T-8 pecularities

bus_driverMarch 15, 2014

Posting here as the lighting forum often gets more into style and design rather than technical considerations.
Today I converted a 4' T-12 fixture to T-8. Used Sylvania electronic ballast (bought a dozen of the ballasts and a box of the tubes) and Philips tubes. Ballast made in Mexico. Both components were selected for price-- were not the most expensive available.
The T-8 lamps start quickly. But at 70 deg, the ends get bright immediately but the center portion of the tube glows sort of red/pink and puts out much less light for some moments. Then very gradually gets whiter and brighter in the center of the length of the tubes.
This is in my unheated shop and I wonder what will happen next Winter.
Anyone done a conversion and what were your results?

This post was edited by bus_driver on Fri, Mar 21, 14 at 18:17

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totally normal when they're first energized, or cold like that.
I've been doing a ton of ballast change outs and re-lamping lately for a rebate program the local power company is offering, and noticed the same thing.
I think the ballasts are rated to start at like -20F or something like that though so you should be fine. Once they heat up a little it will be ok. I have T-8's in my garage and we get weeks of -30 temps and I haven't had a problem.

This post was edited by hexus on Sat, Mar 15, 14 at 22:46

    Bookmark   March 15, 2014 at 10:43PM
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Not sure if this is the exact ballast used for my job. Here are the temperature specs for the ballast linked below.

"Starting Temp:
-20ðF for OCTRON T8 lamps
(instant start);
0ðF for OCTRON T8 lamps
T8 lamps"

So in your experience, it will start at lower temps but takes a while to warm up?

Here is a link that might be useful: Specifications

    Bookmark   March 16, 2014 at 7:45AM
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yes after they're on for a little while and heat up a they're fine. I don't know exactly how cold it's been in my garage but when it's -30 outside and it's totally un-insulated and un-heated I can guess.

    Bookmark   March 16, 2014 at 3:40PM
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Before I saw who was posting, I wondered if the correct sockets, ballast and lamp combos were really used.

I've converted a number of luminaires with GE MVPS "ultrastart" ballasts, low ballast factor for 4-lamp and normal for 2-lamp. It does not get cold where I live, not much below freezing at the coldest and the garage does not dip below 40 under those conditions. The low ballast factor systems have not been in place as long as the normal ones, but both strike better than the 8' T12 slimlines, and 4' T12s, that I still operate close by, under damp or cool conditions. I don't know what type of ballast the latter have since I have not been in the channels to look. I suspect rapid start magnetic.

I have not noticed the behavior that you see. I'll turn on a few when I get home today and watch closely. As you have probably gathered, according to the manufacturers, you should not have trouble striking unless you combine low or ultraslow ballast factors with low output (energy-saving) lamps.

You should notice lower light output at lower temps. How much lower depends a lot on the type of luminaire. Ironically, electric ballasts produce less light than magnetic ballasts in cold conditions in totally enclosed luminaires because they are more efficient and make less heat. T8 like cold a little less than t12s. It is getting more difficult to find comparison curves at this point though T8 vs T5 abound. I bought a case of jacketed T8 lamps on ebay last year. It was a real deal and in my open luminaires, it should help some.

    Bookmark   March 16, 2014 at 4:08PM
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There may be considerable variability between the way the program-start ballasts are configured from manufacturer to manufacturer. Quicker light production from faster warmup vs. slower has to be balanced with electrode sputtering at sustained lower temps, the destruction that a higher voltage strike causes, and energy loss in the ballast.

I meant to include this link in my previous post. Scroll to the bottom.

Here is a link that might be useful: T8 performance at low temps

    Bookmark   March 16, 2014 at 4:16PM
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My tubes fire up uniformly "white" so fast that any intermediates are difficult to notice. I suppose that I could record it and slow it down :-) If anything, they might be reddish at the ends when I first throw the switch.

    Bookmark   March 17, 2014 at 2:08PM
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Today was in the shop twice for just a few minutes each time. First time temp was about 45 and the tubes were brighter on the ends with dimmer, redder, in the middle of the length. Next time temp was about 65 and the tubes were only slightly dimmer in the middle. Was in a hurry both times and the light was on only briefly. Apparently is temperature related condition.
The new T-8 installations I did have been new fixtures in houses and no unusual behavior noted.
Not sure if I will convert any more shop lights.

Here is a link that might be useful: Article

This post was edited by bus_driver on Fri, Mar 21, 14 at 18:13

    Bookmark   March 21, 2014 at 6:02PM
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That link indicates that choice in T8 tubes and ballasts are becoming more complicated. Are we going to approach the recent complaint in the lighting forum for screw-in A-lamps for linear fluorescent?

"Most people just want to buy lightbulbs. They shouldn't need a PhD in lighting design to figure it out.The industry needs to get their act together and create universal products that are cost effective."

The way I currently think, "ordinary" lamp and ballast combos can operate at fine at lower temps. It is only when combining low ballast factors with low output lamps where a problem comes in. That is not so difficult, but might be beyond the capabilities of the average consumer. In the future, it might take consulting compatibility charts to get a luminaire re-lamped.

The whole problem appears to be driven by the desire to make incremental improvements in lighting performance economically possible. To do that you need to keep the existing luminaires. It also cuts re-tooling costs to make new lamp shapes and luminaire components. On the down side, that makes it possible to install incompatible wear elements resulting in a system that does not work well. That is what happens when someone tries to install t8 tubes in a luminaire with T12 ballasts or vice versa.

    Bookmark   March 21, 2014 at 8:36PM
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In the earlier days of fluorescents, the fixtures had separate devices called starters. Tubes for the "Regular" start fixtures would work in the Rapid and Instant start fixtures that were developed later. But tubes specifically for the Rapid and Instant start fixtures would not work in the Regular start fixtures. I think that is called backward(?) forward(?) compatibility.
Today if one needs to buy fluorescent starters, the quality is so poor that the defect rate of the new ones is about 50%.

This post was edited by bus_driver on Sat, Mar 22, 14 at 21:28

    Bookmark   March 22, 2014 at 6:00PM
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My kitchen came with UCL "regular start" and they are, unfortunately, still there. I view the glow starter design to be ingenious. I think this is a form of "preheat" starting. I understand that electronic replacements are available, but I've never seen any on the shelf. They have time-out features that save the lamps, ballasts and starters from continually re striking if when something is amiss. That can save components from self-destruction after another fails.

Don't forget manual pre heat starting -- hold the button until it strikes. I assume that predates the glow starters and earlier thermal starters. I have a couple old lamps with manual pre heat design, but they are not in use.

    Bookmark   March 23, 2014 at 12:46PM
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