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GUIDE TO FLUORESCENT LAMP BALLASTS

• Published by Advance Transformer Co.
• Reprint permission granted

General Information

• Ballast Function
• Circuitry
• Ballast Types
• Performance
• Ballast Life

Troubleshooting Fluorescent Lamp Ballasts

• General
• Preheat
• SlimLine and Instant Start
• Rapid Start

I. BALLAST FUNCTION

UNDERSTANDING LIGHT SOURCES

INCANDESCENT LAMPS

Even though nearly 90% of the energy consumed by incandescent lamps is dissipated as heat, they are still prevalent in most American homes and are used throughout business and industry.

Their operation is simple and self-regulating: when electricity passes through the lamp's filament it heats until it glows (incandesces) and produces light. The amount of light generated depends upon the amount of electrical current that passes through the filament. In addition to producing light, the filament also limits the current to safe operating values. The quantity of light generated by a lamp is measured in lumens.

THE ENERGY-EFFICIENT FLUORESCENT LAMP

Fluorescent lamps operate cooler than incandescent lamps and are more efficient in using energy to create light. Rather than using a standard filament, their operation relies upon an electrical arc passing between two electrodes, one at either end of the lamp. This arc is conducted by a mixture of vaporized mercury and purified gases-mainly neon and krypton or argon-through a tube lined with phosphor The resulting ultraviolet waves cause the phosphor to glow and emit fluorescent light.

WHY FLUORESCENT LAMPS NEED BALLASTS

Unlike incandescent lamps, fluorescent lamps cannot be connected directly to the line. Unless the flow of current is stabilized in some manner, more and more current will rush through the lamp until it becomes inoperable.

The length of an incandescent lamp's filament limits the amount of electrical current passing through the lamp and regulates its light output. However, the fluorescent lamp needs an additional electrical device to regulate the current. This device is called a ballast.

BALLAST FUNCTION

Fluorescent lamps sold in the U.S. today are available in a wide variety of shapes and sizes. They range from miniature versions rated at 4 watts, 6 inches in length with a diameter of 5/8 inches to 215 watt models, 8 feet or more in length with diameters exceeding 2 inches.

Voltage required to start the lamps is dependent on lamp length and diameter, with larger lamps requiring higher voltages. Each fluorescent lamp must be operated by a ballast that is specifically designed to provide the proper starting and operating voltage required by that particular lamp.

In all fluorescent lighting systems, the ballast performs two basic tasks:

• Provides the proper voltage to establish an arc between the two electrodes
• Regulates the electric current flowing through the lamp to stabilize light output

In some fluorescent lighting systems the ballast also provides a controlled amount of electrical energy to preheat lamp electrodes.

To receive peak performance from fluorescent lighting it is essential that the fluorescent lamp ballast-the heart of the fluorescent fixture match precisely the requirements of the lamp it is designed to operate.

II. CIRCUITRY

Three major types of lighting system circuits are in use today: Preheat, Slimline Instant Start and Rapid Start. Additionally, two newer types of circuitry, Modified Rapid Start and Instant Start of Rapid Start Lamps, have also been developed.

PREHEAT CIRCUIT

The Preheat circuit, which requires the lamp electrodes to be preheated by a separate manual or automatic starter switch, was the original system developed for the operation of fluorescent lamps.

During the starting cycle, the ballast limits the current flow to a calibrated value for preheating the electrodes. In a few seconds the electrodes attain the proper temperature, at which time the starting switch automatically opens. The opening of the starting switch breaks the shunting wire path for the flow of current, leaving the gas in the lamp as the only other path to travel.

The Preheat circuit is generally used for low wattage linear and compact lamps (4 to 30 watts).

SLIMLINE INSTANT START

The Slimline Instant Start system produces light instantly without the assistance of a starter. To achieve this quick response, without lamp filaments being preheated, the ballast must provide an open circuit voltage to the lamp electrodes about three times the normal lamp operating voltage to initiate the arc. This high initial voltage requires a larger auto-transformer as an integral part of the ballast.

A larger "choke coil" or "reactor" must also be included to reduce the starting voltage to the rated operating voltage of the lamp.

Two lamp Slimline ballasts are available in two circuit types: Lead Lag and Series Sequence.

The Lead Lag Slimline Instant Start circuit differs from the Preheat circuit in the starting voltage produced and the absence of the lamp starters.

SERIES SEQUENCE CIRCUIT

To reduce the size, weight and cost of the Slimline Instant Start Lead Lag Ballast' a Series Sequence Ballast was introduced. In this ballast circuit two lamps are operated in series with the lamps starting in sequence. This circuit was pioneered by Advance.

