An LED tube light is an LED retrofit lamp that serves as a replacement light source for linear fluorescent lamps. LED tubes are designed to fit into the fluorescent sockets, effectively converting the light fixtures that originally accommodate fluorescent tubes into more energy efficient, longer life LED systems.
As a product developed to address the needs of retrofitting existing fixtures, LED tubes have greatly simplified the job of lighting upgrade, whether the installation involves recessed troffers, wraparound fixtures, linear high bay lights, shop lights, or vapor tight fixtures. Despite the trend towards designing LED luminaires as integrated performance systems, LED tubes are still the workhorse in existing commercial, industrial and institutional buildings such as offices, hospitals, schools, shopping centers, retail establishments, warehouses, manufacturing and assembly facilities
Physical Specifications
As fluorescent tube replacements, LED tubes are also referred to as TLED lights, notwithstanding they are no longer gas-discharge lamps but produce light from an array of semiconductor light sources. As lamp retrofits, LED tubes inherited the form factor and lamp base of linear fluorescent lamps.
Until 1980, almost all fluorescent lamps used for general lighting were T12 lamps which are 1.5 inches (3.81 cm) in diameter. After then, the majority of new installations used T8 lamps which are 1 inch in diameter. Designed with the same G13 medium bi-pin base, T8 lamps are interchangeable with T12 lamps. This interchangeability combined with the ability of T8 lamps to provide more light and operate more efficiently than T12 lamps makes T8 lamps the dominant linear light source for both new construction and renovation projects. T8 lamps are typically available in imperial lengths of 2, 3, 4 and 8 feet, or in metric lengths of 600 mm, 900 mm, 1200 mm, and 2400 mm.
In general, an LED tube light refers to the T8 type LED lamps if not specified, although T5 fluorescent lamps also have their LED replacements. Linear T5 LED lamps are 5/8 inch or 16 mm in diameter. They’re not interchangeable with T8 LED tubes due to the shorter maximum overall length of the T5 (approx. 2″ shorter) and the use of different pin spacing on the bases (T5 uses G5 miniature bi-pin bases).
Fluorescent Ballasts
A fluorescent light fixture typically consists of a housing, one or two ballast and at least one fluorescent light tube. The ballast is used to regulate the current going through the fluorescent lamp.
Electronic ballasts can be categorized into the instant-start type, the rapid-start type, and the programmed-start type. The predominant electronic ballast used in fluorescent light fixtures is the instant-start ballast because it provides maximum energy savings and operates lamps in parallel. Rapid-start ballasts, including programmed-start ballasts, will extend lamp life for circuits switched often, but are more expensive and cause increased energy consumption compared with instant start circuits.
The electronic ballast is typically installed within the fixture housing and electrically connected to the line voltage. This means to retrofit a fluorescent fixture the ballast should be bypassed with rewiring by a qualified electrician, or the LED tube must run off the existing fluorescent ballast so as to simplify installation and save labor cost. While most end users prefer the plug-and-play, direct replacement solution that has the lowest initial cost, a lot of issues may arise due to the incompatibilities between the electronic ballast and LED tube. The electrical incompatibilities constitute the safety, efficiency and reliability issues facing linear LED retrofit solutions.
Types of LED Tube Lights
A lighting upgrade involves considerations on the financial aspect as well as the installation, operations, and maintenance implications. Whether to connect or bypass the existing fluorescent ballasts is not just about saving the installation cost or not, but also affects the energy efficiency, electrical safety, operational features, and maintenance cycle of the LED retrofit tubes. LED tube lights can be grouped into four categories depending on the ballast compatibility and driver integration: Type A (Ballast Compatible), Type B (Ballast Bypass), Type C (External Driver), and Dual Mode (Type A + Type B).
We’ll discuss the different types of LED tubes, the advantages and disadvantages of each, and examine the main issues and concerns associated with different LED tubes in coming articles. It’s very important to know the options and which one will work best for you.
Shunted vs Non-shunted Tombstones
Tombstones are the “sockets” or lamp holders that fluorescent or LED tube lights will be installed into, providing both the mechanical support as well as electrical connection.
There are two types of sockets, shunted and non-shunted. Shunted sockets feature internally connected electrical contacts. This provides a single track for the electrical current to travel from the ballast, through the socket to the lamp’s pins. Non-shunted sockets have separate contacts – or points of entry for the wires – creating two tracks for the electrical current to travel.
In general, fluorescent fixtures that have instant-start ballasts have shunted tombstones, while Rapid-start ballasts, including programmed-start ballasts may have non-shunted tombstones.
Luminous Flux
Luminous flux, measured in lumens, measures the total amount of light emitted from a lamp, and is the best measure to determine the brightness of a lamp.
The best way to make an apples-to-apples comparison is to compare the luminous flux value of the fluorescent lamp with the LED tube light. Generally, a 35W T8 fluorescent lamp emits about 2500 lumens and a 54W T5 lamp emits about 4500 lumens.
In practices that most LED tube lamps claim to replace standard fluorescent tubes but only a few compete in terms of total light output. According a field test by the California Lighting Technology Center at the University of California (CLTC), who compared LED retrofit lighting solutions meant to replace linear fluorescents. The study shows up that overall energy savings are delivered in part by reducing the light output, not just by improving light efficacy. The full report on this study is published on CLTC website.
“While the tested LED products are very efficacious at the system level, overall energy savings are achieved, in part, by reducing light output, not just power. In all three fixtures tested, Type A and Type B LED products, including hybrid Type AB, consistently demonstrated significantly reduced light output as compared to the fluorescent baseline” — Cori Jackson, Director at CLTC
Lumens Efficacy
Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power, measured in lumens per watt (LPW). Lumens per watt (LPW) is a key measure of efficacy in lighting, The higher the LPW number, the more efficient the product is.
Furthermore, consider that efficacy is a major criterion in DLC certifications. If your lamps are not DLC certified, there’s little chance they’ll qualify for any utility rebates. And there are a handful of rebates which offer escalating incentive ranges based on the efficiency of your lighting. Sometimes, the higher the LPW, the higher the incentive.
Correlated Color Temperature
Correlated Color Temperature, or CCT describes a white light source’s appearance. It is the temperature of an ideal black-body radiator that radiates light of a color comparable to that of the light source. It is measured using degrees Kelvin, and there are three common ranges: Warm Light (2700K-3000K); Cool White (3000K-5000K), and Daylight (5000K-6500K). The lower the Kelvin, the “warmer” its appearance, while the higher the Kelvin, the “cooler” its appearance. Research has shown that these three ranges of light have different effects on sleep cycle, productivity, and mood. Warm Light is relaxing which helps people to calm down and prepare for sleep. Cool White and Daylight contain blue spectra which helps people be wakeful, productive, attentive, and improves moods.
Most fluorescent tube lights have a correlated color temperature (CCT) of 4000K or 5000K, as they have been considered to be most suitable for commercial and industrial environments. Similarly, LED tube lights are also available in a wide range of color temperatures.
Color Rendering Index
Color Rendering Index (CRI) is the measurement of how colors look under a light source when compared with sunlight. The index is measured from 0-100, with a perfect 100 indicating that colors under the light source appear the same as they would under natural sunlight.
An lamp’s color rendering index tells an observer how well that source will show fine details in an object. In warehouse operations, shipping yards, factories, or any industrial or commercial facility, this is extremely important. Not just for the obvious safety requirements, but especially where workers need to see markings on boxes, components, shipping containers, instructions, and manuals. Simply put, the LED lights with CRI>90 enables facilities to provide the most productive light levels for working conditions, no longer simply monochromatic blue-white light.
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