Overdriving Fluorescent Lightsby James L. Haworth


Overdriving fluorescent bulbs is a method of getting more light from each bulb than is normally obtained. It involves taking the light fixture apart and rewiring the insides. Each electronic ballast normally drives either two or four bulbs. The ballasts are then tied together in such a way that a two-bulb ballast now drives a single bulb and a four-bulb ballast drives only two bulbs, sometimes it only drives one. Usually, an extra ballast is put into the fixture and wired into the bulb circuit. For instance, if you have four bulbs in the fixture and they have a four-bulb ballast, this ballast now drives two bulbs and another four-bulb ballast is used to drive the remaining two bulbs. If the directions in this article are carefully followed, this rewiring is not dangerous and the bulbs won’t blow up, they simply become brighter. The bulbs are limited by their design to draw only so much current and no more. If you double the amount of current, you won’t get a bulb that’s two times brighter because the efficiency drops off a bit. So even after the increased current is made available, a bulb driven by a factor of two times its normal supply, only gets 1.7 times brighter. You can do a 1x, 2x, or 3x overdrive with a four-lamp ballast, but the efficiency drops. (4x output into one bulb is only 2.4 times as bright as normal).

Put another way; the output of the bulbs does not increase in direct ratio to the amount of power the ballast consumes. The more times you overdrive a fluorescent bulb, the less efficient it becomes, as it is starting to drift out of the bulb's optimal design parameters.

The information for this article was partially gleaned from postings on forums all over the Internet. The forums included gardens (seed starting), fish/aquarium (freshwater and salt water), houseplants, pro studio photography, reptiles, electronics, and others. If you see postings here that you’ve seen elsewhere, keep in mind that I’m just trying to bring some semblance of order out of the inherent disorder of every forum out there that deals with this subject. If you have a question about your particular application, please try some of these forums. There are people who are very knowledgeable about the process of overdriving and they are willing to help you. Many, many people have rewired their fluorescent fixtures with no explosions or house fires that I know of. There are people out there that are deathly afraid of electricity, and if you are one of them, perhaps you shouldn't rewire your lamps. If you haven't overdriven your own fixtures, please don't be a nervous nelly and post gloom and doom predictions of disaster for those who want to try this. The data took many hours to put together into a more or less readable form. Sorry there’s no way to give proper credit to everyone who contributed to this huge Internet pool of information.

This is a rather long article and seems to be very complicated, but really, it’s not bad once you get the core idea of what’s involved. Don’t be apprehensive. Check each step carefully and then recheck. You’ll be fine!

Safety first! 

I must issue a warning or three. If you don't know much about working with electricity, you should read up on electrical wiring techniques.

Don’t even think about using a magnetic ballast, it won’t work for overdriving fluorescent lights, and you might have a very smelly incident as the internals melt down.

Utilizing ODNO (Overdriven Normal Output) fluorescent lighting technology will likely void your warranty on ballast and/or bulbs. We are not responsible for damage caused by improper use or failures due to overdriving fluorescent lights.

Use or install a GFCI fixture to plug your fluorescent fixture into after you’ve rewired it. Use a power strip with a circuit breaker on the strip if you don’t have a Ground Fault Circuit Interrupter. This will offer a degree of protection for you, if you’ve made a mistake in the wiring. Always make sure a ground wire is connected to the fixture! This is for safety and it helps the lamps to start when the metal reflector is grounded.

Be careful if you’re using this setup to power lighting for an aquarium, you know, electricity and water. Nuff said.

Why electronic ballasts?

Fluorescent lights have notoriously been known for flicker and hum. This is no longer a problem with the new electronic ballasts. This is because with magnetic ballasts the fluorescent lamp actually drops out of ionization and get re-ionized 60 times a second. Electrical engineers discovered that once you speed the process up to at least 4,000 Hertz (cycles per second), the gas stays ionized (no more flicker). This is also a bit more efficient. And, since the notorious hum would now become a squeal, engineers design electronic ballast to oscillate above the range of human hearing. No more noticeable hum.

First, you are not rewiring the ballast. You are rewiring the outputs of the ballast (nothing internal). Electronic ballasts which operate more than one lamp often show several wiring options, so the same ballasts can be used in several configurations, thus saving the manufacturer money. What rewiring to overdrive lamps does, is cause the circuitry to see a different load drawing the current. The output transistors can do this and still be functioning within proper specifications. This is neither dangerous nor illegal; it’s simply the way electronic ballasts are designed. The most telling thing about the results is that, using a 2x overdrive; the ballast draws less power with one lamp than it would draw normally with 2 lamps. The two output transistors are teaming up and actually drawing less amperage than normal (with 2 lamps).

Put another way, when you re-arrange the output of the ballast wiring to overdrive a lamp, you are sharing the "lamp load" between the individual lamp circuits. The ballast itself is actually UNDERDRIVEN, since it is now sending LESS total current to a single lamp than it would normally be sending to two lamps. It is the lamp that gets OVERDRIVEN. The ballast is running cooler, the bulb running hotter. This does not burn out the bulb, although it's life is shortened a bit.

The ballasts used for overdriving are actually running below their normal capacity, sharing the duty, and drawing less than normal. I have done this with 7 different types and wattages of electronic ballasts and they ALL worked well.