The Series Sequence circuit differs from all others in that each of the circuits performs a separate function. The starting section supplies sufficient voltage and current to light one lamp with the remaining lamp igniting in sequence from the same voltage and current. Because the lamps are in series, the ballast is not required to supply individual lamp currents.

The reduction in power requirements makes it possible to operate Slimline instant Start Lamps with a fluorescent lamp ballast which is lighter and more efficient at about one-third the size of comparable Lead Lag types.

RAPID START CIRCUIT

Rapid Start lighting system circuits are today's most popular design. Low voltage cathodes are automatically preheated by means of heater windings built into the fluorescent lamp ballast. This eliminates the need for a separate starting switch, although the fixture must be properly grounded and the lamps positioned within 1/2 inch (F40T12), 3/4 inch (F32T8) or 1 inch (800 MA and 1500 MA) of the fixture for proper starting. Continuous lamp filament heating is provided by the ballast after the lamps are started.

Because of the continuously heated electrodes, less voltage is required for the initial surge to start the lamp than with Slimline Instant Start. Rapid Start Lamps light immediately at low brightness and are fully lighted in about two seconds.

OTHER CIRCUIT TYPES

Modified Rapid Start and Instant Start of Rapid Start Lamps are two new types of lighting system circuits that have recently emerged.

Modified Rapid Start circuits start the lamps in the same manner as Rapid Start circuits do, but do not maintain lamp filament heating after the lamps ignite. The lamp filament heating is reduced or eliminated to save energy.

III. BALLAST TYPES

ELECTROMAGNETIC BALLASTS

Because ballasts are essential to fluorescent lamp operation, they have been available for as long as the lamps they start and regulate. Throughout most of their history, fluorescent ballasts have been electromagnetic. As a result of their design, these ballasts are also called "core & coil" ballasts.

The primary component of an electromagnetic ballast is a core of stacked steel laminations around which insulated copper or aluminum coils are wound. This core & coil design functions both as a voltage transformer and a current-limiting choke. As heat produced by the ballast's operation can eventually break down the insulation around the coils and cause failure, the core & coil is "potted" in insulating material such as asphalt to conduct the heat away from the coils. This assembly is usually housed in a steel case.

The capacitor of an electromagnetic ballast improves its power factor, so it can utilize energy more efficiently. An electromagnetic ballast that is equipped with a capacitor is considered to be a high power factor or power factor corrected ballast.

Electromagnetic ballasts are available as Preheat, Lead Lag' Series Sequence and Rapid Start designs.

HYBRID BALLASTS

The hybrid ballast design combines the starting and operating characteristics of the electromagnetic ballast with the energy efficiencies of electronic circuitry to provide an alternative means of operating rapid start lamps.

The construction of this ballast is identical to the electromagnetic ballast in that it also uses a core & coil, a capacitor and potting. This ballast also incorporates electronic circuitry to disconnect the cathode heater windings after the lamp ignites. The starting method for a hybrid ballast is identical to an electromagnetic rapid start ballast. I he difference occurs during normal operation when the cathode heaters are disconnected and the energy consumption is reduced.

Hybrid ballasts are available as modified Rapid Start designs.

ELECTRONIC BALLASTS

Electronic ballasts provide the necessary voltage to start the lamp and regulate the current through the lamps after ignition, much like an electromagnetic ballast. The electronic ballast, however, operates the lamp at a frequency of 20 kHz or greater rather than the 60 Hz operation of electromagnetic and hybrid types. This takes advantages of increased fluorescent lamp efficiencies at these higher frequencies. This high frequency operation is accomplished by using electronic circuitry which generally results in a more efficient, smaller, lighter, and quieter ballast design than the standard electromagnetic ballast.

Electronic ballasts are available as Rapid Start, Modified Rapid Start and Instant Start designs.

IV. PERFORMANCE

CERTIFICATION

There are several organizations involved with ballast standards and testing. They are:

• CBM-CERTIFIED BALLAST MANUFACTURERS ASSOCIATION, manufacturers who produce fluorescent ballasts to conform to ANSI specifications C82. 1, C82.11, C82.2, C82.3 and C78.
• ANSI-AMERICAN NATIONAL STANDARDS INSTITUTE, originates standards on a national level. Composed of over 120 trade associations, technical societies, professional groups and consumer organizations, it creates standards and eliminates duplicates.
• ETL-ELECTRICAL TESTING LABORATORIES INC., a private, independent organization, is a recognized authority in measurements and testing of lamps and lighting equipment. Certified Ballast Manufacturers Association retains Electrical Testing laboratories, Inc., to test ballasts produced by members to ensure they conform to ANSI and CBM specifications.
• UL-UNDERWRITERS LABORATORIES, INC., is an independent, not-for-profit organization testing for public safety. Its function is, through study, experiment and tests, to prevent the loss of life and property from the hazards of fire, casualty and crime.
• CSA-CANADIAN STANDARDS ASSOCIATION, is the testing authority for ballasts used in Canada.
• E-ENERGY EFFICIENT BALLAST, indicates ballast complies with National Energy Conservation Amendments (NAECA) of 1988 to Energy Policy and Conservation Act (EPCA) of 1987.
• CSA-E-Canadian Standards Association Energy Efficient Ballasts, indicates ballast complies with Canadian Energy Standards.

