1. LED Lamp Types
1. Type A Tube
The UL Type A tube is designed with an internal driver that allows the tube to operate directly from the existing linear fluorescent ballast. Most of these products are designed to work with T12, T8 and T5 ballasts.
The Problem
The lifetime of a UL Type A solution is dependent not only on the design life of the LED lamp but also on the linear fluorescent ballast life. Ballast compatibility will vary by manufacturer and must be checked before installation. Additionally, a UL Type A tube sacrifices efficiency due to the additional power loss from the existing ballast and is limited in dimming and controllability. Heat issues can also arise with the fluorescent lamp sockets.
2. Type B High Voltage Tube
Like the UL Type A, the UL Type B tube operates with an internal driver. However, UL Type B’s internal driver is powered directly from the main voltage supplied to the existing LFL fixture, requiring several important and unique considerations. Some systems require an in-line fuse and a change to un-shunted sockets.
The Problem
Installation of a UL Type B involves electrical modification to the existing fixture to connect the tube to the incoming AC power supply. For replacement safety reasons, strict adherence to installation instructions is critical when rewiring existing fixtures and utilizing UL Type B tubes, but safety is now a higher risk due to future incorrect replacements with Type A LED tubes or possibly LFL. UL Type B similarly lacks control capabilities. Heat issues can also arise with the fluorescent lamp sockets.
3. Type C Low Voltage Tube
A UL Type C tube operates with a remote driver that powers the LED linear tube, rather than an integrated driver. Like UL Type B, UL Type C involves electrical modification to the existing fixture, but the low-voltage outputs of the driver are connected to the sockets instead of line voltage.
The Problem
Installation of a UL Type C involves much higher installation labor, and while better than Type A or B, still can have issues associated with heat dissipation effecting both light output and life characteristics.
4. COB Lamp
Typically used as replacements for HID (both Metal Halide and High Pressure Sodium) these LED lamps can be placed into the existing medium or mogul based socket.
The Problem
Existing HID system are more often in high temperature environments or have little to no airflow to provide necessary heat removal from the LED lamp system. In addition, luminaire photometrics can be dramatically modified when using the LED COB lamp.
2. Reliability
The lumen deprecation and life cycle of a luminaire or lamp is determined by performing TM-21 calculations in certified laboratories. To perform TM-21 calculations, the In-SITU Temperature Measurement Testing (ISTMT) of the luminaire or lamp, LM-80 data, drive current, and high-end average ambient temperature of the environment where the luminaire will operate is required. 3 of these 4 requirements are obtained by sending a complete luminaire or lamp to an accredited test lab for testing. ISTMT testing uses the ambient temperature at a set value (typically 25C) when the test is being performed. These tests are typically done in “free air” where generated heat can escape from the lamp’s heat sink. A luminaire operating in an environment that is <= the ambient temperature associated with the ISTMT test has a fairly accurate predictability of performance, light-loss and life-cycle. Luminaires or lamps operating in an environment > the ambient testing could have very different performance characteristics!
And that’s where it gets questionable for LED lamps. When an LED lamp is installed into an existing luminaire housing, the thermal properties can change significantly based on the housing design and ambient temperature of the location. An enclosed (sealed) luminaire housing can substantially decrease the operating performance of the LED lamp system! A luminaire in an industrial facility located three feet from the roof decking could experience temperatures much higher than 25C. Put these factors together and it becomes very difficult to determine how the LED lamp will perform. Installing an LED lamp into an existing luminaire housing becomes a guess as to how long and how well it will perform. Since the goal of LED fixtures is to provide reliable, long lasting, efficient performance for the associated investment, it is critical to look at the complete system. This also includes mechanical/physical aspects which can have a direct impact on thermal capability and thus directly impact performance and reliability.
3. The Issue of Heat
Heat has an exponentially damaging effect on LED lamp electronics—both the components of the LED lamp driver and the diode. An LED lamp typically has much reduced component size and thus is much more sensitive to ambient temperatures. In many cases, this results in reduced lumen output while operating at high temperature due to an inability to move heat away from these components. This depreciation could become permanent over time. Excess heat can also cause a change of CCT or complete failure. In the electronic driver, component failure typically results in a total failure of the LED lamp. To mitigate heat issues, many LED lamp types are equipped with a thermal rollback function. In high heat situations, this feature could automatically dim the LED lamp 20% or more in an attempt to mitigate the potential damage to sensitive electronic components. This may not be an issue in the early life of the LED lamp, but could be a major issue as the lamp experiences normal depreciation. Remember, all LED systems experience ongoing lumen depreciation! Most warranties do not cover lumen depreciation or color changes.
4. Reduced Photometric Performance
Existing luminaire housings come in many configurations. There are lensed housings, housings with parabolic louvers, and housings with no lens. There are housings that are deep, shallow, square, round, conical, recessed, suspended, sealed, and hazardous rated. Depending on the unique attributes of the luminaire housing, an LED lamp could have significantly different photometric performance from different luminaires. There is currently little to no photometric testing done on existing luminaire housings retrofit with LED lamps. So, installing LED lamps into an existing luminaire housing is indeed a guess as to how it will perform, particularly over long periods of time.
By comparison, a new LED luminaire or LED retrofit kit will have defined and tested photometric performance values. By combining photometric design into the solution a more accurate prediction of given LED luminaire performance can be engineered. Using an LED lamp really becomes a rather expensive guess which we can only hope will provide the necessary lighting performance, energy savings, and long-term reliability.
In addition, LED lamps do not tend to have great lumen depreciation factors. Most current LED lamps experience around 30% depreciation in 50,000 hours of operation. Unlike fluorescent lamps which experience most of their depreciation early in operating life and then stabilize, LED systems experience a straight-line depreciation! Simply put, if there is 30% depreciation at 50,000 hours, then there will be 60% depreciation at 100,000 hours! If these systems don’t experience complete failure before this point, the eventual lighting levels could be far below required minimums suggested by the Illuminating Engineering Society. In comparison, complete LED luminaires and engineered board and driver retrofit kits will typically have depreciation rates that are half or less of most LED lamps!
5. Reduced Control Flexibility
Complete luminaires simply have far superior capabilities when it comes to built-in-control and automation. LED lamps currently provide very little control capabilities. From simple dimming capabilities to wireless control of multiple luminaire behaviors, complete luminaires and board and driver retrofit kits offer full featured control capabilities.
6. Safety
There are two main safety concerns with LED lamps and tubes. For COB lamps, the weight of the LED COB lamp as compared to the HID lamp originally installed can create issues. LED COB lamps are typically heavier and longer than the original HID lamps. Be sure to confirm the integrity of the existing sockets.
With LED tube lamps the risk of electrical shock can be a potential hazard. This can be an issue in both Type A and direct wired Type B tube type lamps.