In a two-lamp fixture, overdriving (which requires a ballast that drives 2 or more lights) involves disconnecting the wires from both ends of one lamp's socket, and joining them to the wires of the remaining lamp. This results in a 32w lamp being driven to put out approximately 1.7 times as much light as normally produced. This will reduce the life of the lamp somewhat, but in the overall picture it is very economical to replace a 32w bulb-even twice as often. With fluorescent lights, over 95% of the total cost of using the bulb is the electricity, since the bulbs last so long to begin with. I used both a current meter and a light meter to compare my results. Your own eyes can DEFINITELY see the difference.

On the T8’s and T12 bulbs, this 2-pin plug and socket are called “medium bi-pin”.

This picture shows the power cord crimp twisted out of the fixture to allow more of the cord to be shoved inside the fixture.

The little plastic power cable “pass-thru clip” on the metal case is a little tricky to get loose, if you need to do that. With the right pair of pliers you can compress the clip and pull it gently to squeeze out of the hole. I often remove it for one reason or another, but sometimes it is just easier to splice the wires that you need to lengthen, rather than pulling out the plug to get more length.


The power wires were held together with a crimped connector (lower right in this picture and picture above). I squeezed that connector after I pushed the power wires further into the fixture and pushed it back into the hole in the fixture. Then I used regular twist on wire nuts (red-orange on left side of picture) to add the second ballast as shown here. How you "mount" the second ballast in the fixture: I took the screws out of the existing one and simply wedged the second one in next to it. Get a few sizes of wire nuts. Sometimes you'll be splicing just two wires together. Sometimes you'll be splicing four, and need a bigger wire nut.

Since the wires are longer on one side of the ballast than the other, I found out that I can turn the second ballast around, mount it on the other end, and the wires will reach just fine. I mount it wherever the wires will conveniently fit right.

These two pictures are of the side of the fixture where you combine the blues
and reds on the Rapid Start system. See diagram below.

This is the way the tombstones look on the other end after the ballast is rewired on the Rapid Start system. Diagram to the left.

It was a pain-in-the-butt to figure out how to get the existing wires out of those “push-in-and-stay-in” type sockets. Do not pry the back off of the sockets. I did that once, early on, and broke the plastic socket apart doing it. I finally developed the knack of doing what I can only call a “twist and wiggle” technique to get the existing wires out of their slot. Although I can get most of the wires off, I still end up breaking off 10-15% of them. Since you end up with a couple of extra sockets anyhow, you can afford to mess up a few of them. As a last resort, I would have gone ahead and cut and spliced the wires if I couldn’t get the wires wiggled out of the socket. Once you push that wire in, it wants to stay in. Trial and error will hopefully lead you to a useable technique.

After you use the four-lamp ballast to overdrive two fluorescent lights, take the electronic four-lamp ballast out of another four-lamp fixture and place it in the first fixture. Now wire the second ballast to the third and fourth lamps using the same wiring techniques as you did with the first ballast.

Home Depot sells a GE ballast for 4 lamps, B432I120RH. Another commonly available 4-lamp ballast is the Advance REL-4P32-SC. Both of these can be used to overdrive 2 fluorescent lamps. If you use either of these two ballasts I mentioned above, be aware that those are Instant-Start. Without going into the technical differences now, the instant-start method has only ONE wire going to each socket, and the socket will have the two connections (lamp pins) jumpered together. Instant-Start fixtures have only one wire normally go to each socket with the socket’s two connectors being shorted together. Instant Start ballasts are actually a little simpler to wire together – coupling two wires together instead of two PAIRS of wires.

So far I have overdriven at least 20 ballasts, with no problems. You will be left with a lot of fixtures with bulbs but no ballasts. I used my Dremel tool to cut some of them up and make custom fixtures, reflectors and what not. Try this with overdriving: On the workbench, instead of using one 48”-32w bulb, try lining up 2-24” 17w T8 bulbs in series and jumper two of the bulb end together - sort of making one long 48” bulb. You will find that one Sunpark ballast will overdrive them in series like that. THEN, make yourself a 24” 2-bulb fixture following the wiring you used.

You can make a small, really bright overdriven fluorescent light that way. I made a 24” 4-bulb fixture using 2 overdriven ballasts.

Even better, instead of the standard medium bi-pin sockets, find a 2G11($3.50) socket and a 22” Philips PLL 40w twin tube compact lamp ($10 or less some places). One 40watt lamp of that type will GLOW LIKE ALL GETOUT with that ballast.

Overdriving will also work on black lights, if you have a need for such things.


If you don’t want to monkey around with getting the wires in and out of the sockets you can use solderless tap connectors - the ones I know of are called Scotchloks. Home Depot and Radio Shack should have them; just make sure you get the right ones for your wire size. These let you tap into a wire without cutting it - for example you could cut off the red wires in the middle, then lay the blue wire in the Scotchlok, lay the end of the red wire in it, fold over the top and press it together carefully with pliers.

I located the discussions I had read between several PhD level Electrical Engineers who WERE lighting experts. They discussed the “overdrive” effect and how it is a good and well-established approach to obtaining more useable fluorescent light. One problem I had in searching is that they did NOT use the term “overdrive” in their discussion. Probably because in their eyes it was a simple circuit reconfiguration, which has already been known and has been in use for years.

I did not even try to overdrive fluorescents, until I searched the web. I have to say I was ABSOLUTLEY OVERWHELMED at the amount of information I discovered about the subject. This “overdriving” effect has been a standard, used and perfected, for YEARS in the realms of the “Fish and Coral” enthusiasts.


