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Do T8's fit in T12 Fixtures?

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#1 'Ric


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Posted 10 March 2007 - 05:34 PM

I have a normal four tube 48" T12 Fl. fixture. Is there any problem replacing the bulbs with T8's or even T5's? Will all of the above fit in the same endcaps?


#2 dhoch


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Posted 10 March 2007 - 06:15 PM

I'm not sure I know the T5s will not... but the T8s might...

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#3 jason the filter freak

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Posted 10 March 2007 - 09:38 PM

If you don't mind me hopping on this thread, I get that t12's are what most people think of as normal florescents, and I have T5's ... what the heck is a t8?

#4 Jager


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Posted 10 March 2007 - 11:13 PM

t12 is either 1 inch or 1.25 inches around t6 is smaller size 2/4 inch i think. uses less wattage but has higher light output per watt due to its size

t5 smaller still 1/2 inch and puts out even more light per watt then either of the above

if the t12 fixture says t8 then its ok. otherwise BAD IDEA. bulbs either dont last long, dont light right or blow the ballast.

the opposite though is usually true. if you have a t8 ballast it usually can run t12. they both use the same endcaps. but different wattage.

Edited by Jager, 10 March 2007 - 11:15 PM.

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#5 YBeNormal


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Posted 10 March 2007 - 11:41 PM

To determine the bulb sizes, multiply the number after the "T" by 1/8". So...

T12 = 1.5"
T8 = 1"
T5 = 5/8"

Edited by YBeNormal, 10 March 2007 - 11:41 PM.

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Posted 12 March 2007 - 04:17 AM

T-8 and T-12 has the same pin arrangement and can be interchangable on same sockets depends on ballasts. T-5 has smaller pin arrangment and would require different sockets.

#7 quazi


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Posted 12 March 2007 - 11:52 AM

T-8 and T-12 has the same pin arrangement and can be interchangable on same sockets depends on ballasts. T-5 has smaller pin arrangment and would require different sockets.

TROLL is right:

T8 lamps require an electronic ballast specifically designed to operate lamps at a lower current than T12 lamps. Whenever T12 lamps are replaced with T8 lamps, the ballast must also be replaced. Install an electronic ballast for optimum light quality and efficiency; electronic ballasts dont flicker or hum, and they use less power! T12, T10, and T8 lamps can all use the medium bi-pin base, which allows T8, and T10 lamps to fit into the same luminaires as T12 lamps of the same length. T5 lamps have a different base, and are shorter than T8s, so new lumenaires are needed.

Icecap ballasts can drive all these bulbs no matter the rated bulb wattage.
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