I have this light in our laundry room that only lights up when it felt like it. After trying new bulbs it didn't need, and being only a couple years old, I figured the ballast was ok. So I did some research, and discovered the problem.......all it needed was to be grounded! It appears that the metal reflector acts as a capacitor that aids in startup only when it's grounded.:Smarty: I copied the text......here's some interesting reading: Hello Sterling: The fluorescent lamps you refer to are probably a mix of mercury and argon gas. There are many ways that lead to failure because of interaction between the ionizing electrodes and types of ballast. Here are some pointers for troubleshooting: Bad fluorescent tubes: Unlike incandescent lamps where a visual examination of the bulb itself will often identify a broken filament, there is often no way of just looking at a fluorescent tube to determine if it is bad. It may look perfectly ok though burned out fluorescent will often have one or both ends blackened. However, a blackened end is not in itself always an indication of a bad tube. Blackened ends are a somewhat reliable means of identifying bad tubes in 34 or 40-watt rapid start fixtures. Blackened ends are not as reliable an indicator in preheat or trigger start fixtures, or for tubes of 20 watts or less. Failure of the electrodes/filaments at one or both ends of the fluorescent tube will usually result in either a low intensity glow or flickering behavior or sometimes in no light at all. A broken filament in a fluorescent tube used in a preheat type fixture (with a starter) will usually result in a totally dead lamp as there will be no power to the starter. Dim glow is rare in this case and would probably be confined to the region of the broken filament if it occurs. The best approach is to simply try replacing any suspect tubes - preferably both in a pair that are driven from a single ballast. In fixtures where rapid start ballast runs two tubes, both tubes will go out when one fails. Sometimes one or both tubes will glow dimly and/or flicker. If one tube glows dimly and the other is completely dead, this does not indicate which tube has failed. The brighter tube may be the good one or the bad one. The bad tube usually has noticeable blackening at one end. It may pay to replace both tubes, especially if significant labor costs are involved. In addition, prolonged dim glowing may degrade the tube that did not initially fail. In trigger start fixtures that uses one ballast to power two 20-watt tubes, sometimes both tubes will blink or intermittently dim. Replacing either tube with a known good tube may fail to fix this. The tubes may continue blinking or intermittently dimming until both are replaced with brand new tubes. This sometimes indicates borderline low line voltage ("brownout," etc.), non- ideal temperatures, or a borderline (probably cheaply designed) ballast. Bad starter (preheat fixtures only): Faulty fluorescent tubes continuously trying to start unsuccessfully may damage the little starter. It is a good idea to replace the starter whenever tubes are replaced in these types of fixtures. One way that starters go bad is to "get stuck". Symptoms of this are the ends of the affected tube glowing, usually with an orange color of some sort or another but sometimes with a color closer to the tube's normal color if arcs form across the filaments. Occasionally, only one end arcs and glows brightly, and the other end glows dimmer with a more orange color. Note that this is hard on both the tube and the ballast, and the defective starter should be immediately removed. Should one or both ends glow with a bright yellowish orange color with no sign of any arc discharge surrounding each filament, then the emissive material on the filaments is probably depleted or defective. In such a case, the tube should be replaced regardless of what else is wrong. If both ends glow dim orange colors, then the filaments' emissive coating may or may not be in good shape. It takes approx. 10 volts to form an arc across a healthy fluorescent lamp filament. Defective iron ballast: The ballast may be obviously burned and smelly, overheated, or have a loud hum or buzz. Eventually, a thermal protector built into ballasts will open due to the overheating (though this will probably reset when it cools down). The fixture may appear to be dead. Bad ballast could conceivably damage other parts as well and blow the fluorescent tubes. If the high voltage windings of rapid start or trigger start ballasts are open or shorted, then the lamp will not start. Ballasts for fixtures less than 30 watts usually do not have thermal protection and in rare cases catch fire if they overheat. Defective fixtures should not be left operating. Bad sockets: These can be damaged through forceful installation or removal of a fluorescent tube. With some ballasts (instant start, for example), a switch contact in the socket prevents generation of the starting voltage if there is no tube in place. This minimizes the possibility of shock while changing tubes but can also be an additional spot for a faulty connection. Lack of ground: For fluorescent fixtures using rapid start or instant start ballasts, it is often necessary for the metal reflector to be connected to the electrical system's safety ground. If this is not done, starting may be erratic or may require you to run your hand over the tube to get it to light. In addition, of course, it is an important safety requirement. ou:
