CHAPTER 4

. SCREENING ANALYSIS

TA BLE OF CONTENTS

**4.1 INTRODUCTION** 

**........................................................................................................... 4­1** 

**4.2 SCREENED­OUT**  **TECHNOLOGIES............................................................................ 4­2**

**4.2 .1**  **Water Heaters.......................................................................................................**  **4 ­2** 

**4.2 .1.1**  **Side­Arm Heater**  **(Gas and**  **Oil Storage)** 

**............................................... 4**  **­2**

**4.2 .1.2**  **Flue Damper (Buoyancy Operated) (Gas Storage)............................... 4­3**

**4.2 .1.3**  **Directly Fired (Gas and Oil Storage).................................................... 4­3**

**4.2 .1.4**  **Condensing Pulse**  **Combustion (Gas,**  **O il**  **Storage, and** 

**In stantaneous) ...................................................................................................... 4­3** 

**4.2 .1.5**  **Advanced Forms**  **of Insulation**  **(Gas, El**  **ectric, and**  **Oil Storage)** 

**.......... 4**  **­4**

**4.2 .1.6**  **Thermophotovoltaic and**  **Thermoelectric Generators**  **(Gas, O**  **il**

**St orage,**  **and Instantaneous)** 

**................................................................................. 4­5** 

**4.2 .1.7**  **U­Tube Flue**  **(Gas and**  **Oil Storage)...................................................... 4­5** 

**4.2 .1.8**  **Reduced Burner**  **Size (Slow**  **R ecovery)**  **(Gas, O**  **il Storage,**  **and**

**In stantaneous) ...................................................................................................... 4­5** 

**4.2 .1.9**  **Two­Phase Thermosiphon**  **(Gas and**  **Oil Storage)** 

**................................ 4**  **­6**

**4.2 .1.10**  **CO 2**  **Heat Pump Water Heater (Electric Storage) ................................. 4­6**

**4.2 .2**  **Direct Heating**  **Equipment**

**................................................................................... 4­6** 

**4.2 .2.1**  **Increased Heat**  **Transfer Coefficient**  **(Fan Wall,**  **Gravity Wall,** 

**Fl oor,**  **Room)........................................................................................................ 4**  **­7**

**4.2 .2.2**  **Power Burner**  **(Fan Wall,**  **Gravity Wall,**  **Floor, Room)** 

**........................ 4**  **­7**

**4.2 .2.3**  **Condensing Pulse**  **Combustion (Fan**  **Wall, Gravity**  **Wall, Floor,** 

**Ro om)** 

**............................................................................................................... 4**  **­7**

**4.2 .2.4**  **Improve Fan**  **or Blower**  **Motor Efficiency**  **(Fan W**  **all).......................... 4­8** 

**4.2 .3**  **Pool Heaters......................................................................................................... 4­8** 

**4.2 .3.1**  **Condensing Pulse**  **Combustion**

**............................................................. 4**  **­9**

**4.3 REMAINING**  **TECHNOLOGIES**

**................................................................................... 4­9** 

**4­i 4­ii** 4.1 INTRODUCTION

**Thi s**  **chapter details**  **the screening**  **analysis that**  **the U.S.**  **Department of**  **Energy**

**(D OE)**  **conducted in**  **support of**  **the ongoing**  **energy conservation**  **standards rulemaking** 

**fo r**  **residential water**  **heaters, d**  **irect heating**  **equipment (DHE),**  **and pool**  **heaters.**

**In the**  **market and**  **technology assessment**  **(MTA; chapter**  **3), DOE**  **p resents**  **an**

**in itial**  **list of**  **technologies manufacturers**  **can use**  **to improve**  **the energy**  **efficiency of** 

**re sidential**  **water heaters,**  **DHE, a**  **nd pool**  **heaters. T**  **he purpose**  **of the**  **screening analysis**  **is**

**to evaluate**  **the technologies**  **that improve**  **product energy**  **efficiency to**  **determine which** 

**te chnologies**  **DOE should**  **consider further**  **in the**  **rulemaking analyses.**  **D OE**  **consulted a** 

**r ange**  **of parties,**  **i ncluding**  **industry and**  **technical experts**  **and others,**  **t o**  **develop a**  **list of** 

**te chnologies**  **for consideration.**  **Some of**  **these technologies**  **can reduce**  **annual energy** 

**co nsumption**  **of products**  **in actual**  **applications, b**  **ut m**  **ay not**  **improve the**  **energy factor** 

**(EF ),**  **the annual**  **fuel utilization**  **efficiency (AFUE),**  **or the**  **thermal efficiency**  **of water** 

**he aters,**  **D HE,**  **and pool**  **heaters, r**  **espectively. The**  **EF of**  **water heaters**  **is measured**  **using**

**DO E’s**  **test procedure**  **specified in**  **10 Code**  **of Federal**  **Regulations (CFR)**  **section 430** 

**Sub part**  **B, Appendix**  **E,** U niform Test Method for Measuring t he Energy Consumption of

W

ater Heaters

**. The**  **AFUE of**  **DHE is**  **measured using**  **DOE’s test**  **procedure specified**  **in**

**10 CFR**  **430 Subpart**  **B, Appendix**  **O,** Uniform Test Method for Measuring t he Energy

Co nsumption of Ve nted Home Heating E quipment

**. The**  **thermal efficiency**  **of pool**  **heaters**

**is measured**  **by the**  **American National**  **Standards Institute**  **(ANSI)** Standard for GasF

ired Pool Heaters **(ANSI Z21.65­1994),**  **which DOE**  **has incorporated**  **by reference**  **into**

