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Old 07-02-18, 07:17 AM   #1
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Default My experience with COB LED floodlights

Hi,

As part of my overall conversion of lighting on my property to LEDs, I am replacing some 500W halogen flood lights and some 70W sodium security lights with COB LED floodlights.

The process of getting them and testing them has been interesting.

First off, the best place to get them is not at your local Lowes or Home Depot. Amazon has many options available, and if you "haunt" Amazon Warehouse Deals (their open box department), you'll find them often coming up for less than half of the regular price (which is usually reasonable anyway).

In the last year or so, more and more manufacturers have been moving to the "latest" package of LEDs -- COB (Chips on Board). The COB chips are large arrays of individual high power LED diodes printed on a single chip that can be in a number of different shapes, the most usual being square or rectangular. Here's a link to a site that talks about this newer LED packaging:
what is COB LED chips on board

Most of the latest version of the LED floodlights are built using one or more square COB chips mounted on a large cast aluminum case that acts as a passive heatsink to get rid of the heat generated by these chips.

The floodlights come in various wattages, from 10 watts up to 250 watts and even higher. The general rule of thumb for these is that for every 10 watts of power, these flood lights produce about the same amount of light as 50 watts of halogen bulbs would produce, so here's a rough conversion chart by wattage:

10W LED -- 50watt halogen
20W LED -- 100 watt halogen
30W LED -- 150 watt halogen
50w LED -- 250-300 watt halogen
100W LED -- 500 watt halogen
150W LED -- 750 watt halogen
200W LED -- 1000 watt halogen

I decided to "haunt" Amazon Warehouse Deals looking for open box floodlights and found a bunch of them there for 25-90% of what the regular Amazon price was. Most were in the 40-50% off, but some were much more deeply discounted.

I ordered what seemed to be the best deals, and tested each one as it came in with a kill-a-watt meter, checking to see if they were actually producing the rated watts worth of light. For the ones that were actually using their rated amount of watts, I ran each one for at least 30 minutes to get them up to their normal operating temperature and took heat readings from the back of the housings with a digital infrared thermometer to see what kind of heat was being generated and how well it was being dissipated. The results were very mixed. I expected this due to the wide range of quality control (or lack thereof in some cases) for these Chinese imports.

About 40% of them got returned because of quality control issues -- most of these were because the lights were not producing the appropriate amount of light -- for instance I would find that 50W rated fixtures would only be using 34 watts of power, or 100W fixtures only using 60watts of power. In some cases, there were obvious flaws in the aluminum housings -- some of the aluminum castings were about as thin as tin cans -- could be flexed easily by hand, and had lousy heat conduction and dissipation characteristics. In one case there were voids in the casting -- holes that would allow water to penetrate to the interior.

Some of the lights had full front frames that screwed onto the main casting to hold the front glass lens in place. Some of the lights just had clips holding the glass in place

In one case the clips that were being used to hold the glass front onto the aluminum casting were not locking onto the casting properly, which I am sure would over time have allowed the glass to fall off the front of the floodlight. I contacted the manufacturer about this, and they acknowledged they had a batch with bad clips, and replaced the entire fixture instead of supplying a set of replacement clips as I had requested. I am a bit surprised that instead of recalling the bad batch, they chose to liquidate them on Amazon Warehouse Deals -- the falling glass lenses could cause serious injury....

BTW, the glass lenses used on these is about 1/4 inch thick, but it is NOT tempered. Because these lights don't generate the kind of heat that Halogen lights do, tempered glass is not needed. The gaskets used to seal the glass onto the housing to make them water tight seemed universally to be a custom molded silicone rubber gasket. This seems to work well, and should hold up well with exposure to the elements.

On a couple of the under-powered ones I opened them up to see what was going on, and found that the led drivers being used were undersized -- which explained the low power draw. These contant current LED drivers were capable of operating on various AC voltages from 85 volts up to 270 volts. I suspect that what happened in most of these underpowered lights was that the led drivers would have produced the appropriate power at 220V, but couldn't at 120V. I didn't test to see if this was true, because it didn't matter to me, as I needed fully functional 120V fixtures.

The remaining 60% that passed my testing were well made -- thick and consistent aluminum castings, drawing the rated watts at 120V, and thermally conducting the generated heat and dissipating it well.

One thing I noticed is that many of the lights used the european wiring colors instead of the North American standards. The ground wire was yellow with a stripe, the hot wire was brown, and the neutral wire was blue. Most of these lights only had CE ratings -- they did not have UL certification. Since I was installing them myself I didn't worry about the lacking UL rating and the odd wiring colors. One thing I did notice is that often the ground wire was present on the pigtail coming from the light, but when the fixture was opened up to inspect it, the other end was not attached to the fixture -- not a hard thing to remedy when installing the fixture, but something to keep in mind and check for when installing each fixture.

As the wattage increases on these floodlights, the size of the aluminum casting has to increase in order for it to be able to dissipate the heat generated by the fixture. That means that the 100w, 150w, and 200w fixtures were very large in size.

Due to this size issue, I decided that rather than replace a 500 watt halogen floodlight fixture with a 100 watt LED fixture, I would instead replace it with two 50 watt fixtures. This allowed me to mount them in such a way that the light was more widely dispersed than a single fixture could do. In general these COB LED floodlights have a 120 degree wide light distribution. By pointing the 2 50 watt fixtures slightly outward from each other, I am able to have more like a 160-180 degree wide light distribution. Where the light from them overlaps, I have the equivalent of the 500 watt halogen, and at the outer edges where they don't overlap, I am getting the equivalent of a 250 watt halogen floodlight -- more than sufficient for my flood lighting needs.

I chose warm white versions because I find the harsher colder white color hard on my eyes. The warm white is closer to the color of light generated by the halogen lights too.

I am going to use some 30 and 50 watt COB LED floodlights inside various out-buildings and under some car-ports on my property. I think they will work well.

I also am going to replace some security lights on the property with some of these COB LED floodlights. The 70 watt Sodium security lights will be replaced by 30 watt LED floodlights. I hope to be able to "hack" the dusk-to-dawn sensors in these existing lights to control their replacement floodlights. If this doesn't work out, these sensors are not that expensive.

I'll attach some pictures of a few kinds of these floodlights.

I hope this information is helpful,

Philip

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