Here we describe the different types of fluorescent lamps or "bulbs" by size, shape, connector, wattage, color temperature and other features.

This article series explains how to diagnose the causes of flickering, dim, or dead fluorescent lights at or in buildings.

Watch out:  flickering or dimming lights might indicate a dangerous condition risking a building fire or an electrical shock. If the simple bulb or starter repairs we describe here don't cure the flickering, switch off the bad-acting light fixture, leave it off, circuit and ask for help from a licensed electrician.

Identify Fluorescent Lamp Types / Bulb Codes

Photo: Packaging for T8 fluorescent bulbs. The property owners whose lights I was repairing had kept the original packaging for two generations of GE brand T8, 36-inch fluorescent bulbs that were used in various fixtures in the home.

The Sylvania T8 bulb shown by the bottom-packaging is a perfect replacement.

Keeping the original bulb package (or writing down what type of bulb was installed) means that even if you have the bad luck to break a bulb and your client throws away your carefully-kept bulb base, you can still identify the proper replacement lamp.

Some of bulb specifications below are redundant: for example if you know that it's a T5 bulb you know that it is a 5/8" (15.8mm) diameter lamp with a G5 bi-pin connector.

• Bulb Type
  
• Bulb length:
• Bulb shape
• Bulb diameter: 1/8" (3.175mm) - 5/8" (15.875mm) - 1" (25mm) - 1.5" (38mm)
• Bulb pin specifications: spacing and size
• Bulb wattage: 4 W up to 125 W. Most residential bulbs are in the 4W to 60W range; note that bulb length and wattage generally change together

However there are some substitutions that will work: You can not install a shorter bulb into the existing fluorescent light fixture than the original, but you may find a bulb that is

• a different color temperature
• a different overall diameter - but with connector pins that match the original in spacing

In U.S., Canadian, European and some other communities you'll pay a small recycling fee - an environmental handling charge - that covers the safe-handling and disposal of these older bulbs, some of which contain mercury.

Notes to the table above

Our sketch illustrates that on both older T12 fluorescents and T8 fluorescent lamps the bulb's connecting pin dimensions and spacing are identical even though the T8 is a signifcantly-smaller-diameter bulb.

• Fluorescent lamps (or "bulbs" in normal-speak) are classed by shape, diameter, length, wattage, and often special properties and color temperature.
• In T numbers like Tn or T5, T8, etc. "T" indicates tubular lamp shape
• The fluorescent bulb's T-number in essence gives the bulb diameter and its connecting pin design.
  
  T4 = 4/8" bulb diameter or 1/2"
  
  T5 = 5/8" bulb diameter
  
  T8 = 8/8" bulb diameter or 1"
  
  T12 = 12/8" bulb diameter or 1 1/2"
  
  Within a given bulb size in diameter or thype, the light output or bulb wattage will vary by bulb length.
• Most-common fluorescent bulbs discussed here are straight, of varying lengths, base, wattage and color temperature. U-shaped, circular, spiral and other shaped fluorescents, high output lamps, and lamps with reflectors as well as other designs are available.
• Bi-pin bulbs use a conventional ballast and starter unless the light fixture has been converted to use an LED replacement for a conventional fluorescent bulb - a step that can be taken if the ballast is a newer electronic type. Remember you will have to change older magnetic ballast to the newer electronic ballast if converting from T12 to T8 fluorescent bulbs.
• Single-pin bulbs may use an instant-start ballast and will not have a separate starter
• Fluorescent-lamp formats, retrieved 2018/09/02, includes notes from this original source: https://en.wikipedia.org/wiki/Fluorescent-lamp_formats
• Dimming ballasts are available for fluorescent light fixtures.
• Also see BULB & LAMP TYPES GUIDE - home

Photo Guide to Fluorescent Bulbs by Connector / Base

These photos show the different types of connectors, pins, or bulb bases for various fluorescent lamps. The illustrations are not to scale.

For fluorescent light fixture bulb dimensions see the table above on this page.

[Click to enlarge any image]

Above: T2 Fluorescent bulb, 8 watt, from Bulbrite®

Above: T4 Fluorescent bulb, 28 watt, from PL&T®, pin spacing 4 mm.

Above: T5 Fluorescent bulb, 13 watt, from GE®, pin spacing, 5 mm. Connects to miniature G5 base.

Above: T8 Fluorescent bulb, 32 watt, pin spacing 13mm, sold in a wide range of color temperature and light output in lumens, straight or U-shaped.

Connects to a medium Bi-Pin G13 base.

Above, the 4-pin connector segment of a T9 circular fluorescent, 32-watt.

Above: T10 fluorescent lamp, high output 40-Watt, connects to a medium Bi-Pin G13 base.