SUPPLY VOLTAGE & FREQUENCY

Each ballast is designed to operate at the nominal voltage shown on the Advance label. Abnormal deviation from these values will result in damage to either the ballast or lamp or both. It is therefore recommended that the voltage applied to ballasts bearing the following nominal rating be maintained within the respective limits shown:

* Electronic ballasts may operate over a wider voltage limit of ± 10%.

Most ballasts are designed for single frequency operation; thus best results will prevail when the ballast is used on the frequency that is shown on the ballast label. Frequency limitations are as follows:

* Some electronic ballasts operate over a wider frequency range

POWER FACTOR

The power factor of a ballast is the measurement of how efficiently it converts the voltage and current supplied from the power source into watts of usable power delivered to the ballast. Perfect utilization of electrical current would result in a power factor of 100%. Power factor is not an indication of the ballast's ability to supply light through the lamps.

Fluorescent ballasts are designated high power factor, normal (low) power factor, or power factor corrected.

High power factor ballasts, which are specified for all commercial lighting applications, are those having a ratio of watts delivered to the ballast, compared to the volt-amperes supplied, of greater than 90%(.9).

Because high power factor ballasts employ a lower operating current' more fixtures can be installed per branch circuit. Lower power factor ballasts require about twice the current needed by high power factor ballasts. Low power factor ballasts create added wiring costs, allow fewer fixtures per circuit, and can load branch circuits as well as the circuits of the utility, potentially resulting in penalty charges.

Advantage of High Power Factor Ballasts

1. Avoid possible penalty charges from electric utility.

2. Wiring costs are less because normal power factor ballasts take about twice the line current of high power factor ballasts and may require heavier wire to carry the load.

3. With high power factor ballasts, more fixtures can be installed on each branch circuit.

CLASS P THERMAL PROTECTION

All indoor fluorescent fixtures must incorporate ballast thermal protection according to the National Electrical Code. (Fixtures employing a single reactive type ballast for linear lamps are excepted.)

Ballasts meeting the standard are designated "Class P" by Underwriters' Laboratories, Inc.

Advance Class P Magnetic and Hybrid ballasts incorporate the protector within the ballast case. Operation of this thermally actuated automatic reclosing protective device will disconnect the ballast from the power line in the event of over temperature.

All Advance Electronic ballasts are Class P rated but may not incorporate the protector in their design, these ballasts inherently limit their case temperature below the Class P limits.

Advance Class P ballasts also help protect against excessive voltage supply, internal ballast short circuiting, inadequate lamp maintenance and improper fixture application. They also eliminate the need for individual fixture fusing.

When replacing Class P or non-Class P ballasts be sure to use an exact equivalent. (For instance, nuisance tripping may occur if a non-Class P is replaced with a Class P ballast.)

FUSE PROTECTION

The wide use of Class P ballasts has reduced the need for fusing of ballasts. Individual fusing is sometimes considered when many fixtures operate on a single circuit and where it is desirable to isolate an inoperative fixture quickly This helps avoid complete circuit outage when troubleshooting.

If used, fuses should be of the slow-blow type and should accommodate inrush current and abnormal starting cycle currents of the ballast. Electronic ballasts generally have higher inrush current then electromagnetic ballasts. This will not be a problem if the correct fuse is specified.

BALLAST FACTOR

Ballast factor is the measurement of a ballast's ability to produce light from fluorescent lamps. It is the ratio of light output produced by lamps operating on a commercial ballast versus the light output of the same lamps operating on a laboratory reference ballast specified to ANSI standards for a given lamp type.

A ballast may have different ballast factors for different lamps, e.g., standard lamps as compared to energy saving lamps.

BALLAST EFFICACY FACTOR

The ballast efficacy factor is a ratio of the ballast factor (the ballast's ability to produce light) versus the watts input to the ballast. This measurement is generally used to compare the efficiencies of various ballasts with a given lamp.

The higher the ballast efficacy factor, the more efficient the ballast.

The higher the ballast efficacy factor, the more efficient the ballast. When ballast efficacy factor is multiplied by the lumen rating of the lamp, a ratio of lumens per watt is created which can be used to compare different ballast/lamp systems.

