of the rulemaking , DOE used data from Ap pliance Magazine, AHRI, and ENERGYSTAR to establish historical shipments by product class

. DOE used s hipment proje ctions to calculate the national impacts of standards and to calculate the future cash flows of manufacturers. DOE develop ed shipments projections based on an analysis of key market drivers for a particular product (see chapter 9 )

.

DOE used this data for t wo main purposes. First, the shipment data and market trend information contributed to the shipments analysis and base

- case forecast for residential boilers (chapte r 9 ). Second, DOE used the data to develop the installed stock of equipment for the
nati on al impact analysis (chapter 10 ). Although more detailed shipments data are given in chapter 9 and appendix 09

- B , the shipments shown in this chapter illustrate the level of shipments
from 1990 to 2008

.

Table 3.2

. 8 shows the shipm ent da ta collected from a SAIC report 10 which includes shipments of boilers less than 250,000 btu/hr sold in the United States from 2003 to 2007. 0 5 10 15 20 25 30 35 40 45

80 81 82 83 84 85 86Number of Models

AFUE, % Oil

Gas3

- 14 Table 3.2

. 8 Historical shipments data of hot water and steam b oilers reported from a SAIC report

Units Sold

Year 2003 2004 2005 2006 2007

Gas

- Fired Steam 38,105 36,846 37,127 30,243 33,932

Gas

- Fired Hot Water 186,627 189,417 179,717 155,499 147,873

Oil

- Fired Steam 17,706 19,460 17,256 16,016 15,494

Oil Fired Ho t Water 120,764 133,288 121,678 99,801 93,642

Figure 3.2

. 5 Market Share of Shipments by Product Class (2003

- 2007)

Appliance Magazine 11,12 provides an estimate of annual unit shipments for various applia nces, including residential boiler shipments

. Table 3.2

. 9 shows the shipment data collected
from Appliance Magazine up until 2008

.

Table 3.2

. 9 Appliance Magazine Shipments

Year Gas B oiler Oil Boiler

1990 195,959 132,779

1991 176,814 119,420

1992 176,483 145,459

1993 195,751 151,783

1994 215,887 170,734

1995 187,601 150,402

1996 198,247 161,363

1997 205,717 159,767

1998 185,032 148,178 11%

51% 5% 33%

Gas

- Fired Steam

Gas

- Fired Hot Water

Oil

- Fired Steam

Oil Fired Hot Water3

- 15 1999 200,893 149,050

2000 224,317 144,1 24

2001 221,198 149,457

2002 213,936 147,919

2003 235,226 166,821

2004 236,964 162,468

2005 224,185 145,551

2006 195,827 121,054

2007 201,000 123,320

2008 192,332 121,539

3.3 BOILER TECHNOLOGY ASSESSMENT

The technology assessment focuse s on underst anding how residential boilers use energy and on identifying potential technology changes that would improve the efficiency of these products . Measures that improve the rated product efficiency are analyzed as “ technology options .” The technologies identif ied in this assessment are based on existing technologies as well as working prototypes. In consultation with interested parties, DOE has create d a list of technology options for consideration in this rulemaking. Following research into this list of
techno logy options, those technology options that pass the screening criteria are considered
suitable options for improv ing the efficiency of the product in the engineering analysis, and will assist DOE in determining the max

- tech design as well as the cost of i mproving product efficiency

.

At this time, DOE is aware of a set of technology options (discussed in further detail below) that could be used to improve residential boiler efficiency. The list of technologies below is focused on measures that would improv e either the rated AFUE or reduce standby and/or off mode electrical energy consumption. DOE is aware of technologies that improve overall efficiency of residential boilers but do not improve AFUE or reduce stan dby/off mode energy consumption as measured b y the DOE test procedure, and these technologies are described in
section 3.3.3

.

3.3.1 Boiler and Heat Exchanger Characterization

Fuel burning boilers transfer heat from the combustion gases to water, which is then sent to the heated space through a steam or hot water distribution system. The technology that is used
for steam boilers is generally the same as that used for hot water boilers except that circulating pumps are not required in steam boilers.

Residential boilers can be characterized by the type of heat exchanger material: cast

- iron, steel, stainless steel, copper, and aluminum. The heat exchanger’s function is to transfer heat from the combustion gases to the heating medium ( i

. e. hot water or steam), which is then3

- 16 distributed to the heated space. There are various types of heat exchangers commonly used in
residential boilers

.

