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APPENDIX A. IMPROVED R20 SHORT LAMP

TABLE OF CONTENTS

A.1 INTRODUCTION................................................................................................ A-1

A.2 INTERNAL DIMENSIONAL COMPATIBILITY OF HALOGEN BURNER 

CAPSULES ........................................................................................................................... A-1

A.3 EFFICACY OF IMPROVED DESIGN OPTIONS ............................................... A-2
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APPENDIX A. IMPROVED R20 SHORT LAMP

A.1 INTRODUCTION

This appendix provides detailed information on the analysis conducted to determine if the 

efficacy of 100 watt (W) R20a short (having a maximum overall length (MOL) of 3 and 5/8 (or 

3.625) inches) lamps (hereafter “R20 short lamps”) could be improved to meet energy 

conservation standards. Specifically, the U.S. Department of Energy (DOE) examined the 

addition of halogen capsules to existing R20 short lamps. Tungsten-halogen lamps are a specific 

type of incandescent reflector lamp (IRL) that contain a small diameter fused quartz envelope 

filled with a halogen molecule, referred to as a capsule, that surrounds the filament. The use of 

halogen capsules is known to improve efficacy of IRLs. 

Section A.2 of this appendix describes the teardown testing conducted by DOE to 

determine if halogen capsules are dimensionally compatible with R20 short lamps. Section A.3

presents results of DOE’s analysis of whether a halogen-based R20 short lamp would meet 

energy conservation standards and the special characteristic requirements of the R20 short lamp.

A.2 INTERNAL DIMENSIONAL COMPATIBILITY OF HALOGEN BURNER 

CAPSULES

DOE received conflicting comments regarding the feasibility of incorporating halogen 

capsules in R20 short lamps to improve efficacy. DOE performed teardowns to determine the 

dimensional compatibility of single-ended and double-ended halogen capsules with R20 short 

lamps. The halogen capsules in tungsten-halogen lamps are available in two designs: (1) a 

single-ended burner that contains a lead wire inside the capsule and (2) a double-ended burner 

that features a lead wire outside the capsule. Single-ended burners are less efficacious than 

double-ended due to the presence of the lead wire inside the capsule, which prevents a certain 

amount of energy from reaching the capsule wall and being reflected back to the capsule 

filament. Single-ended burners are also typically smaller in size.

DOE tore down two 100W R20 short lamp models, one from each of the two known 

manufacturers of R20 short lamps. DOE also tore down one 60W PARb

16 model containing a 

single-ended halogen burner and one 60W PAR30 short lamp containing a double-ended halogen 

burner. DOE gathered internal and external dimensions of the lamp components as well as 

general design information from these teardowns.

DOE first compared the dimensions of the 100W R20 short lamps to that of the 60W 

PAR16 model to determine if a single-ended halogen burner could be utilized in an R20 short 

lamp. DOE measured the reflector length and the vertical distance from the end of the halogen 

capsule to the reflector wall of the PAR16 model. DOE then compared these dimensions to the 

reflector length of the two R20 short lamp models to determine dimensional compatibility. DOE 

determined that the PAR16 reflector length was 15.3 millimeters (mm) less than the reflector 

 a “R” denotes a reflector lamp type and “20” denotes diameter in 1/8 inch increments, which translates to 2.5 inches. b “PAR” denotes a parabolic aluminum reflector lamp type.
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length of the first R20 short lamp model and 15.0 mm less than the reflector length of the second 

model. The vertical distance from the end of the single-ended burner halogen capsule to the 

reflector wall of the PAR16 model was measured to be 6.3 mm. Therefore, DOE expects that if 

the single-ended halogen burner capsule was mounted in an R20 short lamp, there would be an 

additional 21.3 to 21.6 mm of vertical space between the halogen capsule and reflector wall. 

It is evident from the results of the PAR16 and R20 short lamp teardowns that a singleended halogen burner capsule could be incorporated into an R20 short lamp. The PAR16 lamp, 

which has a considerably smaller reflector length, is able to utilize a single-ended burner. In 

addition, DOE was able to verify this conclusion with the identification of R20 lamps currently 

available on the market that have a listed MOL of 3.54 inches and contain a single-ended 

halogen burner. These R20 halogen lamps have an MOL less than that of R20 short lamps (3.625 

inches), which indicates that there is sufficient space for a single-ended halogen burner capsule 

in an R20 short lamp. Therefore, DOE has concluded that the use of a single-ended halogen 

burner is dimensionally compatible with an R20 short lamp envelope.

