LED light bulb comparison of Lumens (C) Daniel FriedmanLED Light Bulb Replacements for Fluorescent Tube Bulbs

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Replace a fluorescent tube bulb with an LED light bulb:

How to replace a tube-type fluorescent light bulb with an equivalent LED light bulb in fluorescent light fixtures. This article explains the key steps in installing an LED bulb (top of photo above) to replace a fluorescent light bulb (bottom of page top photo). The LED G-24 type bulb offers long life, lower energy consumption, but at a higher initial cost for the bulb.

Wiring changes, physical fit of the bulb, and heat dissipation are concerns that the manufacturer points out must be considered in making this bulb replacement. It's actually easy but this bulb swap is not suitable for some light fixture types.

Our page top photo illustrates a 15-W Meridian® LED Type G24 bulb (top of photo) that can replace a conventional fluorescent G24 bulb (bottom of photo).

This article series details guidelines for selecting and installing interior lighting to meet the requirements for different building areas.

Green links show where you are. © Copyright 2017, All Rights Reserved.

Installing LED Bulbs in Tube-Type Fluorescent Light Fixtures

Meridien G24 LED bulb can replace a G24 Fluorescent bulb (C) Daniel FriedmanReplacing a conventional tungsten type light bulb with a fluorescent or with an LED light bulb offers considerable energy savings, heat reduction, and longer bulb life. What about replacing a tube type fluorescent light bulb such as the type G24 fluorescent with a G24 LED bulb as shown at the top of this page?

The Meridian G24 LED bulb shown here is rated for 25,000 hours (about 2.8 years if the bulb were left on 24 hours a day, or about 22 years of life if the bulb is left turned-on for 3 hours a day).

The LED G24 has about the same light output (26 Watts) as the fluorescent that it replaces, but its energy consumption is only 15W. At 1500 lumens of light output and an annual operating cost of $1.81 per year (3 hours on per day and 11 cents per KWH) the bulb is an appealing alternative to its fluorescent cousin.

The Meridian G24 LED bulb will replace all -D -X and -Q CFL (fluorescent) bulb types and will fit into any of those lamp sockets or bases.

The company's packaging notes that the lifetime savings of this bulb in energy cost is about $30.00 U.S. which is about the cost of the bulb ($32.97 in September 2015, Home Depot). In short, the bulb, though more expensive than the fluorescent G24 bulb that it replaces, will pay for itself over its life. A note about the abbreviations in these bulb names:

Shown below is the standard, CFL G24 plug-in direct replacement for an un-modified fluorescent light fixture.

Phillips G24-3 4-pin base fluorescent light bulb (C) Daniel Friedman

Our example is a Phillips CFL G24-3 4-pin base fluorescent bulb ($6.47 in September 2015 at Home Depot) has a brightness of 1800 lumens, an estimated 11-year life, and an estimated annual operating cost of $3.13. The color temperature of this fluorescent bulb is 3500K.

Standard G24 type bulb 4-pin base used in fluorescent light fixtures with a ballast that must be bypassed if installing an LED equivalent (C) Daniel Friedman

Above you can see the standard 4-pin base used by G24 type bulbs.

The photographs and comments below explain how an LED bulb can be used to replace some tube-type fluorescent light bulbs and where the restrictions and snafus (LED-G24 BULB CONVERSION SNAFUs) may lie.

Enclosed light fixture using a fluorescent bulb should not take the LED alternative (C) Daniel Friedman

Above is a typical indoor fluorescent light fixture that incorporates a CFL G-24 bulb.

Wiring & bulb details for replacing a short tube type fluorescent bulb with an LED equivalent (C) Daniel Friedman

These bulbs are not pretty and in residential use they will usually be in an enclosed fixture such as this one. At above right you can see the white square ballast; 120V or 220V power from the light circuit enters the ballast at its left side (two white wires) and exits the ballast in four wires at its right-side.

Wiring connections for a typical ceiling light fixture (C) Daniel Friedman

If your electrician is going to modify this light fixture to bypass the ballast to accept the LED G-24 bulb the wiring changes are actually pretty simple, but the wire cuts, connections, and splices must be correctly made and properly secured and insulated or your installation will be unsafe (and it may not work either).

With the electrical power turned OFF to the circuit, and having used a neon tester or DMM or VOM to confirm that power is off at the light fixture, it can be removed.