Will overdriving fluorescent bulbs change the frequency of light emitted?

First, in regards to frequency shift due to overdriving a fluorescent bulb, the light color WILL NOT change. The process is governed by laws of quantum physics, which guarantee that it will not shift color. I will explain.

This is the process that happens, either 60 or 120 times a second with magnetic ballasts, or 22,000 to 45,000 times a second with electronic ballasts. The ballast initially provides a high voltage to the filaments at each end of the fluorescent lamp. When the voltage reaches a critical level, the gas in the tube (mainly argon with a little mercury) suddenly becomes ionized, and current rushes through the tube. “Ionization” means an atom now has more electrons than it normally would contain in its outer shell. In this case, extra electrons have been induced to go racing around the “conduction band” of the mercury atoms to get to the other side of the tube. Sufficient voltage pressure is created by the ballast to force the gas into ionization in the fluorescent tube.


In the process, the electrons in the outer shell of the mercury atoms randomly pick up extra energy and go into a higher sub-orbit that normal. Those electrons then drop back to the original orbit as soon as possible, which releases an EXACT amount of energy (a quantum level) as a photon. That photon will ALWAYS be an exact color frequency based on the atom and it’s outer-shell electron. As far as the mercury atoms go, this will actually be ultra-violet light (UV), and is not the final color output of the lamp.

The actual color that is emitted from the tube is based on the type of phosphors, which coat the inside of the tube. The same process that I just described above is repeated there, at the phosphor coating, when the photons from the mercury atom hit the tube. There the UV photons are absorbed by the phosphor compounds and re-emitted at the SPECIFIC QUANTUM LEVEL, or color, as the phosphors had been designed to emit. The photon(s) emitted cannot possibly violate the energy levels set by nature. More ENERGY (by overdriving) will translate to more LIGHT. In this case, it is just as if you shone more light on an object, and it got brighter, not colored differently.

For those who are interested, here is a link to a major phosphor manufacturer’s list of all their lamp phosphors, the exact color of each and the width (or bandwidth) of color peak: http:// www.nichia.com/lamp.html. I recently read that this one company, Nichia, is the source of phosphor coatings for 40% of the fluorescent lamp manufacturers.


Since I began investigating the overdrive phenomenon, I have done a great deal of reading on both the electronics theory behind how it works and testimonials from real world users. Actually, there are several ballast manufacturers (Fullham, Workhorse, Icecap, etc.) who have been producing high performance electronic ballasts for many years now. Many of these ballasts are designed to drive a wide range of bulbs, with full understanding that many of the allowable bulb combos are definitely being powered by more current than they were initially built for.

Those ballasts were DESIGNED to be able to do that, and this is exactly what people in the know with fish and coral tanks have been doing for years. I was delighted to read several discussions by electrical engineers who discussed how it works, and why it is a good way to get more light from a bulb. The only detrimental effect, they pointed out, was a reduction in lamp life. I do not think the reduction in lamp life is significant, or much of a factor in practical use. The people who have recommended this have usually stated that they change their bulbs at least once a year anyhow, and do not have a burnout by then. I have had 2x overdriven lamps burning for 12-18 hours a day for nearly a year now- with no burnouts yet. Most ALL of the electronic ballasts I have played with were capable of a variety of overdrive scenarios.

Some fixtures use an Instant Start ballast. That is even easier to overdrive than a Rapid Start ballast because there is only one lead going to each end of the bulb, instead of two. You will also find there is a jumper wire, right at the socket, which will connect the two bulb pins together. That is inherent in an Instant Start. 

A Rapid Start ballast has 2 wires connected to each socket because it initially sends a pre-heating current through the filament in the bulb’s end to aid in the initial ionization of the mercury/argon gas. The filament inside the lamp has a small resistance (between the two lamp pins) because it provides a heating function on startup ONLY if you are using a Rapid Start ballast. An Instant Start ballast is designed to provide a higher starting voltage, eliminating the need to pre-heat the filament.

Step by step, this is how we wire our four bulb fixtures.

Since you are gonna do this, we shall vow to avoid both sparks and ballast killing. And as for the “jiggle” technique - actually twisting and pulling at the same time - I was describing removing existing wires from their sockets. All of the fluorescent sockets I have ever seen have connections where, once the wires are pushed in, they require some self-learned trial-and-error method to get them back out. Often they break off right at the point you need to re-insert a different wire. I hate that. Luckily, there are almost always 2 insert slots for EACH of the 2 connecting points. In the case of an Instant Start ballast you can probably still rewire with at least one broken end stuck inside the socket. With luck, you may not even have that problem. Also, if you have any non-working fixtures around, you can scavenge a socket if you need one.

Now, I want to make sure that I know you comprehend one thing in particular about the sockets. The basic fluorescent bulb, or lamp, has two pins at each end of the tube. These two pins plug into the socket. Inside the lamp, each pin attaches to one end of a heating filament. One connection point in the socket for each of the two pins on the bulb. Each one of those two connection points usually has two “self-grasping” slots to insert a wire into. In other words - 4 little insert slots for ballast wires on each socket (see pictures above).

With a Rapid Start ballast, a separate wire goes from the ballast to each of the 2 connecting points on each socket. After the lamp starts up, each of the wires is supplying current to its side of the bulb.

