LED lights have become commonplace in our lives. Due to the high demand for them, many started to produce their models. Because of the increased competition, the price began to drop sharply, so some manufacturers had to look for opportunities for optimization, while others simply began to use cheaper components and give them out for branded ones. You can buy a model with (ostensibly) impressive parameters for the price of a good Chinese lamp, but in fact you will receive junk that will last at best one year.
In a difficult situation were potential customers who are forced to blindly choose a supplier. But there is a way not to fall into the trap of experienced “sellers” – before buying, contact an independent accredited lighting laboratory. I emphasize: it is an independent laboratory that will not lobby anyone. You can be assured of 99% that the manufacturer with his own laboratory will always “draw” himself the highest characteristics (even Philips will nervously smoke on the sidelines).
We recently found ourselves in a difficult situation, competing with a large manufacturer of LED luminaires with our own accredited laboratory. They offered our customer a cheap LED shopping light in a sheet metal casing. Its light output was 146.7 lm/W on their claims, taking into account the losses in the diffuser and the efficiency of the driver! Next we will show only a couple of photos of their LED light, we will tell about the drawbacks in its design and why it is practically impossible to obtain such a light output.
Only an independent
laboratory will help
you in a choice
Light output is the ratio of the total luminous flux of the luminaire, taking into account the losses in the scatterer, to the total active power of the luminaire consumed from the network, taking into account the efficiency of its driver. In simple words: the total luminous flux is divided into the full power of the luminaire. Some cunning manufacturers consider the light output to be different: they take the light flux of the LEDs and divide by the useful power of the driver. Let us explain what is the catch.
Any diffuser, even expensive PMMA, for example Plexiglas (it is used in the LEDiL optics that we use in our e-Industry and e-Road lamps) has a transparency of about 94%, that is, the glass consumes 6% of the luminous flux of the luminaire! Are you surprised? Prismatic glass Novattro Prism from expensive PMMA has a transparency of 88-92%, other simpler compositions of plastics have lower values. Even the matt diffuser from Mitsubishi, which we use in the ledz e-Trade luminaires, allows only 82% of the light output.
We assume that the client may not know the intricacies of lighting. This trick is calculated for such clients. Many dishonest manufacturers use this and in the passport of the luminaire consider the light flux of the LEDs. Tricky manufacturer this “increases” the efficiency of the fixture by 10%, discarding the loss of light in the scatterer. And the client about it can and not learn, as after purchase of such fixtures on it any more do not pay attention. But this is not the whole trick.
LED lamp has two power
The driver also has two capacities: useful is the power of the LEDs, consumed – this is the total power of the luminaire, which it consumes from the network. These capacities differ by the value of the driver’s efficiency, which on average ranges from 80% in inexpensive Chinese drivers to 93% in drivers of eminent manufacturers, for example, LEDEL. If the customer does not specify exactly what power is indicated in the passport, then probably the seller will give exactly the useful power of the LEDs.
That’s only from the network, such a luminaire will consume 56.8 watts, exactly by the amount of efficiency is greater. Having calculated the total (supposedly) advantage over competitors, we will see that a crafty manufacturer in such a simple way can “improve” any of his luminaires with real light output, for example, 110 lm/W to a value of 138.9 lm/W (110/0.88/0.9 = 138.9 ). Now, using the same formula, let’s calculate what light output the LEDs of our competitor should have.
If 146.7 lm/W is the light output of the luminaire with all losses taken into account, we will get the following light output of the LEDs: 146.7/0.88/0.9 = 185.2 lm/W. Now in the world market, only a few manufacturers have announced that their LEDs have exceeded the bar of 180 lm/W, at the shows, while all the dealers reported to each other that they were “raw” and not fully tested samples. For example, LG Innotek bragged about this result and began selling these LEDs at very attractive prices.
Now let’s see what current should be fed to the LED so that it gives out 185.2 lm/W. Open the datasheet on the LEDs of the LG Innotek size 5630. It can be seen from the table (see above) that for this purpose the current on one chip should be 30 mA, while the LED power will be 0.08 W. With this diode power, to get a 1.5-meter luminaire with a power of 31 W, it is necessary to install 387 LEDs on it, respectively, on the ruler they should be located at a distance of 3.9 mm between the centers of the LEDs.
The size of LG’s LEDs is 5.6×3.0 mm, which means that they should be located almost flush with each other without gaps. In the photo below, the LEDs are located at a distance of 1-1.5 cm from each other, which means that in a 1.5 meter long luminaire, there will be 100-150 of them. Therefore, to obtain a power of 31 W each LED should have a power of 0.21-0.31 W, according to the datasheet this corresponds to a light output from 173 to 164 lm/W, which is significantly different from the declared value of 185.2.
