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(A NBS TECHNICAL NOTE 886

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U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

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NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards 1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

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:

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* Part of the Center for Building Technology.
OCT 3 1975

\V£/V ALL

Modification of Fluorescent Luminaires

I ^3 for Energy Conservation

»

Robert W. Beausoliel,

William J. Meese and

Gary Yonemura

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

Sponsored by

Federal Energy Administration Washington, D.C. 20402

***T °F

"e*

U. S. DEPARTMENT OF COMMERCE, Rogers C. B. Morton, Secretary

James A. Baker, III, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

\j,^ t NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Acting Director

Issued October 1975
National Bureau of Standards Technical Note 886

Nat. Bur. Stand. (U.S.), Tech. Note 886, 15 pages (Oct. 1975) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1975

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. C13.46:886). Price 65 cents. (Add 25 percent additional for other than U.S. mailing).
TABLE OF CONTENTS

1

.

Introduction 1

2. Equipment Used In Investigations 2

3

.

Test Set-Ups 3

4. Preliminary Tests 3

5. Basic Approach of Investigation 3

6. Conclusions 10

7

.

Recommendations 11

8 References 11

in

Modification of Fluorescent Luminaires

for Energy Conservation

Robert W. Beausoliel, William J. Meese, and Gary Yonemura

Reducing energy consumption in existing buildings by

reducing the number of lamps presents technical problems

when more than one fluorescent lamp operates from a single

ballast. A preliminary investigation was made whereby

capacitors were substituted for one fluorescent lamp in a two-lamp luminaire which operated with a single ballast.

Under optimum conditions, lighting efficiency (foot- candles

per watt) was nearly as high at reduced power input as it was with two lamps operating normally. No failures in

lighting equipment or capacitors occurred and no fire

hazards, other safety hazards or other unsatisfactory

occurrences were observed. A more thorough investigation

involving a number of parameters is needed to ascertain

the feasibility of this modification.

Keywords: Capacitors; energy conservation; fluorescent

lamp; fluorescent luminaire; lighting efficiency; power factor,

1 . INTRODUCTION

When two or more fluorescent lamps operate from a single ballast,

removing one lamp may not permit the other lamp to operate effectively.

This may cause problems in existing buildings when it is desired to conserve energy by reducing the amount of artificial light. At the request

of the Federal Energy Administration a preliminary investigation of a possible energy saving procedure involving fluorescent lighting was undertaken by the Building Services Section with cooperation from the Sensory

Environment Section of NBS.

1.1 Purpose

The purpose of this investigation was to determine if removing one fluorescent lamp from a two-lamp luminaire with a single ballast and

replacing the lamp with various capacitors would permit the luminaire to

operate safely, reliably and efficiently. This preliminary investigation

was made to determine if it was worthwhile to pursue a more comprehensive

investigation of this proposed modification.

1
1 .

Scope

Appropriate data with a fluorescent luminaire operating both normally

with two lamps and with capacitors substituted for one lamp was obtained.

This data involved luminous flux output, power consumption, power factor,

voltage, current, phase relationships, any observed safety or fire hazards,

any observed reliability problems and any other unforeseen occurrences.

1.3 Fluorescent Luminaire Voltages

Most fluorescent luminaires at the National Bureau of Standards which

are suspended from ceilings operate from a nominal 277 volt, a-c, 60 hertz

supply of electric power to the ballasts. This is a common supply voltage

for overhead lighting systems in commercial and industrial buildings. Howeve]

ballasts which operate from a nominal 120 volt supply are also common.

Conventional rapid start fluorescent lamps of the same wattage are interchangeable in luminaires requiring either nominal 120 volt or nominal

277 volt power supplies. The National Electrical Code [1] prohibits 277

volt power supplies for luminaires in residential occupancies and permits

their use in industrial occupancies only under certain specific conditions,

including the requirement that such luminaires be mounted at least eight

feet above the floor.

2. EQUIPMENT USED IN INVESTIGATIONS

All equipment used in this investigation (luminaires and associated

equipment and capacitors) are readily available on the open market.

2.1 Lamps and Associated Equipment

The luminaire used in the investigation contained two four-foot rapid

start fluorescent lamps (rated 40 watts each) and a single ballast designed

for 120 volt power supply. Marking on the ballast indicated it was for use with two rapid-start 40 watt fluorescent lamps in series.

