Tubular Fluorescent Lamps
How it works
A tubular fluorescent lamp consists of a cylindrical glass tube, coated on the inside with fluorescent phosphors. Each fluorescent tube contains a minute dose of either mercury or amalgam and a mixture of inert gases, such as argon and krypton or neon and argon. At either end of the tube are electrodes (cathodes) which pass an electrical charge from one end to the other, exciting ions in the process. As these ions pass down the tube, they collide with particles of mercury and produce ultraviolet radiation. This in turn radiates onto the phosphor coating which produces visible white light. Colour temperature and colour rendering can be determined by the phosphor mix coating on the inside of the tube.
In the UK, the diameter of Tubular Fluorescent Lamps is identified by using the ‘T’ prefix and then a number which is a fraction of an inch. Historically, T12 and T8 lamps have been utilized which are 12/8ths and 8/8ths of an inch in diameter, which would equate to 38mm and 25mm respectively. Over the years, in new installations or major refurbishments the trend has been to utilise a narrower diameter tube T5 (16mm). T5 fluorescent lamps offer higher efficacy and reduced luminaire size. Thus we see T5 is replacing T8 and T8 replacing T12 lamps. In fact EU legislation is driving increased use of T5 lamps, resulting in a gradual phase- out of T12, and then T8, lamps in the near future.
Lamps with the traditional Halophosphor coating are now being rapidly superseded by lamps with the more efficient Triphosphor (Multi-phosphor) coating. Whereas Halophosphor lamps can only be used with conventional switch-start, electro-magnetic, control gear, Triphosphor lamps can be used for both switch-start and high frequency, electronic, circuits. Triphosphor lamps are more energy efficient; improving the light output of many luminaires and offer long term cost savings. In addition they provide better colour rendering, improved lumen maintenance and longer life. Multi-phosphor coated lamps are also available which offer high efficacy and excellent colour rendering.
Halophosphor is a blend of two different materials which radiate broadly in the blue and orange parts of the spectrum. By changing the ratio of the two components a full range of warm to cool white hues can be achieved. Some typical spectral power distributions for the Warm, Cool and Daylight White Halophosphate lamps are illustrated below. The colour rendering index is typically 50 to 70 and the lamp efficacy approx. 60 – 75 lm/W.
Triphosphor (Triband or Multi-Phosphor)
The following three fluorescent components are generally employed in modern triphosphor tubes:
Barium Aluminate (BAM) Blue 450nm
Calcium Tungstate (CAT) Green 543nm
Yttrium Oxide (YOX) Orange-Red 611nm
These 3 bands correspond closely to the red, green and blue photo-receptors in the eye. By blending together the blue, green and red components in the correct proportions, a net white output of various hues can be realised. The distinctive triple-peak spectra of the triphosphor colours is illustrated below for three popular shades of white. Note that the cooler the colour temperature, the greater the proportion of blue light in the spectrum.
Owing to the proximity of these peaks to the colour receptors in the human eye, a very high colour rendering index is achieved. Typically this is of the order of Ra85 for most products, which marks a considerable improvement over Halophosphate materials.
An advantage of these deeply saturated coloured phosphors is their efficiency of converting UV into visible light. As a result lamp efficacy is typically around 80 – 95 lm/W. Under the EuP Directive, less efficient Halophosphor lamps will be replaced by Triphosphor lamps. The following table illustrates how payback can be achieved in approx 1 year.
Two factors concerning colour need to be considered when selecting fluorescent lamps:
- colour rendering, and
- colour appearance (or temperature)
As we all know natural daylight is not a single colour, but a whole range – as seen in a rainbow. It is this colour spectrum that allows our eyes to see in a way that we perceive to be natural and balanced. Lamps that allow colours to be reproduced similar to that rendered by daylight are said to have a good ‘colour rendering’. This is measured on a colour rendering index (CRI) with a scale of 1 to 100 – the best scoring close to 100. The European standard EN 12464-1 requires that lamps with a CRI of less than Ra80 should not be used in rooms in which people work, or stay, for lengthy periods.
Nomenclature of Colour
The colour appearance of the white fluorescent lamps is defined with a 3-digit code which utilises a combination of colour rendering and temperature as follows:
1st Digit = Colour Rendering Index 2nd & 3rd Digits = Colour Temperature
e.g. 9 = Ra 90-100 e.g. 27 = 2700K
8 = Ra 80-89 35 = 3500K
5 = Ra 50-59 60 = 6000K
For example: Colour Rendering – 80 on the CRI scale is abbreviated to ‘8’, but indicates that CRI maybe anywhere between 80 and 89. Colour Temperature – 3,500 Kelvin is abbreviated to ‘35’. Thus, the lamp is denoted as ‘Colour 835’
Tubular fluorescent Lamps are well suited to Commercial Applications such as Offices, Car Parks, and General Retail Lighting.