Most noncondensing boilers are made with cast iron

, copper , or steel heat exchangers

. The most common heat exchanger design used in residential hot water and steam boilers is the

cast

- iron sectional boiler. In this design, water is heated in cast

- iron chambers called sections. The sections are fit together to form a n assembly , which is typically assembled horizontally . Hot combustion gases form in the combustion chamber nea r the bottom of the boiler and rise through cavities between the sections, transferring heat to the water within. Generally, t he greater the number of sections, the greater the rate of heat output from the boiler.

There are two major categories of cast

- i ron boiler: dry

- base and wet

- base. A dry

- base boiler is commonly used in atmospheric gas

- fired boilers. In a dry

- base boiler, the combustion
chamber is under the fluid

- backed sections. Combustion occurs on the surface of burner tubes suspended below the wa ter

- filled sections. Hot exhaust gases are drawn upward between boiler sections, or through fire tubes, and enter a flue gas collector at the top of the boiler. A wet

- base
boiler is a common configuration for oil

- fired boilers. In a wet

- base boiler, the to p and sides of the combustion chamber are enclosed by fluid

- backed sections. It has the advantage of exposing more of the section's surface area to the combustion chamber, which is completely surrounded by
the water

- filled heat exchanger 13

.

The amount o f metal in cast

- iron boilers makes them relatively heavy. These boilers can contain up to 15 gallons of water. The combination of metal

- and water

- weight enables them to absorb a significant amount of heat into their own material. This high thermal mass is undesirable in situations where the boiler is significantly oversized, and thus experiences extended periods of off

- time between firing cycles. During this time, residual heat remaining in the boiler's metal and water following burner shutdown can be carr ied up to the flue by air currents passing through the combustion chamber. The majority of gas

- fired boilers have flue dampers to reduce th e draft heat loss. T he residual heat is also transferre d through the boiler's jac ket to the air surrounding the boile r.

Another commonly used heat exchanger design in non

- condensing gas

- fired residential
hot water boilers is the copper water tube boiler

. In copper water

- tube boilers, the tubes are directly exposed to the combustion gases. Design variations include both vertical and horizontal

tube arrangements. The tubes are usually manufactured with fins that increase the heat transfer area exposed to the flue gases. The high thermal conductivity of copper, relative to cast iron or steel, means that significantly less surface area is needed to achieve the same rate of heat transfer. This makes for smaller and significantly lighter boilers. Copper water

- tube boilers require constant water circulation while being fired to prevent damage from thermal stress. This requireme nt must be incorporated into the design of system piping and control.

The third material commonly used in non

- condensing boilers is steel. In a steel fire

- tube boiler, water surrounds a group of steel tubes through which the hot combustion gases pass. Sp iral baffles known as turbulators are inserted into the fire tubes to increase heat transfer by inducing turbulence and slowing the passage of the exhaust gases. The fire tubes are welded to
steel bulkheads at each end to form the overall heat

- exchanger as sembly.3

- 17 Most steel boilers are built around horizontal fire

- tubes. Some boilers route the flue gases through multiple tubes before they reach the flue

- pipe connection. This allows additional heat to be extracted from the flue gases.

Condensing boiler s ar e typically made corrosion resistant metals such as stainless steel or
aluminum as other metals will corrode due to the acidic condensate. Condensing boilers have a variety of different heat exchanger designs. Design variations include fire

- tube, water tub e, or sectional primary heat exchanger with a secondary condensing heat exchanger

. The majority of condensing boilers are gas

- fired. Condensing boilers are typically forced or induced draft because they cannot use a natural draft venting system, since the buoyancy of the cooler flue gases is not s ufficient to draw the gases up the vent system

. Condensing boilers are generally sold with more sophisticated controls than non

- condensing boilers.

Figure 3.3

. 1 G as

- Fired Hot Water Boilers Heat Exchanger Materials in the DOE Database

Figure 3.3

. 1 shows the breakdown of heat exchanger materials for gas

- fired hot water
boilers in the DOE database

. In the non

- condensing range ( i.e. , 82 to 8 8 percent AFUE) the majority of the boilers heat exchangers are made of cast

- iron, a smaller number of models are comprised of copper and a small number are made of steel. The heat exchanger of a baseline unit is typically constructed from cast iron. In th e condensing range ( i.e. , at or above 90 percent AFUE) the majority of heat exchangers are stainless steel with a smaller number of models made
of aluminum

. T here are also a few conden sing boilers made of cast iron some of which have an
additional stainles s steel heat exchanger

. 0 10 20 30 40 50 60 70 80

82 83 84 85 86 87 88 89 90 91 92 93 94 95 96Number of Models

AFUE, % Steel

Cast Iron

Copper

Stainless Steel

Aluminum3

- 18 Figure 3.3

. 2 Oil

- fired Hot Water Boiler Heat Exchanger M aterial s in the DOE Database

.