**it s**  **regulations at**  **10 CFR**  **430 Subpart**  **B, Appendix**  **P. DOE**  **removed from**  **consideration**

**th ose**  **technologies that**  **do not**  **increase EF,**  **AFUE, or**  **thermal efficiency**  **per these**  **test**

**pr ocedures.**  **D OE**  **evaluated the**  **remaining technologies**  **pursuant to**  **the criteria**  **in The** 

**Ene rgy**  **Policy and**  **Conservation Act**  **(EPCA), as**  **amended. (42**  **U.S.C. 6311­6317)** 

**Se ction**  **325(o) of**  **EPCA establishes**  **criteria for**  **prescribing new**  **o r**  **amended**

**st andards**  **designed to**  **achieve the**  **maximum improvement**  **in energy**  **efficiency.**

**Fu rthermore,**  **EPCA d**  **irects the**  **Secretary of**  **Energy to**  **d etermine**  **whether a**  **s tandard**  **is**

**te chnologically**  **feasible and**  **economically justified.**  **(42 U.S.C.**  **6295(o)(2)(A)(B)) In** 

**vi ew**  **o f**  **this requirement,**  **10 CFR**  **Part 430**  **Subpart C,**  **Appendix A,**  Procedures,

In terpretations and Policies for Consideration of N ew or Revised Energy Conservation

St andards for Consumer Products **(the Process**  **Rule), guides**  **DOE in**  **its consideration** 

**an d**  **promulgation of**  **new or**  **revised product**  **efficiency standards.**  **Th ese**  **procedures**

**el aborate**  **on the**  **statutory criteria**  **provided in**  **42 U.S.C.**  **6295(o) and,**  **in part,**  **eliminate**

**pr oblematic**  **technologies early**  **in the**  **process of**  **prescribing or**  **amending an**  **energy**

**ef**

**ficiency standard.**  **In p**  **articular, DOE**  **determines whether**  **to eliminate**  **from**

**co nsideration**  **any technology**  **that presents**  **unacceptable problems**  **with respect**  **to the** 

**fo llowing**  **criteria:**

Te chnological feasibility. **If it**  **is determined**  **a t**  **echnology has**  **not been** 

**in corporated**  **into residential**  **products or**  **in working**  **prototypes, t**  **hen the**  **technology will** 

**no t**  **be considered**  **further.**

**4­1**Practicability to manufacture, install, and service. **If it**  **is determined**  **that mass** 

**pr oduction**  **of a**  **t echnology**  **in residential**  **products and**  **reliable installation**  **and servicing** 

**of the**  **technology could**  **not be**  **achieved on**  **the scale**  **n ecessary**  **to serve**  **the relevant** 

**ma rket**  **by the**  **effective date**  **of the**  **standard, then**  **that technology**  **will not**  **be considered** 

**fu rther.** 

Im pacts on equipment utility to consumers. **If a**  **t echnology**  **is determined**  **to**

**ha ve**  **significant adverse**  **impact on**  **the utility**  **of a**  **p roduct**  **to significant**  **subgroups of** 

**co nsumers,**  **o r**  **results in**  **the unavailability**  **of any**  **covered product**  **types with**  **performance**

**ch aracteristics**  **(including reliability),**  **features, size,**  **capacities, a**  **nd volumes**  **that are** 

**sub stantially**  **the same**  **as products**  **generally available**  **in the**  **United Sates**  **at the**  **time, it** 

**wi ll**  **not be**  **considered further.** 

Sa fety of technologies. **I f**  **it is**  **determined a**  **t echnology**  **will have**  **significant**

**ad verse**  **impacts on**  **health or**  **safety, it**  **will not**  **be considered**  **further.**

**In sum,**  **if DOE**  **determines that**  **a t**  **echnology, or**  **a c**  **ombination of**  **technologies,**

**ha s**  **unacceptable impacts**  **on the**  **policies stated**  **in section**  **5(b) of**  **the Process**  **Rule, it**  **will**

**be eliminated**  **from consideration.**  **If a**  **p articular**  **technology fails**  **to meet**  **one or**  **more of** 

**th e**  **four criteria,**  **it will**  **be screened**  **out. The**  **reasons for**  **eliminating any**  **technology are** 

**do cumented**  **in section**  **4.2.**

4.2 SCREENED­OUT TECHNOLOGIES

**Thi s**  **section describes**  **the technologies**  **that DOE**  **eliminated for**  **failure to**  **meet**

**on e**  **of the**  **following four**  **factors: 1)**  **technological feasibility;**  **2) practicability**  **to**

**ma nufacture,**  **install, and**  **service; 3)**  **impacts on**  **equipment utility**  **to consumers;**  **or 4)** 

**co nsumer**  **health or**  **safety.**

4.2 .1 Water Heaters

**DO E**  **eliminated the**  **following technology**  **options for**  **residential water**  **heaters**

**fr om**  **further consideration:**  **side­arm heater,**  **flue damper**  **(buoyancy operated),**  **directly**

**fi red,**  **condensing pulse**  **combustion, advanced**  **forms o**  **f insulation,**  **thermophotovoltaic**

**an d**  **thermoelectric generators,**  **U ­tube**  **flue, reduced**  **burner size**  **(slow r**  **ecovery), two** 

**p hase**  **thermosiphon (TPTS),**  **and CO**  **2 heat**  **pump water**  **heater.**

4.2 .1.1 Side­Arm Heater (Gas and Oil Storage)

**Si de­arm**  **heaters circulate**  **the potable**  **water between**  **the tank**  **and an**  **external heat** 

**ex changer,**  **typically a**  **s hell­in­tube**  **exchanger. The**  **side­arm heater**  **design avoids**  **large**