CREST FACTOR

Crest factor is one of the criteria used by lamp manufacturers to ensure fluorescent lamp life. A measurement of current supplied by the ballast to the lamp, it is basically a ratio of peak current to the root mean square (RMS) current values. Most lamp manufacturers require a crest factor of 1.7 or less on electronic ballasts in order for the lamp to be warrantied properly for its rated life. Current that has a high crest factor can cause materials to be eroded from lamp electrodes, prematurely shortening lamp life.

TOTAL HARMONIC DISTORTION

Harmonics are currents or voltages which have frequencies that are integer multiples of the fundamental power frequency. Each has a name associated with the multiplying number, i.e, if the fundamental frequency is 60 Hz, then the second harmonic is 120 Hz, the third is 180 Hz, etc.

Harmonics occur whenever the wave shape is distorted, i.e., when the wave shape varies from a pure sine wave.

Electric utilities typically generate a voltage which is very nearly a sine wave. If an end user connects a linear load such as a resistive heater, the resulting current will be a sine wave and no harmonics will be present. If, however, the load is non-linear, drawing short pulses of current within each cycle, the current wave shape will be distorted (nonsinusoidal) and harmonic currents will flow. The total current will be a combination of the fundamental plus each of the harmonics. Total harmonic distortion (THD) is the measurement of the magnitude of the input current harmonics compared with the amplitude of the fundamental frequency current.

Harmonics are important because in three phase systems, certain harmonic currents can overload neutral conductors. The troublesome harmonics, called "triplens," consist of the 3rd and odd multiples of the 3rd (i.e., 3rd, 9th, 1 5th, etc.). These harmonics will add rather than cancel in the neutral of a three-phase 4-wire system. Therefore, if the triplen harmonics exceed 33 1/3, more current will flow in the neutral wire then any of the phase wires, even if the phase currents are perfectly balanced.

EMI/RFI

Radio and TV interference is caused by the action of the arc at the lamp electrodes which creates a series of radio waves. This energy may interfere with radio reception and the operation of other communications equipment.

Types of interference:

1. Direct radiation from the fluorescent lamp to the aerial circuit.

2. Line feedback from the lamp/ballast through the power line to the radio.

3. Direct radiation from the electric supply line to the aerial circuit.

To correct the first cause, it is recommended that the radio and aerial circuit be separated at least 10 feet from the fluorescent lamp and the radio provided with a positive ground.

The second and third causes can be corrected in lighting systems that generate objectionable radio interference by additional filtering. Generally this can be accomplished by the addition of an external capacitor-reactor filter It is also desirable for the radio and fluorescent lamp fixture to be provided with a supply voltage from separate branch circuits.

Electronic ballasts which operate the lamp at high frequency may also affect the operation of infrared, powerline carrier and communications equipment. There may be no correction possible for some of these interference problems so care must be taken when specifying a lighting installation.

BALLAST SOUND

The slight hum present in fluorescent lighting installation originates from vibration caused by the inherent magnetic action in the core & coil assembly of the ballasts. There are three possible ways this sound may be amplified:

1. Method of mounting the ballast in the fixture.

2. Loose parts in the fixture.

3. Ceilings, walls, floors and furniture.

The choice of fluorescent lamp ballasts should be made on the basis of selecting the one rated quietest for a specific location. Ballasts are assigned a sound rating, Class A through F, based on the amount of noise produced. Because electronic ballasts lack vibrating parts, and have higher operating frequencies, they generally produce less noise and achieve a lower sound rating.

To make the best selection, the application needs must be considered. It is obvious that consideration of ballast sound is more important in a boardroom than in a busy store. See chart for assistance in selecting the proper sound rated ballast.

SOUND RATINGS

*These sound ratings are based on measurements of Average Ambient noise levels during conditions of normal occupancy. Audible ballast hum may appear amplified during exceptionally quiet periods and at times when area is unoccupied

Note: In planning a lighting installation, careful consideration must be given to the selection of the ballast, the lighting fixture and the room components in the early planning stages to ensure the quietest lighting installation possible.

COLD WEATHER OPERATION

Low temperatures in cold weather applications such as outdoors and walk-in freezers can effect lamp starting and operation. Lumen ratings of fluorescent lamps apply for operation in still air that has a temperature of 25° C (77° F . While many fluorescent lamps and fluorescent lamp ballasts are designed to give their best performance at 25° C, they will provide reasonably good light output down to 10° C (50° F) for standard lamps and 1 6° C (60° F) for energy saving lamps. Further decreases in ambient temperature will result in decreased light output.

