T5: A Brief History

T5 History Before the first indoor fluorescent lamps were sold in the late 1930s, incandescent light bulbs were the standard for interior lighting. Incandescent lamps convert heat to visible light very inefficiently – their light output is just 14 lumens per watt.
 During and after World War II, fluorescent lighting burgeoned in the United States.

In the 1970s, European development led to the compact fluorescent, the direct predecessor of the T5 lamp we know today. Fluorescent lamps work by exciting atoms of mercury with accelerated electrons and emitting ultraviolet (UV) radiation. The fluorescent powder coating converts the UV radiation to visible light.

Fluorescent lamps are far more efficient than their incandescent predecessors. The oldest fluorescent lamp is the T12. Its 1.5-in. diameter has an output of 60 lumens/watt. T12s were eventually replaced by T8s, which have a 1-in. diameter. The T8 boasted an improved fluorescent powder coating and inert gas. Efficiency improved by 33% to 80 lumens/watt.

The T8 lamp is currently being replaced by the T5, which has just a 5/8-in. diameter. The liquid mercury is replaced by an amalgam, formed by the reaction of another substance with mercury. The newest T5 is even more efficient, with 95 lumens/watt. It can operate at 95˚F, whereas the T12 and T8 max out at 77˚F. This evolution was driven by these factors:

• Diameter reduction was made possible by the development of tri-phosphorous, which is more efficient and stable.
• The T5HO lamps smaller diameter lead to reflector designs that take advantage of the lamps size and deliver more light.
• Smaller lamps are more compact and therefore more attractive for the consumer.
• Smaller lamps are more efficient, with better energy savings.

Not surprisingly, the manufacturing process for T5s is far more complex. The three-band phosphorous has three basic phosphors—red, green and blue. The blue phosphorous is unstable and the light output depreciates quickly if the manufacturing process is not spot-on and if the inert gas is incorrect. Off-gassing from the glass can react with the phosphorous, resulting in reduced light output. If the amalgam is not right, the T5 lamp will not be able to operate at the higher temperature of 95˚F. The higher-output T5 lamp is dependent on the use of the best blue phosphorous available on the market. A special glass is used to limit the off-gas reaction with the phosphors. Proprietary amalgams are used to enable the lamp to operate at the higher temperatures of 95˚F and above (these patent-pending components allow for greater lumen output). Each of these components raise the manufacturer’s cost for the quality lamps. With proper thermal design of light fixtures, T5HO lamps can perform across a wide range of ambient temperatures. This flexibility gives Courtlite the opportunity to design fixtures for use in environments ranging from the coldest ice arenas to very warm and humid swimming pools.

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