**fl ue**  **losses by**  **removing the**  **flue from**  **the center**  **of the**  **gas­ or oil­fired**  **storage tank.** 

**Si de­arm**  **storage water**  **heaters are**  **not commercially**  **available, although**  **products**

**in corporating**  **side­arm heaters**  **have been**  **commercially available**  **in small**  **quantities.**

**Ho wever,**  **DOE was**  **not been**  **able to**  **identify a**  **c urrent**  **working prototype**  **for gas**  **or oil** 

**f ired**  **storage water**  **heaters, a**  **nd believes**  **manufacturers no**  **longer use**  **this technology.** 

**4­2 Therefore,**  **it is**  **not technologically**  **feasible and**  **not practical**  **to manufacture,**  **install, and** 

**se rvice**  **side­arm storage**  **water heaters**  **on the**  **scale necessary**  **to serve**  **the relevant**  **market**

**at the**  **time of**  **the effective**  **date of**  **the standard.** 

4.2 .1.2 Flue Damper (Buoyancy Operated) (Gas Storage)

**Thi s**  **flue damper**  **is a**  **s mall,**  **very lightweight**  **aluminum dome­shaped**  **poppet that** 

**is lifted**  **by the**  **buoyancy of**  **the combustion**  **products t**  **o allow**  **f lue**  **gases to**  **enter the** 

**ve nting**  **system. This**  **technology option**  **would reduce**  **off­cycle standby**  **losses by**  **sealing**

**th e**  **flue and**  **preventing convection**  **to the**  **venting system,**  **b ut**  **would have**  **no effect**  **on**

**re covery**  **efficiency because**  **it does**  **not affect**  **the rate**  **of heat**  **transfer. This**  **flue damper** 

**ma y**  **not work**  **with high­recovery**  **efficiency water**  **heaters because**  **there may**  **not be** 

**en ough**  **waste heat**  **in the**  **combustion products**  **to provide**  **sufficient buoyancy**  **to lift**  **the**

**pop pet.** 

**Sa fety**  **concerns exist**  **because the**  **damper may**  **not open**  **due to**  **the low**  **e nergy**  **of**

**th e**  **combustion products.**  **If the**  **flue is**  **blocked, safety**  **interlocks should**  **prevent the**  **gas**

**st orage**  **water heater**  **from operating.**  **Otherwise, harmful**  **combustion products**  **will enter** 

**th e**  **space where**  **the water**  **heater is**  **installed (**  i.e.

**, r**  **esidence). Although**  **safety interlocks** 

**ca n**  **mitigate improper**  **exhaustion, the**  **water heater**  **would still**  **be inoperable.**  **Therefore,**

**DO E**  **does not**  **consider buoyancy**  **operated flue**  **dampers for**  **gas­fired storage**  **water**

**he aters**  **a m**  **eans to**  **improve EF**  **d ue**  **to the**  **adverse impacts**  **on safety.** 

4.2 .1.3 Directly Fired (Gas and Oil Storage)

**A directly**  **fired gas­ or**  **oil­fired storage**  **water heater**  **uses a**  **d irect**  **contact heat** 

**ex change**  **process that**  **puts potable**  **water directly**  **into contact**  **with the**  **burner flame**  **and**

**fl ue**  **products. S**  **praying the**  **water directly**  **at the**  **flame is**  **a m**  **ore efficient**  **means of** 

**tr ansferring**  **heat than**  **in a**  **c onventional**  **shell­and­tube heat**  **exchanger because**  **the heat** 

**r esistive**  **barrier between**  **the water**  **and the**  **flue products**  **is eliminated.**  **However, this**  **can**

**al so**  **lead to**  **contamination of**  **domestic water**  **by the**  **flue products,**  **w hich**  **can cause**  **health**

**an d**  **safety problems**  **for end**  **users. Th**  **is technology**  **can also**  **conflict with**  **local plumbing** 

**co des**  **(** e.g.

**, I**  **nternational Association**  **of Professional**  **Plumbing and**  **Mechanical Officials** 

**(I APMO)**  **1991) with**  **respect to**  **water quality.**  **Therefore, this**  **technology is**  **screened out** 

**be cause**  **of the**  **adverse impacts**  **on health**  **and safety.** 

4.2 .1.4 Condensing Pulse Combustion (Gas, O il Storage, and Instantaneous)

**Pu lse**  **combustion burners**  **operate on**  **self­sustaining resonating**  **pressure waves** 

**th at**  **alternately rarefy**  **the combustion**  **chamber. Pulse**  **combustion systems**  **are capable**  **of**

**se lf­venting,**  **and can**  **draw o**  **utside air**  **for combustion**  **even when**  **installed inside.**  **Pulse**

**co mbustion**  **technologies can**  **achieve high**  **steady­state efficiencies**  **and condensing** 

**ope ration**  **without the**  **use of**  **fans or**  **blowers.**

**Pr ototype**  **gas­ and oil­fired**  **storage and**  **instantaneous water**  **heaters incorporating** 

**pu lse**  **combustion technologies**  **have been**  **developed in**  **t he**  **past. However,**  **this**

**te chnology**  **is not**  **prevalent among**  **commercially available**  **products, o**  **r even**  **among**

**wa ter**  **heater research**  **efforts. A**  **lthough condensing**  **pulse combustion**  **technology shows** 

**4­3 promising**  **results in**  **increasing EF,**  **it has**  **not yet**  **penetrated the**  **gas­fired storage,**  **oil­fired**