Figure 3.3

. 2 shows the breakdown of heat exchanger materials for o il

- fired hot water
boilers. In the non

- condensing range the heat exchangers are mostly made of cast iron, a smaller
number are made of steel.

3.3.2 Technology Options that may I mprove AFUE

DOE has identified the following technology options which have the p otential to improve the efficiency of residential boilers.

1. Heat Exchanger Improvements

2. Modulating Operation

3. Dampers

4. Direct Vent

5. Pulse Combustion

6. Premix Burners

7. Burner Derating

8. Low Pressure Air Atomized Oil B urner
9. Delayed Action Oil Pump Solenoid Valve

10. Ele ctronic Ignition 0 20 40 60 80 100 120

82 83 84 85 86 87 88 89 90 91Number of Models

AFUE, % Steel

Cast Iron3

- 19 3.3.2.1 Heat Exchanger Improvements Improving the heat exchanger for boilers increase s the rate of transfer from the hot combustion gases to the heating medium (i.e. hot water or steam), which is then distributed to the heated space. The improve d heat transfer increases the thermal efficiency and AFUE.

Improvements to the heat exchanger can be achieved by modifying baseline designs of
standard boilers to (1) increase heat exchanger surface area, (2) modify or add heat exchanger surface features, (3) modify or add heat exchanger baffles and turbulators , and (4) increase the corrosion resistance of the heat exchanger to withstand flue gas condensation.

Increase Heat Exchanger Surface Area and addition of Mechanical Draft. The performance of the h eat exchanger can be improved by increasing the surface area relative to the fuel input . An increase in surface area provides a larger surface over which heat transfer can occur. This increases the overall rate of heat transfer occurring in the boiler, the reby improving the boiler’s ability to efficien tl y extract heat from the hot combustion gases. The result is an increase in steady

- state efficiency of the unit, and thus, the AFUE.

Mechanical draft systems can be added to boilers to enable the use of more efficient heat exchangers. Mechanical draft systems allow for increased heat exchange surface area and/or tighter flueways by overcoming the drop in pressure associated with restrictive flow passages in more efficient heat exchangers and by supplementing the loss of buoyancy in cooler flue gases to provide sufficient airflow. Mechanical draft systems can be designed as either induced draft or forced draft systems. An induced draft fan is located downstream of the heat exchanger and pulls flue gases throug h the gas pathway, creating negative pressure in the heat exchanger. A forced draft fan is located upstream of the heat exchanger and creates positive pressure in the heat exchanger that pushes the products of combustion through the system.

Modify or add Heat Exchange Surface Features. An alternative to increasing the size of the heat exchanger is enhancing the effectiveness of the heat exchanger surfaces. One way this may be done is by adding surface features to the heat exchanger. Incorporating surface features, such as dimples, increases the turbulence in the air passing close to the heat exchanger’s surface, which can enhance heat transfer when correctly designed.

Heat Exchanger Baffles and Turbulators. Turbulators and baffles are pieces of metal
that are incorporated into the heat exchanger to improve the heat transfer through the walls of the heat exchanger.

Increasing the Corrosion Resistance of the Heat Exchanger. When efficiency of a combustion heating appliance is increased to the point where combustion gases are cooled below the dew point of the gas, condensate will form. Flue gas condensate is acidic and corrosive. Corrosion due to condensation of flue gases limits the AFUE that can be achieved by boilers
with non

- corrosion resistant heat exc hangers. Using heat exchangers made out of corrosion resistant materials, such as cast aluminum and stainless steel, allows for the recovery of the latent
heat (the heat from condensation of water vapor in the combustion products) and raises the
AFUE to ab ove 90 percent. These types of boilers require the addition of a condensate pump and mechanical draft system

.3

- 20 3.3.2.2 Modulating Operation
Two

- stage and modulating combustion allows boilers to meet heating load re quirements more precisely. When low heating load c onditions exist, a two

- stage or modulating boiler can operate at a reduced input rate for an extended period of burner on

- time to meet the reduced heating load. When combustion air supply is also modulated to match the fuel input rate, the
burner is essent ially derated, making the heat exchanger more effective in periods of lower heat demand, raising the AFUE.

The primary difference between two

- stage and step

- modulating control is that the two

stage control must operate between either the low firing rate and off, or the high firing rate and off, whereas the continuous modulating control can operate between multiple firing rates (e.g.,
off to low

- fire to high

- fire to low

- fire to off).

