Can Ballast be Reason for Short-Lived Lamps?

StandardsGuy, I have experience worse than that, when i replaced the lamp, it's only take 1 second, the new lamp snapped off, then i replace the ballast with new one, and the lamp 'bright' until now, if the winding of ballast is leak, the ballast can shorten the live of lamp.

You can use the ballast designed for 2 lamps with 1 lamp installed by use 1 winding of the ballast ( same watts with the lamp of course ).

Good answer. Let me add that many inexpensive shop fixtures have fairly cheap ballasts, so I am not surprised if one fails. Any time you change the lamp and it is failing within a few months, I would look at changing the ballast. Electronic ones are coming down in price and are usually a good choice. Although their components are quite small, they are usually packaged in the same size package as a standard magnetic ballast (to make replacement very easy).

--JMM

a bad ballast will shorten the life of the bulbs.

Another common problem are the ends / sockets, which can be replaced for less than the cost of a new ballast. However, if this is an inexpensive light to begin with, I would have to agree that it's easier and in the long run cheaper, to just replace the whole fixture rather than swapping out ballasts and sockets.

Another thing to consider is if the lamps are dusty/dirty they may not start which eventually will blacken the ends.

One other thing, not relating to your issue, that will prevent flourescent lights from working is the cover/reflector being left off the fixture.

I forgots to log in when I left my dirty lamp comment.

It's a cheap rapid-start fixture. Last time I priced ballasts, they were more than a complete fixture, but I haven't looked online. The ballast for 2 lamps has 2 yellow wires driving both bulbs (lamps) in parallel, with the black and white for the line on the same end. The other end has 2 red wires for the other end of one lamp, and 2 blue wires for the other end of the other lamp. The ballast for 1 lamp has 2 red wires on one end going to one end of the lamp, and a blue, a black and a white on the other end. The blue and the white (line neutral) goes to the other end of the lamp. Can I wire the 2-lamp ballast the same way for 1 lamp? If so, does it matter which blue wire I choose? Without a complete schematic, I don't know what I have. Since there won't be 2 lamps in series, won't I get too much current in the 1 lamp?

It sounds like an instant-start ballast would light up the lamp I am calling bad, because you don't need the filaments?

Are the T8 lamps the smaller diameter ones? What are their advantages?

S

It makes no sense, but sometimes you can swap the red-wire and blue-wire lamp sockets on the lamps and make them work. Scientifically/electrically it makes no sense to me but I have done it to newly installed two-lamp fixtures and then they would start every time.

Hey there StandardsGuy,

The first ballast you described sounds like an obsolete magnetic type rapid start ballast designed to operate the lamps independently. They used to call this a "companion lamp" technique so that you would still have light if one of the lamps failed. I have seem more than 25 configurations of inductor/auto-transformer windings (for 2 lamps) so, you really need to have the schematic to know if what you want to do will work. And the wire colors only loosely follow a "standard" so it is difficult to tell what they are giving you on the output.

Typically, if a pair of yellow wires go to one end of a couple of lamps, their function is to apply coil heat to that end with both coils in parallel. If one coil breaks, the other coil gets the full voltage and will soon follow its predecessor in death. But in your case, there may be a separate pair of coils from the yellow connection to hot and neutral so that the lamp coils are heated separately. In that case, there will be no open circuit voltage between the yellow wires because they are connected to a common node.

The red wires are a pair as are the blue wires intended to provide 3.6 VAC plus or minus about 2 VAC to the coil. One of the red and one of the blue wires are also connected to a "hot" output end of an autotransformer. They may be at opposite ends of a single winding (like burning a candle at both ends) or they may be parallel coils with negligible open circuit voltage difference. You would have to measure all of this without the lamps connected to determine how the coils "may" be arranged. There are a lot more possibilities which you will have to determine experimentally.

The concerns are: When one lamp is disconnected, does the coil voltage of the other lamp rise above 5 VAC. If so, expect short lamp life of the remaining lamp. Also, when one lamp is disconnected, does the lamp current in the other lamp rise more than 10% after a couple of minutes? You will need a current transformer to read lamp current since you can not short out the two blue or red wires and kill the coil voltage. If you do, the lamp operation will change slightly and you will not get good numbers.