Such variables as humidity, line voltage, fixture design and variations within the particular design of the lamp and the fluorescent lamp ballast play an important part in determining the low temperature starting limit.

The 800 MA and 1500 MA lamps with their higher bulb wall temperatures are recommended for most efficient cold weather operation. Even with high output fluorescent lamps, satisfactory operation of the lamps depends upon adequate shielding to permit them to reach recommended operating temperatures. Care must also be exercised in fixture designs for the prevention of overheating of the fluorescent lamp ballast in summertime operation.

VENTILATION

A fluorescent lamp ballast, like other electrical equipment, generates heat during normal operation. Underwriters' Laboratories stipulates that the temperature limitation of a ballast using Class A insulation in normal operation should have a maximum ballast coil temperature of 1 05¡C (221 ¡F) and a maximum ballast case temperature of 90¡C (1 94¡F) at its hottest spot. Ballast life will be reduced if it is operated at temperatures above these limits.

Possible causes for an increase in ballast temperature include higher than design supply voltage, ambient temperature, ceiling material, distance of fixture from ceiling and enclosed vs. open fixtures, as described in the following sections.

Where more than one ballast is installed in an enclosure, the ballasts should be positioned far enough apart to allow for the combined normal heating effects. To assist in limiting the temperature rise of ballasts, the following procedures are recommended:

• Mount ballast with maximum number of sides in direct contact with metal channel of fixture. Radiators are an excellent means of dissipating heat.
• Provide fixture ventilation.
• Paint the unpainted fixture channels with a nonmetallic finish to increase radiation.
• Place the ballast in a cooler location outside the fixture.
• Place fixture to attain maximum dissipation of heat by conduction, convection or radiation.

V. BALLAST LIFE

BETTER BALLAST PERFORMANCE/LONGER LIFE

The fluorescent lamp ballast has been called the heart of the lighting unit. As important as the ballast is, this vital component has been misunderstood, abused and misused. The end result, in many applications, has been premature ballast failures.

When properly applied, a fluorescent lamp ballast can be one of the most reliable components in an electrical system

The following pages illustrate and explain the effects of the many variables in a lighting installation. By understanding these effects and following the guidance provided, better ballast performance and longer ballast life will result.

EFFECT OF VOLTAGE

A ballast is tested in a lighting unit at rated voltages, e.g., l 20V, 277V However, voltage variations can exist in any installation. Voltages as high as 1 27V to 1 30V operating a ballast rated at 1 20V are common. In new construction, the voltage can become excessive until the electrical system is fully loaded. Lighting is usually installed before the other heavy electrical equipment which will normally reduce voltage.

The ballast industry rates ballasts for ± 7 1/2% voltage variation for electromagnetic ballasts and ± 10% for electronic ballasts. This, however, pertains only to the electrical characteristics of the ballast - not its thermal characteristics. As voltage above nominal is applied, the ballast operating temperature increases. Test results for a 120V ballast fixture combination shows for every 1V increase the ballast case temperature increases approximately 0.8° C.

Considering that for every 10¡C temperature increase ballast life will be cut in half, excessive voltage increase will decrease the life of a ballast.

EFFECT OF AMBIENT TEMPERATURE

All fluorescent lighting units are tested in an ambient temperature of 25° C, which supposedly duplicates the temperature in a normal lighting installation. Yet in new construction before the air conditioning is turned on, or in industrial plants which are not air conditioned, it is not uncommon to have ambient temperatures as high as 40° C to 50° C at the lighting unit location.

This higher ambient will, of course, greatly affect ballast operating temperatures. How much? In a sample fixture ballast combination, a 1° C ambient rise causes a 0.9° C rise in ballast case temperature. Thus, in a 30° C ambient, the ballast case temperature will rise 4.5° C. In a 40° C ambient, the temperature will rise 13.5° C.

EFFECT OF CEILING MATERIAL

Underwriters' Laboratories, Inc. specifies a pine board material be used to test surface-mounted lighting units, except in the cases of low density ceiling mounting. The majority of ceilings used in construction today are some variation of acoustical tile, all of which have a different rate of heat dissipation.

Extensive tests prove conclusively there can be a 10° C variation between a pine board ceiling and various commonly used acoustical ceilings.

Underwriters' Laboratories, Inc. also calls for a recessed lighting unit to be heat tested in a wooden enclosure which represents the wall or ceiling cavity in which the unit is to be installed. Normally, this should present no problem. However, there have been numerous occasions where an insulation fiber glass material is placed over the recessed lighting unit.

Tests indicate there is a minimum of a 10° C rise between the U.L. test enclosure and the extreme fiber glass enclosure.

The type of mounting for fixtures is important. Many lighting units are designed so they can be either surface mounted on the ceiling or suspended.