Here's another one I thought was interesting: Introduction Fluorescent Lamp Basics The fluorescent lamp was the first major advance to be a commercial success in small scale lighting since the tungsten incandescent bulb. Its greatly increased efficiency resulted in cool (temperature wise) brightly lit workplaces (offices and factories) as well as home kitchens and baths. The development of the mercury vapor high intensity discharge (HID) lamp actually predates the fluorescent (the latter being introduced commercially in 1938, four years after the HID). However, HID type lamps have only relatively recently become popular in small sizes for task lighting in the home and office; yard and security area lighting; and light source applications in overhead, computer, and video projectors. Fluorescent lamps are a type of gas discharge tube similar to neon signs and mercury or sodium vapor street or yard lights. A pair of electrodes, one at each end - are sealed along with a drop of mercury and some inert gases (usually argon) at very low pressure inside a glass tube. The inside of the tube is coated with a phosphor which produces visible light when excited with ultra-violet (UV) radiation. The electrodes are in the form of filaments which for preheat and rapid or warm start fixtures are heated during the starting process to decrease the voltage requirements and remain hot during normal operation as a result of the gas discharge (bombardment by positive ions). When the lamp is off, the mercury/gas mixture is non-conductive. When power is first applied, a high voltage (several hundred volts) is needed to initiate the discharge. However, once this takes place, a much lower voltage - usually under 100 V for tubes under 30 watts, 100 to 175 volts for 30 watts or more - is needed to maintain it. The electric current passing through the low pressure gases emits quite a bit of UV (but not much visible light). The gas discharge's radiation is almost entirely mercury radiation, although the gas mixture is mostly inert gas and generally around something like 1 percent mercury vapor. The internal phosphor coating very efficiently converts most of the UV to visible light. The mix of the phosphor(s) is used to tailor the light spectrum to the intended application. Thus, there are cool white, warm white, colored, and black light fluorescent (long wave UV) lamps. There are also lamps intended for medical or industrial uses with a special envelope such as quartz that passes short wave UV radiation. Some have an uncoated envelope, and emit short-wave UV mercury radiation. Others have phosphors that convert shortwave UV to medium wave UV. (Caution: Some specialty UV lamps emit shortwave or medium wave UV which is harmful and should not be used without appropriate protection or in an enclosure which prevents the escape of harmful UV radiation.) Fluorescent lamps are about 2 to 4 times as efficient as incandescent lamps at producing light at the wavelengths that are useful to humans. Thus, they run cooler for the same effective light output. The bulbs themselves also last a lot longer - 10,000 to 20,000 hours vs. 1000 hours for a typical incandescent. However, for certain types of ballasts, this is only achieved if the fluorescent lamp is left on for long periods of time without frequent on-off cycles. Fluorescent Lamp Labeling The actual fluorescent tubes are identified by several letters and numbers and will look something like 'F40CW-T12' or 'FC12-T10'. So, the typical labeling is of the form FSWWCCC-TDD (variations on this format are possible): F - Fluorescent lamp. G means Germicidal shortwave UV lamp. S - Style - no letter indicates normal straight tube; C for Circline. WW - Nominal power in Watts. 4, 5, 8, 12, 15, 20, 30, 40, etc. CCC - Color. W=White, CW=Cool white, WW=Warm white, BL/BLB=Black light, etc. T - Tubular bulb. DD - Diameter of tube in of eighths of an inch. T8 is 1", T12 is 1.5", etc. For the most common T12 (1.5 inch) tube, the wattage (except for newer energy saving types) is usually 5/6 of the length in inches. Thus, an F40-T12 tube is 48 inches long. -------------------------------------------------------------------------------- Back to Flamp FAQ Table of Contents. Safely Working with Fluorescent Lamps and Fixtures There aren't many dangers associated with typical fluorescent lamps and fixtures: Electric shock. There is usually little need to probe a live fixture. Most problems can be identified by inspection or with an ohmmeter or continuity tester when unplugged. Fluorescent lamps and fixtures using iron ballasts are basically pretty inert when unplugged. Even if there are small capacitors inside the ballast(s) or for RFI prevention, these are not likely to bite. However, you do have to remember to unplug them before touching anything! However, those using electronic ballasts can have some nasty charged capacitors so avoid going inside the ballast module and it won't hurt to check between its outputs with a voltmeter before touching anything. Troubleshooting the electronic ballast module is similar to that of a switchmode power supply. See the document: Notes on the Troubleshooting and Repair of Small Switchmode Power Supplies