Reply by JayT

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Posted on Lighting: Help me understand the difference between T8 and T12

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6421 posts in 3273 days

#1 posted 01-12-2014 05:32 PM

T12’s are still being produced, but there had to be a change in the phosphors used (the white powder that glows under electric current, producing the light) and the CRI. The effects of that change are 1) new T12’s are not as quite as bright as previously and 2) they jumped dramatically in price.

The biggest difference, as Joe mentions is efficiency. Overall, T8’s use electricity about 25% more efficiently than T12’s, so you get a lot more light for the same energy or the same amount of light for less energy. Additionally, this efficiency allows lower heat levels in both the bulb and ballast, so T8’s last much longer—up to 40,000 hours in some commercial bulbs. The real key to the longer life, though, is degradation. All fluorescent bulbs become less efficient over their life, but the drop off for T8’s is much slower. For instance after 10,000 hours a T12 might only be putting out 65-75% of its original light, while a T8 will probably still be in the 85-90% range.

In general, switching from magnetic ballasted T12 fixtures to electronic ballasted T8’s will pay for itself in energy savings in around two years. Bulb replacement costs will also be much less, both because of price and longevity. Add the broader choice of light colors and T8 gives the most choices at the moment for good, efficient light.

T5’s are even more efficient, but pricing and readily available bulb options doesn’t make them feasible for most consumers, yet.

Color temperature is another area that you will want to address. These are measured in degrees Kelvin and basically the higher the number, the closer to color is to natural sunlight. Additionally, the higher the number the greater perceived light output, even though the actual lumen output doesn’t change. For a basic rundown.

2900K is soft white—a yellowish light that is easy on the eyes for tasks such as reading, but gives very poor results for determing color.
3500K & 4100K are considered to be cool white. These are the most frequently used color temperatures in office environment. 3500 is a bit more pink and 4100 more blue. Again these temps will not give accurate results for color.
5000K & higher are considerd to be daylight bulbs. 6500K is probably the closest to sunlight that is readily available. Color accuracy is excellent, but the light can be harsh on the eyes and tiring.

In an ideal world, I would have 4100K bulbs over my working areas as the best combination of light output vs eye strain and 6500K in the finishing areas so that colors are seen accurately.

I understand there is a lot of information to try and digest, I deal with it almost daily, but I would really recommend anyone switch to T8 when possible. It pays for itself in very short time.

-- - In theory, there is no difference between theory and practice. In practice, there is.

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