The distance the lighting unit is suspended below the ceiling greatly affects the ballast operating temperature. Tests indicate a ballast case temperature variation of 22.50C between a close-ceiling mounted lighting unit and a unit suspended 6 inches from the ceiling.

Suspension distances greater than 6 inches have no appreciable effect on ballast case temperature. However, if a unit is suspended 1 1/2 to 2 inches from the ceiling, the ballast case temperature will still operate 10° C to 14° C cooler than a surface-mounted unit.

FIXTURE DESIGN

Today, lighting fixture designs permit a unit to be installed as a bare lamp (without shielding) or totally enclosed (100% shielding) unit. The methods of shielding the lamps in a lighting unit are many, varied and too numerous to evaluate here.

Tests taken at the extremes, e.g., the difference in ballast operating temperatures in a bare lamp unit and a plastic wrap-around unit can run as high as 14.5° C.

In a louvered lighting unit, the ballast case temperature runs between these two extremes depending upon the size of the louver cells.

EFFECT OF LIGHT OUTPUT AND OTHER FACTORS

Ballast tests indicate there can be a 4°C variation in the case temperature of a certified ballast (CBM) which provides 95% light output versus a CBM ballast which provides 100% light output.

Ballast material variations can also result in slight ballast temperature variations no matter how rigidly they are controlled.

Other uncontrollable variations which can affect ballast temperatures include lamp tolerances, ballast case contact with the lighting unit, and thickness of lighting unit metal.

ACCUMULATED EFFECT OF VARIABLES

As a test fixture, consider a typical four lamp plastic wraparound unit in an ambient of 25° C, a voltage of 120 volts, and a U.L. pine wood ceiling mounting. Assume the ballast case temperature is 87° C under these conditions. In actual application the lighting unit is surface-mounted to an acoustical tile ceiling in a 30° C ambient and supplied by a 125 volt circuit.

A buildup of all these unfavorable variations can cause the case temperature of the ballast to reach 1 08° C. This places the protector within the ballast in the critical temperature zone and the protector will probably open.

In this case, the lamps and ballast will be taken out of the circuit until the unit has cooled to the protector's reclosing temperature. The protector reactivates the ballast, permitting corrective action to be taken without the necessity of ballast replacement.

TROUBLESHOOTING

VI. GENERAL TROUBLE

ELECTRICAL TEST EQUIPMENT

Note: Voltage and current measurements present the possibility of exposure to hazardous voltages and should be performed only by qualified personnel.

The following equipment is recommended for testing fluorescent fixtures:

True RMS Voltmeter
Ranges: 0-300-1000 Volts AC
Ammeter (clamp-on type acceptable)
Ranges: 0-10 Amperes AC
Multi-meter (with voltage and current ratings as shown above)
Frequency: 60Hz for electromagnetic, above 20kHz for electronic

TROUBLESHOOTING FLUORESCENT APPLICATIONS

SAFETY FIRST: Troubleshooting procedures must take place within these guidelines:

• Those working on the fixtures (and hence, in situations where they may be exposed to hazardous voltages) must be properly qualified to perform such work.
• Ballasts, starters, capacitors and fixtures must be grounded in accordance with the National Electrical Code (NEC). In the case of fluorescent ballasts, the case must be grounded either to the fluorescent fixture or, if remote mounted, by other means such as a wire from ballast case to ground. Without proper fixture and ballast grounding, a shock hazard may exist due to the fluorescent fixture becoming energized by an internal ballast failure. In addition, all ballasts have normal leakage. When the ballast is properly grounded, the leakage current does not constitute a hazard.
• Any work performed on the lighting system, including inspection, troubleshooting and maintenance, should be done with the fixture properly de-energized and the circuit locked and tagged according to Occupational Safety and Health Act (OSHA) requirements.

INOPERATIVE FIXTURE

Often when a fixture becomes inoperative, the cause is not attributable to the ballast. It is therefore important to examine all components of the fixture before removing the ballast for replacement. The following procedure is recommended:

1. Change or check all lamps to ensure satisfactory operation.
2. As lamps are removed, examine all sockets to ensure proper and positive contact with lamp pins.
3. If starters are used, each starter should be checked and replaced wherever necessary.
4. Examine all connections within the fixture to ensure their conformance with the wiring instructions appearing on the ballast.
5. Examine and test ballast.

CYCLING

The National Electrical Code® stipulates that most ballasts installed indoors must contain a cut-out device that protects the ballast from overheating.

If abnormal ambient conditions cause the ballast to overheat, the thermal protection device's switch disconnects the ballast from the line.

Once cooled, the ballast is reconnected and restarts the lamps.

If the conditions persist, the ballast will switch off again repeatedly in a process called "cycling."