After the ceiling light fixture mounting screws are loosened the fixture is rotated slightly to let the screws pass through the larger openings to expose the actual electrical wiring connections to the electrical outlet box.

White wires: neutral

Black wires: hot

Green wire: ground

One white and one black wire will connect to the light fixture or in this case to the ballast in the fluorescent light fixture while the bare copper circuit ground wire connects to a ground connection on the fixture or to the fixture's own ground wire (green).

Electrical wires entering the ceiling light fixture (C) Daniel Friedman

Above you can see two white and one green (ground) wire entering the light fixture. We're looking at the "up" side of the fixture that will be against the ceiling and against the electrical box when the fixture is mounted in place on a ceiling (or wall).

Watch out: When we see two white wires and no black wire here we might think that the manufacturer is telling us that it does not matter which wire gets the circuit "hot" (black) and which gets the circuit "neutral" (white) wires - there is no polarity to be respected at the ballast input wires.

Really? Not necessarily. Flipping the light fixture over and pulling back an outer insulating cover we see that at the input wires to the light fixtures's ballast there is indeed a white and black wire.

Black and white wires to the ballast input side are shown for this fluorescent light fixture (C) Daniel Friedman

Connect white to white and black to black.

Wiring connections for a fluorescent light fixture (C) Daniel Friedman

At above right I've pulled out (temporarily) that extra heat and mechanical damage protecting insulation to show the white, black, and green (ground) wire for the fluorescent light fixture. If you were installing this fixture anew in a ceiling to use a fluorescent light bulb you would not modify any wiring and you'd use a CFL-G24 4-pin base bulb like the Phillips bulb shown earlier in this article.

Check the LED G24 Bulb Fit Before Starting Wiring Modifications

Watch out: before cutting and splicing wires or modifying your fluorescent light fixture to perform the ballast bypass (discussed below), check that the slightly-larger LED-G24 bulb will fit where the fluorescent CFL G24 bulb previously plugged in.

LED G24 bulb installed for test fit in the G24 base of a ceiling light fixture (C) Daniel Friedman

Check the Light Fixture Type, Shape & Cover Before Starting Wiring Modifications

Watch out: before before cutting and splicing wires or modifying your fluorescent light fixture to perform the ballast bypass (discussed below), check as well that the type of light fixture into which you're installing the LED bulb is one that is approved by the manufacturer.

That was when we discovered that the particular ceiling fluorescent light fixture shown in this article was not recommended by Meridian for use with this LED G24 bulb: it is an "enclosed" fixture that will be covered when fully installed.

The concern is that heat generated by the LED G24 bulb may reduce bulb life or cause improper or unsafe operation of the light.

Details are at LED-G24 BULB CONVERSION SNAFUs. We considered installing the bulb in the enclosed fixture anyway then decided to obey the manufacturer's warning. We returned the bulb to its place of purchase.

Ballast Bypass Wiring Changes for Using an LED G-24 Bulb in a Fluorescent CFL G-24 Light Fixture

Wiring details for ballas bypass converting CFL G24 bulb to LED G24 Bulb (C) Daniel Friedman

Modifications of the Ballast: ballast bypass to convert a CFL G-24 light fixture to an LED G-24 light fixture are given by the installation instructions from the manufacturer.

An example is shown here. Be sure to read and follow the instructions provided by the manufacturer for the specific bulb you (your electrician) is installing, including the ballast bypass conversion details.

The illustration at left is adapted from Meridian's instructions for ballast conversion for a 4-wire bulb socket.

2-pin and 4-pin bulb sockets have somewhat different wiring details.

The CFL G-24 light fixture we show above and at left is a 4-pin socket: you'll see in the photograph four wires exiting the ballast and connecting to each of the four pins of the socket. But in both cases the line and neutral wires will, on ballast bypass conversion, be connected respectively to the two diagonally-opposed pins on the LED G-24 bulb that is going to plug into the original four pin socket.

In the example wiring instructions (above left) the "line" or "hot" or "black" wire is connected to wires 1 and 2 on the lamp socket so that one of the two diagonally-opposed pins of the bulb will connect to the line side of the circuit when power is on.

In the wiring instructions above the "white" or "neutral" wire is connected to wires 3 and 4 so that the other diagonally opposed bulb pin will connect to the neutral wire.

