4

- i CHAPTER 4. SCREENING ANALYSIS

TABLE OF CONTENTS

4.1 INTRODUCTION

................................ ................................ ................................ ........... 4

- 1 4.2 SCREENED

- OUT TECHNOLOGIES

................................ ................................ ............ 4

- 2 4. 2.1 Furnace Energy Efficiency Standards

................................ ................................ .. 4

- 2 4.2.2 Central Air Conditioner and Heat Pump Energy Efficiency Standards

............... 4

- 4 4.2.3 Standby Mode and Off Mode Power Consumption Standards

............................ 4

- 4 4.3 REMAINING TECHNOLOGI ES

................................ ................................ ................... 4

- 6 4.3.1 Furnace Energy Efficiency Standards

................................ ................................ .. 4

- 6 4.3.2 Central Air Conditioner and Heat Pump Energy Efficiency Standards

............... 4

- 6 4.3.3 Standby Mode and Off Mode Power Consumption Standards

............................ 4

- 74

- 1 4.1 INTRODUCTION

This chapter details the screening analysis that the U.S. Department of Energy (DOE) conducted in support of the direct final rule for energy conservation standards for residential furnaces and central air conditioners and heat pumps

.
In the market and technology assessment (MTA; c hapter 3), DOE presents an initial list of technologies that manufacturers can use to improve the energy efficiency of residential furnaces

, central air conditioners and heat pumps

, or their standby and off mode electrical powe r consumption

. The purpose of the screening analysis is to evaluate the technologies that improve product energy efficiency or reduce standby and off mode energy consumption to determine which technologies DOE should consider further in the rulemaking anal yses. DOE consulted a range of parties, including industry and technical experts and others, to develop a list of technologies for consideration in the market assessment (see chapter 3 of the TSD)

. Some of these technologies can reduce annual
energy consum ption of products in actual applications but may not improve the annual fuel utilization efficiency (AFUE) , seasonal energy efficiency ratio (SEER), heating seasonal performance factor (HSPF), or reduce standby and off mode electrical power consumption

. Th ese rating metrics are measured according to DOE regulations at 10 CFR 430 Subpart B, Appendices M and N, which incorporate by reference various industry test procedures. DOE removed from consideration those technologies that do not increase AFUE , SEER, or HSPF or reduce standby and off mode electrical power consumption per the DOE test procedures. DOE evaluated t he remaining technologies pursuant to the criteria in t he Energy Policy and Conservation Act (EPCA), as amended. (42 U.S.C. 6311

- 6317)

Section 325 (o) of EPCA establishes criteria for prescribing new or amended standards designed to achieve the maximum improvement in energy efficiency

. Furthermore, EPCA directs the Secretary of Energy to determine whether a standard is technologically feasible and ec onomically justified. (42 U.S.C. 6295(o)(2)(A)(B)) In view of this requirement, 10 CFR Part 430 Subpart C, Appendix A

, Procedures, Interpretations and Policies for Consideration of New or Revised Energy Conservation Standards for Consumer Products (the Pro cess Rule), guides DOE in its consideration and promulgation of new or revised product efficiency standards. These procedures elaborate on the statutory criteria provided in 42 U.S.C. 6295(o) and, in part, eliminate problematic technologies early in the process of prescribing or amending an energy efficiency standard. In particular, DOE determines whether to eliminate from consideration any technology that presents unacceptable problems with respect to the following criteria:

Technological feasibility. Te chnologies that are not incorporated in commercial products or in working prototypes will not be considered further

. Practicability to manufacture, install, and service. If it is determined that mass production of a technology in commercial products and r eliable installation and servicing4

- 2 of the technology could not be achieved on the scale necessary to serve the relevant market at the time of the effective date of the standard, then that technology will not be considered further.

I mpacts on product utilit y to consumers. If a technology is determined to have significant adverse impact on the utility of the product to significant subgroups of consumers or result s in the unavailability of any covered product type with performance characteristics (including re liability), features, sizes, capacities, and volumes that are substantially the same as products generally available in the U.S. at the time, it will not be considered further.

S afety of technologies

. If it is determined that a technology will have signifi cant adverse impacts on health or safety, it will not be considered further. In sum, if DOE determine s that a technology, or a combination of technologies, has unacceptable impacts on the policies stated in section 5(b) of the Process Rule, it will be elim inated from consideration. If a particular technology fails to meet one or more of the four criteria, it will be screened out from further consideration in the engineering analysis

. 61 FR 36974

- 36987 ; 10 CFR part 430, subpart C, ap pendix A, section (5)(b)

. The reasons for eliminating any technology are documented in section 4.2

.

4.2 SCREENED

- OUT TECHNOLOGIES

This section describes the technologies that D OE eliminated based on consideration of the following four factors: 1) technological feasibility; 2) practicability to manufacture, install, and service; 3) adverse impacts on product utility or product availability ; and 4) adverse impacts on health or saf ety

.

