Lutron Diva dimmer broken

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Hi,
I have a Lutron dimmer that dims a 100w (4 x 25w) light fixture in a bathroom. I noticed that one of the 25w bulbs was out and that the dimmer does not dim any more. My question is can a bulb burning out cause a sufficiently high current transient / short to burn out a dimmer?
I read in this news group that bulbs blowing can be a reason that a dimmer fails. Is this true?
best, Mike.
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Some of the clear bulbs hold the filament delicately with wires that can short together and burn the triac out.
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It is true and happens frequently. Also fixtures with candelabra sockets often develope minor short circuits in the socket, just a momentary pop, not enough to trip the breaker, but enough to take out a dimmer

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of the kitchen in my cookie cutter. It has one of those pug-ugly chandelier things that uses those damn candle-base bulbs. (as does the other big ceiling fixture, non-dimmed, also a piece of junk.) Dimmer still works as a switch, so haven't bothered to replace it yet. Been looking off and on for replacement ceiling fixtures for the kitchen, but none of them in the stores seem to have normal bulb sockets. And the current one has one neat feature- a downward-facing flood bulb in the center, to light up the table enough to read newspapers at.
aem sends....
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Yup. Semiconductor triacs act like _extremely_ fast fuses. The mere whiff of a short lasting a few tens of milliseconds can fry one long before a regular fuse or breaker notices anything awry.
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the new dimmer I bought right before I sell it. Being old, I never dim anyway.
aem sends...
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wrote:

I always thought the phrase was plug-ugly, but your words make more sense. Anyone know more about this?

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I've normally heard "plug-ugly", but if your dog is ugly enough to serve as an example... ;-)
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hobbes wrote:

Yes, what occasionally happens when a bulb burns out is that a phenomena called a "tungsten arc" occurs. The filament break develops an arc between the broken ends which melts those ends and vaporizes some tungsten. The arc continues, melting more tungsten and shortening the remaining filament ends and the current increases as more of the filaments melt and the density of the vaporized tungsten increases.
It all happens faster than you can say Jill Robinson, usually accompanied by a bright white flash just as you "turn on the lights".
The current will sometimes surge high enough to blow a panel fuse or breaker, or as in your case, to fry the triac in a dimmer.
Good quality light bulbs used to have special thin wire "fuses" as part of their construction which were just thick enough to let the bulbs be turned on and run but would "blow out" if the bulb developed a tungsten arc. I don't know if that's still the case.
When you are replacing the dimmer, go to Rat Shack and pick yourself up an inline 3AG fuse holder and a few 2 amp 3AG fuses. Wire the fuseholder in series with the hot feed to the dimmer (it should fit inside the dimmer box) and you'll be pretty well be protected against a future burnout. You may have to replace a burned out fuse, but the dimmer should be OK.
That's just what I did with the four table lamps in our home which are fitted with "touch dimmers". After the second dimmer blew I added 2 amp fuses to all of them. I've probably replaced six fuses in the last five years, but all the dimmers are still alive and well.
HTH,
Jeff
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I find it hard to imagine that a fuse would blow fast enough to protect a triac. But, if it works...
Make sure you get fast-blo.
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Chris Lewis wrote:

Thanks, I realized too late that I forgot to mention that.
Not to be pedagogical, but I sized the fuses for my lamps by looking up the specs of the triacs in my lamps' touch dimmers, the ones which were punching through, and found on their maximum I^2*t rating. (eye squared times tea)
Then I looked on Buss' website and found that the blowing energy (also expressed as I^2*t) of their 3AG 2A fast blow fuses was somewhat less than that of the triac, so I figured it should work.
And work it has....I use two 75 watt bulbs in a "Y" adaptor in each of those table lamps cause the two are cheaper two purchase than one 150 watter in most places, plus when one bulb dies I still can get light to see my way around from the other one, assuming it didn't expire with one of those tungsten arc blasts and take out the fuse. I think I probably have three or four "normal" bulb burnouts for every one which takes a fuse along with it.
And some people accuse me of being a geek who "gilds turds"....Wonder why that is....<G>
Jeff
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Jeff Wisnia wrote:
...

