Weird Fluorescent Light Problem...

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  #1  
Old 07-10-14, 06:24 PM
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Weird Fluorescent Light Problem...

Hi,

I have a weird problem going on with my kitchen light. Today, I turned on the light switch, and the light didn't come on. The fixture has two long fluorescent bulbs in it, and is probably as old as the house (25 years-ish). I turned the switch back off and on again, and the light magically comes on, full power...

After it was off for a while, i tried it again, and while it didn't come on, I noted a small glow in one end of one of the tubes, so I can tell the fixture is getting power, and then after i turn it off and back on again, it comes on. Usually after i do that once, sometimes might take another time or two...

It seems that once it's on, I can turn off/on and it comes on with no problems, but once it 'cools' down the problem surfaces...

So questions...is this a problem with the light or the switch? (i'm thinking light, but...). if the light, easier to replace the whole light (being as old as it is, an
updated fixture is probably due). Lastly, I currently have the switch off and am
putting tape over it so that i don't turn it on, as i'm not sure how dangerous this could be. Should i worry as much as i am?
 
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  #2  
Old 07-10-14, 06:55 PM
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Welcome to the forums.

It's not something that is dangerous. No need to tape off the switch.

It sounds like you may need a new ballast. You can replace the ballast with a new electronic style and install new matching T-8 tubes or replace the whole fixture.
 
  #3  
Old 07-10-14, 07:09 PM
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thanks, i'll sleep much better hearing that :-)
 
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Old 07-10-14, 07:22 PM
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I think we've all stood there and played with the light switch trying to get the fluorescent lights to work. Usually we weren't successful and the tubes would only partially light or just the ends would glow.
 
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Old 07-10-14, 07:38 PM
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It sounds like you may need a new ballast. You can replace the ballast with a new electronic style and install new matching T-8 tubes or replace the whole fixture.
You might be able to get away with just installing new T12 lamps, but they aren't cheap. I like PJ's suggestion to convert the fixture to T8 lamps or just replace the fixture as T12 lamps have not been manufactured since July 2013.
 
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Old 07-11-14, 03:56 AM
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This is a handy reference:

Fluorescent Lighting Troubleshooting
 
  #7  
Old 07-12-14, 08:33 PM
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I've seen this problem before. It's also described in the troubleshooting guide referenced in the previous post. It's typically a result of insufficient capacitance between the lamps and ground. It may also be caused by a bad connection to one of the lamp pins, resulting in the cathode not being heated on that side. It can be a sign of a failing ballast, and replacing the ballast might help given that modern electronic ballasts are less susceptible to this issue, but often times there is nothing wrong with the ballast at all.

1. Confirm that the fixture is grounded, and that the metal reflector or channel cover is securely installed. The reflector must be grounded for reliable starting.
2. Verify that the leads from the ballast to the sockets are tightly attached (they are usually push-in, and occasionally use screws).
3. Check that there is no corrosion on the lamp pins or socket contacts.
4. Clean the tubes if they are dirty. Doing so may increase capacitance.
5. If it's still not working, install new bulbs if they are old. Despite the new efficiency requirements that went into effect a couple years ago, suitable replacements for most older sizes are still made.
6. Make sure the bulbs are the correct type for the ballast. This problem can also occur when T8s are installed with a ballast designed for T12s. Note that in the 18" (15W) size, T8 and T12 are interchangeable. However, F15T12s typically have fewer starting issues when operated on magnetic rapid/trigger start ballasts.

If all else fails, replace the ballast. Cold temperature and high humidity can also result in unreliable starting. Unless it's below 50 degrees in your kitchen, temperature shouldn't be the cause, but lowering humidity might help.
 
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Old 07-13-14, 05:55 PM
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thanks for the info. Certainly a lot more involved in fluorescents than I ever imagined. I swapped bulbs earlier today to see if that could be a problem. The 'first position bulb' (I call it that because if only one bulb is in, it'll light in the first position, but not in the second position) had a major black spot on one end. If that doesn't help over the next week, I think i'll just replace the whole fixture. With the changes in bulbs a few years ago (that I also didn't know about), I'd need to replace it eventually and this is a good excuse to do so if I can find one I like :-)
 
  #9  
Old 07-13-14, 09:02 PM
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The lamp that glows faintly even when the other is removed is is first in the series. It's connected to the blue wires of a typical rapid start ballast, and a trickle of current will flow though it even with the other lamp removed. The other lamp is wired to the ballast's red leads. The end with a dark spot is low on emitter, and has likely raised the minimum voltage needed to start the lamp. Swapping lamps probably helps because some current can flow though the better lamp when it's first in the series, making it easier to get the second one going. I'd still recommend popping the cover open and confirming that it's grounded, but my hunch is that at least your one bulb doesn't have much life left.

As for replacements, I think most of us have been assuming 4'. Shorter sizes are not affected by the new efficiency standards. You can still get 4' tubes in T12, but beware that many that are still on the market are there because the manufacturers worked around the new efficiency standards (usually be increasing the CRI to be exempt). The result is that some of the T12s being made now are actually dimmer than their predecessors. So if you end up sticking with 4' T12 and you want your light to be bright, first look for 40W rather than 34W. For reducing energy consumption, 32W T8 is much better than 34W T12. 40W T12 can have decent output, however. Next check the lumen rating. If it's below 2,500, then it's not a very bright bulb. It might have nice color, but it'll be dimmer than average. I'd recommend looking for 3,000 lumens or close to it. The bulbs dim over time anyway, so whatever you put in will probably be brighter, if your current bulbs are 20+ years old.

There are a lot of advantages to moving to T8 and electronic ballasts, including higher efficiency, higher frequency (no visible flicker), faster starting, and quiet operation. There is one drawback however, and that's reliability. You'd be lucky to get 25+ years out of an electronic ballast. If your current ballast turns out to be OK, I wouldn't be surprised at all to see it outlast a new electronic one.
 
  #10  
Old 07-15-14, 07:50 PM
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A couple days later, and it seems that swapping the two bulbs has at least for now fixed the problem. I obviously would still need to find a new bulb for the one that's on it's last legs, but does this mean that the ballast is fine and I don't need to replace the entire lamp?
 
  #11  
Old 07-16-14, 04:50 AM
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I obviously would still need to find a new bulb for the one that's on it's last legs, but does this mean that the ballast is fine and I don't need to replace the entire lamp?
The terminology is lamp = bulb. Assuming these are 4 foot fluorescent lamps since you described them as being long, the lamps will be available for quire a while although they are no longer made. The price will continue to rise just as R12 refrigerant rose after production stopped. You may have bought some time and may not have to change the ballast, but future lamp changes and/or possible ballast change as well as excessive energy use will be greater than a modern new fixture with T8 lamps.
 
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