Where previously, colour appearance was largely a matter of taste, this has now become a critical factor in lamp selection, particularly in the working environment. The general preference is to use cool colours (4,000 Kelvin) for a business-like atmosphere (e.g. in offices, factories, shops), and warm colours for a social atmosphere (e.g. in restaurants and the home).
The most popular choice for offices is triphosphor light colour 835 (white). With a colour temperature of 3,500K it strikes a balance between cool and cosy.
To create a bright and cosy atmosphere, triphosphor light colour 830/930 (warm white) is often the preferred choice with a colour temperature of 3,000K. Applications include shops, schools, meeting rooms, offices, auditoriums, etc.
The warmest light, with a colour temperature of 2,700K, is triphosphor light colour 827 (extra warm white). It is most commonly used in hotel foyers, restaurants and theatres to create a relaxing atmosphere. This would be most ideal for use in the home.
To generate a cooler light there are principally two options – cool white and daylight. Triphosphor light colour 840/940 (cool white) lies somewhere in between daylight and incandescent light. Typically, it would be a working light for factories, workshops, offices, sports halls, and even shops.
Triphosphor colour 860/865/950/954 (daylight) is ideal for where precise colour matching is required such as at dentists’ practices, reprographic workshops, etc. Some manufacturers also produce a ‘cool daylight’ lamp aimed at the clothing retail market where colour rendering is important for customers.
However, with more investigation into the positive effects of light on the individual, we now see special lamps being used, commonly known as ‘feel-good’ lamps, which offer a colour temperature ranging from 8,000 up to 17,000 Kelvin. These lamps have been proven to alleviate the effects of the SAD syndrome, or ‘winter blues’. The enhanced blue light content and unique phosphor coating generates a light spectrum with an optimal balance between light for vision and blue light to positively influence well-being. Tests show that ‘feel-good’ lighting makes people feel more alert, awake and energized.
The light output for a tubular fluorescent lamp is typically measured in Lumens, which is the SI measure of "luminous flux". This is a measure of the total number of packets (or quanta) of light produced by the light source or ”quantity” of light emitted. When selecting the appropriate tubular fluorescent lamp, the decision will include considering the light emitted or lumens.
Lamp Operating Temperature
The luminous flux of a fluorescent lamp depends to a considerable extent on the mercury-vapour pressure present in the tube. The pressure is determined by the temperature of the coolest part of the tube, which is usually the wall. The maximum luminous flux is reached when the wall temperature is 40°C, which for many T8 fluorescent lamps corresponds to an ambient temperature of 25°C. For T5 lamps, the ambient temperature may be closer to 35°C. SEE FIGURE 7. The wall temperature of lamps in closed luminaires can be very much higher. In such conditions a high luminous flux can still be attained by using a suitable amalgam in place of pure mercury. This has the effect of lowering the mercury pressure and also of keeping it more or less stable over a broad temperature scale.
Mercury or Amalgam
Fluorescent lamps need a small quantity of mercury in the gas discharge for light generation. This may be present in liquid or pellet form. Mercury is very effective within a narrow operating temperature. However outside of this range, the mercury-vapour pressure will be effected and hence light output.
Amalgam fluorescent lamps use a low mercury content alloy (amalgam), often in pellet form, to control the mercury vapour pressure and have a number of advantages over equivalent mercury lamps. The use of amalgam technology ensures that the mercury vapour pressure within the lamp is less temperature sensitive than normal liquid mercury lamps. The mercury vapour pressure varies less with temperature and thus the light output, which is dependant on mercury vapour pressure, remains more stable over a wide temperature range. In most normal mains lighting applications this will give superior performance and is particularly beneficial for the higher running temperatures of more compact luminaires.
High Efficiency (HE), High Output (HO) and Very High Output (VHO)
Linear Fluorescent Lamps are available in a wide range of types and wattages from 14 to 80 Watt and above. An 18W T8 lamp is the most popular size but will no doubt be superseded by the T5 550mm 14W lamp. However, aside
from standard linear fluorescent, manufacturers also offer various high performance lamps. High efficiency (HE) versions have been developed to maximise light output per watt consumed, offering efficacies up to 104lm/w. High Output (HO) and Very High Output (VHO) lamps offer the highest light output for a given size of lamp. So a user could choose HO 24W/840 for High Output with a luminous efficacy of 89 lm/w or a HE 14W/840 with a luminous efficacy of 96lm/w for High Efficiency, depending on the particular application.
