New Fluorescent Tube Won't Light Up

dallasbillAugust 25, 2007

We had the fluorescent light in our laundry room burn out and I replaced it with the same -- a 48in F32 32w tube. However, only the very ends of the tube barely glow when I turn it on. I thought it may be a bad tube but 3 others do the same thing.

Is something up with the fixture? It's barely 2 years old.

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If it's not the tube, it's probably the ballast, which is part of the fixture. It's possible to replace only the ballast, but if the fixture is an inexpensive one then it may be more expedient to just switch out the whole thing.

    Bookmark   August 25, 2007 at 6:14PM
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Thanks... it's very inexpensive. I'll do that.

    Bookmark   August 26, 2007 at 11:40AM
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If the ends are glowing, you may have a rapid start ballast. It would be somewhat unusual for a fixture using F32 T8 lamps to have a rapid start ballast. Not unheard of though; I think the cheap "Commercial Electric" shoplights sold at Home Depot a few years ago had RS (electronic?) ballasts.

    Bookmark   August 28, 2007 at 1:23AM
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Seeing as how I won't be getting to this for at least another week, this is great info.

I found this with a search: "After a lighting designer has selected electronic ballasts, the next decision is between rapid and instant start. The standard T8 lamp, the F32T8, is a rapid-start lamp, so the optimal choice would be a rapid-start ballast. However, this is only absolutely required when system dimming is occurring. Rapid-start ballasts are also strongly recommended when the average "on" time for the lamps is under three hours per start, for example where occupancy sensors have been installed."

Since this is an under-counter, single tube fixture in a laundry rooom, maybe that's what I have. If it's any help, the fixture has an on-off rocker switch on it, in addition to the wall switch we use for it. The tube I bought is not exactly the same as the F32T8 it replaced -- and both are Sylvania.

What do I need to look for -- either inside the fixture's cover, or on the bulb? By looking on the Lowes website just now, they say that the one I bought is an "instant start" Sylvania. However, nowhere on the packaging itself do I recall seeing "instant start."

Will a "rapid start" tube say so on it? Is the only way a rookie knows it's "rapid start" is if it actually says so on the package??!!

    Bookmark   August 29, 2007 at 4:50PM
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HD's commercial electric brand uses "instant on" the way Lowes used "instant start." These are the cheapest sorts of ballasts, and not the same as "rapid start." In any case, these designations refer to the ballast, not the tube.

    Bookmark   August 29, 2007 at 5:35PM
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Sorry, I didn't realize this was an undercabinet fixture. I thought you were talking about 4' T8 lamps. Although 4' T8 lamps are almost always actually rapid start lamps, most electronic ballasts used with them today are instant start types and don't actually use the filaments except as arc electrodes. If you look at their wiring diagrams you'll see that they tell you to connect both pins together at each end of the lamp.

However, typical cheap tack-up GE / Lithonia / American Fluorescent / Lights of America / Lampi / No-name Dollar Store / etc. undercabinet fixtures are magnetic ballast type. Often they're not even rapid start ballasts, but rather preheat ballasts with starters or even hold-to-start switches. Take one apart and you'll see a ballast about the size and shape of an old 5-tube ac-dc table radio's audio output transformer (if you're old enough to remember those).

Most 15 or 20 watt T8 lamps will work tolerably well with any of these ballasts - instant start, rapid start, or preheat.

However, you may find that your real problem is the starter inside the fixture. Some of these starters are technically not replaceable - apparently you're supposed to chuck the entire fixture when the starter goes south, as they are permanently wired into the circuit. However, you can probably get the light working again with some minor surgery. Just replace the dead starter with the guts out of a can-type 15 or 20 watt (as appropriate) hardware store fluorescent starter.

Or do as the manufacturer intended - feed the landfill and buy another cheapie.

    Bookmark   August 29, 2007 at 7:28PM
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OK... I found this: Instant start ballasts have the lowest power losses but can decrease the life of the lamp because of degradation of the emissive coating on the electrodes from the high starting voltage. Each end will turn black.

Since the tube went out at less than 2 years, and the ends were blackened, it must be an instant start.

This is what it looks like -- except mine just has the on-off switch and no outlet. It is a 32 watt, 4 foot, single lamp T8. I think it may take less overall time for me to just buy a new one.

    Bookmark   August 30, 2007 at 11:57AM
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You can tell which you have by how many wires go to each end of the lamp. If one wire goes from the ballast to each end (and then is spliced to the other pin right at the lamp), it's instant start. If two wires go from the ballast to each end of the lamp, it's rapid start.

The lamp life difference between a rapid start and instant start ballast is somewhat significant in typical use - 25,000 - 30,000 hours for rapid start and 20,000 - 25,000 hours for instant start. OTOH, instant start ballasts use less energy because they don't energize the filaments. RS ballasts leave them on all the time, even after they're no longer needed.

Sylvania says this about the financial impact : "For a normal 12 hour/day, 4000 hour/year operation, rapid start ballasts provide 7 years of lamp life while instant start ballasts provide 6 years. The 5W of coil heat costs $1.60/year in power costs for a 3-lamp ballast, or about $0.53/lamp/year. Over 7 years this would require $3.70/lamp in additional power costs to gain the year in lamp life."

So, you would spend more in electricity than the lamp costs, in order to gain an additional year of life. All other things being equal, you'd be money ahead to use the instant start ballast and replace the lamp sooner. But the actual financial impact depends on what relamping labor costs you (if anything). For some people lamp disposal issues are worth considering (either for cost or environmental reasons).

IMO, the best of both worlds is the programmed rapid start ballast, which uses the filaments for starting so strike voltage is lower, then shuts them off after starting. The downside is that they are significantly more expensive then either rapid start or instant start ballasts, so you don't see many of them.

Rather than replace the fixture, I'd put in a good quality new ballast. I like the GE Ultramax range. Although they're made in China (sigh) they seem to have a softer start than most instant start ballasts, and they are (at least to my ears) dead silent - no audible hum at all.

    Bookmark   August 31, 2007 at 3:12AM
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Thanks Davidr... I've printed that out for my next trip to the store!

    Bookmark   August 31, 2007 at 10:36AM
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DavidR/dallasbill - you guys are talking about different types of ballasts. The two choices for today's F32 T8 ballasts are Instant Start and Rapid Program Start, and dallasbill there is no difference in the lamp. The rapid start technology that sylvania mentions is gone, I think. We are seeing a wash in the cost difference between IS and RPS, so RPS should be used in areas of infrequent use, or where occ sensors are used, and instant start should continue to be used in areas where the lights will be on for long periods of time. On the residential side, I think lamp life would be best with RPS, esp. in bathrooms, the garage, etc. Not extra energy usage from RFP, btw.

good call on the GE fixture David, I will have to check it out....

    Bookmark   September 1, 2007 at 1:31PM
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The two choices for today's F32 T8 ballasts are Instant Start and Rapid Program Start ...

I think that's true in commercial settings, but AFAIK you can still use old-school rapid start magnetic ballasts in residential lighting - and most of the mass-market fixtures seem to still do so. I may have missed some DOE regulation about that though.

We are seeing a wash in the cost difference between IS and RPS ...

That's good news. When last I checked (admittedly a few years ago), programmed rapid start ballasts were significantly more expensive than instant start ballasts.

I don't recall seeing any fixtures in the big-box stores (where most homeowners shop) that claim to use programmed rapid start, but again, I may have missed some.

    Bookmark   September 1, 2007 at 5:03PM
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