FAQs about LED Tubes

How many watts of T8 LED tube produces equivalent brightness with a traditional fluorescent tube?

If we consider a typical 1.2-meter traditional T8 fluorescent tube, this will consume around 40 watts in total – 36W in power and then an extra 4W in ballast. If we take the average brightness within the market, the average lumen output is around 2,200lm. However, as much as 40% of the light emitted can be reflected and cause shade as fluorescent tubes emit over 360 degrees. After this reflection, only half of this light is utilized. Instead, LED tubes offer around 95% utilization and the majority of light will reach the target.

 

light emit angle of fluorescent vs LED tube

When LED tubes were first introduced to the market, it was thought that around 24W and 1,900 lumens could replace a fluorescent tube. However, LED tubes have improved and this is now just 16W; when in place, it should outperform a brand new Philips or OSRAM fluorescent tube.

 

Is there light decay with LED tubes?

Despite popular belief, LED tubes have an extremely low light decay rate which is yet another advantage of choosing them over fluorescent tubes. If we take the T8 iLUXZ LED tube as an example, the data available suggests that light decay will be 12.73% after 15,000 hours of use. On the flip side, some studies and research have shown that 5,000 hours can lead to as much as 25% decay with fluorescent tubes. With most fluorescent tubes, they need replacing at the 8,000 hour mark.

 

By activating the mercury vapor with electrons, fluorescent lights can emit by providing strong UV rays. Then, these illuminate the inner wall of the tube which uses a tri-phosphor coating. As the temperature increases, the filament stays oxidised with the phosphor. When black appears at the ends of the tube, this is the oxidised metal that has escaped from the filament and generally warns that a replacement is needed.

 

Why all these drivers in the LED tubes are so different?

Ultimately, there are two types of driver for LED tubes – built-in and external driver. Commonly, built-in is the option you will see most and it means that the driver compartment is held within the lamp. When choosing this option, you benefit from having a standard lamp with no change to the shape or form. Since the structure is the same as fluorescent lamps, the fit will be perfect. As the driver is built into the aluminum radiator, the whole thing needs to be insulated with the protective sleeve we discussed previously to avoid leakages. Let’s take a look at the differences in more detail.

Isolated Constant Current Driver – In this version, an isolation transformer will sit in between the output and input side. With this in place, the high-voltage alternating current will be turned into low-voltage direct current whilst being kept isolated. Inside, a complex design gets to work to avoid any risk of an electric shock. However, there are disadvantages in that more power is consumed, costs are high, and volume can be high which removes flexibility.

Non-Isolated Constant Current Driver – With no insulation, there is a real danger of the input and load side connecting which can lead to electric shocks if touched. However, there are advantages such as saving power, low cost, simple design of the circuit, low consumption of energy, and it is easy to be efficient. On the other hand, quality can sometimes be a problem which leads to highly charged metal elements within the driver. When manufacturers choose this method, they must be produced with care and all components must be high quality.

Centralized External Driver Finally, this is a high-power AC/DC switching driver and unified supply power. Here, the tubes will be separated into DC/DC constant current modules. With this in mind, the maximum power and efficiency can be achieved. Also, this structure makes it easy to achieve a dimming program.

In terms of pure security, the isolated driver is recommended. With non-isolated options, they can sometimes fall foul of the safety requirements. Even though the radiating capacity might be poor, the problem of insulation can be removed with a non-metallic shell which is now an option on the market.

 

How do LED tubes deal with the fluorescent ballast?

In order to function, traditional fluorescent tubes would be driven by magnetic or electronic ballast. To make this change into LED, this ballast must be bypassed in some way or completely removed. For the sake of saving labor costs, some LED tubes will be compatible with ballast which means that it will simply plug in with no rewiring required. For retrofitting, this is a huge concept but, unfortunately, there isn’t any LED tubes that are 100% compatible with all ballasts from each manufacturer in each country.

Ultimately, each ballast has different principles and even similar ballasts can have varying output sequences which can confuse the situation even more. Nowadays, we are moving ever-closer to full compatibility with some manufactures claiming that their LED tubes work with 90% of mainstream ballasts but we are still a long way off the ultimate goal. If we want to reach full capability, the design of the circuit would have to be unbelievably complex; for example, many electronic components would be needed and the more components in use, the higher the cost and lower the efficiency becomes.

 

How to evaluate LED tubes’ thermal design? 

With most of the early LED low-power options, they are very limited and most choose to go for a 5mm DIP LED. In this, the pin contact area has to be non-metallic because it passes through the circuit board with a main plastic frame. Since this produces heat, the tubes are sealed and thermal conduction is of poor quality. Often, failures will be seen within 2,000 hours.

However, we have since seen the introduction of SMD LEDs and these are electronically connected by using an aluminum-based PCB. Considering the plate itself is made of aluminum too and has good conductivity, a good balance is found between thermal design and insulation. These days, a mixture of PC and aluminum alloy make up the market with the latter guaranteeing the heat radiation and the PC being used for the side of the light transmission.

In recent years, there has been great steps forward when it comes to LED chips as well as LED packaging. For this reason, an improvement has been seen in the heat radiating capacity, weight, and even the metal radiator size. Just last year, iLUXZ conducted an experiment attempting to use no auxiliary heat whilst lighting the lamp plate of 18W. With a target of 1,000 continuous hours, 18.7% was the luminous flux compared to the original. With this result in mind, it showed that the heat sink doesn’t have to be relied upon as heavily as we have seen previously. Sadly, we are still a long way from removing the radiator level completely but the quality of heat sinks is still a major issue within the market.

For some, a simple touch of the surface will tell them all they need to know about thermal design within LEDs but this shouldn’t be relied upon since many different factors can impact the perceived temperature. How can the thermal design be tested quickly and efficiently? In truth, the process is easy actually as the ‘illuminometer’ is a great piece of equipment for doing so. By letting the probe on this device see the surface that emits the light, it will note a value. If you keep the LED tube on for a period of twenty minutes or so, that value will stabilize and you can compare this new figure with the first value. The LED tube is said to be of poor thermal design if the second value is below 85% of the first value. When a good thermal balance is found, less than 10% is expected for the decrease of the luminous flux.

 

Is LED Tube Flickering?

With the classic fluorescent tubes, a heavy flicker comes from the electromagnetic fluorescent. However, there is no visible flicker for LED tubes since they convert AC current into DC current before then driving the tube. Of course, the use of a digital camera will allow you to see the flicker. Despite belief, invisible flicker does not harm health as much as visible flicker. In order to reduce invisible flicker, many engineers at iLUXZ have been working on new LED tubes. As a safe and reliable option, even high resolution cameras will not pick up any flickering.

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