CHAPTER 4. SCREENING ANALYSIS

TABLE OF CONTENTS

4.1 INTRODUCTION

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

- 1 4.2 TECHNOLOGIES THAT DO NOT IMPACT AFUE OR S TANDBY AND OFF MODE ENERGY CONSUMPTION

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

- 2 4.3 SCREENED OUT TECHNOL OGIES

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

- 3 4.3.1 Pulse Combustion

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

- 3 4.3.2 Control Relay for Models with Brushless Permanent Magnet (BPM) Motors (Standby/Off Mode)

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

- 4 4.4 REMAINING TECHNOLOGI ES

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

- 4 4.4.1 AFUE Efficiency Standards

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

- 4 4.4.2 Standby Mode an d Off Mode Power Consumption Standards

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

- 54

- 1 C H APTER 4

. SCREENING ANALYSIS

4.1 INTRODUCTION

This chapter discusses the screening analysis conducted by the U.S. Department of Energy (DOE) of the technology options identified in the market and technology assessment for residential boilers (chapter 3). In the market and technology assessment, DOE pr esented an initial list of technology options that can be used to reduce energy consumption of residential boilers . The goal of the screening analysis is to identify any technology o ptions that will be eliminated from further consideration in the rulemakin g analyses.

The candidate technology options are assessed based on information gathered during DOE research, as well as inputs from stakeholders including manufacturers, trade organizations, and energy efficiency advocates. Technology options which are j udged to be viable approaches for improving energy efficiency are retained as inputs to the subsequent engineering analysis. Technology options which are not incorpor ated in commercial products or in working prototypes, or that fail to meet certain criteri a as to practicability to manufacture, install and service, as to impacts on product utility or availability, or as to health or safety will be eliminated from consideration in accordance with 10 CFR 430, subpart C, appendix A, section 4(a)(4)(i

- iv).

DOE uses the following four screening criteria to determine which technology options are suitable for further consideration in an energy conservation standards rulemaking:

1. Technological feasibility

. DOE will consider technologies incorporated in commercia l products or in working prototypes to be technologically feasible.

2. Practicability to manufacture, install, and service

. If mass production and reliable installation and servicing of a technology in commercial products could be achieved on the scale

ne cessary to serve the relevant market at the time the standard comes into effect, then DOE will consider that technology practicable to manufacture, install, and service.

3. Adverse impacts on product utility or product availability

. If DOE determines a
t echnology would have a significant adverse impact on the utility of the product to significant subgroups of c onsumers , or would result in the unavailability of any covered product type with performance characteristics (including reliability), features, siz es, capacities, and volumes that are substantially the same as products generally available in the United States at the time, it will not consider this technology further.

4. Adverse impacts on health or safety

. If DOE determines that a technology will ha ve significant adverse impacts on health or safety, it will not consider this technology further.

.4

- 2 4.2 TECHNOLOGIES THAT DO NOT IMPACT AFUE OR STANDBY AND OFF MODE ENERGY CONSUMPT ION

DOE eliminated 4 technologies that were identified in the technology assessm ent because they have no effect on or do not increase AFUE as measured by the DOE test procedure at Appendix N to Subpart B of 10 CFR Part 430 . However, these features ( i.e.
, Micro Combined Heat and Power, Improved Motor Efficiency

, Positive Shut

- Off Valve for Oil Burner Nozzles

, and Heat Pump Boilers ) can reduce the energy consumption of the residential boilers in actual applications. Although these technologies were not considered in the analyses, DOE does not discourage their use by manufacturers because of their potential to reduce annual energy consumption. For each technology removed for this reason, DOE provided an explanation of why the technology does not affect AFUE.

Micro Combined Heat and Power (Micro

- CHP)

It is possible to use the heat generat ed by the boiler’s combustion system to generate electricity opportunistically. Self

- generated electricity can be used to operate the elec trical components of the boiler or can be sold back to the grid. Known methods of micro

- CHP include fuel cell generat ors, thermophotovoltaic (TPV) generators, thermoelectric generators, and thermionic conversion. Other techniques use engines based on the Rankine cycle, Brayton cycle, Stirling cycle, or Otto cycle, where the engine drives an electrical generator or provid es direct mechanical power and the waste heat from the engine is used for space heating. Neither the boiler’s electricity use nor the heat generated by its electrical components, however, contribute to the calcul ation of AFUE . Therefore, this technology wi ll have no effect on AFUE.

