T8 fluorescent tube + 5yr-old fixture = dying fixture with burned electronics???

[Jeff7]

New, thinner T8 tubes are more efficient than the older T12 style, in terms of lumens per watt. Problem: I bought some T8's and put them into a fixture that's about 5 years old. The lights did initially power on just fine, but after about 20 minutes, one turned off, so I switched the fixture off to remove the tube to look at it. I soon noticed the smell of burning electronics, which I assume is coming from the fixture.
What gives? New bulbs, with pinouts identical to T12's, but they apparently aren't meant for the same fixtures?



Edit: The fixture is Lights of American brand, model 8045. I've taken the ends off. Magnetic ballast, of course - the ones that look like a small transformer.
It also looks like there is no ballast-replacement available. Have to buy a whole new fixture. Or rather, they are available, but they cost more than a whole new fixture.:roll:

 

[MrPickins]

I could be wrong, but I seem to remember that t8's take an electronic ballast.
You can replace it yourself if you have any electrical knowhow. (It's really simple)

Here ya go:

http://oikos.com/library/energy_outlet/tubular_fluorescents.html

 

[Jeff7]

Originally posted by: MrPickins
I could be wrong, but I seem to remember that t8's take an electronic ballast.
You can replace it yourself if you have any electrical knowhow. (It's really simple)

Here ya go:

http://oikos.com/library/energy_outlet/tubular_fluorescents.html

Thanks for the info.

T8 lamps require an electronic ballast specifically designed to operate lamps at a lower current than T12 lamps. Whenever T12 lamps are replaced with T8 lamps, the ballast must also be replaced.

It might be nice if the T8 packaging said "WARNING, Fire hazard if used in T12 fixture."
Or maybe other brands do have a warning. This one doesn't. Half the box is dedicated to printing in another language, so I guess there's no room for a warning.
Philips brand tubes, BTW.

 

[MrPickins]

Ya, you would think they would have a incompatibility warning...
I suppose they leave it up to the fixture manufacturer.

Still suprising considering the people are ready to sue at the drop of a hat lately.

 

[BoomerD]

Most ballasts tell you what bulb they will run. Bulb manufacturers apparently ASS-U-ME that people are smart enough to match bulb & ballast...

 

[Rubycon]

Yes those lamps will actually draw more power from the wrong ballast than the T12 lamps will as you found out.

 

[AlienCraft]

Originally posted by: MS Dawn
Yes those lamps will actually draw more power from the wrong ballast than the T12 lamps will as you found out.

T8's are dimmable by virtue of their electronic "ballast".
If you're smelling a transformer, that transformer is most likely toast.
Replace it before it catches fire.

 

[Eli]

Um, the incompatibility warning is in the model number of the tube...

T8 != T12.

 

[Rubycon]

Originally posted by: AlienCraft

Originally posted by: MS Dawn
Yes those lamps will actually draw more power from the wrong ballast than the T12 lamps will as you found out.

T8's are dimmable by virtue of their electronic "ballast".
If you're smelling a transformer, that transformer is most likely toast.
Replace it before it catches fire.

The dimmable feature is actually a feature of the lamp driver - ballast is an outdated term used in the old days of the tar filled electromagnetic choke used for limiting current to discharge lamps.

There are expensive drivers that will dim practically any kind of FL lamp from T12 VHO down to T5 slims.

Most class P rated drivers (including tar) will have a bimetal protector that's inline with the unit primary that breaks power when the windings overheat. Electronics may be protected with a similar device, polyswitch (resettable) or even a single shot microtemp.

The T suffix is actually the number of eights of an inch in diameter (OD) the tube is. So a T8 bulb is exactly an inch thick.

oops!

 

[Jeff7]

Originally posted by: BoomerD
Most ballasts tell you what bulb they will run. Bulb manufacturers apparently ASS-U-ME that people are smart enough to match bulb & ballast...

I'm afraid that, like most of the population I'd imagine, I am not a well-versed expert on the nuances of fluorescent light bulbs.

Originally posted by: MrPickins
Ya, you would think they would have a incompatibility warning...
I suppose they leave it up to the fixture manufacturer.

Still suprising considering the people are ready to sue at the drop of a hat lately.

Especially considering that this sort of thing could lead to house fires.

Originally posted by: Eli
Um, the incompatibility warning is in the model number of the tube...

T8 != T12.

Most of the general population, if asked, "Are you using T12 or T8 fluorescent tubes in your garage?" how many do you think would be able to answer?
"Uh, I think they're 4 feet long, and they're white."

If they're incompatible, perhaps they should use differently-spaced pins?
If not, then a warning on the package would do the job just as well. Come on, we have warnings on coffee cups. Something that could wind up igniting your house might also warrant a warning on it, especially something as seemingly benign as a fluorescent light.


Light bulbs are generally not considered to be an overly complicated thing. Historically, you go to the store, buy one, screw it in place, and turn it on.

 

[Jeff7]

Another question: Is there any way, besides complete disassembly, to tell what kind of ballast a fixture uses? This assumes that the fixture is already installed, and no documentation survives.
The dead fixtures I have, which have magnetic ballasts (discovered by disassembly), do not have any indication anywhere on them as to what is within. They also do not have any labels on them to indicate that certain tubes may cause a fire hazard. How can I avoid this in the future? Or do I need to disassemble any fixture that I'm not sure of?

 

[Rubycon]

What kind of fixtures are you talking about? Standard 2x4 recessed?

