In the early days of your LED re-lamp project, you’ll need to determine what “type” of replacement you’ll be working with- Type A, B, or C. These “types” are also referred to as “Plug and Play,” “Direct Drive,” and “Lamp and Driver,” respectively. The differences in each stem from whether a ballast or driver is being used and how the LED is connected to that power source. All LED lamps use drivers to convert the AC (alternating current) power into DC (direct current). How that power gets to your lamp depends on the type of fixtures and ballasts you already have in place.


Type A

Type A LED tubes are ballast compatible. This is the “plug and play” or “lamp for lamp” scenario most commonly used in re-lamping projects, where you simply replace the bulb with an LED lamp while retaining the original ballast and fixture of the fluorescent. Of the three options, this is the only installation that doesn’t require any electrical or mechanical changes. However there are quite a few exceptions that make Type A’s ballast compatibility not so universal. Even LEDs and ballasts that come from the same manufacturer aren’t necessarily going to work together. In addition to ensuring that your new lamps work with your old ballasts, the cost efficiency of a Type A solution is dependent on the remaining life of the ballast.


 Example of “Type A” Example of “Type A”


Type B

LED tubes that have the driver incorporated into the lamp are called Type B. There are two versions of a Type B bulb—single ended power and double ended power. If you think you’ve figured this one out, you’re probably right. Single ended power tubes take power from only one end of the tube. One end is a non-shunted socket (a socket with separate points of contacts for the wires) and the other is a dummy. Double ended power is similar to how fluorescent tubes run, making them a better choice for retrofit projects where you’re replacing a fluorescent tube with an LED. Power is sent to both ends of the tube, with one end running line voltage and the other neutral.


 Example of “Type B” with single ended power Example of “Type B” with single ended power


In this type of installation, with single or double ended power, the ballast is removed completely. While there’s significantly more labor involved with a Type B replacement, you’ve now eliminated the risk of ballast failure/replacement or ballast-lamp incompatibility. Unfortunately, we’re still seeing significant risks with Type B single ended power lamps including lamp failure and sparking. Double ended Type B lamps relieve this issue because the electrical current can no longer travel across the fixture. While this may be the simplest solution type, it also has the highest installation cost, requiring electrical rewiring work and additional safety precautions. Fluorescent tube sockets are not designed to carry line voltage, which can be up to 277 in a typical commercial setting, so you need to be particularly attuned to the condition of your sockets.


 Example of “Type B” with double ended power Example of “Type B” with double ended power

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Type C

Type C offers the best compatibility, future-proofing, and overall performance, but it also requires more installation time and a higher up-front cost for the LED driver. With this type of solution, you’re removing the ballast, replacing it with an external LED driver, and connecting that to your new LED lamp. The driver is placed in the same location as the old ballast and the same wiring is used. The system also works with any controls such as dimming or daylight harvesting that are already installed or may be installed in the future. Type C re-lamping is also known to have the longest useful life. By pairing lamps with drivers custom-made to feed them power appropriately, you eliminate dissonance and early failures you might see in a Type A solution. By moving the power source away from the LED, you create less heat on the LED chips than you would with Type B.


 Example of “Type C” with isolated driver. All drawings  via U.S. Department of Energy  Example of “Type C” with isolated driver. All drawings via U.S. Department of Energy


Type A/B

Last but not least, there’s the hybrid option or “Type A/B”. This type of LED can work off the existing fluorescent ballast or line voltage if the fixture is rewired to bypass the ballast. This is a good option when  you aren't sure of the useful life remaining on your ballasts. Hybrid A/B lamps give you the flexibility to do a plug and play installation, and simply remove ballasts from the system as they fail. There are not, however, many good hybrid tube products on the market to choose from, largely because making them safe and cost effective has proven difficult.

The type of LED replacement needed for your project is highly individual. If your existing ballasts are relatively new and upfront cost is a priority then Type A might be the best option. If you’re tired of your old ballasts failing or you’re purchasing new, LED-ready fixtures, Type B or C could be the way to go. Understanding the electronics you already have, the wide-range of available products, and the needs of your space is crucial to implementing an effective LED lighting system.


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