T-8 Fluorescent System

T-8 fluorescent systems are a good option for anyone needing to replace both lamps and ballasts. Standard fluorescent lamps are referred to as T-12 (12 being the diameter of the lamp in 1/8ths of an inch). A T-12 lamp is therefore, 1 1/2 inches in diameter. More efficient, smaller diameter lamps (1-inch diameter) are available and are referred to as T-8 lamps. They go by such vendor names as "Octron" for Sylvania, "Trimline" for General Electric and "Octolume" for North American Philips. The T-8 lamps incorporate more costly rare earth phosphors to coat the inside of the lamp. These phosphors result in more efficient light output. The small diameter lamp also allows more usable light to exit the fixture.

Why Use a T-8 System?

There are several reasons to use a T-8 fluorescent system. The first reason is cost savings. The table below displays cost comparisons of the T-8 versus T-12 systems. In addition to the cost advantage they present, T-8 fluorescent lamps also provide good color rendition for merchandising. T-8 lamps have a color rendering index (CRI) of 75, compared to standard T-12 lamps which typically have CRIs of 50 to 60. Four T-8 lamps may be operated by a single T-8 electronic ballast, thus reducing the cost of ballast replacement (only two or three T-12 lamps may be operated by T-12 ballasts). They also have a long life, 20,000 hours, and excellent lumen maintenance. But straight and U-tube T-8 fluorescent lamps can operate on the same type of ballast, simplifying inventory requirements.

OPERATING COST COMPARISONS
T-8 versus T-12 Fluorescent Systems
Fixture
Lamp Type
#/Type Lamp
Ballast Type
Watts/Sq. Ft.
Annual Oper. Cost
2'x4'
T-12
3 40-Watt Straight, 4' Magnetic
1.5
$2,700
2'x4'
T-8
3 32-Watt Straight, 4' Magnetic
1.0
$1,800
2'x4'
T-8
3 40-Watt Straight, 4' Electronic
0.8
$1,440
2'x2'
T-12
2 40-Watt U-tubes Magnetic
1.5
$2,700
2'x2'
T-8
3 31-Watt U-tubes Magnetic
1.2
$2,160
2'x2'
T-8
3 31-Watt U-tubes Electronic
0.9
$1,620
*Based on $0.06/kWh, 3,000 br/yr operation in a 10,000 ft. building area with 50 footcandles maintained.

When to Use a T-8 Fluorescent System

Fluorescent T-8 systems are ideal for use in new construction or renovation. In new construction or renovation, a T-8 system will require fewer fixtures than a T-12 system, reducing project costs. In new construction, the cost of air-conditioning equipment is reduced because the T-8 fluorescent fixtures are more efficient, giving off less heat than a T-12 system. U-tube fluorescents are an ideal replacement for existing incandescent fixtures. Their smaller size allows the use of a 12"x12" fixture and a significant reduction on operating costs. A 150-Watt incandescent lamp can be replaced with two 16-Watt T-8 U-table lamps.

Things to Remember

  • T-8 fluorescent lamps use different ballasts than T-12 lamps.
  • T-8 lamps yield good color rendition.
  • New construction or renovation should use T-8 fluorescent systems for reduced energy costs.