From the photo of the internal components of this fixture (see below), let us explain what we consider to be flaws and why:
- a lamp in a sheet metal casing, which very poorly removes heat from the LEDs. Since any LED on any current is heated, then because of poor heat sink its resource is drastically reduced. In comparison with the aluminum case sheet metal loses more than 10 times the rate of heat removal, and powder painting additionally worsens the heat sink in half. The aluminum case is made thicker (1-3 mm), and the sheet metal is made on the contrary thin to facilitate the housing and make it cheaper;
- on the photo in this model, the LED rulers do not fit closely to the body, but are isolated from it by means of strips taped into pieces (they are marked with arrows in the photo). Air is a very poor conductor of heat, this design worsens the heat sink and the LED resource is reduced. Many experienced manufacturers use thermal greases and compositions of various manufacturers to eliminate the air layer between the ruler and the body and improve heat dissipation;
- this luminaire does not have a cover that would protect it from even small external influences, the wires are laid open inside this profile, so when the fire and the sprinkler system are switched on everything will be flooded with water, which will lead to a short circuit. This is unacceptable for use in shopping centers, since most often there are installed exactly water fire extinguishing systems. The likelihood that such a lamp will continue to work when evacuating people is very small in our opinion;
- the price of a competitor’s lamp is very good, only if it is not compared with a worthy analog. Specifically, this model with all its design flaws at a price almost equal to our LED ledz e-Trade 50 CM in an aluminum housing with dust protection IP54. If to compare fairly, both lamps should be in aluminum cases and with IP54, in this case the competitor’s lamp will be more expensive almost twice, even taking into account the additional discount for the delivery volume.
The lamp test protocol is more important than the list of completed objects
We are confident that when testing this lamp in an independent laboratory, the claimed luminous efficiency will not be confirmed. Testing your lamps in your own laboratory is tantamount to giving the deputy the right to count the votes of his constituents – he will always count them in his favor. Despite the fact that the laboratory continues to work and periodically interlaboratory comparisons, new facts of falsifications can appear, until someone catches the dishonest producer by the hand.
This can be done if you get your own test report from the manufacturer, then pass it yourself to the manufacturer’s laboratory and then to an independent one. If the numbers in the protocols differ by more than the amount of error, then we have discovered the fact of falsification. At the same time, the manufacturer can say: “We tested a special model in the laboratory, which was collected exclusively for you, and the sample you bought is serial and it differs from what we will supply you with the object.”
It looks like this: we have a protocol for the lamp, but it’s not on sale, because it is made only for you, but we will sell it only to your object in volume, for example, 800 pieces. First buy, and then check: the luminaire complies with the declared characteristics or not. Of course, it is possible after the tests to confirm the claimed light output. But this is unlikely, since the question arises why other manufacturers did not copy this know-how with a light output of 146.7 lm/W. Can eat any secret?
How to choose the right supplier of LED lighting fixtures
Summarize. When comparing any LED fixtures, other parameters are important besides the price: power consumption and luminous flux, confirmed by the independent laboratory protocol, LED resource by the manufacturer’s datasheet, driver resource, warranty on the luminaire. We must warn business owners: choosing a LED lighting system for only the price, you and your employees risk buying a product that will have to be repaired frequently and maybe replaced again with a new one after 3, 5 or 7 years.
If engineers offer you to buy the cheapest – take a decision in your hands. Ask applicants to make lighting calculations with equal illumination and with equal parameters. Check the height of the luminaire suspension, the safety factor, and whether the equipment is equally spaced. From the calculations, take the values of the total light flux (Flux) and the total power (P) of all luminaires, specify the guarantee (G), the life of the LEDs (R), check the luminaire parameters with the protocol of the independent laboratory.
Parameters in the calculation and protocol should not differ by more than 5%, otherwise reject this applicant. Take also the cost of the solutions (Price) and for each applicant calculate the value of X by the formula: Price/(Flux/P)/G/R = X, where X is the ratio of the price to the whole object to the average luminous efficiency, warranty and LED resource. In fact, the bidder with the least X of all will be the most profitable offer at the highest profitability. Ask for a simple table for you that contains only three columns:
For example, for the shopping center Red, the candidate Blablategra has an average illumination of 885 lux, the cost of lighting is 60.986 thousand rubles, the total luminous flux of all luminaires is 3.07 Mlm, the total power is 23.3 kW, the warranty is 5 years, the life of Samsung LEDs is 70 kh, and the applicant ledz average illumination 1061 lux, the cost is 72.819 thousand rubles, the total luminous flux of all lamps 3.48 Mlm, full power 29.7 kW, warranty 5 years, life of LEDs OSRAM 100 khours.
The indicator X of Blablategra will be equal to 60.986/(3.07/23.3)/5/70 = 1.322, the indicator X of ledz will be equal to 72.819/(3.48/29.7)/5/100 = 1.243. The lower indicator X was by ledz, so this option is most beneficial for the owner of the business than Blablategra, even though it is slightly more expensive. Please note that ledz light has a longer LED life and warranty of 5 years, and its effectiveness is fully confirmed by this test protocol lamp in an independent laboratory of the NAS of Belarus.
Once you have selected the applicant, see the list of implemented objects and their photos, as well as see reviews of the company. If there is enough time, visit at least a couple of objects and make sure that you are satisfied with the result. Look for broken lights or possible shortcomings on the site, and if you find more than one, then they probably go out of order too often and so do not buy these lamps, because your energy will often spend their time on these problems. Choose you.