Sometimes, on a 2-lamp Rapid Start ballast, there will be ONLY 2 wires supplying two lamps. This kind of ballast can’t be overdriven. The current flows through one wire, and then through the filament of the first lamp, then through a jumper wire to other lamp filament, then back to the ballast via the second wire. They are connected in series. If one lamp fails, both will go out.

On a 4-lamp Rapid Start ballast, there are double the number of wires (2 red/2 blue/2 yellow). Both yellow wires are actually connected to the same common point inside the ballast, or at least they behave that way.

I also want to mention that I used the term “pre-heat” because that is what the filaments in a Rapid Start ballast are doing. Officially though, there are ballasts which are called Pre-heat ballasts. They are in the fixtures that use an extra starter device and are only found in Magnetic ballasts, usually the lower-wattage ones. Do NOT use these magnetic ballasts for overdriving fluorescent bulbs(ODNO).

With an Instant Start ballast, only ONE wire runs from the ballast to each socket. There, at the socket, there should be a short jumper wire between connection points which links the 2 pins of the bulb together. This SINGLE ballast wire can supply current to both ends of the lamp’s filament at once, because the jumper wire is there. This jumper is a necessary connection for an Instant Start ballast, so that the lamp works correctly. There are some sockets used by manufacturers that already have an internal jumper in the socket - for Instant Start ballast use only.. I haven’t seen one of these, but take note if you have this type.

For an Instant Start (2-lamp) version, that “common” side of the ballast always seems to have a single shared red wire.

On a 4-lamp Instant Start ballast, the “common” side usually has 2 yellow wires, each shared by a pair of bulbs.

For anyone else reading this, the following information is for 4-lamp Instant Start ballasts only to overdrive 2 lamps by 2 times. What you want to do is, either - pair up 2 reds and 2 blues (preferred for simplicity), - or - pair up a blue/red and a blue/red.

On the other side of the ballast(s) you will have 2 yellow wires. One wire usually runs to just one side of one socket. There will then be a jumper wire, from that socket, to the other socket at that end of the fixture. Each of those 2 sockets should have a smaller jumper wire to short the connecting points (lamp pins) together. What you want to do is REMOVE the longer jumper (between the two sockets) and leave the short jumpers (the ones shorting the lamp pins). Now, that yellow wire is supplying just one lamp socket, instead of two.

Remove the second yellow wire, which should be running to the other two lamps, from the socket it is inserted into. Then re-attach that yellow wire into the socket you disconnected (the one where you removed the jumper). You have finished the “yellow” side of the first 2 lamps.

Note: Now you know what the function of the smaller jumpers are - to short the 2 lamp pins at the end of the tube together for an Instant Start ballast. If you find you have the type of socket with the lamp pin connections already shorted, then good. You do not need to short them together.


On the RED and BLUE side of the ballast, you will be pairing up either red/red and blue/blue - or - red/blue and red/blue, as described above. (Repeated experiments have shown that either way will work). Insert one wire into one side of the socket (the lead to one lamp pin) and the other wire into the other side of the socket (the lead to the other lamp pin). If you have the kind of sockets which are already internally shorted, you must connect your pair of wires together at the socket. If so, there probably will be 2 push-in slots at that spot. Once you have one pair of wires going into each socket you are finished with that side.

Now, you will have the wires that once went to 4 sets of sockets (4 lamps driven normally), going to 2 sets of sockets (2 lamps overdriven).

Since you already have an Instant Start ballast, you ought to buy the GE/Magnatek B432I120RH that Home Depot sells. It is also a 4-lamp Instant Start electronic ballast, about $25 to $30. A GE ballast you buy should be wired in exactly the same way as a Sylvania. They are both Instant Start and the wire colors are the same. Just mount it on the second fixture side and duplicate the wiring.


Finish by wiring both of the ballasts AC supply wires together and remember to keep the ground wire attached. When it comes to AC power supply wires, don’t forget: black-HOT, white-NEUTRAL, green (usually)-GROUND. Always keep black wires together, white wires together, and green wires together, within the same wire nuts, do not mix them.


From my searches, it would seem like a good idea to buy one of the many "adaptable" aka "universal" electronic ballasts available and put it in a decent fixture. You could then run any number and type of bulb on a single ballast.


Many ballasts have circuitry to prevent feedback of some sort that prevents being able to connect more than one ballast to one bulb. On a forum on reefcentral's site, someone tried connecting two separate ballasts to a bulb, and fried the ballasts. So don’t use two ballasts on one bulb!




Cheap fluorescent ballast/fixtures

Posted by Zink on Garden Web forum.


Being very comfortable with electronics, I played around extensively with the concept of "overdriving" fluorescent lights, by a simple rewiring of the ballast wires. This can be done with a wide range of the newer electronic ballasts, but NOT the older, heavy magnetic ballasts. I have found that the better brands (Advance, Sylvania, Magnatek, Universal, GE) seem to work very well. While experimenting, I happened upon the least expensive and most versatile electronic ballast available. Even without using the concept of overdriving, which I will explain, these fixtures are a very good (and bright) deal.


The light is a Home Depot "Commercial Electric" Shop Light, which uses an electronic ballast - a Sunpark SL15. The fixture sells for less than $10.00 at the local Home Depots. Electronic ballasts are designed to power the newer and more efficient T8 bulbs on the market, but can also operate the old standard T12 bulbs. (T12 = 12/8 inch diameter, T8 = 8/8 inch diameter). Side by side, 32w T8 bulbs in an electronic ballast fixture are brighter that 40w T12 bulbs in a magnetic ballast fixture. That is just the start. Although I bought and played around with many types of electronic ballasts (32w, 59w, 110w, HO, etc) I ended up buying many of the Home Depot fixtures after finding out what I could power with them, mainly by "overdriving".