Above: T12, center pin, F96T12/DX/ALTO fluorescent bulb from Philips, 75 Watt, connects to a single pin Fa6 base.

Above: a T12 LED replacement bulb for T12 fluorescents using a type R17D base connector.

Above: a T17 fluorescent lamp produced by GE. This 180-Watt T17 lamp connects to a Mobul Bi-Pin (G20) base.

Flouorescent Lamp Color Temperatures

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The color temperature of fluorescent lamps is adjusted by the manufacturer by changing the chemistry of the phosphorescent coating lining the inside of the lamp tube.

Above in order we show four CFL edison base (screw-in type) fluorescent bulbs of different color temperatures. We kept the camera on the same "automatic" white balance setting for all four bulb color photographs.

• Soft white compact fluorescent bulb
• Bright white compact fluorescent bulb
• Daylight compact fluorescent bulb

The accuracy of color rendition of different lights and the CRI scale are explained at Color Temperature and CRI for Indoor Lights.

These colors are not exactly what your eye will see, nor do they consider the effects of the colors of surroundings, but you can see the color temperature differences among these light bulbs.

The applications for these bulb color temperatures (corresponding to order of the photographs above) are:

• Soft White - a warm full glow light ideal "lifestyle" light. Color corrected fluorescent bulbs operate at about 3600^o K and skin tones look somewhat normal under these lights.
• Bright white - a crisp, white light ideal for kitchen and task areas.
• Daylight - simulates natural sunlight, ideal for reading & detail oriented activities. Full spectrum fluorescent bulbs operate at about 5000^o K, producing lighting simulating daylight but with skin tones slightly greenish.

Most fluorescent lamps such as the USHIO bulb shown just above include the bulb's color temperature (5000K in this example) right next to lamp's WATT data.

Exampes of fluorescent lamp color temperatures

• 3000 K lamps such as GE's F13 T5 13-watt lamp is considered soft white
• 3200 K lamps such as Bulbrite's FM8 T2 8-watt lamp is also considered a soft white color temperature, often found in compact flourescents.
• 3500 K lamps, for example GE's F48 T12 "high output" 48-watt lamps are in-between daylight and soft white
• 4100K lamps such as offeredin the T4 28-watt series from PL&T are considered a daylight bulb with softened light sometimes referred to as "industrial smog" conditions.
• 5000°K (or Kelvin) like the USHIO lamp shown above is considered the daylight temperature color range. Fluorescent lamps rated as "artificial daylight" have color temperatures of 5,000 ^oK or 7,500 ^oK
• 6500K (such as Philips 800-series fluorescent lamps) is considered Whitest light. Some sources rate this as "overcast light" 2 - good for reading.

Please see details at BULB COLOR TEMPERATURE COMPRARISONS

...

Continue reading  at FLUORESCENT LIGHT STARTER REPLACEMENT or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• ASBESTOS in LAMPS & LIGHT BULBS
• DIRECTORY OF ELECTRICIANS
• ELECTRIC POWER LOSS / FLICKERING LIGHTS
• FLUORESCENT LIGHTING GUIDE INDOORS for Indoors and Guide to Using Compact Fluorescent Lights
• FLUORESCENT LIGHTS COMPACT INDOOR
• FLUORESCENT LIGHT REPAIRS
• HOW FLUORESCENT LIGHTS WORK
• ELECTRIC POWER LOSS / FLICKERING LIGHTS
• DIAGNOSE a BAD FLUORESCENT LAMP / BULB
• REPLACE a FLUORESCENT LAMP / BULB
• FLUORESCENT LIGHT BALLAST TYPES
• FLUORESCENT LIGHT BULB CODES & TYPES
• FLUORESCENT LIGHT BULB PHOTOS
• FLUORESCENT LIGHT BULB COLOR TEMPERATURE
• FLUORESCENT LIGHT FLICKERING CAUSES
• FLUORESCENT LIGHT STARTER REPLACEMENT
• FLUORESCENT LIGHT TRANSFORMER / BALLAST REPLACEMENT
• FLUORESCENT LIGHT TRANSFORMER / BALLAST TYPES
• FLUORESENT BULB SOCKET TYPES
• FLUORESCENT LAMP CONNECTOR / SOCKET REPLACEMENT
• FLUORESCENT LIGHT FIXTURE BULB / BALLAST DISPOSAL
• FLUORESCENT LAMP INSTRUCTIONS, PARTS, REPLACEMENTS
• FLUORESCENT vs INCANDESCENT BULBS

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FLUORESCENT LIGHT BULB CODES & TYPES at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to ELECTRICAL INSPECTION & TESTING

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