My Experiments With Led Lighting 2: Downlights, Tubes and floodlight

Jul 14, 2013

After my last post, I have quite a few updates, which deserves a new separate post.

#1 For my home, it was strangely decided to buy LED downlights for general lighting(not for reading or work that requires concentration). I didn't have knowledge of this and the downlights unfortunately was bought from a shop in Madurai with poor quality. In my experience in window shopping at Madurai for LED lamps earlier, I had found the lights to be of pathetic quality. Outraged, I demanded that all the lamps be first rectified and only then used. Below is a disassembled down light:

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Figure 1: LED Downlight - disassembled

There were two problems - poor LED quality and low constant current driver output. The LED had a small die and poor luminous efficacy and the driver's output was 160mA when it should be giving 350mA.

I bought many Edison 146 lumen 1W LEDs and drivers from Precious lighting Solutions in Ritchie street, Chennai. I found out that one of the 146 lumen LED was equivalent to 3 nos of the pathetic ones. For most of the lamps, I replaced three poor quality ones with one good quality one as the brightness was enough. Since I'm going to setup solar installation for my entire home, every watt of power saved is critical. I didn't replace the driver for all downlights though. Downlight used for lighting staircase required high brightness and hence I replaced both there. For rest, I used the original driver and the one 146 lumen LED, which was enough. I don't know how much was the cost of the original focus lamp was, but refitting a downlight cost me Rs.120 for the 3W constant current LED driver + Rs.150 for 3 LEDs, totaling Rs.270.

The problem I think is that most shopkeepers in Madurai didn't know anything about LEDs and hence they were probably conned into buying it in the first place. Whereas, in Chennai, the shopkeeper is reasonably knowledgeable and hence knows what he is buying.

#2 I bought an 18W LED tube for Rs.1600. The total lumen output was mentioned as 1600 lumen by the shopkeeper. The brightness was considerably more than the 36W LED tubelight that I mentioned in earlier post. The light, though not spread 360 deg evenly like a FTL because the back side of it was made up of aluminum heat sink. But it was good enough, unlike my attempts to assemble tubes using short aluminium heat sink in earlier post. It was almost twice as bright as my other LED tube, which consumes 12W and cost Rs.1100. After this I spend a glut and bought 4 such LED tubes.

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Figure 2: 18W LED Tube

My brother didn’t like the LED tube as he feels that spending 40 times the amount of a normal tube (Rs.40 for T8 Fluorescent tube) for 50% decrease in power consumption is not economical, considering low domestic tariff. Also, LED technology is improving day by day and we’ll soon have better technology tomorrow. But I pointed out that since we’re going solar soon, decreasing the power consumption helps considerably as it reduces the size of the solar setup. But for commercial usage, it would require 16000 hours in operation to justify for the cost of LED tube over fluorescent tube at commercial rates. Also, I now feel that 15W(Rs.1300) from the same shop would have been enough as this is considerably brighter than a 36W FTL.

These tubes come with a one year warranty, but I do hope it lasts for 7-10 years.

#3 I assembled 4 LED 12W bulbs too recently. I used 146lumens/W LEDs to assemble. But before assembling, I read this concerning report about LED lights which says that blue light from LEDs can damage the eyes on the long run. The solution, apparently was to use warm white lights. Hence I assembled 12W LED bulbs using 9*1W cool white LEDs and 3*1W warm white LEDs. The light in the end had a yellowish tinge instead of a bluish one. The bulb is brighter than a 25W CFL. Though unlike a CFL or a FTL, the light is not very much distributed. Two of these bulbs will soon be operated at atleast 12 hours a day, thereby subjecting them heavy duty. It cost Rs.950 per bulb to assemble.

My calculations show that it will have be used at 12 hours per day for 3 years to be economically benificial at commercial rates of Rs.7/KWh over a 25W CFL. One problem was that only a Edison screw type base(E27) was available for the bulbs. These base cap holders are uncommon in India.

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Figure 3: LED Bulb raw-> finished

#4 From 1-Feb-13, I had switched on an 1W LED in order to possibly determine the durability and hence reliability of the LED drivers from Precious Lighting solutions. As of 14-july, the LED driver has operated successfully for 3900 hours. That translates to 2 years at 6 hours per day. Hopefully the driver will last much more than that.

#5 There is a 400W halogen in operation at my mother’s hospital and it needs to be replaced. To replace it, I would need 3*50W LED flood lights, according to a shop in Chennai. My calculations suggest that I’d save Rs.2375 for the first two years and Rs.15150 for four years. Here’s how

Capital cost:

For 150W LED – Rs.5800*3 = Rs.17400

For 400W halogen = Rs.7000

Difference: Rs.10400 more cost for LED flood light

Running cost for two years (assuming 10 hours per day at Rs.7 per unit)

For halogen: 0.4KWh*10hours*730days*Rs.7 = Rs.20440

For LED: 0.15KWh*10hours*730days*R.7 = Rs.7665

Difference: Rs.12775 more cost for halogen

Cost savings for first two years using LED = Rs.12775 – Rs.10400 = Rs.2375

Cost savings for next two years (assuming I don’t have to replace LED drivers which costs Rs.5000) = Rs.12775

Cost savings for four years total = Rs.15150

That’s much more than what a fixed deposit could give! Factor in rising power prices and usage of Diesel Generators for backup, the savings would be higher.

My college has been using LED streetlights, out of which 80% of them have never failed in my two years there. Hence the LED drivers can be deemed reliable for 2 years.. and hopefully the chance to fail in the 3rd and 4th years is also less as the quality seems good. Hence I’ll be buying it shortly.

More Buying tips:

  1. Quality of LED products is critical. You don’t want to buy a LED driver that costs Rs.100 and that has to replaced ever few months or so. Also you don’t want to buy LEDs that are dimmer than CFLs. For people in South India, you can try asking from Precious Lighting solutions in Ritchie street. They are willing to ship. They assemble LEDs buy buying parts from Edison optronics. You can either get parts in non-assembled form to save some cost or get in assembled form if you don’t have time to solider. Shah infotech, another shop in Ritchie street is also an option, though their collection of products is lesser.
  2. Buy from shops that know about the product they’re selling. If they don’t know stuff related to lighting like luminous efficacy, then most probably they’re conned themselves by merchants. For example my experience in Madurai revealed shops that knew absolutely nothing about the products and were of very inferior quality.
  3. Cost of the LED lights at present is such that you’ll have to use it heavily to be economically beneficial.

I’ll probably merge the buying tips into one post later.

Environmental Impact:

The most important reason why I go for LEDs. But I’ll probably have to deal with this in more detail in a separate post. But anyhow..

  1. Environmentally, LEDs have slightly reduced impact compared to CFLs, according to a 2012 report which compared a 60W incandescent bulb with 12.5W LED and 15W CFL. Today however, a 60W incandescent(12lumen/W) can be replaced with 7W LED bulb(110-150lumens/W), hence the gap would have widened. Also in recessed lighting, LED requirements will be a third to half that of CFLs and the footprint will be reduced considerably in that case. By 2017 LEDs will be much better off, as the technology is exponentially improving while Fluorescent technology has saturated.
  2. Energy Star, an US government certifying organization has a list of certified products (both LED and CFL) which can be used for reference for buying. Here’s the pdf

That’s it for now. Will be back with an update on the Floodlight later in a few months.

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