Nasty chemicals: While the phosphors on the inside of fluorescent tubes are not particularly poisonous, there is a small amount of metallic mercury and contact with this substance should be avoided. If a tube breaks, clean up the mess and dispose of it properly and promptly. Of course, don't go out of your way to get cut on the broken glass! And take care around sharp sheet metal! -------------------------------------------------------------------------------- Back to Sam's F-Lamp FAQ Table of Contents. Fluorescent Fixtures and Ballasts Fluorescent Fixtures The typical fixture consists of: Lamp holder - the most common is designed for the straight bipin base bulb. The 12, 15, 24, and 48 inch straight fixtures are common in household and office use. The 4 foot (48") type is probably the most widely used size. U shaped, circular (Circline(tm).) and other specialty tubes are also available. Ballast(s) - these are available for either 1 or 2 lamps. Fixtures with 4 lamps usually have two ballasts. See the sections below on ballasts. The ballast performs two functions: current limiting and providing the starting kick to ionize the gas in the fluorescent tube(s). Switch - on/off control unless connected directly to building wiring in which case there will be a switch or relay elsewhere. The power switch may have a momentary 'start' position if there is no starter and the ballast does not provide this function. Starter (preheat fixtures only) - device to initiate the electrode preheating and high voltage "kick" needed for starting. In other fixture types, the ballast handles this function. Fluorescent Lamp Ballasts For a detailed explanation, check your library. Here is a brief summary. A ballast serves two functions: 1. Provide the starting kick. 2. Limit the current to the proper value for the tube you are using. In the old days fluorescent fixtures had a starter or a power switch with a 'start' position which is in essence a manual starter. Some cheap ones still do use this technology. The starter is a time delay switch which when first powered, allows the filaments at each end of the tube to warm up and then interrupts this part of the circuit. The inductive kick as a result of interrupting the current through the inductive ballast provides enough voltage to ionize the gas mixture in the tube and then the current through the tube keeps the filaments hot - usually. You will notice that a few iterations are sometimes needed to get the tube to light. The starter may keep cycling indefinitely if either it or one of the tubes is faulty. While the lamp is on, a preheat ballast is just an inductor which at 60 Hz (or 50 Hz) has the appropriate impedance to limit the current to the tube(s) to the proper value. Ballasts must generally be fairly closely matched to the lamp in terms tube wattage, length, and diameter. Types of Iron Ballasts Instant start, trigger start, rapid start, etc. ballasts include loosely coupled high voltage windings and other stuff and do away with the starter: The ballast for a preheat fixture (combined with a starter or power switch with a 'start' position) is basically a series inductor. Interrupting current through the inductor provides the starting voltage. The ballast for a rapid start fixture has in addition small windings for heating the filaments reducing the required starting voltage to 250 to 400 V. There are probably the most common types in use today. Trigger start fixtures are similar to rapid start fixtures. The ballast for an instant start fixture has a loosely coupled high voltage transformer winding providing about 500 to 600 V for starting in addition to the series inductor. The electrodes of "instant start" bulbs are designed for starting without preheating. In fact, they are shorted out internally and are thus incompatible with preheat and rapid start ballasts (and they have only a single pin at each end!). The electrodes still emit electrons due to thermal emission but since they are shorted out cannot be pre-heated. That is why they require a higher starting voltage from the ballast. They they light instantly, but this slightly reduces lamp life. Starting voltage is either provided by the inductive kick upon interruption of the current bypassed through the starter for (1) or a high voltage winding in (2) and (3). In all cases, the current limiting is provided primarily by the impedance of the series inductance at 60 Hz (or 50 Hz depending on where you live). (From: Vic Roberts (kirther@ix.netcom.com).) The most basic ballast is nothing more than a current limiting device, such as an inductor, resistor or capacitor. For 50 and 60 Hz applications, the most common current limiting device is an inductor. A simple current limiter works best when the line voltage is at least 2 times the lamp voltage. So, a simple inductor can be used in Europe, where the line voltage is 220 to 240 VAC, to operate a 4 foot lamp, which operates at 85 to 100 volts, depending upon design. In the US and other places that use 120 VAC lines the ballast is a combination autotransformer (to raise the voltage) and inductor (the current limiter). In addition, a Rapid Start ballast has additional windings to supply about 3.6 VAC to heat the filaments. (From: Asimov (Asimov@juxta.mn.pubnix.ten).) A ballast is a simple transformer with a very high impedance secondary winding which