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Frequently Asked Questions
- Does turning a LED light on and off shorten the bulb life?
- Do LED light bulbs come on instantly or do they have a delay like compact fluorescent lights (CFLs)?
- Where are the best places to put LEDs in my home or business?
- Can all LED lighting be dimmed or used with dimmer switches?
- How come some LED lights last longer than others?
- What about using LED lighting in fully enclosed housings?
- What does Color Temperature (CT) or Correlated Color Temperature (CCT) refer to?
- Do LED bulbs emit UV and IR radiation?
- What does Beam Angle refer to?
- What is a lumen?
- What is the Color Rendering Index (CRI)?
- Is LED lighting suitable for damp or wet locations?
No, unlike fluorescent bulbs, LED lighting is not affected by being turned on or off.
Most LED lights switch on instantly at full brightness just like incandescent or halogen bulbs. They do not suffer from the “blooming” effect of CFL bulbs.
For the quickest return on investment one should look for locations where the lights are left on the longest amount of time. These areas usually include the kitchen, common spaces, outdoor security lights, office hallways and lobbies. Due to their long life, LED lights are also ideal for hard to reach spots like high ceilings cans or track lights. From a quality of light standpoint, LED lights offer a very energy efficient dimmable light with a high color rendering index number.
The quick answer is no, not all LED lighting can be used with dimmer switches. Make sure to buy a LED light bulb or light fixture that specifically states on the packaging, or within the product description, that it’s dimmable. Also, be sure to look at any additional requirements the lights may have in order to dim properly. This may include using low voltage electronic or magnetic dimmers or making sure to have enough LED light bulbs on a dimmer so that the lights dim to their lowest possible setting. The dimmer switch you already have may work great, but be prepared for the possibility that another type of dimmer switch may work better. For more information, please see our Dimming LED Lighting article.
All light bulbs suffer from a diminished amount of light output over time. However, unlike incandescent light bulbs, LED light bulbs don’t typically fail completely but continue to lose brightness over thousands of hours. The industry considers an LED light bulb’s life span to be over when it reaches 70% of its initial brightness. Most well designed LED lights will last 25,000 to 50,000 hours. The actual lifespan of an LED light depends on several factors. Heat is produced around the LED chip and causes an accelerated decrease in the life and performance of an LED light if not dealt with properly. A well designed LED light will have high quality components designed to move the heat generated by the LEDs away from the LED itself. Also, some lesser quality LED bulb makers overdrive the LED inside the bulb with more electrical current than they are designed to handle. This will yield more initial brightness from the LEDs but results in a shortened lifespan and shifts in color temperature. WARNING: Manufacturer’s who claim 100,000 + hours for their LED lights are publishing a half truth because they are typically making claims based on lab tests of the LED chip itself and not the LED light bulb or LED fixture as a whole!
As mentioned in the previous question, LED light bulbs do not like excessive heat particularly around the LED chip and circuitry. Operating LED bulbs in tightly enclosed spaces results in higher ambient temperatures and reduces the ability of the bulbs to dissapate heat. This may result in a dramatic decrease of bulb life and shifts in color temperature of the light being produced. If possible, always try to provide some means of airflow to allow for convective cooling around the LED bulb. Many LED bulb manufacturers include product labeling stating that their bulbs are not for use in totally enclosed fixtures and that doing so will void the warranty on these products.
LED lighting is available in a wide range of color temperatures from the warm yellow color of an incandescent bulb to the neutral color of a halogen to a cool blue color similar to a bright but overcast day. We recommend familiarizing yourself with the color temperature scale used to define what hue of light a specific LED bulb emits. Color temperature is based on the Kelvin temperature scale, measured in degrees, and ranges from 2600°K on the low end to over 6000°K on the high end for most lighting applications. Most home applications should utilize lighting with a CCT at or below 4000°K. Light emitted above 3500°K is popular for commercial environments or very modern decors that seek to reproduce a daylight look.
Most LED bulbs produce a "cold" beam that contains only visible light. In other words, no ultraviolet (UV) or infrared (IR) light is emitted. There are several advantages to using a light that only emits electromagnetic radiation in the visible spectrum, as a light withouth UV or IR will not fade colors, degrade artwork or radiate thermal energy (heat) in the beam. This makes LED lighting an ideal candidate for retail shops, galleries and museums, all of which need lighting with good color rendering and that won't adversely affect the merchandise or art displays.