The luminaire which was used in this investigation originally contained

a ballast designed for 277 volt power supply. This ballast was replaced

with a ballast designed for 120 volt power supply for reasons of safety and

convenience in performing the tests.

2.2 Capacitors

Capacitors used in the investigation were rated for 200 volts d. c. and the tolerance of their capacitance values were + 20%. Higher quality,

more expensive capacitors, including capacitors designed to withstand

higher voltages are available. A 2 ampere fuse was used in series with

the capacitors for protection.
3. TEST SET-UPS

Figure 1 illustrates the basic test set-ups for these investigations.

The principal instruments used in the tests were:

1) A multi-purpose meter which measured supply voltage, current and

power and with which the supply voltage could be regulated. All

measurements were made with a supply voltage of 120.

2) An illumination meter with a cosine and color corrected detector.

The lamp under test was shaded from other light in the laboratory.

The detector was placed six inches from and was centered with

respect to the lamp under test. All illumination measurements

were made under identical conditions.

3) A volt meter to measure the voltage drops across capacitors in

the luminaire.

4) A dual trace oscilloscope to display the current and voltage waves,

Tests were made with the ambient temperature at 23°C. In Figure 2,

Item I illustrates two fluorescent lamps in the fixture as they would

appear in a normal installation. Items II, III, and IV illustrate methods

whereby one or more capacitors were connected when one lamp was removed

from the luminaire.

4. PRELIMINARY TESTS

A tests was made to determine if one lamp would operate with the other

removed. Referring to Figure 2, Lamp A did not operate if Lamp B was

removed. However, when Lamp A was removed, Lamp B would very dimly light.

Its illuminance was so low -that it would not register on the illumination

meter. When capacitors with two microfarads or more were used in either

lamp position, the lamp in the other position lit brightly.

Tests were also made to determine the effects of connecting capacitors

in different positions as shown in Item II, III and IV in Figure 2. The

results were the same with the parallel combination of capacitors between

outboard pins (Item II) of the lamp holder or the inboard pins (Item III)

However, connecting across pins in each lampholder had no effect (see Item

IV); the lamp did not operate.

5. BASIC APPROACH OF INVESTIGATION

The basic approach was to obtain appropriate data with two fluorescent

lamps in the fixture (for reference) and with various values of capacitors

substituted for one lamp.
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5 «, 1 Measurements

The following measurements were made

(1) Total power input in watts.

(2) Supply voltage - adjust to 120 volts.

(3) Current in amperes.

(4) Whether input current was leading or lagging the supply voltage.

(5) Voltage drop across capacitors.

(6) Luminous flux output of lamp.

With two lamps in the fixture the illuminance of one lamp, which

was Lamp A in Figure 1, was measured.

5.2 Calculations

From this information apparent power (volt-amps) , power factor and

lamp efficiency calculations (foot-candles per watt) were made.

5.3 Tabular Results

Basic measurements and calculations are listed in Table 1. Explanation

of symbols is as follows:

C - capacitance (microfarads)

FTC - illuminance (foot-candles)

W - power (watts)

FTC/W - lamp efficiency (foot-candles per watt)

V - supply voltage (volts)

I - current (amperes)

VA - apparent power (volt-amps)

PF - power factor (percent)

Ld/Lg - current leading (Ld) or lagging (Lg)

VD - voltage drop across capacitors (volts)

5.4 Graphic Results

Figure 3 contains plots of (1) illuminance as a function of power

input and (2) power factor as a function of power input. Values of

capacitances which were substituted for one fluorescent lamp when measurements were made are indicated.

Figure 4 is a plot of lamp efficiency as a function of power input.

Values of capacitances used when measurements were made and power factors

with each capacitance value are shown.

5.5 Observed Results

No obvious fire or safety hazards were observed by the investigators.

There were no failures with lamps, associated equipment or with any capacitors used. No unforeseen events occurred. There were no events, happenings or other observations which would indicate that any reliability or durability aspects would be unsatisfactory in the brief period of testing.