4.2.1 Furnace Energy Efficiency (i.e., AFUE) Standards

DOE eliminated the following technology options for residential furnaces from further consideration: condensing and near

- condensing technologies for weatherized furnaces; pulse combustion; low NO X

4.2.1.1 Condensing and Near

- Condensing Technologies for Weatherized Gas Furnaces prem ix burners; derating; advanced forms of insulation; and low

- pressure, air

- atomized oil burner s

.

Non

- weatherized g as furnaces can yield efficienc ies of up to 98 percent AFUE by utilizing condensing technology

. However, a lthough weatherized gas furnaces are nearly identical to their non

- weatherized counterparts, they cannot reliably achieve the same efficiency levels b e cause they are installed outdoors and are often exposed to harsh weather conditions

. Installing a condensing furnace in below freezing outdoor temperatures can lead to frozen condensate, which can disrupt proper operation of the furnace, rendering it unreliable and decreasing consumer utility

. W eatherized gas fur naces are limited by their inability to prevent condensate from freezing when the outdoor temperature drops below freezing.4

- 3 T o the best of DOE’s knowledge, m anufacturers and others have not succeeded in developing a weatherized gas furnace that can preven t condensate from freezing. DOE notes, however, that a U.S. patent has been granted for a condensate drainage system for condensing, weatherized furnaces. 1

4.2.1.2 Pulse Combustion However, the grant of a patent does not necessarily indicate a proof of concept. In this case, DOE w as unable find evidence that the patented design had been demonstrated in a working prototype. As a result

, because DOE could not identify this technology in commercial products or in working prototypes, DOE did not consider condensing or near

- condensing w eatherized gas furnaces to be technologically feasible. Furthermore, as noted above, DOE believes that frozen condensate has the potential to disrupt proper operation of the furnace, which will ultimately decrease consumer utility. For these reasons, DOE e xclude d this technology option f rom further consideration in these rulemaking analyses.

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

- heating of the mixture to its flash point) . Pulse combustion systems are capable direct venting without the assistance of mechanical draft. Because the p ulse combustion process is very efficien t, pulse combustion is generally used in condensing appliances.

In contrast to natural draft and induced draft furnaces , pulse combustion furnaces generate positive pressure in the heat exchanger. This cre ates a potential safety problem becau se combustion products can contaminate the circulation

- air stream if the heat exchanger breeches

.
Pulse combustion gas furnaces were available in the United St ates for more than two decades. However, they were withdrawn from the market because manufacture rs found that competing technologies

, such as condensing

, secondary heat exchanger s , cost significantly less to manufacture and operate. In light of the ability of furnace manufacturers to cost

- effectively achieve high efficienc ies without the use of pulse combustion, DOE believes that the technology’s risks to health and safety do not outweigh its benefits. DOE did not further analyze this technology option as part of this rulemaking.

4.2.1.3 Low NO X Premix Burners

Premix burners work by completely mixing primary air and fuel prior to combustion, eliminating the need for secondary air. However, atmospheric burners cannot entrain sufficient primary air to completely premix the air and gas. Therefore, to ensure suffici ent and complete mixing, the burner incorporates a fan to deliver combustion air at positive pressure. T o the extent of DOE’s knowledge, low NO X premix burners have not yet been successfully incorporated into a residential furnace design ; and technological feasibility in a furnace has not been proven. For this reason, D OE did not consider this technology option further in the rulemaking analyses.4

- 4 4.2.1.4 Burner Derating

Decreasing the burner size to increase the ratio of heat transfer area to fuel input

, or burner derating, can increase the AFUE rating of gas and oil

- fired furnaces . However, because heat output rate is directly related to burner size, derating also reduces the amount of heated air available to the consumer. This reduction in heat output adversely

a ffects the utility to consumers. Therefore, DOE did not consider this technology option.

4.2.1.5 Advanced Forms of Insulation

Insulating furnaces with foam, a vacuum, inert gases, aerogel, or evacuated panels is an alternative to increasing the thickness of the in sulation to decrease jacket heat loss

. Manufacturers may elect to use alternative types of insulation because increasing the thickness of insulation may create shipping and installation problems if the footprint exceed s typical dimensions

. However, DOE notes that none of these technologies has been applied to residential furnaces in the past or present, and as a result, DOE has insufficient information to judge the merits and practicability of incorporating advanced forms of insulation into residential f urnaces. DOE eliminated this technology option from further consideration.

4.2.1.6 Low

- Pressure, Air

- Atomized Oil Burner

To overcome the low input limitations of conventional oil burners, Brookhaven National Laboratory developed a low

- pressure , air

- atomized oil burner that can operate at firing rates as low as 0.25 gallons of oil per hour (10 kW). In addition, i t can operate with low levels of excess combustion air (less than 10 percent) for lean

- burning, ultra

- clean combustion. A lower level of excess air genera lly improves AFUE rating. This burner design is also capable of firing fuel at a high or low input rate , which is manually actuated by a switch, allowing the burner to closely match the smaller heating loads of well

- insulated modern homes.

