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As mentioned in last week’s blog, Has the time arrived for LED tube replacements?, there are two different types of T8 LED tubes available on the market today: those that must run directly off the line voltage and those that can run off the fixture’s pre-existing ballast.
So which one is right for you?
Fluorescent tubes require ballasts in part because they require a high start-up voltage—which the ballast provides—to overcome initial resistance. The ballast then adjusts to carefully regulate the electrical power delivered to the tube. Since LEDs do not require either the high start up voltage or power regulation, the ballast is not required. Initially all LED T8 tubes ran directly off line voltage, which is accomplished by bypassing or removing the ballast. The majority of LED T8s on the market today still operate in this fashion. In this post I will refer to these as direct line voltage tubes. Recently, however, LED T8 tubes that can run using ballasts have been introduced to the market. I’ll refer to these as plug-and-play tubes.
In this blog, we will examine the advantages and disadvantages of both types of LED T8 replacement tubes.
|Issue||Direct line voltage tubes||Plug-and-play tubes||Comments|
|Service||Requires the services of an electrician to remove or bypass the ballast, and then in most North American jurisdictions, requires an electrical inspector to approve the modified ballast for use. One can expect the average charge for the electrician’s work to generally come to ~$25/fixture.*||No electrician or safety inspection is required because the tubes run off the ballast that is already installed.||The plug-and-play tubes cost approx. 40%-50% more than direct line voltage tubes. In general, for retrofit applications, there is little difference in up-front costs between these two approaches.|
|Efficiency||The better direct line voltage tubes are now equaling or exceeding 100 lm/W. The efficiency of the tube is the actual wall-plug efficiency, as there is no ballast to interfere with power received by the tube.||To ascertain the true efficiency of a lighting fixture containing a plug-and-play tube, one needs to take into account the efficiency of the ballast. This varies rather widely from ballast to ballast —both by ballast type and by brand/model**. For example, electronic ballasts exhibit efficiencies that are superior to both hybrid and magnetic ballasts. Older magnetic ballasts can consume as much as 20% of the overall system efficiency. Modern ballasts are much more efficient at 90% to 95%.||Depending on the ballast, the loss of efficiency it introduces, (though not generally large) adds up over time and affects the overall total amount of electricity saved. Although it is difficult to make specific statements about which approach is the better one, in general, the wall plug efficiency with direct line voltage tubes will be higher than with plug-and-play tubes.|
|Regulations||UL certification of the fixture, which is generally granted based on the assumption that a ballast is or will be part of the system, is lost when the ballast is removed from the fixture. In most jurisdictions, the resultant new LED system requires electrical inspection and approval before it is allowed to go operational. Depending on the regulations and practical considerations in certain localities, achieving this can range from an inconvenience to very difficult and time consuming.||UL certification of the fixture is maintained because the fixture is not modified.||In general, the plug-and-play approach will make it easier to achieve or maintain UL certification.However, some states offer greater rebates when one replaces an entire system (troffer + fluorescent tubes), so it could be more cost effective to purchase an approved LED system than modify an existing fixture or buy plug-and-play tubes.|
|Safety||Some direct line voltage tubes are wired so that the two electrical connections are at one end, and some are wired with the two electrical connections at opposite ends. When replacing a direct line voltage tube with a fluorescent tube the installer needs to be cognizant of how both the fixture and the tube have been wired (one-ended or two-ended) or the installation could produce quite shocking results. Literally. In addition, all maintenance personnel must be aware of all fixtures running direct current, placing increased emphasis on not only accurate and clear labelling, but communication.||With an unaltered, UL-certified fixture, there are no safety concerns.||From a safety perspective, plug-and-play tubes appear to have the advantage.|
|Buzz / Hum||Without a ballast, there is no hum or buzz.||Almost all ballasts hum to some degree, with magnetic ballasts humming far more than the newer electronic ballasts. Plug-and-play tubes, which make use of the existing ballast, will not provide the opportunity to eliminate the humming sound of the ballast.||From the perspective of humming, which in most modern installations is rather minor, direct line voltage tubes appear to have the advantage.|
|Convenience||Removing or bypassing ballasts requires approximately 15 to 20 minutes of labour per fixture. In a retrofit situation, the inconvenience of relocating existing people (and possibly equipment) out of the facility and later, back in, must be considered.||Changing the tube is simple—just put in the new tube in the same manner as a fluorescent one. This generally takes just a few minutes and in general, provides only a minor amount of inconvenience to the people using the facility.||From the perspective of convenience to the users of a facility under retrofit, plug-and-play tubes appear to have the advantage.|
|Lifetime||The lifetime of the lighting system is dependant only on the lifetime of the LED T8 tube itself, which can generally be up to 40,000 hours for the better quality LED tubes.||The lifetime of the lighting system is dependent on the lifetime of not only the LED T8 tube, but the ballast as well. Ballasts last between 30,000 and 80,000 hours, depending on ballast type and usage characteristics.||In general, ballasts will last at least as long as the LED tubes so ballast lifetime may not be a major consideration.|
|Compatibility||Ballast compatibility is not an issue for direct line voltage tubes.||Many plug-and-play tubes claim to operate on most ballasts. To date, this claim is often misleading as almost all plug-and-play tubes have some limitations and are not truly universal.||Do your homework prior to placing large orders for a retrofit, as you don’t want to experience a tube-ballast incompatibility in the midst of the project.|
* According to engineering.com, labor represents approximately 40% of the cost of replacing fluorescents with LEDs.
**In today’s North American market, almost all T8 fluorescent tubes are operated with electronic ballasts and most T12 fluorescent tubes are operated by magnetic ballasts. In most situations, the life-cycle cost of an electronic lamp/ballast system will be less than for a magnetic lamp/ballast system with equivalent light output so a driver of the decision ballast vs. no-ballast) may be reduced for practical purposes to whether you have T12 or T8 right now.
Based on these factors, which tube would you select for your retrofit project? Which factors are the most important to you?