Just pull the center piece out and the driver will be right there. The label will have all the information you need.

 

[Jeff7]

Standard shoplight fixture, that hangs from the ceiling.

Center piece - you mean like a metal strip on the underside (reflective side)? I did that on this fixture. I'll post pics in about 5 minutes, have something else to take care of quick (brake light is burned out, and my dad doesn't know how to replace it).

 

[Rubycon]

Oh geez those shoplights are super cheap - 40W tar ballast for driving a pair of F40CWt12 lamps. Now if they are made by an importer named Lights of America, they probably have a solid state high frequency driver that's super cheap and produces a torrent of harmonics too.

 

[Jeff7]

Well we tend to have an unfortunate policy in this house:
"How much does it cost?"

It's never "How well does it work?" That is secondary. If it's the absolute cheapest on the shelf, that's what gets bought. Nevermind that the thing is made out of such thin sheet metal that it's as flimsy as a sheet of cardboard. I am trying to change that policy though, in part because I'm sick of this attitude of "It's cheap, so if it breaks, we'll just throw it away and buy another one," as well as the problem of "This isn't working right, fix it." Which of course falls on me. So we buy cheap, and I get to fix the cheap sh!t that invariably fails early.

Fixture - the green shaded portion. Is that the "center piece" you speak of?

Inside there was a tiny circuitboard tied to the transformer things at either end of the fixture.

 

[Rubycon]

Yes the green shaded area is where you usually pull off.

LOL looks like they're running preheat start mode. That's cheap alright. Then again so is a good old fashioned Advance ballast!

Head over to Sam's FAQ - lots of good info there.

 

[Jeff7]

So what in particular should I look for when I go shopping tomorrow? Please don't shudder, but I had in mind Home Depot, as they're about the only hardware store in the area that stocks that kind of thing. I think they have Commercial Electric brand fixtures.


Precisely why is this "preheat start mode" such a bad/LOL thing?

 

[Rubycon]

CFL's are "what's in" now.

Problem is again many cheap vendors out there. Caveat Emptor!

Originally posted by: Jeff7

Precisely why is this "preheat start mode" such a bad/LOL thing?

You're limited to the type of tube you can put in there. Also what's important as efficiacy increases (as well as the watts) is the socket /endcap type. Cheap endcaps are a fire hazard.

 

[Jeff7]

The guy at Home Depot (yes, I know their sales reps are renowned for exemplary knowledge of the merchandise) had said that a lot of newer fixtures have electronic ballasts, and that T12's are being phased out. What I've found online seems to concur with this.
Are electronic ballasts generally safer and more reliable than magnetic ballasts of the past? Or have the manufacturers cut so many corners to make them cheap that they're still just a step above being worthless junk?

 

[Rubycon]

The cheaper drivers will produce much more THD which will interfere with other electronics like 802.11, X10, TV/AM, etc. They also are susceptible to frequent failures. POOF! Sometimes they will produce a slightly off zero beat which produces the ever familiar Geissler effect where you get flickering to striations (light and dark bands like a zebra) dancing around in circles or back and forth. Ok for discoteque but definitely bad for a workshop or even the crapper.

 

[Jeff7]

And I'll assume that there's no good way of telling the POS models from the good ones?

 

[Rubycon]

Originally posted by: Jeff7
And I'll assume that there's no good way of telling the POS models from the good ones?

Price in most cases.

 

[AlienCraft]

Originally posted by: MS Dawn

Originally posted by: Jeff7
And I'll assume that there's no good way of telling the POS models from the good ones?

Price in most cases.

DAMNNNNNNnnnn, I have never seen ANYONE with such a repository of technical knowledge on FRICKEN flourescent lights!
Do you work for Phillips or something?

 

[Jeff7]

Originally posted by: AlienCraft

Originally posted by: MS Dawn

Originally posted by: Jeff7
And I'll assume that there's no good way of telling the POS models from the good ones?

Price in most cases.

DAMNNNNNNnnnn, I have never seen ANYONE with such a repository of technical knowledge on FRICKEN fluorescent lights!
Do you work for Phillips or something?

Everyone's got their thing. One of mine seems to be batteries. Standard cell voltage:
NiMH/Nicad: 1.2v
Lead acid: 2.0V
Lithium-Ion: 3.6V
Alkaline: 1.5V

Want to know about the Mars Exploration Rovers? I could tell a lot about that too.
Fluorescent tubes though? Phosphor coating, excited inert gas....glass tube.....um, that's about it. Ms Dawn on the other hand....

 

[Rubycon]

Don't work for Philips. (that's one L for the lighting company hehe)

I do work with a lot of different lighting and switching technologies.

Oh we can talk about batteries too. Actually a battery is more than one power cell - yes a single AA/C/D etc. is actually not a battery but a cell.

And don't forget zinc-air, mercury (banned now) and the exotic sources such as radiophotovoltaic power sources (produce a weak but extremely stable EMF by converting the light from radionuclide decay - similar to those scintillating flashes on an old radium dial altimeter - to electricity via a high efficiency solar cell). RTG (radioactive-thermal-generators) use a much higher energy isotope that produces sufficient heat to excite one end of a thermocouple (see Seeback effect) to generate an EMF. Thermocouples used in RTG's in space vehicles are tweaked so their cold side is sunk to the coldest area of the craft (far from any sun, space is pretty cold!) and of course the other end is heated by the nuclear reaction. It works well and provides many years of steady power for craft such as the Cassini research project.