Fluorescent Bulb Burned Out – What Size For Replacement?

(Last Updated On: March 31, 2021)

Fluorescent light bulb has burned out. When a fluorescent bulb is not lighting, it needs to be replaced. You may ask yourself, how do i know what size fluorescent tube I need? When replacing a fluorescent light you need the information printed on the tube itself. The sizing, wattage, and other information tells you the size and type of tube you need for replacement. This info will assist you in finding the exact bulb for replacement.

Common Fluorescent Light Tube SizesCommon Fluorescent Light Tube Sizes

A fluorescent lamp will have info printed on it like so…
EXAMPLE INFO ON BULB: F20T12/CW/ALTO
F – Indicates “fluorescent” lamp.
20 – Tells the wattage of the lamp.
T – Indicates the shape, this lamp is “TUBE” shaped.
12 – The diameter of the bulb in eighths of an inch; this lamp is 12/8 (1.5) inches in diameter.
CW – Indicates color, COOL WHITE Lamp.
ALTO – The manufacturer “description”. These descriptions vary from manufacturer to manufacturer.

To find out the length of your fluorescent tube, simply measure the tube to the end of the tube including the pins. Use that info combined with the information printed on the side of the bulb to find the exact replacement.

Size printed on Fluorescent BulbSize printed on Fluorescent Bulb
Information printed on the bulb helps you to identify the size and type

How To Replace A Fluorescent Light Bulb:
1. Turn the light fixture off.
2. Carefully remove the light from the fixture.
3. Take a picture of the information printed on the side of the bulb.
4. Use the information printed on the bulb to replace it.
5. Find length of the tube by measuring the tube including the pins.
6. Take the bulb with you to a home improvement store or…
7. Order the bulb online by using the information printed on it.
8. Install the new bulb by sliding in and twisting.
9. Test new bulb by turning on light switch.
10. If light does not work, check light tube installation.
11. If the light still does not work, check or replace the ballast.

Here is how to troubleshoot a fluorescent light fixture that will not turn on or flickers

T5 Fluorescent 4100K Cool WhiteOrder Fluorescent Tubes Here

MORE FLUORESCENT TUBE SIZE INFO:
The “T” indicates the bulb is shaped in a “TUBE” shape.
The “5” denotes that it is five eighths of an inch in diameter.
The larger fluorescent lamps T8 (eight eighths inch = 1″) and T12 (twelve eighths inch = 1½” tubes).
“FC” instead of “F” means the lamp is circular.
“FB” or “FU” instead of “F” means the lamp is bent or U-shaped.

What’s the difference between T5, T8, T9 and T12 fluorescent lights?
Mostly the difference is the diameter of the tube. The diameter simply means the tubes are either thicker or thinner. Fluorescent tubes are categorized according to their diameter, wattage, and shape. The different numbers such as t5 T8 and T12 mean the size and type of bulb. The “T” indicates the shape of the bulb TUBE type. The number “5, 8, or 12” indicates size (diameter).

T5 Fluorescent BulbT5 Fluorescent Bulb – Diameter

T8 Fluorescent BulbT8 Fluorescent Bulb – Diameter

T12 Fluorescent BulbT12 Fluorescent Bulb – Diameter

ALL LIGHTS IN FLUORESCENT FIXTURE NOT WORKING:
If both or all fluorescent tubes in the light fixture seem to be burned out at the same time, most likely the ballast is faulty and the tubes are not burned out. Test the tubes by installing them in a working light fixture. If the tubes are in working order, then you know the ballast is most likely faulty. Replace the ballast by finding a replacement ballast below…

Ballast replacement for fluorescent lightBallast Replacement Here

Ballast in fluorescent light fixtureGeneral ballast wiring in fluorescent light fixture

LOCATION & LED TYPE TUBES:
In most homes fluorescent lights are in laundry rooms and garages. Fluorescent lights can be hurtful to the eyes for some people. Instead of replacing the light fixture, a fluorescent tube can be replaced with an LED light tube. Switching out a fluorescent light with an LED light will stop the flickering that fluorescent lights emit. LED Tubes Here. LED tubes emit a different type of light so check the brightness of the LED tubes before you purchase.

Having issues with a tripping breaker when you turn on the light switch? Breaker Trips When I Turn The Light On – How To Troubleshoot?


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