Knowing the beam angle of a light bulb helps to ensure that you’re buying a product which will give you adequate lighting in a particular application. Light bulbs are often referred to as ‘spotlights’ or ‘floodlights’, and while these terms do relate to beam angle, they still leave some ambiguity due to the wide variation of bulbs that fall into each particular category. For instance, one floodlight bulb may have a beam angle of 30° while another may have a beam angle of 75°. Quite a difference! Beam angle specifically refers to the angle at which the light output has been reduced to 50% of the maximum center beam brightness. For instance, let’s say a PAR30 LED light bulb has a center beam candlepower measurement of 800. If at 30° to one side of the beam the candlepower has dropped to 400 then we know that the beam angle is 60° (see diagram below). It's best to buy spotlight bulbs when trying to highlight a particular object or concentrate light in a smaller area. Use floodlight bulbs when trying to achieve more general illumination, such as in recessed downlighting.
In layman’s terms, lumens are a measurement of light output. The technical definition goes beyond the scope of our frequently asked questions, but the fact is that knowing something about the lumen is becoming much more important as we move away from using traditional light bulbs. With incandescent lighting most people are used to associating brightness with certain wattages (i.e. a 100W bulb is brighter than a 75W bulb), but wattage is really a measurement of the power required to light the bulb and not a measurement of light output. A 60 watt incandescent bulb produces about 800 lumens of light and yet an LED bulb can output the same amount of light using 12 watts or less. It’s the lumens that are really important here, and the less wattage it takes to supply a given amount of light the better and more efficient your lighting really is. In the near future most types of light bulbs will require the lumen output to be listed on the bulb packaging. This will make it much easier to compare different types of lighting and how efficient they are.
The Color Rendering Index is a measurement of how accurate certain colors look when viewed under the light from a particular light source as compared to an ideal or natural light source radiating at the same color temperature. The CRI of a bulb does not relate to the color of light the bulb produces. That falls under the Color Temperature measurement (see above). The index scale ranges from 0-100 with 100 being a perfect score. There is some discussion in the lighting world that CRI will not accurately reflect the ability of new lighting technologies to render colors properly and new methods are being looked at for measuring this component of lighting. It can certainly happen that people may think colors look more accurate to their eye under a light source with a lower CRI than one with a higher CRI. When it comes to LED lighting the current recommendation is to purchase products with a CRI of 80 or higher.
Many LED lighting products are UL listed as 'Damp Rated' or 'Wet Rated' and can be used in locations where moisture has the possibility of condensing or coming in direct contact with the light. Just what do all the different UL environmental location markings mean? We're glad you asked. Here's the answer from the the UL Marking Guide for Luminaires:
1. DRY LOCATIONS — A luminaire intended for use in a location not normally subject to dampness, but may include a location subject to temporary dampness, as in the case of a building under construction, provided ventilation is adequate to prevent an accumulation of moisture is marked “DRY LOCATIONS ONLY.”
2. DAMP LOCATIONS — Only luminaires marked “SUITABLE FOR DAMP LOCATIONS” or “SUITABLE FOR WET LOCATIONS” are intended to be installed in damp locations. A damp location is an exterior or interior location that is normally or periodically subject to condensation of moisture in, on, or adjacent to, electrical equipment, and includes partially protected locations.
3. WET LOCATIONS —- Only luminaires marked “SUITABLE FOR WET LOCATIONS” are intended to be installed in wet locations. A wet location is a location in which water or other liquids may drip, splash or flow on or against electrical equipment. A luminaire marked “SUITABLE FOR WET LOCATIONS” may be additionally marked as specified below:
a. Covered Ceiling Mount Only — A wet locations luminaire marked “COVERED CEILING MOUNT ONLY” is intended for locations such as a vehicle washing area where the luminaire will not be subjected to water and precipitation from the back side. A ceiling mounted luminaire not identified for covered ceiling mount only is suitable for mounting in locations where it may be subjected to precipitation from the back side, such as under a metal grate-type catwalk.
b. Less Than 1.2 M (4 Feet) Above Ground Level — A wet locations wall or post mounted luminaire may be installed within 1.2 m (4 feet) of ground level if it is marked “SUITABLE FOR MOUNTING WITHIN 1.2 M (4 FEET) OF GROUND.” luminaires with this marking are intended to be subjected to water from lawn and garden sprinkler systems, but are not intended to be installed at or below ground level where they may be subjected to immersion in water.
Exception: A luminaire with an integral post (bollard type luminaire) needs to be so marked.
c. Below Ground Level — A wet locations recessed luminaire may be installed at or below ground level if it’s marked “SUITABLE FOR GROUND-MOUNTED RECESSED.” A luminaire with this marking is intended to be subjected to infrequent immersion under water which may occur because of heavy precipitation. The luminaire is provided with instructions for its proper installation.