differance... t-8 / t-12

human124(IN)July 12, 2005

what would the advantage between the t-8 and t-12 bulb be other then size?

i looked at the bulbs and but had the same info... so would going to the smaller bulb be better? or worse?

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If you already purchased a fixture, then buy whatever type is specified on the box. A fact you may already know is that the number following the T(#) represents the tube diameter in 8ths of an inch.

Originally, there were only T12's, with a few oddball T9,8,5,4,2's on the market. They all ran on heavy magnetic, or tranformer ballasts. Ballasts were designed for each different wattage range of T12Âs, each having no tolerance for driving anything but the tube it was designed for. All of the normal T12's (excluding HO and VHO lamps) were designed to operate at a current of 430mA, which the magnetic ballasts were designed to deliver.

The first T8Âs that were manufactured began as 430mA designs, but T8Âs were eventually re-engineered and now operate universally at 265mA. This is why T8 lamps are not compatible with magnetic ballasts. Although there are a few magnetic ballasts designed for some series of T8 lamps, most of the T8 lamps are being driven from a myriad of electronic designs.

Electronic ballasts, besides being more efficient, are LOT more versatile, and tolerant of different lamp lengths and wattages  the ballastÂs design range being the limiting factor. Some electronic T8 ballasts for 32w bulbs also claim to drive 40w lamps, along with a small range of lamps. I am currently using 40w bulbs in an electronic 32w fixture, and the light is great. Since better electronic ballasts are being made for 32w lamps, companies have also created 40w electronic ballasts which are also readily available.

Overall, more recently engineered T8 lamps are probably the better, more versatile lamp to invest in. Since they already use a more efficient, electronic ballast, they are a prefered choice. But, there are also some perfectly good, recently re-engineered, T12 lamps available. The PhilipÂs "Home Light" series sold at Home Depot are very good lamps with a fairly high output.

Just make sure you using an electronic ballast. They are also quieter - operating well above human hearing


    Bookmark   July 13, 2005 at 1:26AM
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You know, after reading these posts again, I realize that I went into a lot of facts about the 2 lamps, but I never really gave a definite answer.

The major maufacturers of fluorescent lamps, Philips, Osram/Sylvania, GE and a few others, are using the same quality manufacturing (depending on the originating country) and phosphor mixes when making both their 32w and their 40w lamps. There is not much quality or efficiency difference between the 32 and 40, except they are designed to use a different amount of lamp current, hence they use different ballasts. Some electronic ballasts are able to drive both 32 and 40 watt lamps. Some ballasts are designed to run varying combinations and number of lamps of the same design type, up to some maximum total lamp length.

So consider this: With both wattage lamps being of equal quality (from reputable companies), you will find an overall higher lumen output from the 40 watt lamps, versus the 32 watt. For instance, a 48" 40w lamp is brighter than a 48" 32wl lamp.

As long as you go with an electronic ballast, you will find it pleasingly brilliant. Try to find a ballast with a BF (ballast factor) rating of 1.10 or greater, if you can. Unfortunatly, these high BF's are more to be on a 32w ballast - if you do find a high BF source.

Good Luck,

    Bookmark   July 15, 2005 at 1:22AM
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Once again... I meant to mention that Home Depot sells a series of very good 40 watt lamps called "HomeLight", made by Philips. They are fairly high-lumen 40w lamps and come in a range of color temperatures.


    Bookmark   July 15, 2005 at 11:29AM
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shrubs_n_bulbs(z8/9 UK)

I'll make it even simpler.

Get a T8 :)

For all the reasons Zink describes, a new T8 fitting and bulbs should be an efficient plant light. You would have to look hard for a T12 that was as good, and many still on the market are downright poor. Theoretically they could both be equally good (almost) but T12 is becoming an obsolete technology and the best fittings tend to be for T8s, or even T5s.

    Bookmark   July 15, 2005 at 4:52PM
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lol zink... reading your post it looks more like u like t8's better... sence u dont get into t12s really at all.
I like the t8's for the fact that they are smaller and the fixtures are smaller... but the t12's i can find a wider range of bulbs for. And at home depot i only can find one t8 bulb style, i think it was a 5200k (from what i know it has a little bit more blue then 4800k).
But ive never ever tryed using fluorescent and this will be my first experiment this winter, but i just wanna do reserch on what to buy b4 i do buy. mostly im just sick of spending a lot from a high pressure (stupid energy bills.. its not like u dont spend enuff during the winter on heating your house!) and all garden stores u hear they say they are the only way to grow with. Im sure my tomatoes and whatnot will grow fine.

    Bookmark   July 16, 2005 at 12:34AM
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oh also i seen a t-12 10,000k bulb... any good?
it looked like it had tons of blue... but it was like 35$ a bulb

    Bookmark   July 16, 2005 at 12:40AM
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lightmaster(z8 Salem, Ore.)

oh also i seen a t-12 10,000k bulb... any good?
it looked like it had tons of blue... but it was like 35$ a bulb

This is what they call an "antic" bulb...

No, it is not really good, I believe it is because it is beyond the spectrum that plants can use...


    Bookmark   July 16, 2005 at 12:45AM
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shrubs_n_bulbs(z8/9 UK)

Actinic bulbs are for aquariums, not for plants.

Human, do I understand that you currently have HPS lamps for growing your veggies? And they cost too much? Fluorescents won't cost less to get the same amount of light, probably more.

    Bookmark   July 18, 2005 at 6:02AM
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