Efficacy is the measurement of Light Output / Power Consumed or to put it simply, the light output in lumens produced by a source for each Watt of electrical power supplied to the source. Efficacy is a key measure when determining the efficiency of a light source. Tubular fluorescent lamps offer a high efficacy so are an excellent choice for office environments where good levels of light and low energy consumption are key factors.
Their efficacy ranges from: 45 lm/W for low wattage or 54 lm/W for low colour rendering for T8 halophosphate Lamps and up to 95 lm/W for T5 triphosphor Lamps with a colour rendering index > 85. Under optimal conditions this can increase up to in excess of 100 lm/W (for a T5-High Efficiency 35W lamp operated at 35oC with a high frequency ballast).
The life of a fluorescent lamp is measured in a number of different ways. Two measures tend to be employed: mortality (i.e. the number of operating hours elapsed before a certain percentage of the lamps fail) and lumen output (i.e. the depreciation of the lumen output over time). Both sets of data are useful measures. The rated life of tubular fluorescent lamps can range from 6,000 hours up to 60,000 hours, or more, depending on lamp type and control gear.
They can have a lifetime of up to 23,000 hours for normal T5 lamps (90% service lifetime at 12 hr switching cycle). Special long life lamps also exist where the life time is up to 68,000 hours with the same energy efficiency. Halophosphate lamps have a lifetime of only 6,000 hrs and are soon to be discontinued under the EuP Directive. All tri-phosphor lamps have a high CRI (typically >80) and are also 20-30% more efficient than halo-phosphor types with low CRIs. Better energy saving can be achieved when the lamps are operated on an electronic HF-ballast, and when daylight controls and presence detectors are used appropriately.
The last 12-18 months has seen the introduction of ‘Energy-Saving’ lamps. Based on the standard T8 and T5 tubular fluorescent lamps, with the addition of Xenon gas, these lamps operate at a reduced gas pressure, thereby enabling lower operating voltages and hence lower power consumption. Life is typically the same as a standard triphosphor tube but lumen output is slightly lower than the equivalent standard lamp type. The performance of these lamps is highly dependent on the control gear used in the application.
Dimming of fluorescent lighting offers significant benefits; giving users the opportunity to control of their own lighting, and deliver energy savings. HF dimming can be used for: visual needs, personal control, daylight harvesting, scheduling and other control strategies. It can offer distinct advantages related to intelligence, flexibility and two-way communication.
Dimming creates a rich visual experience and adds flexibility to any room, providing the right lighting environment for a variety of activities.
Dimming saves electricity and reduces the demand on HVAC systems. Dimming fluorescent lighting instead of repeated switching helps to maintain expected long lamp life .
Allowing employees to choose light levels for specific tasks results in greater employee comfort and improved performance.
Using occupancy/movement sensors, daylight sensors and automated time-based controls with fluorescent dimming helps to manage the lighting in an entire building and further reduce electric demand.
There are a number of recognised interfaces for dimming fluorescent lighting. The original HF dimming electronic gear had a 1-10V dc control input which altered the light output in proportion to the applied voltage. This is often referred to as an analogue interface. A digital alternative called DSI (digital serial interface) was developed in order to offer more consistent dimming across a large number of HF ballasts operated by one channel. This technology formed the basis of the new industry standard, DALI (Digital Addressable Lighting Interface), which has been introduced to allow the use of equipment from multiple vendors without compatibility problems. In effect DALI adds to the intelligence of the ballast by giving it an address and permitting two-way communication with a control system.
Today, our society uses a huge variety of electrical equipment to make life more comfortable. However, every piece of electrical or electronic equipment creates an electromagnetic field (EMF) in the close surrounding area of the equipment within which it operates. This also applies to electric lamps. EMF emitted by fluorescent lamps are well within safety limits. European scientific experts identified no health impact from EMF emitted by fluorescent lamps. LIF member companies are committed to, and responsible for, ensuring that all of their products meet the appropriate quality and current EMC standards.