**st orage,**  **and instantaneous**  **water heater**  **markets. T**  **herefore, it**  **is not**  **technologically**

**fe asible**  **and not**  **practicable to**  **manufacture, install,**  **and service**  **condensing pulse** 

**co mbustion**  **technology on**  **the scale**  **necessary to**  **serve the**  **relevant market**  **at the**  **time of** 

**th e**  **effective date**  **of the**  **standard.**

4.2 .1.5 Advanced Forms of Insulation (Gas, E lectric, and Oil Storage)

**In sulating**  **gas­fired, electric,**  **and oil­fired**  **storage water**  **heaters with**  **vacuum,**

**in ert**  **gases, a**  **erogel, or**  **evacuated panels**  **is an**  **alternative to**  **increasing the**  **thickness of** 

**th e**  **insulation to**  **decrease heat**  **transfer and**  **standby losses.**  **M anufacturers**  **elect to**  **use**

**al ternative**  **types of**  **insulation because**  **increasing the**  **thickness of**  **insulation may**  **create**

**sh ipping**  **and installation**  **problems if**  **diameters exceed**  **standard building**  **clearance**

**wi dths.**  **H owever,**  **several factors**  **limit the**  **inclusion of**  **advanced forms**  **of insulation**  **into**

**pr oducts**  **today.**

**To t**  **he best**  **of DOE’s**  **knowledge, vacuum**  **insulation technology**  **has not**  **been**

**de monstrated**  **for water**  **heater applications**  **for either**  **production or**  **prototyping.**

**Du rability**  **and maintaining**  **the seal**  **over the**  **life of**  **the storage**  **water heater**  **are some** 

**pr oblems**  **of vacuum**  **insulation. Although**  **vacuum insulation**  **shows promising**  **potential**

**fo r**  **increasing EF,**  **no manufacturer**  **has incorporated**  **this technology**  **into a**  **c ommercially** 

**av ailable**  **product. Thus,**  **t he**  **reliability over**  **the life**  **of the**  **water heater**  **has not**  **been**

**de monstrated.**  **Therefore, it**  **is not**  **technologically feasible**  **and not**  **practicable to** 

**ma nufacture,**  **install, and**  **service vacuum**  **insulation technology**  **for gas­fired,**  **electric, and** 

**oi l­fired**  **storage water**  **heaters on**  **the scale**  **necessary to**  **serve the**  **relevant market**  **at the** 

**ti me**  **of the**  **effective date**  **of the**  **standard.**

**Ga s­filled**  **panel technology**  **has not**  **been demonstrated**  **for water**  **heater**

**1 applications**  **for both**  **production and**  **prototyping, to**  **t he**  **best of**  **DOE’s knowledge.** 

**P rototypes**  **have been**  **developed for**  **other applications**  **and insulation**  **improvements have** 

**be en**  **achieved. However,**  **gas­filled panel**  **technology has**  **not yet**  **penetrated the**  **gas­fired,**

**el ectric,**  **and oil­fired**  **storage water**  **heater markets.**  **Therefore, it**  **is not**  **technologically**

**fe asible**  **and not**  **practicable to**  **manufacture, install,**  **and service**  **gas­filled panel** 

**te chnology**  **for gas­fired,**  **electric, and**  **oil­fired storage**  **water heaters**  **on the**  **scale**

**ne cessary**  **to serve**  **the relevant**  **market at**  **the time**  **of the**  **effective date**  **of the**  **standard.**

**Ae rogel**  **insulation technology**  **has not**  **been demonstrated**  **in any**  **commercially**

**av ailable**  **water heater**  **applications to**  **the best**  **of DOE’s**  **knowledge. Although**  **aerogel**

**in sulation**  **shows promising**  **potential for**  **increasing EF,**  **it has**  **not yet**  **penetrated the** 

**st orage**  **water heater**  **market. Manufacturers**  **need to**  **address potential**  **problems. A**  **erogel**

**in sulation**  **is vulnerable**  **to shock**  **and vibration,**  **which may**  **create shipping**  **and**

**in stallation**  **problems if**  **specific handling**  **techniques are**  **required. In**  **addition, it**  **is**

**hy groscopic**  **and requires**  **thorough sealing**  **within the**  **cavity to**  **prevent exposure**  **to water** 

**so urces.**  **Th erefore,**  **it is**  **not technologically**  **feasible and**  **not practicable**  **to manufacture,** 

**in stall,**  **and service**  **aerogel insulation**  **technology for**  **gas­fired, electric,**  **and oil­fired** 

**st orage**  **water heaters**  **on the**  **scale necessary**  **to serve**  **the relevant**  **market at**  **the time**  **of the** 

**ef**

**fective date**  **of the**  **standard.**

**4­4 Evacuated­panel**  **technology has**  **not been**  **demonstrated for**  **water heater** 

**ap plications**  **for both**  **production and**  **prototyping, to**  **t he**  **best of**  **DOE’s knowledge.** 

**Pr ototypes**  **have been**  **developed for**  **other applications**  **and insulation**  **improvements have** 

**be en**  **achieved. However,**  **evacuated­panel technology**  **has not**  **yet penetrated**  **the gas** 

**f ired,**  **electric, and**  **oil­fired storage**  **water heater**  **markets. Th**  **erefore, it**  **is not** 

**te chnologically**  **feasible and**  **not practicable**  **to manufacture,**  **install, and**  **service**

**ev acuated­panel**  **technology for**  **gas­fired, electric,**  **and oil­fired**  **storage water**  **heaters on** 

**th e**  **scale necessary**  **to serve**  **the relevant**  **market at**  **t he**  **time of**  **the effective**  **date of**  **the**