Next, DOE compared the teardown results of the 60W PAR30 short lamp and 100W R20 

short lamps to determine if a double-ended halogen burner capsule could be utilized in an R20 

short lamp. The 60W PAR30 and 100W R20 models are described as short lamps because they 

both have a shortened MOL of 3 and 5/8 inches. DOE measured and compared the reflector 

length and the vertical distance from the end of the halogen capsule to the reflector wall of the 

60W PAR30 and R20 short lamps. DOE determined that the 60W PAR30 short lamp reflector 

length was 2.9 mm less than the reflector length of the first R20 short lamp model and 2.6 mm 

less than the reflector length of the second R20 short lamp model. The vertical distance from the 

end of the double-ended halogen burner capsule to the reflector wall of the PAR30 short lamp 

model was measured to be 4.6 mm. As a result of the component dimensions, DOE expects that 

if the double-ended halogen burner capsule was mounted in an R20 short lamp, there would be 

an additional 7.2 to 7.5 mm of vertical space between the halogen capsule and reflector wall.

The PAR30 short lamp and R20 short lamp teardowns indicate that a double-ended 

halogen burner capsule could be utilized in an R20 short lamp. The PAR30 short lamp reflector 

length was slightly less than that of the R20 short lamp which suggests there is sufficient space 

for a double-ended burner. Because the PAR30 short lamp is able to accommodate the doubleended burner, DOE has concluded that a double-ended burner is also dimensionally compatible 

with an R20 short lamp.

Through the results of the independent teardown testing discussed in this section, DOE 

was able to confirm that single-ended and double-ended halogen burners that are the appropriate 

size for R20 short lamps exist.

A.3 EFFICACY OF IMPROVED DESIGN OPTIONS

After establishing that single-ended and double-ended halogen burners are dimensionally 

compatible with R20 short lamps, DOE next performed testing to determine the potential 

improvement in efficacy for R20 short lamps through the use of these technologies. DOE did not 

identify any commercially available R20 short lamps for use in spa applications with a single-
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ended or double-ended halogen burner. Therefore, to determine the improvement in efficacy of a 

100W R20 short lamp containing a halogen burner, DOE developed theoretical models by 

scaling from a commercially available product. DOE developed 75W modeled R20 lamps with 

halogen technology, expecting manufacturers to reduce the wattage when developing more 

efficacious lamps. 

DOE tested a 120V, 45W halogen R20 lamp that contained a single-ended burner to 

determine the lamp’s performance. DOE then used the measured lumen output and wattage with 

equations from the Illuminating Engineering Society of North America (IESNA) Lighting 

Handbook to scale to a higher wattage halogen R20 lamp with a single-ended burner. DOE 

scaled the 45W lamp to determine the lumen output of a 75W R20 halogen lamp assuming 

constant voltage and lifetime. The equations that DOE used from the IESNA Lighting Handbook 

are as follows:

d

volts

VOLTS

LIFE

life = ( )

Eq. A.1

k

VOLTS

volts

LUMENS

lumens = ( )

Eq. A.2

n

VOLTS

volts

WATTS

watts = ( )

Eq. A.3

 DOE determined through this scaling calculation that the efficacy of an R20 short lamp 

improves with the use of a single-ended halogen burner. The efficacy of the 100W R20 short 

lamp was measured to be 8.5 lumens per watt (lm/W), while the theoretical efficacy of the 75W 

modeled halogen R20 with single-ended burner was calculated to be 10.3 lm/W. However, the 

efficacy would not increase enough to allow the lamp to meet the current energy conservation 

standard of 12.5 lm/W set forth by the Energy Independence and Security Act of 2007 (EISA 

2007) or the standard of 16.0 lm/W prescribed in the “Energy Conservation Standards and Test 

Procedures for General Service Fluorescent Lamps and Incandescent Reflector Lamps” final rule 

(hereafter “2009 Lamps Rule”) that becomes effective in July 2012. 