The Sunpark SL15 ballast (which drives two bulbs) has 2 red wires and 2 blue wires going to one side of the fixture, with 1 blue, 1 red, and 1 yellow wire going to the other end of the fixture. On the first end, combine 1 blue wire to 1 red wire (either one), then the other blue to the other red wire. On the other end, combine the single red to the single blue wire. The yellow wire on one end will also be jumpered from one socket to the other. Just remove the jumper from the unused socket. Now, one socket will have a red/blue attached to each side of the socket. The other socket will have a red/blue and a yellow attached to it. You have "paralleled" the ballast output and can now drive an incredible array of standard bulb types: 48"-32w, 48"-40w, 36"-30w, most any 24" bulb. I actually lit bulbs that would no longer light in a normal fixture. The extra current gooses them into working.


The coolest discovery of all, though, was that I could really light up some special bulbs I was interested in. The power compact twin-tubeT5 bulbs that come in 36,40,50 and 55 watts (and are about 22" long) could also be lit. The 40w bulb was INCREDIBLY bright. In this case, one $6.50 ballast with one FT40w (also called PLL40, Dulux-L 40) bulb was WAY brighter than a normal 40w 2-bulb fixture. I also was able to light up a 54w T5 High Output to a blazing fury. Those 54w bulbs are recent, very efficient (lumens/watt) bulbs on the market. I built a fixture with 4 54wattT5HO bulbs and 4 Sunpark SL15 overdriven ballasts, which is as bright as a 250w High Pressure Sodium.


The other ballasts that I listed here are not the only ballasts that can be overdriven. These are just some of the common ones. If the ballasts are electronic and are wired the same as these diagrams show, then they are probably overdriveable.


 Even though the electronic ballast is powering the lamps with a 22kHz or higher current, it is still being derived from 60Hz line current. You may find an individual ballast that hums loud enough to annoy you This is disappointing to those of us expecting very silent non-flickering power. Some ballasts are "noise" defective. You might try to exchange it, electronic ballasts are quiet, period! Any noise indicates it’s defective. 


So basically, all you need to do is buy 2 fixtures, remove the Sunpark SL15 ballast from one and mount it in the other fixture. Each fixture uses a single ballast to operate 2- 48” lamps. Essentially, what I am doing to “overdrive” is to use that TWO-lamp ballast to drive only ONE lamp. I am removing the wires going to lamp #2, and pairing them up with the wires going to lamp #1. (There is really no designated #1 or #2 lamp in the fixture. That is just for the explanation.) That will “overdrive” one lamp to about 1.7 times its normal output. You will now have 2-lamp fixture, which puts out more light than 3 lamps. Each bulb is being powered by it’s own 2-lamp (but inexpensive) ballast.


They are sold in a grey and white box marked Commercial Electric Shoplight. The part number is 140-904. They do NOT say anything about the ballast inside, and the Home Depot employees should not be expected to know that either. I did notice that above the UPC code on the back is HBSL-15, a reference to the Sunpark SL15 ballast. That is the only indication I ever saw on the box. Our local Home Depots seem to have had these fixtures constantly in stock for at least 10 months. Oddly, in my nearest HD store, they currently have a pallet of these shoplights which has a ballast that looks the same, but without a label, and have only 2 wires (1 red + 1blue) coming out of one end. That end of the lamp is wired slightly different, and is NOT the correct ballast to use. This incorrect ballast DOES have the HBSL-15 written on it, but IS NOT the “overdriveable” ballast. The correct ballast has 4 wires (2 red + 2 blue) out of one side, and 3 wires (1 red, 1 blue and common yellow) out of the other side. There also are the black (hot) and white (neutral) which are the power wires coming into the ballast.


One more minor thing to be aware of:

I found that one pallet of fixtures one of the Home Depot stores got in had a slightly different ballast with only two wires going to one end instead of three. The ballast apparently worked on a slightly different principle and could NOT be overdriven. Return it if you get one of these. After purchasing the wrong fixture once, I decided to open the box in another Home Depot and look. They had a fresh shipment of the shoplights in and they WERE the correct ballast. What was going on with that one odd shipment, I do not know. I would open the box first and check for the Sunpark SL15 label on the ballast AND that there are two blue and two red wires coming from one side of the ballast.




T12 lamps are 1 1/2" in diameter and T8 lamps are 1" in diameter. Each number in the T# convention equals 1/8".


A T12 bulb (one and a half inch) won't appear quite as bright as a T8 (one inch) bulb because the same light output is being distributed over a larger bulb area. But the overall luminosity will still be slightly higher.


A T8 and T12 bulb has the same pin configuration, though, so you could use T8 bulbs in the same sockets/strip lights that T12 are used. If you have those rubberized endcaps that fit around the light tube, they have separate ones for T8 and T12 bulbs.


One relevant fact – The reason that your store-bought fixtures are not already overdriven is because of the efficiencies mandated by such things as the 1992 Energy Act, which requires standards of environmental impact and energy efficiency. The nice result of that energy legislation is that the 32wT8 lamps, with an electronic ballast, now put out more light, more efficiently, than 40wT12 fixtures used to. Overdriving IS a less efficient use of energy, but. will get you 70% more light per bulb. For the special case of the plant grower or fish tank enthusiast, overdriving fluorescent bulbs is a welcome application for their hobby.