Improved Motor Efficiency

More

- efficient electric motors could be used in hot

- water boiler pumps and draft inducers. Most hot

- water boiler pumps use a permanent split capacitor (PSC) design. PSC motors are reasonably efficient (above 70 percent) when operating at high speed ; h owever, when these motors are operated at low speed, their efficiencies may d rop into the 20 percent range. E nergy consumed by the pump or other electrical components, such as draft inducers, is not accou nted for by the AFUE calculation.

Positive Shut

- Off Valve for Oil Burner Nozzles

One option for oil

- fired boilers is a positive shut

- off valve on the fuel nozzle, which reduces smoke and soot production during burner start

- up and shutdown. This valve is generally installed directly in the nozzle tip and prevents oil from dripping into the combustion chamber. This option can also be retrofitted on existing burners. A positive shut

- off valve in an oil burner nozzle does not affect the efficiency of the appl iance, but plays a role as an emission

- control device.

Heat Pump Boilers4

- 3 Heat pump boilers use heat pump technology to extract heat from the surroundings for heating hot water. For electric boilers , this is an alternative to resistive heating. Since he at does
not naturally transfer from a low temperature to a higher te mperature, a mechanical system consisting primarily of a closed refrigeration loop containing a refrigerant vapor compressor, an evaporator (a type of heat exchanger), a condenser (another heat exchanger), and an expansion device is used to transfer the heat. The working fluid in the loop, the refrigerant, extracts heat from the surrounding air. Typically, the evaporator captures heat from the ambient air, and the condenser d elivers this he at to the water inside of the boiler . The pump and expansion device facilitate pressure and phase changes to allow for these heat transfer processes. This technology does not improve AFUE, as the test procedure currently sets the AFUE at 100% for indoor el ectric boilers. Gas

- f ired a bsorption heat pump boilers also use a refrigera tion loop to transfer heat to the water, and similarly, this technology do es not improve AFUE as it is not captured by the test method

.

4.3 SCREENED OUT TECHNOL OGIES

This section desc ribes the technologies that DOE eliminated for failure to meet one of the following four factors: (1) technological feasibility; (2) practicability to manufacture, install, and service; (3) impacts on product utility or product availability; and (4) advers e impacts on health or safety. DOE eliminated Pulse Combustion and Control Relay’s for Brushless Permanent Magnet Motors

.

4.3.1 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 heating of the mixture to its flash point). Pulse combustion systems feature high heat transfer rates, and have high combustion efficiency

. How ever, manufacturers have indicated that pulse combustion boilers have had reliability issues in the past , and therefore, they do not consider this as a viable option to improve efficiency

. Further, manufacturers indicated that similar or greater efficienc ies to those in pulse combustion boilers can be achieved using alternative technologies. For this reasons, DOE is not including pulse combustion as a technology option as it would reduce customer utility

.4

- 4 4.3.2 Control Relay for Models with Brushless Permanent Magnet (BPM) Motors (Standby/Off Mode)

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

consume power while in standby and/or o ff modes , while PSC motors 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 cont rol relay to further reduce 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. However, manufacturer feedback in the furnace rulemaking (which was reconfirmed during interviews for the boiler rulemaking) indicated that ECM motors are subjected to large currents upon start up and using a control relay to completely depower them could reduce the lifetime of the moto rs, leading to a reduction in utility of the product. Manufacturer feedback at the framework public meeting also indicated that this feature would reduce the lifetime of the motors. For this reason, DOE is not including control relays as a technology opti on.

4.4 REMAINING TECHNOLOGI ES

After eliminating those technologies that have no effect o n improving the rated AFUE or reducing the standby and off mode energy consumption, and screening the other technologies using the four criteria listed above, DOE passed the remaining technologies to the engineering analysis for consideration in developing the cost

- efficiency relationship

.

4.4.1 AFUE Efficiency Standards

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

• Heat Exchanger Improveme nts

• Burner Derating

• Modulating Operation

• Direct Vent

• Delayed Action Oil Pump Solenoid Valve

• Premix Burners

• Low Pressure Air Atomizing Oil Burner

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

_ furnaces_cac_hp_final_rule .html4

- 5 DOE also considered Dampers and Electronic Ignition, but found that they are already incorporated in baseline products.

4.4.2 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 boilers , a separate screening analysis

was conducted for standby and off mode design options. (42 U.S.C. 6295(gg)(2)(A))

DOE considered the following design options that are capable of reducing the standby and off mode electrical power consumption of residential boilers:

• Transformer Improvements

• Switching Mode Power Supply