LAMP "SWIRLING"

Another problem that may occur is a process known as swirling or spiraling, where light does indeed appear to swirl or spiral inside the tube. This is normal for some lamps when first lighted, and in these cases the problem will correct itself after a few hours of operation.

• This problem may also be caused by cold temperatures. In this case, the lamps may need to be jacketed or otherwise shielded from the cold drafts. Also, check that the lamps are rated for the actual temperature measured.
• This problem may also be caused by low input voltage; check and correct.
• Next, check for ballast and lamp compatibility and replace the wrong component.
• Replace lamp with known good lamp. If condition still exists, change ballast.

VII. PREHEAT

To measure starting current and operating current, the ammeter must be connected between the colored high voltage secondary lead of the ballast and the lamp.

To determine starting voltage, remove lamp and connect voltmeter between respective primary and secondary leads of each lamp according to ballast wiring diagram.

TROUBLESHOOTING PREHEAT INSTALLATIONS

One of the major causes of trouble with a Preheat circuit is the miswiring of the fluorescent ballast. This condition can be noted by short lamp or starter life, non-starting of lamp, or premature failure of the ballast. For example, with a two lamp ballast, the starter leads from the two pairs of lamp holders may be crossed. If both starters open at the same time, the lamps will start. However, if one lamp starts before the other, the nonstarting lamp may blink on and off for a long time before starting if it will start at all.

To determine if wired correctly, short the terminals of a fluorescent starter with a fine bare wire. Remove all starters from the fixture but leave the lamps in. Insert the shorted starter in one starter slot. If the fixture is wired properly both ends of the same lamp will glow. If it is crosswired, one end of each lamp will glow.

There have been many installations of Preheat fluorescent lighting in which two lamp ballasts are operating with one lamp on and one lamp out, or with shorted starters. These conditions will cause premature ballast failures due to the ballast coils being operated above their coil temperature limitation. Thus it is advisable that all inoperative lamps and starters be immediately replaced.

Other causes of difficulty could be (1) low or high circuit voltage, (2) improper lamp holder contact, (3) pinched wires or (4) improper lamps.

VIII. SLIMLINE & INSTANT START

To determine starting voltage, the lamp must be removed and voltmeter connected between the respective primary and secondary leads of each lamp as designated on ballast label. For series-sequence ballasts, the red lead must be in position while measuring the starting voltage of the remaining lamp.

For Single Lamp, measure voltage between Red & White leads.

For Two Lamp (SERIES SEQUENCE), measure voltage between Red & White

Insert lamp in Red & White position, then read voltage between Blue & Black

For Two Lamp (Lead Lag), measure voltage between Red & White and Blue & White Leads.

For Electronic (parallel), measure voltage between Red & Blue leads.

TROUBLESHOOTING SLIMLINE & INSTANT START INSTALLATIONS

There are two common electromagnetic ballast circuits for the two lamp operation of Slimline lamps: The Lead Lag circuit and the Series Sequence circuit. Electronic ballasts operate the lamps in parallel.

The Lead Lag Slimline Ballast operates one lamp independently of the other. Thus, if one lamp becomes inoperative, the other lamp will still light. There are two legs in the Lead Lag circuit: one leg of the circuit is called the lead section and contains an inductive coil and a capacitor in series with the lamp. The other leg just contains an inductive coil and is called the lag section. This is how the name "Lead Lag" was derived. It is permissible to use Lead Lag Slimline Ballasts for starting of Slimline lamps down to temperature of 0° F and above.

The Series Sequence Slimline Ballast was introduced in order to reduce the size, weight, and cost of the Slimline Ballast. In this circuit two lamps are operated in series, with the lamps starting in sequence. If one lamp becomes inoperative the other will not fully light or light all.

Short lamp life or premature end blackening can be due to (1) low supply voltage, (2) improper lamp-socket contact or (3) miswiring and eventually fail.

The open circuit voltage of a Slimlline Ballast, in many cases, is great enough to start a lamp with one lamp filament de-activated. This lamp will become extremely black at one end and flicker. If the lamp is not replaced, the ballast will overheat and eventually fail.

If an Electromagnetic Slimline Ballast is operated with one lamp on and one lamp off, the ballast will experience higher coil temperatures which could result in premature ballast failures. In cases of short ballast life generally are not effected by lamp failure.

IX. RAPID START

To measure starting voltage, connect voltmeter between the highest reading Red lead and Blue lead with lamp removed.

To measure filament voltage on a single lamp unit, read between Red-Red and Blue-Blue leads. For two lamp units, read voltage between Red-Red, Blue-Blue and Yellow-Yellow leads.