If you want to use T12 GE Plant & Aquarium bulbs (I love 'em!) then go on and use them. They won't be as efficient as T8 bulbs, meaning they'll need more watts to produce the same lumens, but should still produce about the same light. The ballast should just work harder.


The intensity two (ODNO)F32T8 lights put out is amazing. More intense than a 55w Power Compact bulb, and far cheaper to replace bulbs. The bulbs get considerably warmer than normal, but not even as hot as a Power Compact bulb. A fan is useful to help extend bulb life, which should be approximately 1-2 years.

The 4x ODNO F32T8 bulb consumes only 80 watts, but produces 6500 lumens. The standard convention of "watts per gallon" comes from a 2000 lumen, 40-watt standard F40T12 bulb. This ODNO F32T8 bulb is far more efficient, so it produces as much light as 125 watts of standard lighting (like three 40 watt tubes).

The 4-F32T8 (electronic) ballast will still make that 40watt bulb glow like crazy. I haven't been able to find an electronic ballast designed for four 40watt tubes, only magnetic (You remembered not to overdrive with magnetic ballasts? Good!) Electronic ballasts are mostly used in industrial applications, because they're efficient and quiet, with low power consumption, and F32T8 bulbs are mostly used in industrial apps because they are also more efficient as well as smaller.


. The T8's will provide almost as much intensity with much less power consumption. The T12's will provide slightly more light, but will consume more power. Home Depot or Lowe's may not have the 5000k T8 bulbs. Find a local lighting supply store in your Yellow Pages if you want the T8 bulbs, but I'd just go with the T12 bulbs if I were you.


I have definitely been curious to know the temperature of some of my lights. Fluorescent lamps do have a temperature curve for optimum brightness. I have always thought that most bulbs seem to burn a lot hotter than what is recommended. Since the cold weather set in, I noticed that a couple of compact fluorescents in my garage are a lot brighter than they were before. They still get warm, but definitely burn brighter.


One of the effects of overdriving fluorescents is that the bulbs do get hotter. I used my infrared pyrometer and measure the heat from the regular fluorescent bulbs and compared it with the heat coming off the lights of the overdriven fluorescents. The regular lights inflos-4 foot T8's-were 100F, while the overdriven ones were burning at 120F. In spite of that, the light output is definitely increased. I originally found the overdriving technique in the fish/coral forums. Those folks like to overdrive by 4X to achieve maximum brilliance. I tried that, but they got too hot for my taste. Burning at 2x is more efficient.


I've been looking into T8's and T12's recently at the Phillips website and I found two bulbs that look promising:

T8 "Advantage… universal start ultimate performance" 32watts, 4ft, 3000,3500,4100,and 5000K availability, 3200/3040(initial/design lumens) CRI

of 86. 24,000hr life. From what I can tell, this is the highest output T8 I've seen that isn't a "High output" version.

T12 "Advantage..." 40watt 4ft. 3000,3500,4100,and 5000K, 3600/3250(initial/design lumens). 24,000hr life.


Love them lumens!


I've found a light that looks interesting. These are 38 watt GE 2d lights. The bulbs are T5 compact fluorescent and are 8 inches square. Ace Hardware has them in the form of the Cool Star 2D Job Light for sale for about $20. These lights are 38 watts, 3500 Kelvin and they put out 2850 lumens. That's over 75 lumens per watt efficiency which is better than most compact fluorescents but not as good as T8's. Those Lights of America 65 watt bulbs put out less than 62 lumens per what I believe, and they are something like 6500 Kelvin, which is more, white and not as good for flowering as lights that are 2700 or 3500 Kelvin like the GE 2D lamps.

I bought one of these and took it apart. The ballasts are tiny and it would be really easy to remove one from the bulky fixture and mount just the thin lamp on a small shelf over a plant(s) with a homemade shiny reflector. The ballast could be hidden on the side or on the back of the shelving unit.


What's good about these is their efficiency and the amount of light that is concentrated into a small area. These put out as much light as a 4 foot 40-watt tube in an area of 8 inches squared. I was thinking these would be perfect for a 10 by 20 inch mini shelf garden in my daughter's room on a small bookshelf. They even have replacement lamps in 2700 Kelvin for better flowering.


Growing plants with overdriven bulbs


I have read and accumulated an extraordinary amount of data on lights and growing. I often see posts concerning their low lumen count, but keep in mind that lumens are a measurement for human eyes, not plants. A Gro-Lux bulb has a concentrated light frequency in the 450 nm range. Therefore, it's great for stimulating photosynthesis in plants. Overdriving the seemingly dim Gro-Lux Standard bulbs is rewarding. They aren’t dim anymore! I recommend Gro-Lux bulbs. I found out that the light that the bulbs put out is almost perfectly matched and balanced to the nanometer ranges that chlorophyll requires. It just doesn't put out any of the rest of the visible spectrum. I am referring to the standard Gro-Lux, not the Wide-spectrum. Wide-spectrum Gro-Lux is not any better for plants - fish tanks, maybe yes.

