LED Direct Replacement: A Guide for 26W, 32W and 42W 4-Pin CFLs

Before LED replacement lamps arrived on the scene, CFL pin-based lamps were the preferred light source for commercial downlights. Because of lower energy and demand costs compared to incandescent or halogen, CFL recessed downlights became a common feature in commercial, retail, hospitality and similar spaces.

Various independent studies have shown that the installed base of downlights using a CFL light source in commercial buildings has steadily declined over the last five years. This decline, has been caused by the improved performance and decreasing cost of LED pin-based replacement lamps and retrofit kits.

This post will take a closer look at the LED options available for facility managers thinking about an upgrade. It will focus specifically on the common 26, 32 and 42 watt CFL configurations in many commercial downlights.

CFL 4-Pin Lamp Lumens

26W, 32W and 42W CFLs all use G24q or GX24q bases. They can be mounted horizontally or vertically in the downlight. Most operate with an electronic ballast.

The rated life of these CFLs ranges from 8,000 to 16,000 hours.

Initial Lamp Lumens

• 26W CFL = 1600 to 1800
• 32W CFL = 2000 to 2400
• 42W CFL = 2700 to 4000

LED 4-Pin Replacement Lamp Lumens

LED replacement lamps are available that use 4-pin G24q and GX24q sockets. The lamps are designed for either horizontal or vertical mount applications. If the existing CFL ballast is compatible, these LED lamps offer a simple direct replacement into the original socket. No wiring is required. The existing ballast will operate the new LED lamp.

The rated life of LED 4-pin replacement lamps ranges from 35,000 to 50,000 hours.

Initial Lamp Lumens

• 9W to 12W LED = 800 to 1200
• 17W to 18W LED = 1800 to 2000

LED Lumens Suitable Replacement For 26W and 32W CFL

Comparing the lamp lumens of CFL and LED indicates that LED replacements will provide the necessary light output to replace most CFL downlights up to 26W. Some LED replacement lamps may produce sufficient light to replace 32W CFLs. However, 42W CFL upgrades to LED currently look doubtful on the basis of lamp lumen output.

Studies done by the Lighting Energy Alliance and the Lighting Research Center at Rensselaer arrive at similar conclusions.

A key assumption when looking at the light levels is that the downlight spacing will remain the same – which will be the case in most common upgrade scenarios.

The Lighting Energy Alliance study included a photometric simulation of downlights in a hallway and found that the downlights with an LED light source exceeded IESNA illuminance and uniformity recommendations when replacing 26 watt CFL downlights. The spacing of the downlights was not altered from the normal CFL spacing.

Other conclusions from the Lighting Energy Alliance study:

Power demand with LED downlights decreased by an average of almost 50% compared to CFL.

Color temperature and CRI provided by the LED bulbs were within the acceptable specifications for most commercial downlight applications.

Power quality issues (power factor, total harmonic distortion) were not a problem when the LED lamps were installed in downlights with compatible ballasts as specified by the LED manufacturer.

Fast Payback for Direct Replacement Depends on the Ballast

2-3 Year Payback - Assuming the existing ballast is compatible and still has 10 years of useful life, the LED direct replacement strategy delivers a roughly 2 year to 3 year payback given the typical cost of LED 4-pin bulbs in 2018. Payback will be variable depending on energy and labor costs in different locations.

Compared to a ballast bypass LED replacement approach or an LED downlight retrofit, direct replacement using the existing CFL ballast has the advantage of not requiring an electrician . The labor savings reduces the payback period.

The existing ballast must meet two criteria.

1. The ballast must be on the list of compatible ballasts supplied by the LED bulb manufacturer. The illuminance level for an LED bulb is partly dependent on the ballast. If the ballast is on the list, it's a good idea to first purchase one or two of the LED bulbs and make sure they deliver the expected illumination.
2. The ballast must not be so old that it will need to be replaced in a few years. The economics change dramatically if you need to start replacing ballasts. An LED downlight retrofit may be the better approach when the life expectancy of the ballast is less than 10 years.

Other issues to be aware of:

Lensed downlights: installing LED bulbs in a lensed downlight (IC or non-IC) might generate temperatures that exceed the LED manufacturer specifications. Elevated temperatures will significantly reduce the life of the LED bulb.

Horizontal position lamps: the LED replacement bulbs may be shorter than the original CFL. This could affect the light distribution. Some adjustments to the position of the sockets may be necessary. By initially installing a couple of test bulbs, you can determine the extent of this potential problem.

Bottom Line

LED 4-pin (G24q and GX24q socket) direct replacement lamps for 26W and 32W CFL installations will provide an energy saving, maintenance reducing upgrade, usually with an attractive payback assuming the existing ballast is compatible and has at least 10 years of life remaining.

While many manufacturers claim some of their LED replacement lamps will replace 42W CFL, the studies done to date show that very few produce enough light - assuming the fixture spacing remains the same as it was for CFL.