Control Gear (Ballasts)
All gas discharge lamps, including fluorescent lamps, require a ballast (or control gear) to operate. The ballast provides a high initial voltage to initiate the discharge, then rapidly limits the lamp current to safely sustain the discharge. Lamp manufacturers specify the required electrical input characteristics (lamp current, starting voltage, current crest factor, etc.) to achieve rated lamp life and lumen output specifications.
Two different types of ballast are presently being used to drive fluorescent lamps – electro-magnetic and electronic. With the same input power, a fluorescent lamp can deliver more light using high frequency input signals, which means there is a higher system efficiency and hence energy conservation. This gain in overall efficiency can be utilised to provide either lower power consumption for the same light output or additional light output for the same power input (compared to 50Hz control gear). Normally the choice is to reduce power for the same light output. Moreover, a lamp generates virtually no flicker with a high frequency input. Therefore, since electronic ballasts provide better light quality and save energy, they have become more and more popular, and it has become desirable to replace magnetic ballasts with electronic ballasts.
Magnetic/Switch Start Ballast
Magnetic ballasts are inefficient compared to electronic ballasts. They use more electricity in operation and operate at higher temperatures than electronic ballasts. Because of the large inductors and capacitors that must be used, Magnetic ballasts tend to be large and heavy. They commonly also produce acoustic noise (line-frequency hum).
To operate a fluorescent tube using a magnetic ballast also requires a starter and possibly a power factor (PF) capacitor (to correct PF to 0.95).
High Frequency Ballast
An electronic ballast uses solid state circuitry to provide the proper starting and operating conditions to power one or more fluorescent lamps. Electronic ballasts usually change the frequency of the power from the standard mains (e.g., 50 Hz in UK) frequency to between 20,000 and 50,000 Hz, substantially eliminating the stroboscopic effect of 100Hz flicker (a product of the line frequency) associated with electro-magnetic geared fluorescent lighting.
In addition, because more gas remains ionized in the arc stream, the lamps actually operate at about 9% higher efficacy above approximately 10 kHz. Lamp efficacy increases sharply at about 10 kHz and continues to improve until approximately 20 kHz.
Instant (or ‘cold’) start Ballast
An instant start ballast starts lamps without heating the cathodes at all by using a high voltage (around 600 V). It is the most energy efficient type, but gives the least number of starts from a lamp as emissive oxides are blasted from the cold cathode surfaces each time the lamp is started. This is the best type for installations where lamps are in continuous use or at least not turned on and off very often. These types are not compatible with lighting controls using movement sensors.
Rapid start Ballast
A rapid start ballast applies voltage and heats the cathodes simultaneously. It provides superior lamp life and more cycle life, but uses slightly more energy as the cathodes in each end of the lamp continue to consume heating power as the lamp operates. A dimming circuit can be used with a dimming ballast, which maintains the heating current while allowing lamp current to be controlled.
Programmed start Ballast
A programmed-start ballast is a more advanced version of rapid start. This ballast applies power to the filaments first, then after a short delay to allow the cathodes to preheat, applies voltage to the lamps to strike an arc. This ballast gives the best life and most starts from lamps, and so is preferred for applications with very frequent power cycling such as communal areas and toilets with occupancy sensors.
Choice of Ballast
16 mm diameter T5 fluorescent tubes are designed to operate only from dedicated high frequency electronic control gear. Both krypton filled and argon filled 26mm diameter T8 fluorescent lamps can be operated on HF control gear, the former at reduced wattage from their marked value.
Until recently, linear fluorescent lamps have been the preferred choice for emergency lighting. Because of their long life, high efficiency and virtually maintenance free, LEDs are increasingly being used in emergency lighting.
Linear fluorescent lamps can be used in Universal burning position i.e. in any position, vertical or horizontal without detrimental effect to their performance
Run Up or Start Up time
The run-up time of a fluorescent lamp will vary dependent on the lamp selected, particularly whether it contains Mercury or Amalgam. In general, a Mercury lamp will come to full light output quicker than Amalgam. Ballasts are also a significant factor because a wide choice of electronic ballasts are now available, which enables the specifier to select a unit to suit the particular application, and each type has different characteristics.
Re-strike time (Rapid Switching)
In general, linear fluorescent lamps can be switched on and off but the rated life will be reduced by frequent switching. However, certain ballasts i.e. ‘warm-start’ has been designed to lessen the load on linear fluorescent lamps, thereby reducing lumen depreciation and hence life. Also, the use of the lamp also affects its service life and hence, although there may be more frequent switching events, its overall installed life may still be lengthened by a lighting control system.