**st andard.** 

4.2 .1.6 Thermophotovoltaic and Thermoelectric Generators (Gas, O il Storage, and

In stantaneous)

**Bo th**  **thermophotovoltaic and**  **thermoelectric generators**  **convert a**  **p ortion**  **of the** 

**en ergy**  **produced by**  **a g**  **as­ or oil­fired**  **water heater**  **burner into**  **electricity to**  **supply**

**au xiliary**  **components. T**  **his avoids**  **the requirement**  **of a**  **c onventional**  **auxiliary power** 

**sup ply.**  **Industry has**  **conducted research**  **on developing**  **thermophotovoltaic and** 

**th ermoelectric**  **technologies to**  **supply electricity**  **to water**  **heaters. For**  **example,**

**th ermoelectric**  **generators are**  **used for**  **pilot light**  **s afety**  **valves. H**  **owever, this**  **technology**

**opt ion**  **has not**  **been developed**  **to supply**  **auxiliary power**  **for larger**  **applications, s**  **uch as** 

**fa ns**  **or electromechanical**  **dampers, f**  **or use**  **with water**  **heater products.**  **C urrently,**  **it is**  **not**

**pr actical**  **to manufacture,**  **install, or**  **service thermophotovoltaic**  **and thermoelectric** 

**ge nerator**  **technology for**  **water heaters**  **on a**  **s cale**  **necessary to**  **serve the**  **relevant market.** 

**The refore,**  **these technology**  **options are**  **not considered**  **technologically feasible.** 

4.2 .1.7 U­Tube Flue (Gas and Oil Storage)

**The standard**  **length of**  **a f**  **lue in**  **a g**  **as or**  **oil­fired water**  **heater is**  **doubled by** 

**in corporating**  **an inverted**  **U­shaped flue**  **into the**  **water heater.**  **A U**  **­tube flue**  **increases the** 

**he at**  **transfer by**  **increasing the**  **heat transfer**  **surface area.**  **Additionally, a**  **U ­tube**  **reduces**

**st andby**  **losses because**  **the shape**  **resists heat**  **convection, similar**  **to a**  **f lue**  **damper.**

**U­ tube**  **flue technology**  **is not**  **incorporated into**  **any commercially**  **available gas**  **or**

**oi l­fired**  **water heaters.**  **P rototypes**  **have been**  **developed and**  **research is**  **currently**

**un derway.**  **However, this**  **technology has**  **not been**  **successfully demonstrated**  **in the** 

**ma rket,**  **and the**  **energy efficiency**  **benefits can**  **not be**  **determined due**  **to the**  **lack of** 

**av ailable**  **products. Th**  **erefore, it**  **is not**  **practical t**  **o manufacture**  **U­tube flue**  **technology to** 

**se rve**  **the relevant**  **market at**  **the time**  **of the**  **effective date**  **of this**  **standard.**

4.2 .1.8 Reduced Burner Size (Slow Recovery) (Gas, O il Storage, and Instantaneous)

**De creasing**  **the burner**  **size to**  **increase the**  **ratio of**  **heat transfer**  **area to**  **energy**

**inp ut**  **can increase**  **the recovery**  **efficiency of**  **gas and**  **oil­fired and**  **instantaneous water** 

**he aters.**  **H owever,**  **the decreased**  **input decreases**  **the recovery**  **rate, which**  **in turn,**  **would**

**mo st**  **likely reduce**  **the first­hour**  **rating. (First­hour**  **rating directly**  **relates to**  **the amount**  **of**

**ho t**  **water the**  **water heater**  **can supply**  **to the**  **consumer.) Th**  **is derating**  **of the**  **water heater** 

**ad versely**  **affects the**  **utility to**  **consumers. Additionally,**  **first­hour rating**  **is directly** 

**4­5 related**  **to burner**  **size: as**  **burner size**  **decreases, th**  **e amount**  **of hot**  **water available**  **to the** 

**co nsumer**  **also decreases.**  **Therefore, DOE**  **will not**  **consider this**  **technology option.** 

4.2 .1.9 Two­Phase Thermosiphon (Gas and Oil Storage)

**TPTS removes**  **the flue**  **from the**  **center of**  **a g**  **as or**  **oil­fired storage**  **water heater** 

**an d**  **places a**  **h eat**  **exchanger outside**  **of the**  **storage tank**  **reducing standby**  **losses. Th**  **is is** 

**si milar**  **to the**  **side­arm heater**  **technology option.** 

**Ma nufacturers**  **have developed**  **working prototype**  **water heaters**  **using TPTS.** 

**Se veral**  **units are**  **commercially available**  **for solar**  **water heating**  **applications, b**  **ut not**  **for**

**ga s**  **or oil­fired**  **storage water**  **heating. TPTSs**  **used for**  **solar applications**  **rely on**  **large**

**de signs**  **with large**  **surface areas**  **to maximize**  **sun exposure.**  **Large TPTSs**  **are not**  **practical**

**fo r**  **indoor installations**  **using gas**  **or oil.**  **Also, incorporating**  **the TPTS**  **s ystem**  **would**

**ca use**  **a d**  **rastic redesign**  **of all**  **gas and**  **oil­fired storage**  **water heaters**  **with little**  **increase in** 

**en ergy**  **efficiency. The**  **redesign would**  **involve removing**  **the center**  **flue and**  **relocating it** 

**ou tside**  **the tank.**  **As a**  **r esult,**  **only the**  **standby losses**  **would decrease**  **with no**  **affect on** 