I'm mostly using my lights on fish tanks, reptile cages, and a couple of seedling trays. (palms, passion flowers, agaves, etc..will also be using them for starting heirloom tomatoes, peppers, artichokes, etc). In my opinion these overdriven ballasts are an excellent replacement for the "commercial security lights" many people are currently using for their seedlings, like the 65w compact fluorescent from Lights of America. I have three (two on fish tanks, and one on a seedling tray), and I think my 2 foot overdriven setups are every bit as bright and effective (in fact maybe more effective, because I get a better spread of light) as those. As a bonus, the new setups only cost $11 each instead of $30, are a better quality than the LOA (I've had several die on me) and apparently use 54 watts instead of 65.


Most plants don't get enough light under ordinary fluorescents. So I think your plants would be better off under the brighter light of overdriven fluorescents. You might want to do a search, on the Internet and in bookstores, for the light requirements in foot-candles of the plants you intend to start under lights. Fortunately plants can do well enough to get to transplanting size under less light than they would require for sustained growth to maturity.


A big problem with seed starting is that after they have germinated and got their first true leaves they need a cooler temperature than most houses are kept at. For stocky sturdy transplants you should grow them at 50 F to maybe 65 F tops. Growing them warmer makes them spindly. You might want to think how you can make it cooler for your seedlings. If you had a cool basement or some other room that didn't require human habitation, you would probably be better off putting your fluorescent plant growing fixtures in there. Incidentally, seedlings develop stronger stems if they are exposed to some wind. Some people use a small electric fan to provide that "wind". I plan to put a small fan on a timer for our seedlings.


The most important thing to mention is that I put some houseplants under my overdriven lights, and they have taken off like I've never seen them do before


Aquarium use with overdriven bulbs


For those of us who with planted fish tanks, we have one of two options for lighting. We can either use the expensive commercial setups like metal halide or power compact bulbs, or we use a shoplight or two with from two to four 32 watt bulbs. Two shoplights can be had from Home Depot for under fifty dollars, but you won’t have much room for other stuff like heaters and filters. The shoplights are fine for tanks that are four feet long such as 55, 75 or even 90 gallons. Here’s another reason to overdrive two bulbs instead of buying into a normally driven four-bulb setup. It has to do with light intensity. Which do you think will give more light, a 100watt incandescent light bulb or four 25watt bulbs?  The light output theoretically should be the same, but you can see that the single 100watt bulb is much brighter. It works in a similar fashion by overdriving two fluorescent bulbs as opposed to a normally driven four-bulb setup.


The bulb life may not be quite as long, but most aquarists replace their bulbs every six months to a year anyway, because their normally driven bulbs begin to lose their light output.The replacement life is not so critical for plants, but corals are more sensitive and you should be safe replacing coral-use bulbs every six months.


Use the overdriving method to power bulbs of any size. If you have a smaller tank, you can do this with 18” or 24” bulbs. One 2-F32T8 ballast will replace your old ballast which only drives one 18 or 24 inch bulb, and give you more light!


If you use regular fluorescent bulbs and not specific color bulbs, you may consider T8(one inch diameter) instead of the older T12s. T8 bulbs are designed to use less electricity and put out more light, which sounds like a good deal to me. One overdriven T8 should put out about 6500 lumens.




If you have a glass cover, the regular endcaps will be fine. If they are exposed to the water surface, definitely go for the waterproof endcaps. Just go with new endcaps with screw mount bases (not the notched ones that slide onto a PC board or metal reflector).


I had an empty 75G tank and two 4-foot strip lights, the thought of spending $300 for a good PowerCompact fluorescent tube setup was very unappealing to me. So I was off to the lighting supply store. I purchased 2 Damar electronic ballasts-Item No 3093A, these are for 4 lamps with wattage of 12, 25, or 32 watt T8 lamps. I took the two strip lights from my tank, and removed the old magnetic 1-lamp ballasts and old T12 lamps. I also removed all of the old end caps and wiring. It was then a simple matter to push the four leads (two blue and two red) from the new ballast into the four slots of the new end caps. At the other end of the strip light I pushed the two yellow leads into the end cap slots. Connecting the power leads only required twisting off the wire nuts and wiring in the new power leads. Start to finish was less than 20 minutes.


Not being extremely confident of my electrical skills I closed my eyes when I plugged the "new" strip light into the power outlet. This was a good idea...the light is simply blinding. I was truly amazed. I took my 55W PC's and laid them beside the "new" strip light, certainly to the eye the T8 light is quite a bit brighter. In fact, it is not possible to look directly into the T8 lamp with a mirror reflector. Here's what I spent for what is likely equal to at least 200W of NO (normal output) T12 lighting. You could use the old T12 bulbs until they burn out, if you want. Then buy the more efficient T8 bulbs.

2- 4-foot strip lights I already had. $0.00

2- Damar Electronic Ballasts (4 lamps T $19.54 each.

2 sets of end caps $2.94 each.

2 F32T8 6500K lamps $3.65 each

For less than $60.00 I almost tripled my lighting. For me this was simply a test to prove to myself that this works. It does. Now I'll build a new DIY wooden hood to house a mirror reflector and three overdriven T8 lamps. This should give me lighting equal to approx. 300W of NO T12 lighting, and it should cost about $100 total for the wood, ballasts, end caps, and bulbs.


Measurements have shown that a F32T8 lamp configured just as I just did generally puts out approximately 6500 lumens. Most 55w PC's put out between 4000-5000 lumens. CSL's BriteLite 65w PC's put out 5500 lumens.