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1 101 18.0 5.61 120 0.30 36 0.50 Ld

2 144 22.5 6.40 120 0.26 31.2 0.72 Ld 175

4 185 27.5 6.72 120 0.25 30.0 0.92 Ld 140

8 236 34.0 6.94 120 0.34 40.8 O.83 Ld 105

12 249 36.0 6.91 120 0.37 44.4 0.81 Ld 80

14 265 39.5 6.71 120 0.41 49.2 0.80 Ld i

16 275 41.0 6.70 120 0.4J 51.6 0.79 Ld 70

20 284 42.0 6.76 120 0.45 54.0 0.78 Ld 60

24 293 44.0 6.66 120 0.47 56.4 0.78 Ld 55

28 293 44.5 6.58 120 0.48 57.6 0.77 Ld 36

32 297 45.0 6.60 120 0.49 58.8 0.76 Ld 33

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7.11 120 0.86 I103.2 0.93 Ld

TABLE 1

For the one lamp under test
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Voltage drop measurements across capacitors are listed in the table.

Data on transient voltage "spikes" when the lamp is turned on was not

obtained. Static and transient voltages had no observable effect on capacitor life during these limited experiments.

5.6 Reversing Lamps and Capacitors

Measurements listed in this report are with Lamp A (see Figure 2) in

place and with capacitors substituted for Lamp B. With Lamp B in place

and with capacitors substituted for Lamp A, measurements involving power

input, voltage and current were made with each value of capacitance.

These measurements were substantially the same when capacitors and the

lamps were in the reversed positions.

6. CONCLUSIONS

1. The preliminary investigations indicated quite promising results.

Luminous output in relation to power consumption (ft. candles/watt)

under optimum conditions was nearly as high, with one fluorescent

lamp and capacitors as it was when two lamps operated normally.

Power factors under optimum conditions were also substantially as they were when the lamps operated normally.

2. No hazards, equipment failures or other unfavorable results were observed during the preliminary investigations. It appears that

dummy tubes with capacitors could be manufactured and installed

and would satisfactorily operate with less power.

3. A more comprehensive investigation of this proposed energy saving

measure should be undertaken to address parameters listed in Section

7 of this report on Recommendations.

10
7 . RECOMMENDATIONS

Before any widespread use is made of this proposed energy conservation

measure, an investigation should be made to determine:

. designs and types of fluorescent luminaires most common in

government and other office buildings

. effects on different designs of fluorescent lighting systems

(there are many)

effects on lighting quality

noise and interference with radio and t.v. , if any

durability of capacitors

. durability of fluorescent lamps in this mode

durability of ballasts in this mode

effects of high ambient temperature, humidity or other

environmental conditions

effects with 277 volt supply

effects of transient voltages

effects on different sizes of fluorescent lamps

• optimum capacitance and types of capacitors for various loads

and designs

costs and projected energy savings

. data which approaches "statistical significance"

thorough assessments of any long term effects, including

potential safety or fire hazards.

8 . REFERENCES

[1] National Electrical Code, 1975 edition, NFPA #70=75, published by

the National Fire Protection Association.

11
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN-886

2. Gov't Accession

No.

4. TITLE AND SUBTITLE

MODIFICATION "OF FLUORESCENT LUMINAIRES FOR ENERGY CONSERVATION

3. Recipient's Accession No.

5. Publication Date October 1975

6. Performing Organization Code

7. AUTHOR(S) Robert W. Beausoliel, William J. Meese, and

Gary Yonemura

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 462-4193

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

SAME AS ABOVE

13. Type of Report & Period Covered

3/1/75 - 4/W7S

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less (actual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

Reducing energy consumption in existing buildings by reducing the number of

lamps presents technical problems when more than one fluorescent lamp operates

from a single ballast. A preliminary investigation was made whereby capacitors were substituted for one fluorescent lamp in a two-lamp luminaire which operated with a single ballast. Under optimum conditions, lighting efficiency (footcandles per watt) was nearly as high at reduced power input as it was with two

lamps operating normally. No failures in lighting equipment or capacitors occurred

and no fire hazards, other safety hazards or other unsatisfactory occurrences were observed. A more thorough investigation involving a number of parameters is

needed to ascertain the feasibility of this modification.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Capacitors; energy conservation; fluorescent lamp; fluorescent luminaire;

lighting efficiency; power factor.

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