3.3.2.3 Dampers
Off

- cycle (which refers to the burner off

- cycle) dampers restric t the intake and exhaust air flow through the venting system during standby mode by closing when the burner is not operating, thereby trapping residual heat in the heat exchanger. During the burner off

- cycle, the boiler loses heat by natural convection and conduction through the combustion air inlet and flue.
Installi ng a damper at these points improves AFUE by prevent ing heat from escaping and minimizing off

- cycle heat losses

. Today most atmospheric boilers have dampers, including
those at the baseline ef ficiency level.

3.3.2.4 Direct Vent
Direct

- vent appliances use ducts to provide outdoor air for combustion. Non

- direct

- vent appliances typically use air from the appliance's environment for combustion. Direct

- vent systems may use a combustion

- air preheat system that passes the outdoor combustion air through a heat exchanger in contact with the flue gases. The combustion air does not mix with the flue gases. The so

- called direct

- vent with preheat design uses a concentric vent/combustion air system in which the flu e gases pass through a central

- vent pipe and the combustion air passes through a concentric duct surrounding it. This arrangement creates a counter

- flow heat exchanger that recovers some heat from the flue gases to preheat the combustion air.

The direct

- v ent

- without

- preheat design is the same as the direct

- vent

- with

- preheat design, except that the combustion air is not preheated by the flue gases. There are separate vent and combustion air systems and the combustion air is not preheated. The current test p rocedure does not differentiate between the performances of direct

- vent with and without preheat technology;
both are evaluated as isolated combustion system ( ICS ) installations. Direct vent boilers improves AFUE by reducing the heat loss through infiltrat ion

.

3.3.2.5 Pulse Combustion Pulse combustion burners operate on self

- sustaining resonating pressure waves that alternately rarefy the combustion chamber (drawing a fresh fuel

- air mixture into the chamber) and pressurize it (causing ignition by compression heatin g of the mixture to its flash point). Pulse combustion systems feature high heat transfer rates, and have a high combustion efficiency in comparison to conventional boiler designs. DOE notes that similar efficiencies can be achieved3

- 21 through the use of othe r technologies, and manufacturers currently typically no longer use this technology to improve efficiency.

3.3.2.6 Premix Burners

P remix ing fuel gas and combustion air prior to arrival at the flame results in more complete combustion using lower levels of excess a ir. The lower levels of excess air raise the temperature of the gases entering the heat exchanger which enhances heat ex change and improves efficiency. Lower levels of excess air also raise the water vapor dew point which
facilitates condensation and the recovery of latent heat and improves AFUE. Premix burners
have lower NO X emissions than traditional burners.

3.3.2.7 Burner Derating Reducing burner firing rate for gas and oil boilers while keeping heat exchanger geometry and surface area and the fuel

- air rati o the same will increase the ratio of heat transfer surface area to energy input, thereby increasing the AFUE . However, DOE notes that the lower energy input means that less heat would be provided than with conventional burner firing rates.

3.3.2.8 Low

- Pressure, Air

- Atomized Oil Burner The residential oil burner market is currently dominated by the pressure

- atomized
retention head burner. The fuel input rate is controlled by the size of the nozzle orifice. Pressure

atomizing nozzles that are designed for low firi ng rates suffer rapid fouling of the small internal passages, leading to bad spray patterns and poor combustion performance. To overcome the low input limitations of conventional oil burners, Brookhaven National Laboratory 14 developed a
low

- pressure, air

- a tomized oil burner. In addition, it can operate with low levels of excess
combustion air for lean

- burning, ultra

- clean combustion. A lower level of excess air generally imp roves AFUE rating.

3.3.2.9 Delayed

- Action Oil Pump Solenoid Valve A delayed

- action oil pump solenoid valve is installed between the oil pump and the burner nozzle to supplement the fuel pump regulator . It does so by delaying the fuel release by three to six seconds after the igniter and burner blower start until the oil pressure reaches the
level required to fully discharge the oil into the combustion chamber without dripping. This ensures that the oil burns more completely , which improves efficiency

.

3.3.2.10 Electronic Ignition

B oilers are equipped with electronic ignition systems, which light the burne r with an electrical component upon a call for heat. Unlike standing pilot ignition systems that consume fuel continuously, electronic devices and their control modules operate only during the active
mode this improves AFUE

. Electronic ignition is already required for all gas boilers and is present on oil boilers.