Watch out: you will want to double check the bulb base to observe how the bulb plugs into the lap socket and to triple check the manufacturer's wiring ballast bypass instructions to be sure that you are making the correct connections. Ultimately the circuit line wire will connect to one of the LED G24 bulb base pins and the circuit neutral wire will connect to the second LED bulb base pin.

Comparing the 4-pin CFL G24 bulb to the 2 pin LED G24 Bulb (C) Daniel Friedman

Above you can see the two-pin LED G24 bulb base (above left) compared with the four-pin original fluorescent CFL G24 light bulb. Notice the two projecting flanges or ears on the right and left side of each base that assure that the bulb can not be plugged in improperly.

Install the "Fixture Modified" Sticker on your Light Fixture

Watch out: after bypassing the ballast on a fluorescent light fixture you must attach the manufacturer-provided warning sticker to tell future electricians or homeowners that the fixture has been converted to LED-bulb use.

The manufacture warns that once the ballast has been bypassed (in fact we think you should remove it completely) you can no longer use this light fixture as it was originally intended: that is you cannot later install a conventional fluorescent bulb - the CFL G24 bulb that was originally used. That may be just fine considering the 22-year life expectancy of the LED G24 that you've installed.

Reader Question: Can I install an LED tube to replace a Fluorescent Tube Light?

LED replacement for fluorescent bulb (C) Daniel Friedman

(Feb 13, 2015) BD said:
what about installing LED tubes where fluorescent fixtures and ballasts were before?

Reply: Yes but ... watch out!

There are LED tube type lights that can replace some fluorescent light fixtures but I include these warnings:

1. LED Bulb fit space: Be sure that the LED tube light you purchase can physically fit where the fluorescent bulb fit before; some replacements are a bit larger due to a base that includes additional circuitry

2. Re-wiring needed for this LED bulb:

Watch out: you'll have to "bypass" the ballast in the original light fixture by following re-wiring instructions included with the LED bulb that was designed to replace the fluorescent bulb. Failure to perform this wiring change risks shock or fire or injury.

Typically, because you'll be using the existing bulb connection socket you'll disconnect wires from the ballast and feed the proper pairs of wires to the proper bulb base terminals.

I tried one of these replacements recently and found a third problem that caused me to give up and return the LED bulb:

3. Cannot use (some?) LED Replacement Bulbs in enclosed light fixtures:

LED light bulb comparison of Lumens (C) Daniel Friedman

Watch out: The LED bulb may include a warning that it is "not intended for use in enclosed fixtures" and that "Installing in an enclosed fixture will reduce bulb life".

This advice does not expressly prohibit the bulb's use in an enclosed light fixture, leaving us confused about whether the concern is bulb life or electrical and fire safety.

Since many fluorescent bulbs are used in enclosed fixtures, and since this warning is hidden inside the bulb packaging (not visible on the store label, not visible on the package exterior) you wont' discover this critical limitation until you've bought the bulb, opened its packaging, and read the instructions.

In my OPINION the bulb manufacturer and perhaps its lawyers knew perfectly well that the "do not enclose" restriction would make this bulb undesirable for at least some applications for which purchasers would buy the bulb, take it home, then discover that they could not or should not use it.

The package front and back do include multiple warnings

Really? We ask that any readers who have ever used such a scan code to read the installation instructions before purchasing the bulb should let us know using the page top or bottom CONTACT link as we suspect the number who have used this nice feature is infinitesimally small.

OPINION: The cost and trouble of returning even an expensive $30. bulb to the store will perhaps be too much for a homeowner who took a bus across town to buy a replacement bulb during her lunch hour. The bulb goes in the trash or into storage instead.

Really? Really? Yeah: on the original package of the Meridian LED G24 the warning that you cannot use this bulb in an enclosed fixture did not appear on the package exterior. That image is below.

LED G24 installation instructions - photographed at a Home Depot Store, Poughkeepsie NY- Daniel Friedman

[Click to enlarge any image]

Meridian LED G24 online instructions -  Contact Meridian Lighting at

However the company's online instructions shown at above right make this restriction entirely clear. The online instructions are excerpted at below right. - retrieved 24 Sept 2015 original source

Contact Meridian Lighting at


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