Normal lamp current for a 40 Watt T12 is 460 mAmps (but lower for "Super Saver" 34 watt lamps due to the addition of Krypton gas). A 32 Watt T8 lamp only uses about 235 mAmps. There are also 30 Watt, 28 Watt, and 25 Watt versions of T8 lamps that have increasing percentages of Krypton Gas in the mix.

T8 lamps give you about the same amount of light (in lumens) without as much energy consumption. Magnetic ballasts consume about 10% of the total circuit energy in order to regulate the lamp current. Electronic ballasts typically use less than 1% to do the same thing.

Lastly, Instant Starts will run a lamp with a broken coil until all of the emiter material is consumed. Then it dies. Only one wire is required to connect to either pin or both on one end of the lamp.

I have encountered situations where mismatching the bulb type to the ballast results in problems. Essentially, using 32 watt bulbs with a ballast rated for two 40 watt bulbs (magnetic type) resulted in significant 60 Hz flicker and significantly shorter bulb life. Using 40 watt bulbs with 32 watt ballasts also seems to result in significantly shorter bulb and ballast life.

Unfortunately, where I live and work, one does not always have a choice in quality when purchasing lamps, bulbs and ballast. I have purchased cases of lamps where maybe 10 % would not light straight out of the box (a well-known international brand, made in Mexico). I have also had significant problems with electronic ballasts being short-lived, but I suspect that is because they have been "shopped" to some factory where quality concern is a very low priority and they like to source low-end components. The situation can get so bad that some of my customers consider flourescent lighting unacceptable because of the short life expectancy...

Amen to you cwarner7

Did you know that in the USA there are three big manufacturers of fluorescent lamps yet all compact fluorescent lamps come from outside the USA.

It may have something to do with the fact that China has about 4000 fluorescent lamp manufacturers.

Quality? Never heard of it!

Thanks for the info. It looks like T8 lamps have the same pin spacing as T12s, but can they be used in the same fixtures? The lamp would be farther away from the grounded metal base, and that seems to be of some importance in getting them started.

S

Have you considered using LED lighting you can then do away with the ballast completely

I use LED lighting wherever I can- unfortunately, the output just isn't there yet, in this part of the world...

In my vast experience of group re-lamping hundreds of thousands of all type lamps, over the last 40 years, the number one problem with bi-pin type fixtures is that most people do not install the lamps properly.

If you consider the bi-pin socket slot at 6:00 o'clock then if inserted

properly, the lamp pins

will be at 9, and 3 o'clock.

If one lamp is not seated properly, then that lamp will soon have black ends.

Also, the bi-pin lamps usually have a tit, or a slight indentation which makes it easier to know if you have the lamp seated properly. This tit or indentation could be considered the american football, and the two bi-pins could be considered the goal post uprights..

Make sure the tit, or indentation is exactly in the middle of the bi-pins.

Blaming cheap shoplight ballast is not the reason that these lamps are only lasting 6 months, unless the ballast is indeed defective, as I have seen these cheap ballast work fine for 6-8 years and more..

Also, to answer you other question, No, T8 lamps will not work in a fixture originally designed for T12, as T8 are used with newer style electronic ballast.

Also, your idea of installing two single lamp ballast is actually not a bad idea if you are just concerned with function.

I have done this many times, as they make a small core and coil reactor ballast that powers a single f40t2 lamp just fine, plus the cost is minimal compared to a standard single, or double lamp rapid start ballast.

The only problem you would have doing this, is if in fact you are using the very thin type "shop light" as those ballast would not fit in that small space provided for the ballast.

Donald

if that shop light fixture is the really cheapy type that wal mart type outlets sell, it most likely has that crappy little electronic ballast in use that is meant to fail quickly, so you can buy another complete fixture from them. unfortunatly normal sized one or two lamp f40 style ballast will not fit inside these enclsures. i have wired them on top of the fixture on a light where i could closely monitor it, in case of failure, hoeever, i woul NOT reccomend any else doing this! (inventors sometimes try things others would not do, you should see some of the LED lights i have built -:)

by the way, that cheapy electronic ballast will also just light one lamp if you twist the other lamp, so it goes out,

don, Campbell lighting inc