There are different types of electronic ignition systems including: (1 ) Hot Surface Ignition: The igniter in this system is an electrically heated resistance element that thermally ignites the m ain burner directly without the use of a pilot light. (2) Intermittent Pilot Ignition: This is a device that lights a pilot light by generating a spark. The pilot light in turn lights the main burner. (3) Direct Spark Ignition: DSI ignites the main burne r directly by generating a spark.3

- 22 ( 4 ) In terrupted Duty Ignition Systems: all modern oil burners have a type of electronic ignition called interrupted duty ignition. A step

- up transformer supplies power to two electrodes, which causes a spark to jump. The i nterrupted duty ignition system for an oil burner activates the spark only until either a steady flame is established or the end of a
timed trail

- for

- ignition (TFI) period.

3.3.3 Technologie s That Do Not I ncrease AFUE or Standby

DOE has listed technologies th at may improve overall efficiency of residential boilers but do not improve AFUE or reduce standby/off mode energy consumption

. T hese technologies are described in detail in chapter 4. As discussed in chapter 4, these technologies were not considered beyon d the screening analysis because they do not impact the rated efficiency.

• Micro Combined Heat and Power (Micro

- CHP)

• Improved Motor Efficiency

• Positive Shut

- Off Valve for Oil Burner Nozzles

• Heat Pump Boilers

3.3.4 Technology Options that Improve Standby Mode a nd Off Mode Energy Efficiency

On October 20, 2010 DOE published a final rule in the Federal Register in w hich it
concluded that it is not technically feasible to create an integrated metric that incorporates standby mode and off mode energy consumption in to the statutorily

- identified efficiency descriptor, AFUE. The October 2010 final rule amended DOE’s test procedure for furnaces and boilers to establish a method for measuring the electrical energy use in standby and off mode for gas and oil

- fired boiler s pursuant to requirements established by EISA 2007. 75 FR 64621. The technologies described in this section would reduce the standby mode and off mode energy consumption as measured by the DOE test procedure.

3.3.4.1 Transformer Improvements
T ransformers contin ue to supply power to the control board in all modes of operation, including standby mode

. I ncreasing their operating efficiency will reduce the boiler ’s standby electrical power consumption.

A toroidal transformer has an annular core made of very tightl y

- wound, grain

- oriented,
silicon steel ribbons , which are arranged such that all their molecules are aligned with the direction of flux. This allows better performance (i.e., more quiet and efficient operation) than a traditional laminated transformer, in which unaligned molecules increase the core’s reluctance, or capacity for opposing magnetic induction. These improvements in efficiency allow an up to 50 percent reduction in size and weight, such that they can be used in new, innovative applications. Over all efficiency of toroidal transformers is 90 to 95 percent 15

.

Research has shown that larger, low loss transformers (LLTX) use four times less energy in standby th an do off

- the shelf transformer 16

.3

- 23 3.3.4.2 Control Relay for Models with Brushless Permanent Magne t (BPM)

Motors During testing of standby and off mode components performed for the DOE furnace and central air conditioner rulemaking c , DOE found that BPM motors and their associated controls

consume power while in standby and/or off modes , while PSC moto rs did not have any standby

or off mode power draw. Therefore for those boilers that utilize them , the BPM motor and
associated controls could be disconnected while the system is in standby mode or off mode through the use of a control relay to further red uce a system’s standby/ off mode power consumption. A typical control relay activates a switch when current runs through it and when there is no current a spring holds the switch in the open position.

3.3.4.3 Switching Mode Power Supply While linear power supplie s regulate voltage supply to the dc circuit with a series element, switching mode power supplies (SMPS) do so in an alternative, more effective way. In a switching mode power supply, power handling electronics switch on and off (where ‘on’

means the switch is closed and voltage drop is negligible and ‘off’ means the switch is open and current is negligible) with high frequency, effectively connecting and disconnecting the output (load) to the input source. Continuous power flow to the load can be maintained /controlled by varying the duty cycle or frequency of the SMPS.

Linear power supplies experience significant heat losses because they use resistance elements, which convert electrical energy to heat energy, to regulate power supply. By using a
switch to control energy flow instead, switching mode power supplies avoid such heat losses and have much higher efficiency. SMPS do introduce transient losses that increase with frequency, but these losses are negligible in comparison with the energy saved

. Thus, r eplacing a linear power supply with an SMPS has the potential to reduce the electrical power consumption of residential boilers in standby and off mode.

c See: http://www1.eere.energy.gov/buildings/applian ce_standards/residential/residential

_ furnaces_cac_hp_final_rule
.html3

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.

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