All lighting equipment is designed to work best at a specific voltage (230VAC for Europe) and any variations in supply voltage to the fixture may be the result of fluctuations in the building’s power distribution system or a voltage reduction programme initiated by the energy provider. Higher or lower voltage supplied to the ballast affects lumen output and input wattages. Generally, a ballast receiving a high supply voltage produces high lumen output at the expense of an increase in input wattage. Conversely, a ballast receiving a low supply voltage would produce a lower lumen output with a reduction in input wattage. Electronic ballasts are not as sensitive to small variations in supply voltage. Some newer versions provide constant lumen output variations of up to + or -10% fluctuations in supply voltage.
All lighting equipment is designed to work best at a specific voltage (230VAC for Europe) and any attempt to supply outside the harmonised limits will invalidate warranty.
Some consumers are concerned about medical problems such as epileptic fits, or mental disturbances (e.g. migraines) caused by fluorescent lamps. A small number of cases have been reported by people who suffer from reactions to certain types of linear fluorescent lamps. In the majority of these cases, the lamps in question were used in offices, restaurants (in certain European countries) and in limited places in domestic households (such as kitchens and garages) These isolated cases were almost certainly triggered by OLD technology which operated on a conventional (Copper-Iron) ballasts with a low frequency - usually 100Hz; this is not the case with new energy efficient linear fluorescent lamp technology which, unlike earlier energy efficiency technologies, operates on high frequency drivers (50kHz). Health related problems can be reduced, or avoided, if consumers opt for new technologies using high frequency drivers.
Mercury is an essential component in the function of fluorescent lamps. The EU ROHS Directive limits the levels of Mercury to no more than 5mg per lamp. No mercury is released when the lamps are in use and they pose no danger when used, and recycled, properly. However, fluorescent lamps are made of glass tubing and can break if dropped or roughly handled. Care should be taken when removing the lamp from its packaging, installing it, or replacing it.
Other types of fluorescent tube are T5 and T9 ‘ring’ or ‘circular’ lamps, offering the same benefits as the linear T5 & T8 types but in a circular format. This alternate shape, allows luminaires to be designed which are more compact and stylish.
Ultra-slim 7mm diameter (T2) lamps are available for special applications where unobtrusive light sources are required e.g. under shelf lighting, picture lighting and display cabinet lighting. T2 lamps may actually be joined together to create a block of lamps, giving a higher light output, compared to T5 lamps of the same dimensions.
Shatterproof tubes are used in factories and workshops and in particular food processing industry where there can be no possibility of glass fragments getting into the products. Basically, they are a normal fluorescent tube with an additional outer skin designed to contain the contents of a lamp if broken.
Linear fluorescent Lamps provide high colour rendering, near constant light output throughout their life, are highly efficient, low-cost in terms of both initial expenditure and running costs, and offer a long life.
Linear Fluorescent Lamps are quite fragile, having a thin glass wall and delicate internals. All linear fluorescent lamps contain small quantities of Mercury which needs to be disposed of correctly at end of life or if the tube is shattered. Linear fluorescent Lamps also require a ballast which adds cost to the lighting package.
BS EN 61195: Double-capped fluorescent lamps. Safety specifications
BS EN 60081 : Double-capped fluorescent lamps - Performance specifications
COMPACT FLUORESCENT LAMPS
Compact fluorescent lamps (CFLs) have the characteristics and advantages of linear fluorescent lamps, but with compact size. Lamp designers have been able to fold the discharge path to reduce the overall size of the lamp, whilst retaining high efficacy. The phosphors used are triphosphors.
As with tubular fluorescent lamps, CFLs consist of a circular glass tube but bent into a more compact shape, coated on the inside with fluorescent phosphors. CFLs contain a dose of mercury in liquid or pill form and a mixture of inert gases. At either end of the tube are electrodes (cathodes) which pass an electrical charge from one end to the other, exciting ions in the process.
There are two types:-
• Single capped CFLni - Compact Fluorescent Lamp – Non-Integrated Ballast
• Self ballasted CFLi - Compact Fluorescent Lamp - -Integrated Ballast
Unlike, linear fluorescent Lamps, where they are of a standardised length and diameter, CFL manufacturers have perfected their own designs of CFL, so you will see differences in the shape and size of the glass envelope and base. The glass tubes may comprise of a single, double, triple, or even quadruple tube which may be linear, tubular or in the case of CFLis, various other shapes. The individual glass tubes are joined together to enable the discharge to pass from one cathode to another. Some versions are enclosed in an outer envelope to more closely resemble the lamps they are designed to replace.