**st eady­state**  **efficiency.**

**TPTS for**  **gas and**  **oil­fired water**  **heaters is**  **currently being**  **researched. Therefore,** 

**it is**  **not practicable**  **to manufacture,**  **install, and**  **service this**  **technology on**  **the scale** 

**ne cessary**  **to serve**  **the relevant**  **market at**  **the time**  **of the**  **effective date**  **of the**  **standard.**

4.2 .1.10 CO 2 Heat Pump Water Heater (Electric Storage)

**CO 2**  **heat pump**  **water heaters**  **use carbon**  **dioxide as**  **a n**  **atural refrigerant**  **to**

**tr ansfer**  **heat from**  **the surrounding**  **air to**  **the water**  **stored in**  **the tank**  **through a**  **h eat**  **pump**

**lo op.**  **Current products**  **and prototypes**  **can achieve**  **coefficients of**  **performance as**  **high as** 

**2 3.0, which**  **correspond to**  **EFs ranging**  **from approximately**  **1.0 t**  **o 3.0.**  **This range** 

**ac counts**  **for differences**  **in ambient**  **air conditions,**  **storage tank**  **efficiency, and** 

**ef**

**ficiencies of**  **the components**  **that make**  **up t**  **he heat**  **pump loop.**  **Additionally, p**  **roducts**

**ar e**  **capable of**  **functioning in**  **cold weather**  **climates without**  **freezing pipes**  **or frosting** 

**ev aporators**  **on outdoor**  **installations. P**  **roducts are**  **predominantly available**  **outside of** 

**U.S**

**. markets**  **where they**  **have been**  **made available**  **by government**  **subsidy rebate** 

**3 programs.**  **The necessary**  **infrastructure to**  **support manufacturing,**  **installation, and** 

**se rvice**  **of a**  **C O**  **2 heat**  **pump water**  **heater is**  **not available**  **in the**  **United States**  **on the**  **scale**

**ne cessary**  **to serve**  **the relevant**  **market at**  **the time**  **of the**  **effective date**  **of the**  **standard.**

**The refore,**  **DOE no**  **longer considers**  **CO 2**  **heat pump**  **water heaters**  **for the**  **engineering**

**an alysis.** 

4.2 .2 Direct Heating Equipment

**The following**  **technology options**  **are screened**  **out for**  **residential direct**  **heating**

**eq uipment:**  **increased heat**  **transfer coefficient,**  **p ower**  **burner, condensing**  **pulse**

**co mbustion,**  **and improved**  **fan or**  **blower motor**  **efficiency.**

**4­6**4.2.2.1 Increased Heat Transfer Coefficient (Fan Wall, Gravity Wall, Floor, Room)

**An alternative**  **to increasing**  **the size**  **of the**  **heat exchanger**  **is enhancing**  **the inside** 

**an d**  **outside heat**  **transfer coefficients**  **of the**  **heat e**  **xchanger. Incorporating**  **dimples or** 

**so me**  **other surface**  **feature to**  **enhance turbulence**  **can increase**  **the heat**  **transfer coefficient** 

**wh en**  **correctly designed.**  **Also, the**  **heat exchanger**  **may be**  **constructed of**  **a m**  **aterial with** 

**a h**  **igher thermal**  **conductivity than**  **the standard**  **cold rolled**  **steel that**  **is typically**  **used.**

**In creasing**  **the heat**  **transfer coefficient**  **for direct**  **h eating**  **equipment is**  **still in**  **the**

**re search**  **stages and**  **prototypes have**  **been developed.**  **However, this**  **technology has**  **not**

**be en**  **demonstrated in**  **the relevant**  **market, and**  **the energy**  **efficiency benefits**  **cannot be** 

**de termined**  **due to**  **a l**  **ack of**  **available products.**  **C urrently,**  **it would**  **not be**  **practical to** 

**ma nufacture**  **this technology**  **to serve**  **the relevant**  **market at**  **the time**  **of the**  **effective date** 

**of this**  **standard. DOE**  **does not**  **consider increased**  **heat transfer**  **coefficient any**  **further as** 

**a t**  **echnology for**  **direct heating**  **equipment.**

4.2 .2.2 Power Burner (Fan Wall, Gravity Wall, Floor, Room)

**Fa n­assisted**  **combustion can**  **be accomplished**  **by power**  **burner systems** 

**po sitioned**  **upstream of**  **the combustion**  **zone. Power**  **burners use**  **blowers upstream**  **of the** 

**co mbustion**  **zone to**  **supply a**  **m ore**  **efficient fuel­air**  **mixture to**  **the burner.**  **Power burners** 

**al so**  **reduce off­cycle**  **losses by**  **restricting air**  **flow and**  **convection of**  **warm air**  **to the**  **vent**

**sy stem,**  **similar to**  **a v**  **ent or**  **combustion box**  **damper.**

**Po wer**  **burners are**  **typically associated**  **with larger**  **scale applications**  **including**

**co mmercial**  **furnaces, b**  **oilers, a**  **nd oil­fired**  **water heaters.**  **A dditionally,**  **p ower**  **burners are** 

**ty**

**pically used**  **for high**  **input devices**  **that operate**  **over 100,000**  **Btu/h, although**  **units**

**ope rating**  **below t**  **his level**  **do exist.**  **The direct**  **heating equipment**  **identified in**  **this**

**pr eliminary**  **rulemaking operates**  **below t**  **his rating,**  **on average.**  **The product**  **classes**

**id entified**  **for this**  **rule range**  **from 10,000**  **Btu/h and**  **less to**  **46,000 Btu/h**  **and higher,**  **and**

