Linear fluorescent fixtures

Linear fluorescent fixtures use tube-shaped lamps, which are connected to the voltage supply from both ends. They are not designed to use AC power directly, and instead they are connected to a ballast that regulates the current input. The fluorescent tubes and ballasts are both contained in the fixture housing, and the tubes can be exposed or covered by an acrylic lens, depending on how the fixture is designed.

A key advantage of linear fluorescent fixtures is that their tubes can be easily replaced, while using the same housing and internal connections. Fluorescent tubes typically have two pins at their ends, which are inserted into special lampholders and locked in place. You can also use compatible LED tubes to retrofit linear fluorescent fixtures, reducing their consumption by over 40% with minimal changes.

Types of Linear Fluorescent Fixtures

Linear fluorescent fixtures can be classified by lamp type, and this determines the ballast and lamp holders needed. Most fluorescent tubes have a length of 2 ft or 4 ft, but you can also find sizes like 3 ft and 8 ft. The three most common lamp types are T5, T8 and T12.

The letter “T”  stands for “tubular”, while the number indicates lamp diameter in eighths of an inch. This means a T5 lamp measures 0.625” (5/8 in), a T8 lamp measures 1” (8/8 in), and a T12 lamp measures 1.5” (12/8 in). The typical electricity consumption of the most common fluorescent lamp types is the following:

• T5, 4 ft = 28W

• T5, 2 ft = 14W

• T5 High Output, 4 ft = 54W

• T5 High Output, 4 ft = 24W

• T8, 4 ft = 32W

• T8, 2 ft = 17W

• T12, 4 ft = 40W

• T12, 2 ft = 20W

T12 fluorescent tubes are the least efficient, and they have already been banned in many locations. However, you may still find them in operation in older buildings.

Linear fluorescent fixtures can also be described based on the number of tubes used. For example, fluorescent fixtures for offices typically use 2, 3 or 4 light tubes (T8), while industrial fluorescent fixtures may use 6 or 8 tubes (T5 High Output).

Fluorescent tubes are used in many types of fixtures, which include troffers, shop lights, strip lights, vapour tight fixtures, and linear high bays. All these fixture types can also use equivalent LED tubes, which improves their energy efficiency.

How To Install Linear Fluorescent Fixtures

Linear fluorescent fixtures come in many sizes and configurations, but they generally follow a similar installation procedure: 

• The fixture body and its internal connections are installed first, without the tubes. In most cases, the fixtures are suspended from chains or surface-mounted. There are 2x2’ and 2x4’ fixtures, which are specially designed to fit in suspended grid ceilings.

• Once the fixture is firmly attached and wired, the tubes are inserted into the lampholders, where they can be locked in place by rotating them slightly.

• Depending on how the fixture is designed, fluorescent tubes may be exposed, or covered by an acrylic lens.

Once a fluorescent fixture has been installed, tube replacements are very simple. You only need to rotate the existing tubes out of their locked position, and they can be removed from lampholders to install their replacements.

When retrofitting fluorescent fixtures to LED, there are three main options, and you can expect typical energy savings of over 40%:

• Using ballast compatible LED tubes, which are simply connected to the lampholders like any fluorescent tube. These are also known as plug-and-play LED tubes.

• Using ballast bypass LED tubes, which are wired directly to AC voltage, bypassing the ballast - this means the fixture must be rewired to use these tubes. They are also known as direct-wire LED tubes.

• Using an LED retrofit kit, which completely changes the internal wiring and light source. Retrofit kits often use integrated LED arrays, like those used in newer fixture designs, instead of light tubes.

Keep in mind that fluorescent tubes contain small amounts of mercury, and special disposal is required by law in most jurisdictions. However, you should follow proper disposal procedures even in places where they are not mandatory, to avoid releasing mercury into the environment.

What Are the Benefits of Linear Fluorescent Fixtures?

When linear fluorescent fixtures first became commercially available, their main advantage was energy efficiency, saving 75% compared with incandescent and halogen lamps. Now that LED lighting has become mainstream, it offers savings of up to 90%. However, fluorescent lamps are still a close second in terms of efficiency.

Fluorescent lamps also have a longer service life than older lighting technologies:

• Incandescent and halogen bulbs typically last less than 2,000 hours, while fluorescent tubes have a typical service life of 20,000 - 30,000 hours.

• LED tubes last 50,000 hours or more, but fluorescent tubes are more durable than the lamp types before them. Actually, some manufacturers  have already developed extra-long-life fluorescent tubes, which can match the service life of LEDs.

In general, linear fluorescent fixtures have a versatile design that has been used in many commercial and industrial applications. The number of lamps and fixtures can be specified based on the application, and damaged or burnt lamps are easily replaced. Since this fixture design has been so successful, many LED products also use it.