Compact Fluorescent Lamp – Non-Integrated Ballast (CFLni)
How it works
Compact Fluorescent Lamps are highly energy-efficient, low-pressure discharge lamps with a phosphor coating to transform the mercury UV radiation into visible light. CFLni’s utilize specific pin based fittings (see below) to enable connection to separate control gear. High quality ballasts last longer than the lamps and can enable greater energy savings as well as control options such as dimming, daylight control and presence detection. A further environmental benefit over integrated lamps is the fact that when a lamp fails the ballast is not thrown away and can be used to operate a replacement lamp.
CFLnis require separate control gear and are split into 2 main categories:-
· 2-Pin – with an integral starter in the base – these operate on a magnetic ballast. The 2 pin product is scheduled for phase out in Europe under the Energy Using Products Directive.
· 4-Pin – utilising separate control gear and starting device and are designed for operation on high frequency control gear. These lamps can be used for emergency lighting luminaires and where dimming is required.
When luminaire manufacturers are designing fixtures, the size of the lamp is of critical importance. CFLni lamps utilize a T4 tube diameter. The smallest CFLni would be a 7W twin-tube (single) lamp which would enable the design of a very small compact fixture. The largest CFLnis are multiple tube lamps which are designed to replace HiD lamps, for example, in swimming pools where maintenance and instant restrike are key decision making factors.
The light output for a CFLni lamp is typically measured in Lumens, which is the SI measure of "luminous flux". This is a measure of the total number of packets (or quanta) of light produced by the light source or ”quantity” of light emitted. When selecting the appropriate CFLni, the decision will include considering the light emitted or lumens.
The wattage of a CFLni ranges from as little as 5W for a ‘single’ 2-pin lamp, through the most popular 26W double’ to the most powerful 80W ‘long’ lamp. There are now CFLni lamps with multiple tubes, offering up to 120W rating.
A typical efficacy for a CFLni would be between 50 lm/w and 70 lm/w. This is a critical threshold for lamp makers as it is the minimum level to meet Part L of the Building Regulations. Also, when comparing CFLni lamps to linear fluorescent in office applications.
As CFLni benefit from further development, lumen maintenance is improving. The IEC standards stipulate lumen maintenance to be over 75% after 10,000 hours. See EST V6 Appendix C Fig 1
The last 12-18 months has seen the introduction of ‘Energy-Saving’ versions. Based on the standard lamps, these lamps operate at a reduced gas pressure, thereby enabling lower operating voltages and hence lower power consumption. Life is typically the same as a standard tube. Lumen output is slightly lower than the equivalent lamp type.
The majority of CFLnis are used in internal applications such as offices and corridors. As with linear fluorescent lamps, dimming of fluorescent lighting offers significant benefits; giving users control of their own lighting, and energy savings.Digital dimming can be used for: visual needs, personal control, daylight harvesting, scheduling and other control strategies. It can offer distinct advantages related to intelligence, flexibility and two-way communication.
There are a wide range of codes for the cap types on plug in CFLnis. The table below lists these.
The newest development is the G28d plug-in cap which has been developed to reduce the length and size of the lamp holder, as well as the operating temperatures of the lamp in the fixture. This will mean that more compact fixtures can be designed.
There are also possibilities of introducing CFLni lamps into the domestic market. By enabling plug-in CFLs to be used in the residential market, a replaceable ballast can be used, either incorporated into the lamp holder or separately in the fixture.
Ballasts tend to have a longer life than the lamp which means that the lamp can be replaced thereby reducing material going into the waste-stream.
CFLnis enable the design of new compact, energy efficient luminaires. Long length CFLs such as the CFL-L lamp with 2G11 base are now replacing 3 or 4 600mm (2ft) T8 linear fluorescent lamps in modular office fittings, as 1 single CFLni is rated at 80W and offers an efficacy of 85 lm/W.
The CFLni is more popular for with professional users, for example in lighting such as offices and public buildings. However, high Frequency control gear is now available integrated into CFL lampholders, making luminaire conversion from GLS to CFL a relatively simple operation. This is ideal for energy efficient lamps with pendants in domestic housing applications.
CFLni Lamps are low cost, offer long life, a high-efficacy and a very broad range to suit every application. As they operate on a separate ballast, the lamp can be replaced at end of life without disposing of the ballast.
CFLni Lamps can take approx 1 second to light up initially and 1-2 minutes to run up to full brightness.