Two 75 watt bulbs produces a lot less light and are a lot less efficient than one 150 watt bulb. You will pay more for the electricity:
75 watt GE "standard" 1190 lumens 150 watt GE "standard" 2850 lumens
That's 20% more light for the same power or 20% more efficient. Also, you would probably find the quality of light more desirable from the 150 watt bulb (higher color temperature).
Over the estimated 750 hour lifetime, you will use 112.5 KwH. If you are fortunate enough to pay only 10 cents per KwH, thats $22.50 of electricity.
Also note, that when you use a dimmer, although you use less power, the bulb gets much less efficient.
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M Q wrote:

Points well taken. I hadn't thought that one through.
I may just buy a few 150 watt bulbs this weekend, the additional lumens will probably make it easier for my aging eyes to read stuff.
Thanks,
Jeff
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Jeff Wisnia wrote:

Well, I followed through and bought some 150 watt bulbs yesterday. While I was at the store looking at the lumen ratings of frosted incandescents I noticed that the 150 watt output of a "three way" 50-100-150 watt bulb was also considerably lower than that of the plain 150 watter.
I replaced the "Y" adaptor and its two 75 watt bulbs in just one of our two living room table lamps with a 150 watt bulb.
the results were pretty dramatic, the lamp with the 150 watt bulb was noticably brighter, so I put a 150 watter in the other one too.
Now I need someone to understand why the single 150 watt incandescent puts out 20 percent more lumens than the pair of 75 watt bulbs. (Are you reading Don Klipstein?) I'm guessing it might have something to do with more thermal energy being tossed away through four filament supports than through two, or something like that.
I'll be kicking myself for a while over not thinking about the lumen output when I decided to install those "Y" adaptors with pairs of 75 watt bulbs.
As my mother-in law used to say, "Jeff, for a smart guy, every once in a while you do stupid pretty good."
Thasnks again,
Jeff
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Jeff Wisnia wrote:
...

I can give you a partial answer. The filaments in higher wattage bulbs are designed to run at a higher temperature. At the higher temperatures, more of the radiated energy is in the visible light portion of the spectrum (see http://en.wikipedia.org/wiki/Black_body ) (however still only around 3-5%). Why don't we just run all bulbs hotter? That dramatically decreases the lifetime of the filament. Why can we get away with running higher wattage filaments hooter than lower wattage ones? That's the part that I don't know.
P.S. Halogen is a technology for increasing the lifetime of the filament, allowing you to run it hotter.

Most people are unaware of that, including many energy conservation advocacy organization that encourage people to use lower wattage bulbs. Also, it is getting harder to find light output figures on many types of bulbs.
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M Q wrote:

Maybe another reason is because the bases of both bulbs are the same diameter but the 75 watt bulb is physically smaller than the 150 watt one. That puts its filament closer to its the base which makes the base obscures a larger solid angle in the total sphere of radiation, thus blocking a greater percentage of the visible light?
Jeff
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Jeff Wisnia wrote:

I am sincerely genuinely impressed. The application is specific to the triac and type of Buss fuse used, but has a good chance of working in general.
Nitpicking - also check the fuse voltage ratings, and fuseholder ratings.
There may be more room to install a fuse at the light fixture.

Doesn't everyone guild turds?
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wrote:

Right, but in the dimmer, there might be room for a glass fuse without a fuseholder. Either one with pigtails (wires soldered to the ends) or small endcaps that are barely bigger than the metal ends of the glass fuses. I don't know what Jeff actually used.

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There may be enough room for it, but not after you've taped it so that they don't short against the dimmer box. "Inline" fuse holders (like the automotive variety) are plastic and don't expose any metal bits. But they are kinda bulky, as are dimmers. Wouldn't lay odds you could install one in anything but the deepest receptacle box.
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mm wrote:

Well, as long as you sort of asked....
All four of the table lamps with touch dimmers in our home are Asian styles with "full metal jacket" brass bodies. I installed the touch dimmers in all of them myself, inside the lamp bases.
When the time came to add those fuses I Installed panel mount 3AG fuse holders through holes I drilled in the side of the lamps bases, near where the lamp cords exited.
Things being what they are, every few years we get a new cleaning person and it sometime takes a little time for them to get used to those touch switches. So, after the first few housecleanings (we're absent when those happen) I'l maybe find the original manual switch on a lamp's bulb socket turned to the OFF position, and once a lamp wouldn't turn on when I touched it because the lady thought the fuseholder cap was a switch and twisted it so that it sprang out enough to open the circuit. <G>
Jeff
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