**th e**  **majority of**  **products fall**  **between these**  **ranges. The**  **average product**  **has an**  **input**

**ra ting**  **of approximately**  **39,000 Btu/h.**  **Space near**  **the combustion**  **chamber must**  **be**

**al located**  **for the**  **power burner**  **as well.**  **DOE surveyed**  **manufacturing literature,**  **which**

**su ggests**  **that approximately**  **1 c**  **ubic foot**  **of space**  **is r**  **equired for**  **power burners**  **with**

**inp uts**  **from 30,000**  **to 200,000**  **Btu/h. Assuming**  **no space**  **is available**  **for a**  **p ower**  **burner,**

**1 c**  **ubic foot**  **would be**  **approximately more**  **than a**  **1 0­percent**  **increase in**  **volume for**  **the**

**av erage**  **heater covered**  **by this**  **rule.**

**Po wer**  **burners are**  **still being**  **researched, and**  **development for**  **small applications** 

**su ch**  **as gas­fired**  **direct heating**  **equipment is**  **still underway.**  **It is**  **not practical**  **to**

**ma nufacture**  **this technology**  **to serve**  **the relevant**  **market at**  **the time**  **of the**  **effective date** 

**of this**  **standard. DOE**  **will not**  **consider power**  **burners any**  **further in**  **the engineering** 

**an alysis.** 

4.2 .2.3 Condensing Pulse Combustion (Fan Wall, Gravity Wall, Floor, Room)

**Pu lse**  **combustion burners**  **operate on**  **self­sustaining resonating**  **pressure waves** 

**th at**  **alternately rarefy**  **the combustion**  **chamber. Pulse**  **combustion systems**  **are capable**  **of**

**4­7 self­venting,**  **and can**  **draw o**  **utside air**  **for combustion**  **even when**  **installed inside.**  **Pulse**

**co mbustion**  **technologies can**  **achieve high**  **steady­state efficiencies**  **and condensing** 

**ope ration**  **without fans**  **or blowers.** 

**Si milar**  **to the**  **condensing pulse**  **combustion technology**  **option considered**  **for**

**re sidential**  **water heaters,**  **this pulse**  **combustion technology**  **is not**  **prevalent among** 

**co mmercially**  **available DHE**  **p roducts.**  **Th erefore,**  **the pulse**  **combustion technology** 

**opt ion**  **will not**  **be considered**  **as a**  **m eans**  **to condense**  **flue gases**  **in direct**  **heating**

**eq uipment**  **because it**  **is not**  **technologically feasible**  **for DHE**  **applications.**

4.2 .2.4 Improve Fan or Blower Motor Efficiency (Fan Wall)

**Fa n**  **or blower**  **motor efficiency**  **can be**  **increased to**  **reduce the**  **electrical energy** 

**co nsumption**  **of the**  **DHE by**  **using a**  **b rushless**  **direct current**  **(DC) motor,**  **which**

**el iminates**  **the friction**  **caused by**  **the brushes**  **of a**  **p ermanent**  **split capacitor**  **(PSC) motor.** 

**As suming**  **a f**  **an or**  **blower motor**  **installed in**  **DHE is**  **a 1**  **/20 horsepower**  **motor**

**(a**

**pproximately 127**  **Btu/h) and**  **is operating**  **as low**  **a s**  **50­percent efficiency,**  **the resulting** 

**en ergy**  **consumption of**  **the motor**  **is small.**  **Assuming a**  **h eater**  **operates at**  **an input**  **of**

**ap proximately**  **45,000 Btu/h**  **or greater,**  **the motor**  **accounts for**  **less than**  **one percent**  **of**

**th e**  **total power**  **consumption of**  **the direct**  **heating equipment.**  **Motor efficiency**  **could**

**im prove**  **by approximately**  **20 percent**  **when switching**  **from PSC**  **to brushless**  **motors;**

**ho wever,**  **the overall**  **improvement to**  **the DHE**  **is less**  **than one**  **percent.**

**Ma nufacturers**  **of DHE**  **use high­efficiency**  **PSC motors**  **d ue**  **to their**  **modest cost,** 

**hi gh**  **efficiency, compact**  **design, and**  **durability. Achieving**  **more efficient**  **PSC motor** 

**de signs**  **for DHE**  **applications is**  **an ongoing**  **challenge and**  **no substantial**  **gain in**  **energy**

**ef**

**ficiency has**  **occurred in**  **recent years.**  **E fficiency**  **could be**  **improved by**  **increasing rotor** 

**su rface**  **area, which**  **would increase**  **overall motor**  **size. However,**  **energy efficiency** 

**im provements**  **are difficult**  **to achieve**  **because of**  **size constraints**  **within DHE**  **and**

**be cause**  **the affect**  **on energy**  **efficiency would**  **be low.**  **Brushless DC**  **motors may**  **increase**

**en ergy**  **efficiency, b**  **ut this**  **technology has**  **not yet**  **penetrated the**  **market due**  **to cost** 

**co nstraints.**  **Th erefore,**  **it is**  **not practical**  **to manufacture,**  **install, and**  **service this** 

**te chnology**  **for fan**  **wall DHE**  **on the**  **scale necessary**  **to serve**  **the relevant**  **market at**  **the**

**ti me**  **of the**  **effective date**  **of the**  **standard.**

4.2 .3 Pool Heaters

**The following**  **technology option**  **is screened**  **out for**  **pool heaters:**  **condensing**

**pu lse**  **combustion.**

**4­8**4.2.3.1 Condensing Pulse Combustion

**Pu lse**  **combustion burners**  **operate on**  **self­sustaining resonating**  **pressure waves** 

**th at**  **alternately rarefy**  **the combustion**  **chamber and**  **draw o**  **utside air**  **without fans**  **or**

