FL58W835: Understanding fluorescent tube codes

FL58W835: Understanding fluorescent tube codes

The code FL58W835 or similar conveys information about the tubes specifications.  It allows you to work out the size and colour temperature.  Understanding these codes is important when coming to replace the tube and ensures compatibility with the control gear.

Deconstructing the code FL58W835

• FL = Fluorescent lamp
• 58W = The wattage of the tube
• 835 = Colour specs

1.  Lamp type (FL) - is the standard identifier for fluorescent lamps 
2. Wattage (58W) - wattage indicates the power consumed by the lamp.  Any tubes you want to replace must match the original wattage of your tube so as not to damage the ballast and reduce the lamps life
3. Colour Specification (835) - this 3 digit code determines the light quality and colour emitted.  The first digit 8 represents the colour rendering index CRI and when multiplied by 10 gives you the minimum CRI value, so 8x10 = 80 which is considered a good CRI.  The last 2 digits 35 represents the colour temperature and when you multiply x 10 = 3500K which is standard white.

How can I identify what fluorescent tube I have?

To identify your tube you would need to physically inspect it to read off the tubes specs

1. Examine the markings - Read the markings printed on the tube as it should contain all the necessary information needed.  The key information needed is the wattage and colour temperature.
2.  Determine physical characteristics (diameter and length)

• T8 tubes are 25mm diameter and T5 tubes are 15mm diameter.
• Base/Cap type - G13 is a T8 tube and G5 is a T5 tube
• Length - The wattage on a T8 and T5 tube will determine its length, for example t8 58w is 1500mm while a T8 36W is 1200mm.

Inspect the fixture or ballast

If the markings on the tube are illegible you can look at the ballast for the information on the tube that it runs.