Converting from fluorescent to LED Lighting - Covering The Basics

Making the switch from conventional fluorescent tubes to LED tube lights can often be a daunting task that leaves consumers with more questions than answers.  Understanding the basics of LED tube lighting is a must whether you're retrofitting existing fixtures or installing from scratch on a new construction project.  In this article I'll cover some of the most common areas we receive questions about and provide some general knowledge you'll want to know when shopping for tube lights.


Your intended application is one of the single most important factors in your decision. Since pricing and lumen output can vary widely for LED tubes of the same length knowing what is best suited for your application is a must.  Below is a list of helpful basic questions in determining which type of tube best fits your application.

  1. How will the tubes be used and what is the primary activity within the space the tubes will illuminate? 
  2. What is the ceiling height in the space these will be installed?
  3. How many other luminaires (light fixtures) will share this space?
  4. Do you intend to use the tubes with a fluorescent ballast?  If so, do you know what type of ballast and fluorescent tube you're currently using? Most LED tubes will only work with specific electronic T8 ballasts. If you're using T12 fluorescent or can't find your T8 ballast model number on the compatibility list for your intended tubes then chances are you'll need to purchase Type B ballast bypass LED tube lights. If your ballast is on the compatibility list then proceed with Type A ballast compatible tubes.
  5. Will you be submitting a rebate application? If so then you'll need DLC Listed tube lights. Fortunately, the vast majority of the tubes we offer are DLC Certified but there are certain types that are not eligible for certification so if in doubt this is something you'll want to be sure of before making your purchase.
  6. Where will these tubes be used? Will it be installed indoors, outdoors, or in a walk-in cooler or display case? Tubes for cooler lighting or outdoor lighting applications have a better tolerance for extreme temperatures and humidity unlike conventional tube lights which are best suited for dry locations indoors.

Lumens and Light Distribution

Lumen: a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candle intensity.

Fluorescent Light Distribution VS LED Tube Light Distribution

This is often one of the most confusing aspects for customers. Fluorescent lumens to LED lumens is not a 1:1 equation. The lumen rating on LED tubes comes in way under fluorescent lumens. How can it possibly be enough to achieve the same foot candles? The answer is light distribution.

With a fluorescent tube you have an electrical charge emitted from a cathode and creating an arc that travels down the tube and reacts with mercury, phosphorus, and other chemicals inside the tube to produce light. The direction of the light output is not controlled and is disbursed 360 degrees coming out of the tube. A substantial portion of the lumen output is lost in reflection as the light bounces around inside of the luminaire rather than being directed towards the area where illumination is needed.

With LED tubes light output is directional often ranging from 180-270 degrees. LED tube lights contain a long strip of LED chips mounted end to end on a board and directing all or most of the light output in a single direction focused out of the luminaire. The difference in how the two technologies distribute light results in comparable foot candle readings being delivered with vastly different lumen counts.

Switching from T12 to T8 tubes

Unless you're intending to use a ballast compatible tube which requires no rewiring, T8 and T12 are irrelevant.  

In fluorescent nomenclature "T" was used to designate a Tubular shaped lamp and the number following the T represents the number of 1/8 inch increments the tube diameter is measured in.  So a T12 indicates 12/8 (1.5) inches in diameter and a T8 is 8/8 (1) inch in diameter.  This mattered to a fluorescent ballast but for LED it is simply a convenient and familiar designation to use and is at best only loosely adhered to.  In reality most LED tubes somewhat exceed one inch in diameter even when listed as a T8.

Common fluorescent tube base types encountered when switching to LED

Covering your bases

More important than tube diameter is the base size.  What do we mean by base size?  We mean the size, shape/structure, and orientation of the connection point(s) located at each end of your tube lights.

The most popular size for 2ft-4ft tubes (whether T8 or T12) is a G13 Medium Bi-Pin base.  This means the tube has  two pins spaced 13mm between them center to center at each end.  With 5ft to 8ft tubes things can start to change.  It is not uncommon for these tube sizes to instead have FA8 (single Pin) or R17D.  R17D means recessed double contact with 17mm spacing between the contacts.  R17D typically indicates an HO or, high output fluorescent tube.  