**bl owers.**  **A dditionally,**  **p ulse**  **combustion technologies**  **can achieve**  **high steady­state** 

**ef**

**ficiencies and**  **condensing operation**  **without fans**  **or blowers.**  **H igh­efficiency**  **gas­fired**

**bo ilers**  **using pulse**  **combustion are**  **currently available.**  **However, p**  **ulse combustion**  **pool**

**he aters**  **are not**  **known to**  **exist, and**  **DOE did**  **not identify**  **any prototypes**  **or research** 

**ef**

**forts. Th**  **erefore, DOE**  **is not**  **considering this**  **technology option**  **further because**  **it is**  **not**

**te chnologically**  **feasible at**  **this time,**  **and it**  **is not**  **practical to**  **manufacture, install,**  **and**

**se rvice**  **on the**  **scale necessary**  **to serve**  **the relevant**  **market at**  **the time**  **of the**  **effective date** 

**of this**  **standard.**

4.3 REMAINING TECHNOLOGIES

**Af ter**  **eliminating those**  **technologies that**  **have no**  **effect or**  **do not**  **increase energy** 

**ef**

**ficiency and**  **screening out**  **those technologies**  **that that**  **do not**  **meet the**  **requirements of** 

**se ctions**  **4(a)(4) and**  **5(b) of**  **the Process**  **Rule, DOE**  **i s**  **considering the**  **technologies in**  **the**

**fo llowing**  **list.**

• **Water Heaters** 

• **Insulation improvements** 

• **Increased jacket**  **insulation (gas,**  **e lectric,**  **oil storage)** 

• **Insulated tank**  **bottom (electric**  **storage)**

• **Plastic tank**  **(electric storage)** 

• **Foam insulation**  **(gas, e**  **lectric, oil**  **storage)**

• **Heat Exchanger**  **Improvements**

• **Increased heat**  **exchanger surface**  **area (gas,**  **e lectric,**  **oil storage,** 

**in stantaneous)** 

• **Enhanced flue**  **baffle (gas,**  **o il**  **storage)**

• **Submerged combustion**  **(gas, o**  **il storage)** 

• **Multiple flues**  **(gas, o**  **il storage)** 

• **Direct vent**  **(instantaneous)**

• **Alternative flue**  **geometry (helical)**  **(gas, o**  **il storage)** 

• **Heat traps**  **(oil storage)** 

• **Power vent**  **(gas, o**  **il storage,**  **instantaneous)**

• **Flue damper**  **(electromechanical) (gas,**  **o il**  **storage)**

• **Electronic (or**  **interrupted) ignition**  **(gas, o**  **il storage,**  **instantaneous)**

• **Integral heat**  **pump water**  **heater (electric**  **storage)**

• **Condensing (gas,**  **o il**  **storage, instantaneous)** 

**4­9**• **Direct Heating**  **Equipment**

• **Heat exchanger**  **improvements**

• **Increased heat**  **exchanger surface**  **area (fan**  **wall, gravity**  **wall, floor,** 

**ro om)** 

• **Multiple flues**  **(fan wall,**  **gravity wall,**  **floor, room)** 

• **Multiple turns**  **in flue**  **(fan wall,**  **gravity wall,**  **floor, room)** 

• **Direct vent**  **(concentric venting)**  **(fan wall,**  **gravity wall,**  **floor, room)** 

• **Electronic ignition**  **(fan wall,**  **gravity wall,**  **floor, room)** 

• **Thermal vent**  **damper (fan**  **wall, gravity**  **wall, floor,**  **room)**

• **Electrical vent**  **damper (fan**  **wall, gravity**  **wall, floor,**  **room)**

• **Induced draft**  **(fan wall,**  **gravity wall,**  **floor, room)** 

• **Increased insulation**  **(floor)**

• **Condensing (fan**  **wall, gravity**  **wall, floor,**  **room)**

• **Two­stage and**  **modulating operation**  **(fan wall,**  **gravity wall,**  **floor, room)** 

• **Air circulation**  **fans (floor,**  **room)**

• **Sealed combustion**  **(fan wall,**  **gravity wall,**  **floor, room)** 

• **Pool Heaters** 

• **Improved heat**  **exchanger design** 

• **More effective**  **insulation (combustion**  **chamber)**

• **Power venting** 

• **Sealed combustion** 

• **Condensing**

**4­10**REFERENCE

**1 L**  **awrence Berkeley**  **National Laboratory.**  Gas F illed Panels

**. Last**  **accessed March** 

**19**

**, 2008.**  **< h**  **ttp://gfp.lbl.gov/applications/default.htm>.**

**2 En**  **hanced, Compact**  **and Ultra­Compact**  **Heat Exchangers:**  **Science, Engineering** 

**an d**  **Technology.** D evelopment of a New Type Heat Exchanger for Natural Refrigerant

CO 2 Heat Pump Water Heaters. **Last accessed**  **March 19,**  **2008.**

**<h ttp://www.r744.com/knowledge/papers/files/pdf/pdf_190.pdf>.** 

**3 Th**  **e Latest**  **Developments in**  **the Use**  **of CO**  **2 as**  **Refrigerant.** IEA He at Pump News

Le tter

**. Volume**  **24, No** 

**. 3/2006.**  **Last accessed**  **March 19,**  **2008.**

**<h ttp://www.heatpumpcentre.org/publ/HPCOrder/ViewDocument.aspx?RapportId=396>** 

**.**

**4­11**