OverDrivenNormalOutput lights can definitely be intense. I generally consider them roughly just as bright as 55w PC's, but the nicest thing is the bulb replacement cost. $3.65 instead of $18-$30 per bulb. And bulb life is only slightly less.


A 120vac fan is all you'd need to keep them cool and the bulbs will live longer as well.


Get a four-bulb ballast even if you're not sure about driving the bulb 4x or even 3x. You can overdrive just about any fluorescent tube, but some are more effective than others. Modern electronic ballast are load sensing - so if you buy a 4F32T8 ballast, it can run just about ANY bulb. The ballast adjusts and limits current automatically. You can at least drive two bulbs 2x apiece. It's not REALLY four times, because the ballast and bulb become less efficient, the more current you drive through it. Overdriving two 18" fluorescent bulbs won't bring them to 60watts each, but rather approximately 60 watts total.


If you wanted to overdrive your two 36" 30 watt bulbs, you could. Several guys on reef central have done it. I'd recommend one 4F32T8

ballast per bulb. With all four outputs driving each bulb, I'd estimate the output would approximately double (60watts each).


You might be able to try and find an electronic ballast for six-foot bulbs (F96T8) but they're a lot more expensive. But you could wire both 36"

bulbs in series and only need one ballast. They're definitely going to be hard to find, though.


On reef central as well as a few Canadian reef boards (apparently, intense lighting fixtures are very expensive in Canada) there are dozens,

maybe even hundreds of hobbyists who have used this method without a single report of fire or severe hazard. The worst I've heard is a few

burned out ballasts from incorrect wiring. I certainly haven't heard about any bulbs exploding.


Fluorescent bulbs were designed to carry more current than they usually see. Not only do they have a certain factor of safety built in, but most

ballasts are energy saving at 88% delivered current. When you actually deliver 2x that amount, it is still not far beyond the bulbs standard

output, and definitely not over capacity.


For a planted tank - you can consider each F32T8 bulb to be the equivalent of 125 watts (overdriven with a four bulb ballast per bulb) - enough to grow most plants in a 55gallon tank. Two of these bulbs (again, each with their own ballast) would be enough light on even a 75 gallon to grow intense light plants.


The reason they mention four ballasts on the reef site post is because they are actually driving four separate bulbs, each with their own 4-F32T8 ballast. That's a LOT of light, but that's what SPS corals need. If each F32T8 bulb being driven by its own 4-F32T8 ballast (with all four outputs connected to the one bulb) makes 6500 lumens, we're talking 26,000 lumens here! In the standard watts per gallon convention - this translates to well over 500 watts of light! The electricity cost is not cheap to run a setup like this, but what the hey.


One person calculated the cost of running a four lamp setup and said “It's actually pretty amazing at how much electricity a Planted Tank or Reef Tank can consume. A set of four ODNO bulbs will draw roughly 6.7A. Pretty significant! At anywhere between 10 cents and 13 cents per kilowatt/hour, that's $1.00-$1.20 a day for a 12 hour photoperiod!”



Q.I only want to have about 160-170 Watts for a two-foot deep tank. Should I OD each bulb with it’s own ballast (4x)? Or should I just use one 4F32T8 ballast to overdrive both of the bulbs (2x)?

  1. You could always start with a single 4F32T8 ballast and 2X OD each bulb and buy an additional ballast in the future if you find it isn't bright enough. If you're targeting around 160 watts of light, you better go with the two 4F32T8 ballasts. Better yet, for the same price as a 4F32T8 ballast, get a Fulham Workhorse 5 ballast. You can find them at local lighting distributors but Pet Supply Liquidators has them here for $25 apiece: get the 128w WH5-120-Long Case ballast.

Q. Can you use overdrive setup with the F32T8 ballast with T12 bulbs?

A. Yes, I'm using this setup right now on my tank. I have a 4F32T8 ballast 2X OD'ing a pair of Sylvania Gro-Lux F40T12 tubes. It's definitely brighter than it was with the original magnetic ballast, but not twice as bright. OD'ing 4x would definitely achieve that. Anyway, the reason I go with the less-efficient F40 tubes is because Sylvania makes them in the Gro-Lux phosphors. The light output in these bulbs that are beneficial to plants and is stunning.


Q. If you have the kind of sockets which are already internally shorted, you must connect your pair of wires together at the socket. My Question: Does this mean they go in the same hole on one side of the socket?

A. No, not necessarily. There probably will be 2 push-in slots at that spot. That is to say, two holes for each tube pin and each pair are for the shorted lamp pins. Put one wire into each slot and thus avoid having to tie them together first and pushing into one slot. There will be a total of 4 holes per socket (two slots for each pin).


Q. I currently have one 2 light 48" fixture, and was planning on getting another when I ran into this thread. Wouldn't I be better off to run the four lights as they are than 2 extra bright ones???

A.Yes, you will get more light using 4 bulbs in normal fixtures than using 2 bulbs in overdriven fixtures. The idea of overdriving fluorescent lights is to maximize the light per fixture, usually because of limited space or “high-light” loving plants. Or just because it’s so cool once you see it.


Q. I double-checked all my wiring and still my overdriven lights don’t work right. What went wrong?

A. Basically, if the fixture I am messing with doesn’t light, I check my wiring first and then jiggle the connections. That usually works.




If you want information about what others are doing with overdriving fluorescents, try these forums. I copied some of the postings from a few of them to write this article.























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