While t ests per formed at the Brookhaven National Laboratory seem to have successfully demonstrated enhanced oil boiler AFUE performance per the DOE test procedure for furnaces an d boilers, the prototype was never tested on a furnace. 2

4.2.2 Central Air Conditioner and Heat Pump Energy Efficiency Standards Therefore, the technological feasibility of the burner prototype for incorporation into a residential oil

- fired furnace remains unknown, and DOE does not consider low

- pressure, air

- atomized oil burners to be a viable technology for efficiency improvement a t this time.

DOE did not eliminate any technology options from consideration in its SEER and HSPF standards rulemaking analysis for central air conditioners and heat pumps.

4.2.3 Standby Mode and Off Mode Power Consumption Standards

DOE screened out from consideration electronically commutated motor ( ECM ) control relays in its residential furnaces standby power consumption standards analysis4

- 5 and its central air conditioner and heat pump off mode p ower consumption standards analysis

.

4.2.3.1 ECM Control Relay

While PSC blower motors do not draw any power w hen off , ECM blower motor s and their associated controls consume an average of 3 watts in order to provide power to

an integral control board for modulat ing the fan speed. To reduce standby power consumption of a furnace and off mode consumption of a central air conditioner or heat
pump equipped with an ECM blower, DOE considered adding a relay to the circuit to disconnect the blower motor ’s control circui t when not in use. A typical relay activates a switch when current runs through it

, and a spring holds the switch open when there is no
current flow

. Manufacturer fee dback provided during the interview process (see chapter 12 of this TSD) indicated that EC Ms are subject to an inrush of current upon start up . The power supply on the ECM’s control board, which is typically a switching mode power supply

, cannot withstand the repeated surge of current that occurs at ECM startup and, therefore, completely depower ing and reactivating the motor by use of a control relay

w ould shorten the motor’s lifetime significantly

. DOE considers a premature failure of the blower to be a reliability issue that has an adverse impact on product utility to the

consumer. Therefore, DOE believes that disconnection of an ECM fan motor when the blower is not in use should not be consider ed in the engineering analysis. In addition, DOE has not found any HVAC products that utilize a control relay or other mechanism to disconnec t the ECM fan when the product in standby or off mode

. Therefore, DOE did not consider this technology option for this rulemaking.4

- 6 4.3 REMAINING TECHNOLOGI ES

After eliminating those technologies that have no effect or do not increase energy efficiency and scr eening out those technologies that that do not meet the requirements of sections 4(a)(4) and 5(b) of the Process Rule, DOE considered the technologies in the following sections.

4.3.1 Furnace Energy Efficiency Standards

For its AFUE standards rulemaking analysis , DOE considered the following technology options:

**•** Condensing secondary heat exchanger for non

- weatherized furnaces

**•** Heat exchanger improvements for non

- weatherized furnaces

o Increased heat exchanger surface area

o Heat exchanger surface features

o Heat exchange r baffles and turbulators

**•** Two

- stage and modulating combustion

**•** Insulation i mprovements

o Increased j acket i nsulatio n

**•** Off

- cycle dampers

o Electro

- mechanical flue damper

o Electro

- mechanical burner inlet damper

**•** Concentric venting

**•** High

- static oil burner

**•** Delayed

- acti on oil pump solenoid valve

4.3.2 Central Air Conditioner and Heat Pump Energy Efficiency Standards

For its SEER and HSPF standards rulemaking analysis, DOE considered the following technology options:

**•** H igher efficiency fan motors

**•** H igher efficiency fan blades

**•** H igher efficiency expansion valves

**•** I mproved evaporator coils

**•** I mproved condenser coils

**•** H igher efficiency compressors

**•** M icrochannel heat exchangers

**•** F lat

- tube heat exchangers

**•** I nverter technology

**•** H eat pump defrost cycle controls4

- 7 4.3.3 Standby Mode and Off Mode Power Consumption Standards

Because DOE is required by EPCA, as amended by EISA 2007, to include a descriptor for standby mode and off mode energy consumption for residential furnaces and a descriptor for off mode energy consumption for central air conditioners and heat pumps, a separate screening analysis was conducted for standby and off mode design options. (42 U.S.C. 6295(gg)(2)(A))

DOE identified the following design options that are capable of reducing the standby and off mode electrical power consumption o f furnaces and central air conditioners and heat pumps, respectively :

Table 4.3

. 1 Screened

- In Standby Mode and Off Mode Design Options

Design Option Residential Furnaces C entral Air Conditioners and Heat Pumps Toroidal transformer X X Switching mode power supply X Thermostatically controlled crankcase heater X

Self

- regulating ( i.e., variable resistance) crankcase heater X
Compressor cover X4

- 8 REFERENCE S

1 United States Patent US6684878
, http://www.freepatentsonline.com/6684878.pdf

2 Butcher, T. A., R. Krajewski, L. R., Y. Celebi, F. L., and B. Kamath. Residential Oil Burners with Low Input and Two

- Stage Firing . ASHRAE Transactions . 1997. 103 Pt. 1: pp. 928

- 935.PH

- 97

- 13

- 4.