DOE utilized a similar scaling process to determine if the incorporation of a doubleended halogen burner would successfully increase the efficacy of an R20 short lamp by a 

sufficient amount to meet the EISA 2007 standards or the 2009 Lamps Rule standards. DOE first 

identified a commercially available 120V, 60W PAR30 short lamp that contained a doubleended burner and verified through teardown testing that the burner was dimensionally 

compatible with an R20 short lamp (see section A.2). DOE acknowledges that a lamp’s reflector 

efficiency, which affects the overall lamp efficacy, is dependent on the envelope shape. During 

past reflector efficiency testing, DOE determined the average reflector efficiency of R20-shaped 

lamps to be 62.2 percent. Therefore, in order to more accurately determine the efficacy of an R20 

short lamp with a double-ended halogen burner, DOE performed efficacy testing of the PAR30 

short lamp’s halogen capsule with the PAR-shaped reflector removed. DOE then applied the 
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reflector efficiency value of 62.2 percent to the halogen capsule efficacy to determine the 

combined efficacy of the double-ended burner capsule with the R-shaped reflector.

DOE used Eq. A.1, Eq. A.2, and Eq. A.3 to scale the theoretical 60W R20 halogen lamp 

to a 75W lamp. DOE calculated the lumen output of a 75W R20 halogen lamp assuming constant 

voltage and lifetime. DOE determined through the scaling calculation that the efficacy of an R20 

short lamp improves with the use of a double-ended halogen burner. The efficacy of the 100W 

R20 was measured to be 8.5 lm/W, while the efficacy of the 75W modeled R20 halogen lamp 

was calculated to be 13.8 lm/W. DOE determined that the use of a double-ended halogen burner 

would likely enable the 75W modeled R20 halogen lamp to meet the EISA 2007 standard of 12.5 

lm/W; however, the efficacy would not increase enough to meet the 2009 Lamps Rule standard 

of 16.0 lm/W. 

DOE also concluded through testing and research that R-shaped reflector lamps are the 

least efficacious reflector lamps due to their blown glass shape. R-shaped reflector lamps also 

contain a reflective coating that is made by vaporizing the reflector inside the envelope and is, 

therefore, not guaranteed to be uniform. In comparison, PAR-shaped reflector lamps contain an 

aluminum metal reflector as well as a plastic lens over the aperture of the lamp that can be 

optimized to control light output. This inherit deficiency of R-shaped reflectors affects the ability 

to improve the efficacy of R20 short lamps despite the use of a halogen capsule. 

In addition to testing, DOE interviewed manufacturers of R20 short lamps to gather 

supporting information on the comments DOE received that suggest improving the efficacy of 

R20 short lamps was not possible. DOE was particularly interested in receiving manufacturer 

feedback on whether single-ended and double-ended burners had been successfully integrated 

into R20 short lamps. DOE confirmed during interviews that manufacturers had attempted to 

improve the efficacy of R20 short lamps through the use of halogen capsules. The information 

shared by manufacturers supports DOE’s findings that while some halogen capsules are 

dimensionally compatible with the R20 short lamp envelope, the use of halogen capsules does 

not improve the efficacy enough to meet the 2009 Lamps Rule standards.

DOE considered whether the 75W modeled R20 halogen lamps successfully replicated 

the necessary performance specifications of lumen output and beam spread using the theoretical 

calculations previously described in this section. DOE determined that the 75W modeled R20 

halogen lamp with single-ended burner would have a lumen output of approximately 769 

lumens, which is within the established R20 short lamp range of 637 to 1,022 lumens. DOE also 

determined that the 75W modeled R20 halogen lamp with double-ended burned would have a 

lumen output of approximately 1,036 lumens, which is slightly higher, but comparable to the 

established range. DOE anticipates that the beam angle could be affected by the use of a halogen 

capsule; however, prototypes would need to be constructed and tested in order to determine to 

what degree. Because DOE determined that the 75W modeled R20 halogen lamp was not a 

viable option due to insufficient efficacy improvement, DOE did not conduct prototype testing to 

verify the effect on beam angle.