Note: Electronic ballasts generally provide starting voltages higher than those listed in the above tables. These open circuit voltages are listed on the ballast's label. Filament voltages for electronic and electromagnetic ballasts are the same.

TROUBLESHOOTING RAPID START INSTALLATIONS

The Rapid Start circuit eliminates the annoying flicker associated with starting Preheat systems. Rapid Start circuits also simplify maintenance since no starter is used.

The Rapid Start lamp operates on the principle of utilizing a starting voltage which is insufficient to start the lamps while the cathodes are cold but is sufficient to start the lamps when the cathodes are heated to maintain emission temperature. This voltage range between starting cold and starting hot is a very narrow band of voltage which must be closely controlled in order to prevent either failure of the lamps to start or instant starting of the lamps with cold cathodes which is detrimental to the lamps.

In order to stay within this range of voltage, it is necessary to excite the gas within the lamps by means of an external voltage which is applied to the gas within the lamps to create ionization. This external excitation is created by means of the capacity that is present

between the lamp and the reflector or channel. In order to act effectively, the fixture must be connected to ground and the white lead of the ballast connected to ground lead of power supply. Thus it is stated on the label of Rapid Start ballasts "MOUNT LAMPS WITHIN 1/2 INCH (3/4 INCH or 1 INCH) OF GROUNDED METAL REFLECTOR."

The majority of new fluorescent installations today use ballasts of the Rapid Start design. The HIGH OUTPUT (800 MA), and VERY HIGH OUTPUT (1500 MA) lamps are of the Rapid Start design.

BLUE-BLUE, YELLOW-YELLOW, RED-RED LEADS are the built-in filament windings which supply a voltage of 3.4 to 4.5 volts to the lamp cathodes. If the cathodes are not properly heated, premature lamp end blackening will result. The lack of heating could be due to:

1. Improper seating of the lamp within the socket.

2. Broken sockets.

3. Broken lamp pins.

4. Too great of socket spacing.

5. Damaged lamp cathode(s).

6. Ballast lead wire not properly connected to socket.

7. Low supply voltage.

8. Inadequate ballast filament voltage.

9. Improper wiring.

To determine if there is adequate voltage at the lamp cathodes, measure the voltage at the socket terminals. The voltage at the sockets should read between 3.4 and 4.5 volts. If there is adequate voltage, the lamp end blackening can be due to conditions 1, 2, 3, 4, or 5. If the voltage is not adequate it can be due to one or more of conditions 6, 7, 8, or 9.

If random starting of Rapid Start lamps is experienced, be sure the fixture is properly grounded. As previously stated, for completely reliable starting in Rapid Start circuits it is necessary to have a starting aid.

The starting aid should be an electrically grounded metal strip at least 1 inch wide and extending the full length of the lamp. The lamp should be within 1/2 inch of the grounded step for 40 watt lamps and smaller, (3/4 inch for T8 lamps) and 1 inch for higher output lamps.

If, under high humidity conditions, Rapid Start lamps start or do not start at a I although the cathodes are properly heated, this may be due to dirt on the lamps which is offsetting the silicon coating on the lamps, or t may be due entirely to a poor silicon coating. If t is a new installation (in operation only a few months) which experiences random starting under high humidity conditions, in most cases n will be due to low supply voltage or poor silicon coating on the lamps.

When random starting is experienced under high humidity conditions in an installation in operation for a longer period of time this is usually due to dirt on the lamps. The lamps should be washed in water to remove the dirt.

Sometimes with a two lamp Rapid Start series ballast only one lamp will light to full brilliance and the other will not light. Refer to the figure below. If the lamp between the Red leads and Yellow leads is lit and the other lamp is out, look for a pinched Yellow lead. If the lamp between the Red and Yellow leads does not light and the other does, t is probably due to a short within the ballast.

MODIFIED RAPID START

This type of ballast starts and operates the lamps similar to Rapid Start Ballasts, so troubleshooting on pages 44-48 would also apply. The only difference is that filament heating is reduced or eliminated after the lamps ignite so the 3.4-4.5 volts specified cannot be measured during normal operation. Also, some two lamp ballasts require that only one lamp be removed when measuring starting and filament voltages. If both lamps are removed, these voltages cannot be accurately measured.

INSTANT OF RAPID START LAMPS START

This type of ballast does not provide filament heating to the lamps. Only the starting voltage which is listed on the ballast label can be measured when the lamp is removed. The wiring of this ballast requires that the lamp filaments be shorted together and then connected to the ballast to obtain rated lamp life. If the filaments are not shorted, the lamps will ignite properly but fail prematurely. Rated lamp life when using this Instant Start Ballast may be reduced vs. a Rapid Start Ballast last depending on how frequently the lamps are started.