makes its current self-limiting. It also has windings for each lamp filaments. At startup the filaments get most of the power and heat up to facilitate ionization. Meanwhile the secondary builds up a very high EMF which finally fully ionizes the plasma between both filaments. At this point the effective resistance of the conducting plasma is quite low and the current flow is limited by the secondary's impedance. This also partially saturates the core and as consequence reduces power to the filaments. The usual failure in ballasts is that the secondary's insulation deteriorates and it starts leaking to ground. Often because the proper wiring polarity was not observed. The secondary can thus no longer generate the high EMF required to start the plasma conducting. The KISS test method is to use a known good lamp. If it lights, the ballast is good too. The ballast can also be tested with the power off by checking for continuity in the filament windings and a very high resistance to ground for each filament. Don't try this with power on! (From: Craig J. Larson (larson@freenet.msp.mn.us).) Call Magnetek, a ballast manufacturer on 1-800-BALLAST. Ask for a copy of their Troubleshooting & Maintenance Guide for Linear Fluorescent Lighting Systems. Its a nice little guide book for teaching you the basics. Electronic Ballasts These devices are basically switching power supplies that eliminate the large, heavy, 'iron' ballast and replace it with an integrated high frequency inverter/switcher. Current limiting is then done by a very small inductor, which has sufficient impedance at the high frequency. Properly designed electronic ballasts should be very reliable. Whether they actual are reliable in practice depends on their location with respect to the heat produced by the lamps as well as many other factors. Since these ballasts include rectification, filtering, and operate the tubes at a high frequency, they also usually eliminate or greatly reduce the 100/120 Hz flicker associated with iron ballasted systems. However, this is not always the case and depending on design (mainly how much filtering there is on the rectified line voltage), varying amounts of 100/120 can still be present. I have heard, however, of problems with these relating to radio frequency interference from the ballasts and tubes. Other complaints have resulted due to erratic behavior of electronic equipment using infra red remote controls. There is a small amount of IR emission from the fluorescent tubes themselves and this ends up being pulsed at the inverter frequencies which are sometimes similar to those used by IR hand held remote controls. Some electronic ballasts draw odd current waveforms with high peak currents. This is due to the fact that these ballasts (low-power-factor type) have a full-wave-bridge rectifier and a filter capacitor. Current can only be drawn during the brief times that the instantaneous line voltage exceeds the filter capacitor voltage. Because of the high peak currents drawn by some electronic ballasts, it is often important to size wiring properly for these high peak currents. For wiring heating and fuse/circuit considerations, one should allow for a current of 4 to 6 times the ratio of lamp watts to line volts. For wiring voltage drop considerations (drop in voltage the ballast's filter capacitor gets charged to), the effective current is even higher, sometimes as high as 15 to 20 times the ratio of the lamp watts to RMS line volts. For less than 50 watts, the current drawn by low-power-factor electronic ballasts is usually not a problem. For multiple ballasts or total wattages over 50 watts, it may be important to consider the effective current drawn by low-power-factor electronic ballasts.
bad things about flourescent lighting is the wavelength at which they operate. makes many people prone to mingraines and eye strain.. They are too extra reliant upon the grounding for harmonics.. yes even smaller fixtures need to be harmonized so to speak in order to work. in older days the common was the ground and everything was bonded. (neutrals and grounds) Today theyve broken that habit and everthing has a seperate ground.. Utilising the ground as a super neutral so to speak but on a lower scale. Other problems with flourescents is they produce one helluva magnetic field and in tight areas and create alot of static discharge.. most critical industries that use volatile materials resort to magnetic illuminescance than flourescent since they produce almost no resistance and arcing and low impedant shorts are nil. Way more expensive to install but you never needs to change lightbulbs ever again and the light is 100% natural white light. underground gov installations use magnetic illuminescance . Runs like low voltage too and gets twice the light. Did you know that part of the kioto accord included a standard to eliminate all incandecant bulbs by the 2012? There's plenty of more efficient lighting tech out there thats not on the affordable platform yet cuz of interference from companies like siemens and GE & sylvania.. bite too much into their profits...Most of the money spent in america on energy bills has to do with crappy incandecent bulbs the second are inefficient heatpumps in florida and california Constellation doesn't want efficiency on the civil sector.. It bites into their profits as well. ...
