- What is Lumens/w
Lumens is the actual unit of light. Higher lumens /w, need less wattage light to get same light output.
For example, 150W at 110 lm/w and 100w light at 165 lm/w gives same light
but consumes 50 less watt… that’s right same light output at 50 less watt.
- Why all lights are not made at highest lumens output:
most significant factor is the cost. As the lm/w output increases, cost increases too. to keep prices lower, lots of manufacturing facility keeps lower lm/w.
- What is the saving between 100w and 150w lights if the same light output?
If the light works for 24/7/365, and energy cost is 10c/kwh
It will Cost 44$/year per fixture.
- What is CCT?
Co-related color temp is the color of the light on a spectrum. Energy Star and DLC certification agency only certify products between 2700k-5000k (indoor lights) and 2700k-5700k for outdoor lights. There are so many companies and online vendors selling higher CCT but they are not certified and goes intense lights making more strain to human eyes. This is the reason people think the lights are bright at 6500k than at 5000k, even though it measures the same FC on a meter.
- What is DOB?
Driver on board, its new technology to make LED lights having separate LED drivers. In these fixtures, driver components are actually integrated on the same PCB with LED Chip. Its cheaper and clean technology and it needs to replace the whole fixture in case of any failure/issue etc.
- What is CRI?
Color rendering index is a measure of any light of its color rendering. CRI 100 is ideal and most LED has CRI over 80 in some fixtures CRI may go below 70 as a compromise to get efficiency improvement.
- What is IP rating?
IP ratings are ingress protection ratings for the particular fixtures and it has two numbers as rating, like IP67, IP40. The first digit is for ingress of foreign object protection and the second digit is waterproof protection. Exterior fixtures must be IP65 and in water, fixtures require IP68 ratings.
- What is UL?
UL (underwriter laboratories) is a standard for the safety and any products certified by UL labs are considered safe and are in compliance with NEC codes. Its always preferred to use UL certified light to avoid any safety-related issues. ETL, MET, etc. are considered as good as UL as they all follow UL standard.
- FC measures explained:
FC (foot candles) is a measure of actual light intensity on a particular surface. Higher the lumens output of the light gives higher FC. Lower the height gives more FC. This is only true for under the light measurement. For well-distributed light and getting better FC ratio i.e smooth distribution of light (highest to lowest FC in particular area desired <1.5) to achieve this compromise must be made between Lumens output and height of the fixture. If it’s not properly designed then it will leave a bright and dark spot.
- Photometry of a LED fixture:
Photometry is kind of graphical presentation of distribution of light for a given fixture on a 360 plane and angular plane. The photometric graph gives lots of data and it helps the designer to select the right fixture for the application. Distribution of the light is vary important factor and is decided by the optics on the LED. From the photometry, one can also design for controlling any lights going out of property line and help comply with ordinances. The photometric file in numerical data is known as .ies file.
- What is Full cut off light fixture?
Full cut off light fixture are the fixture does not have any light going above the Nadir angle. Nadir is a horizontal plane in line with a fixture and some cities and municipalities are now passing an ordinance to have no lights lighting up the sky
- Main Components in LED: LED Chip, Driver and Heat Sink
LED Chip is the actual source of light and is the most important component in LED light. There are several makers of Chips and the size of chips. Also driving current for the chip is a very important factor in deciding the life expectancy.
Driver: Driver is the components gets AC input and provide the necessary load requirement by the chips (DC). Quality of the driver in most cases decides the quality of the light. In majority of the cases, the driver is the main cause of failure in LED lighting. Also, driver is the main Cost factor also as the same driver made by an inferior manufacturer may cost substantially lower…drives the total cost of fixture.
Heat Sink: This is very important component for the performance point of view for light. If the heat sinks are not properly designed, LED chip want to get proper/enough Cooling which leads to fast deterioration of life expectancy of the chip and causes light fixture to lose its light intensity faster. What it means is if u compare two light one with proper heat sink and one with not good heat sink, Both lights looks same and light level is same but after elongated time say 6 months light with bad heat sink may lose 30-40% light intensity and looks dimmer than one with good heat sing which is still the same bright after that long time.
Most of the LED light/chips are rated for 50000 hrs, and it means light intensity will reduce to 70% after 50000 hrs.