BS EN 61199: Single-capped fluorescent lamps. Safety specifications
BS EN 60901: Single-capped fluorescent lamps – Performance specifications
Compact Fluorescent Lamp – Integrated Ballast (CFLi)
How it works
A compact fluorescent lamp (CFLi) is also commonly referred to as an energy saving bulb. Many CFLis are designed to replace an incandescent lamp and can fit in the existing light fixtures formerly used for incandescents.
CFLis radiate a different light spectrum from that of incandescent lamps. Improved phosphor formulations have improved the subjective colour of the light emitted by CFLis such that the best 'soft white' CFLis available are subjectively similar in colour to standard incandescent lamps.
There are two main parts in a CFLi: the gas-filled tube (also called bulb or burner) and the electronic ballast. An electrical current from the ballast flows through the gas, causing it to emit ultraviolet light. The ultraviolet light then excites a phosphor coating on the inside of the tube. This coating emits visible light (see Fluorescent lamp).
Electronic ballasts within a CFLi are miniaturized to provide the smallest lamp profile possible while maintaining the component operating temperatures within their design parameters to achieve claimed lamp life. The majority of ballasts for CFLi do not respond well in dimming applications and special ‘Dimmable’ versions are required. These come in two forms switch dimmable and dimmer dimmable.
Originally CFLis were only available in stick type. Many consumers have been put off by the size, appearance and slow-start of CFLis. However, recent developments mean that not only have the most common stick-type CFLis become very compact in size but there are in fact like-for-like replacements for almost every Incandescent lamp on the market. See below.
CFLis are often described as:-
- GLS Look-a-Like
Tube diameters have reduced from T5, to T4, to T3 and the majority are now T2 design.
The light output for a CFLi lamp is typically measured in Lumens, which is the SI measure of "luminous flux". This is a measure of the total number of packets (or quanta) of light produced by the light source or ”quantity” of light emitted. When selecting the appropriate CFLi, the decision will include considering the light emitted or lumens.
The wattage of a CFLi ranges from as little as 5W for a ‘candle’, through the most popular 11W and 20W ‘stick’ types to as much as 36W ‘Spiral’ or 42W ‘tube’, designed to replace double-ended halogen lamps.
A typical efficacy for a CFLi would be from 45 lm/w. This is a critical threshold for lamp makers as it is the minimum level for specifying lamps for EST approval or to meet Part L1 of the Building Regulations.
Run Up or Start Up Time
Incandescents give light almost immediately upon the application of voltage. CFLs take a perceptible time to achieve full brightness, and can take much longer in very cold temperatures. Certain styles of lamp using a mercury amalgam can take up to three minutes to reach full output.
To maximize lamp life lamps should be started with a hot cathode, this minimizes damage to the electrode during starting. The disadvantage is that there is a small delay prior to starting while the cathode reaches the correct temperature. For this reason some lamps are designed to start while the cathode is cold producing an “instant” start with the compromise that this limits the achievable lamp life.
Lamp Operating Temperature
Like Linear Fluorescent lamps, CFLi are affected by the temperature of the environment. Due to the ballast and electronics being enclosed and in the vicinity of the lamp there is an increase in the temperature of the lamp, as opposed to a non-ballasted CFL or Linear Fluorescent lamp. Consequently, the ideal operating temperature for the greatest light output is closer to zero Celsius.
Mercury or Amalgam
Traditionally, CFLis have been criticized for the length of time for them to strike up and achieve full light output. As with fluorescent lamps, light output will vary significantly as a function of temperature unless an amalgam is used in place of pure mercury. Thus a CFLi utilising Amalgam will have a more constant light output across a temperature range. Often, this has a detrimental effect on start-up time. However, by combining the latest electronics with amalgam, some manufacturers have managed to achieve an excellent balance between stable light output and initial run up time.
Ballast and Power Factor
All CFLi lamps have a ballast integrated into the lamp housing. The ballast provides the proper starting voltage, limits the current through the lamp and on long life lamps provides electrode preheating. For some special application lamps the ballast also allows for dimming and may also include circuitry to automatically switch a lamp on and off depending on the ambient light level.
Traditional CFLis have a Power Factor (PF) of approximately 0.6. However, with the ongoing drive for greater energy efficiency, the latest versions are able to offer up to 0.95 PF.
