HOW DO THE SAVING COMPARE BETWEEN AN INCANDESCENT BULB TO A CFL AND LED?
Answer: To compare the equivalent light levels (lumen) of a basic 60W incandescent light bulb, you would select a CFL in the 13-16W range, or an LED in the 6-8W range. These would all provide about 800 lumens. Although the initial purchase price of an LED bulb is much greater, the anticipated savings over a 10-year period is also the greatest. An LED will last 10-years and saves 85% in energy costs. A CFL saves 75% in energy costs but you would need to purchase 3 bulbs within the 10-year period. The lowest purchase price is the 60W incandescent, but over this same period you would end up purchasing 16 bulbs, and spending 75% - 85% more in energy costs. The 60W incandescent is by far the most expensive choice.
What is a LED?
Answer: LED refers to Light Emitting Diode. It is a semiconductor light source that emits light when current flows through it. LED lights last much longer than traditional incandescent and fluorescent and consume less energy.
WHAT IS A KILOWATT-HOUR?
Answer: When you buy gas they charge you by the gallon. When you buy electricity they charge you by the kilowatt-hour (kWh). One kilowatt-hour equals 1000 watts. As an example, a 400 watt metal halide using 455-watts, operating 730 hours (all month) will use 332 kWh. However if that same fixture was retrofit with a comparable 220-watt T8 fixture, it would only use 160 kWh over that same period. That represents more than a 50% savings
WHAT IS DAYLIGHT HARVESTING?
Answer: Through the use of photo sensors, light levels are automatically adjusted to take into account ambient natural sunlight entering the building. Appropriate light levels are maintained and artificial lighting is dimmed when necessary.
HOW CAN WE LOWER OUR ENERGY COSTS FURTHER WHEN WE ALREADY HAVE T8 LAMPS?
Answer: If you're currently using 32 watt lamps, a great way to shave an extra 14% off your energy costs is to simply re-lamp with 28-watt lamps. The visible light level difference is negligible, and the average office operating 2500 hours per year will save about $1.00 per lamp. That can quickly add up to serious savings!
HOW TO SELECT ACCEPTABLE LIGHT LEVELS?
Answer: Recommended light levels have been developed by the Society of Illuminating Engineers (IES) and these recommendations form the basis for all new designs and retrofits. The determination of the appropriate light level can be complex and many factors have to be taken into consideration:
- The type of building / activity taking place
- The visual task required – high or low contrast, the size of the parts being viewed, the length of time people will be in the environment
- The reflectance of the background – levels must be higher where a low reflectance exists
- The speed of the activity taking place and the accuracy required – for example are people walking or are fork lifts moving in tight areas.
- The age of the people in the building. Older people need higher light levels As a result a light level range is typically recommended subject to adjustment to take into account local conditions.
WHAT IS A FOOTCANDLE?
Answer: A foot candle is a measurement unit of illuminance or light falling on to a surface. One foot candle is equal to one lumen per square foot.
WHAT IS BALLAST FACTOR?
Answer: The ballast factor is a measure of the power output of the ballast. A ballast with a standard or normal ballast factor typically has a rating of 0.85 to 1.0. A ballast with high ballast factor can have a rating of up to 1.2 allowing the lighting system to produce higher light levels while consuming more energy. A ballast with a low ballast factor of between 0.70 and 0.8 will allow lower light levels and lower energy consumption. The lighting designer will select the correct luminaire system to optimize the light level to meet the requirements while minimizing energy use.
WHAT IS A HIGH INTENSITY DISCHARGE LAMP?
Answer: The family of High Intensity Discharge (HID) lamps includes high pressure sodium, mercury vapour and metal halide. All the HID lamps have an inner arc tube within another tube. Metal halide is the most common of the HID fixtures for high bay applications as a result of the better colour rendering index.
WHAT IS A LUMINAIRE?
Answer: A luminaire is the complete assembly of a lighting fixture with lamps and ballasts.
WHAT IS LUMEN MAINTENANCE ?
Answer: Lumen maintenance is a measure of the lamps ability to maintain its initial lumen output over time. All lamps degrade with operating time and this must be considered during the design of a lighting solution. The standard definition of lumen maintenance is the light output of a lamp at 40% of its rated life divided by the lumen output at installation. Lumen maintenance of metal halide systems may be as low as 50% and show continuing degradation until failure is reached. Lumen maintenance of T5 and T8 fluorescent lamps is typically greater than 95% and this level is maintained over the full lamp life.
WHAT IS A LUMEN ?
Answer: A lumen is the measure of the flux of light emitted from a light source. Lamp manufacturer’s provide data on the number of lumens produced by specific lamp and ballast systems when installed and after operating time. Total lumen light output from a light fixture must consider the lamp and ballast system, the number of lamps and ballasts and the efficiency of the light fixture itself.
WHAT IS THE COLOUR RENDERING INDEX (CRI)?
Answer: The colour rendering index (CRI) is used to describe the effect of a light source on the colour appearance of an object with respect to natural sunlight. The top of the scale is 100 and is considered to be equal to natural sunlight. The higher the CRI the more natural the colour of objects appear to be and the better the environment is for working. For example high pressure sodium lights have a low CRI of 25-30 giving a yellow colour of light. It is very difficult to differentiate between different colour objects. Metal halide fixture typically have a CRI of 65 and colours can begin to be differentiated. T5 and T8 fluorescent lighting has a CRI 0f 85+ providing very good colour rendering and a high quality of light. People and objects generally appear natural colour.