It is important to know which base type your current sockets are compatible with, unless you plan to replace sockets as part of your retrofit project.  With the exception of converting G13 to R17D we do not carry any fluorescent socket adapters.  In most cases, even if you could find an adapter to convert one base type to another, the added length of the adapter to the tube would prevent the tube from fitting properly in your fixture.

The T5 Exception

When converting fluorescent T5 to LED - tube diameter matters.  Unlike T8 or T12 in which the lengths and base types are easily matched, T5 lengths are different and at the time of this articles publication, the vast majority of T5 LED replacement tubes are ballast compatible only.  In addition, T5 due to its smaller diameter, cannot accommodate the larger base sizes mentioned above and instead most commonly uses a G5 Miniature bi-pin base which indicates two pins at either end spaced 5mm apart center to center.

What is a non-shunted socket?

Non shunted tombstone socket for LED T8 tube lights

We get asked all the time what a non-shunted or un-shunted tombstone socket is.  Tombstone is simply a reference to the shape of the socket.  Many of our ballast bypass tubes utilize single end wiring configurations which require the use of a non shunted socket at the powered end of the tube.  This means that there is no continuity or no connection between the two pins within the socket.  Each pin can be powered independently of the other.  This is necessary for single end direct wiring on Type B tubes where one pin connects to the hot wire and the other connects to the neutral wire.  

An easy way to tell if your sockets are non shunted is to take a look at the number of wire inputs on the socket.  4 input points is usually indicative of a non shunted socket while two input points would indicate a shunted socket where both pins utilize a shared connection.  Of course, we recommend testing for continuity between the connection points to be sure.  If you need more help with this part you should absolutely call in a licensed electrician for help.  

Safety Concerns

LED tubes contain no mercury or loose phosphorus powders.  No HAZMAT protocol is required to cleanup breakage and they do not put the environment or people at risk of exposure to hazardous materials.  Additionally, the reduced consumption creates less greenhouse gas pollution by reducing electrical demand.

While it is completely safe, higher voltage to the socket poses a concern for some customers.  If this is the case with your installation there are numerous ballast compatible and external driver tube options that do not increase voltage to the sockets.

Tube Types

  • UL Type A
    • can operate off an existing fluorescent ballast
    • do not require mechanical or electrical changes to the fixture
  • UL Type B
    • do not operate off the existing fluorescent ballast
    • require rewiring of the existing fixture to bypass the ballast and send line voltage directly to the lamp holders
  • UL Type C
    • employ lamp holders to connect to the fixture being retrofitted
    • do not operate off the existing fluorescent ballast
    • require rewiring of the existing fixture to replace the ballast with an external driver
    • wired to receive only the low voltage electricity supplied by the external driver
  • Cooler Tubes
    • Self contained unit with IP rating suitable for damp location
    • May have integral driver or external driver
    • Uses wire leads to connect to line voltage
    • require rewiring of the existing fixture to bypass the ballast and send line voltage directly to the lamp
    • do not operate off the existing fluorescent ballast
  • LED PL Lamps
    • Made to replace bi-axial 4 pin compact fluorescent lamp types PL-L Single Biax, PL-C Double Biax, and PL-T Triple Biax.
    • can operate off an existing electronic compact fluorescent ballast.

We hope this information helps shed a little light on the basics of our LED tube light selection.  If you need more help just use the Q&A section on the product page of the item you need help with or send us an email from our Contact Us page.  We're always happy to assist! 

SAFETY FIRST: If at any time you are not absolutely sure of what to do when it comes to the wiring portion of any retrofit or installation we recommend calling in a licensed electrician to perform the work for you.  The risk associated with an improper installation could be anything from simply shorting out the product to sparking a catastrophic fire or causing great bodily harm to yourself or others. We are happy to give instruction as it relates to how a product is powered but we cannot give electrical advice over the phone nor do we recommend accepting electrical advice over the phone from anyone. Any advice you receive should be the result of an on site evaluation by a licensed professional. Damage to products caused by improper installation is not covered under warranty and is not refundable in any way by Green LED Zone.

Got something to add? We want to hear your thoughts! Sound off in the comments below!

Ballast bypassBallast compatibleCflConvert fluorescent to ledExternal driverFa8 single pinFluorescentG10q-4G13 medium bi-pinG5 miniature bi-pinInternal driverPl-cPl-lPl-tR17d recessed double contactRetrofitT12T5T8Tube lightUl type aUl type bUl type c

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