Historically, all CFLi’s on the market have been non-dimmable. This is because current dimmer switches or electronic dimmer systems on the market have been initially designed for the dimming of incandescent or halogen lamps and because of the complexities of designing CFLis with integrated dimming capability - to create a CFLi into a dimmable lamp, special circuitry is required.
Non-dimmable CFLs should not be used in dimmable applications because they tend to have a small amount of electricity running through them even though a lamp is shut off, therefore the lamp continually tries to turn itself on, which shortens the CFL life.
In order for CFLis to offer true like-for-like replacement, manufacturers have developed 2 distinct types of Dimmable CFLis:-
· ‘Switch’ Dimmable(Known as ‘DorS’ Dimming) - Using a conventional plate switch, the user can control and select the preferred light levels
· ‘Dimmer’ Dimmable – Fully dimmable from 100% down to as low as 3% (in some instances), at 1% (barely visible) increments
The range available now extends to GLS, Candle, Ball, Tubular, PAR38 and GU10.
There are dimmable compact fluorescent bulbs sold specifically for dimmable applications. The package should clearly state if the bulb is dimmable
The initial driver for the introduction of CFLis as replacements for incandescent lamps was their longer life. CLFis tend to range in life from 3,000 hours up to 15,000 hours. UK Energy Companies subsidise programmes to promote and distribute CFLis to consumers – the longer the life the greater Carbon Savings can be claimed. The average life of CFLi is now 10,000 hours. For a domestic dwelling at 3 hours per day, this equates to 1,000 hours per annum i.e. a 10 year life.
As CFLis benefit from further development, lumen maintenance is improving. The IEC standards stipulate lumen maintenance to be over 75% after 10,000 hours. See EST V6 Appendix A Fig 2
Whereas the incandescent lamps which they replace have been offered in a wide choice of colours, developed over the years, CFLis tend to be available in 3 main colours:
- Warm White – Colour 827 – Ideal for Homes and Restaurants
- Cool White – Colour 840 – Ideal for more business-like environments such as dental surgeries, opticians, pharmacists. However, some consumers prefer to choose a cooler light to create a modern, sophisticated environment in the home
- Daylight – Colour 860 or 865
Good quality CFLis utilise a triphosphor coating on the glass wall which offers excellent colour rendering.
Some CFLis are available with a silicon coating on the outside of the glass to prevent damage.
Some consumers are concerned about medical problems such as epileptic fits and other mental disturbances (e.g. migraines) caused by fluorescent lamps. CFLis give a constant, nearly flicker free, non-stroboscopic light. They operate at high frequency through their electronic controller at between 30,000-50,000 hertz (normal mains voltage cycles at just 50 hertz or cycles per second). Some of the older style CFLis may have used traditional wire wound ballasts which could have result in a very small number of reactions. Health related problems can be therefore reduced if consumers ensure that all their CFLis utilise the latest technology. In addition there are a very small number of people with photo-sensitive conditions that can be triggered by CFLis. Alternative low energy light sources are required for these patients.
CFLi Lamps are now suitable for almost every application where Incandescent and Halogen lamps have previously been used. Not only are they applicable in Residential applications but they are also perfectly suited to hotels, bars, reception areas.
CFLis have been the main vehicle for achieving carbon/energy savings on lighting in the UK, over the last 10 years. Compared to general service (GLS) incandescent lamps giving the same amount of visible light, CFLis use less power and have a longer rated life, but generally have a higher purchase price. A CFLi can significantly reduce electricity costs over the lamp's lifetime compared to an incandescent lamp and save many times its own weight in greenhouse gases. Like all fluorescent lamps, CFLis contain mercury and fall under the remit of the WEEE regulations.
CFLi Lamps offer long life, a high-efficacy and a full range to retro-fit incandescent and halogen lamps.
CFLi Lamps can take approx 1 second to light up initially and 1-2 minutes to run up to full brightness, which incandescent or halogen lamps achieve very quickly.Some CFLis are not very aesthetic as they utilize exposed tubes.
BS EN 60968: Specification for self-ballasted lamps for general lighting services. Safety requirements
BS EN 60969: Self-ballasted lamps for general lighting services – Performance requirements
BS EN 61000-3-2: Electromagnetic compatibility (EMC) part 3-2: Limits - limits for harmonic current emissions
BS EN 61547: Equipment for general lighting purposes - EMC immunity requirements
BS EN 55015: Limits and methods of measurement of radio disturbance characteristics of electrical lighting and similar equipment
Copyright © 2009 Lighting Industry Association Ltd. All rights reserved. No reproduction full or partial without consent.