Life ratings are calculated by controlled starting of a defined test batch with a predetermined mortality limit, under laboratory conditions with a reference ballast.
Normal fluorescent testing is 3 hours on, 15 minutes off, repeated until 50% mortality of the test batch is reached. This time value is recorded as "average rated life". Typically we see 20,000 hours for "standard" fluorescent T8 and T12 lamps. High output versions may be rated as low as 12,000 hours, while premium lamps may reach 24,000 - 36,000 hours. Higher Wattage HID testing (400W metal halide and high pressure sodium) is based on 10 hours per start, 50% mortality; we see life ratings of 20,000 hours for standard MH, 24,000 hours for HPS under these test metrics.1000W MH may be as low as 10,000 hours.
T5 technology is relatively new (around 15 years). Using accelerated life testing, lamp manufacturers originally rated T5 at 20,000 hours per start with the 3 hours/50% mortality criteria. However, considering the frequent application of T5 technology in highbay applications and other commercial & industrial installations, further investigation and real-life case studies are now listing 36,000 hours @ 3 hours/start, and 40,000 hours @ 12 hours/ start, with less than 30% mortality of the test batch.
One example is a major microelectronics company customer of The Light Edge that used 8,750 one-lamp F54T5HO MONSOON™ luminaires, installed in March 2002, in a 24/7 application. As of May, 2007 (at 45,260 hours burn time), less than 700 of the lamps had burned out - which equals less than 10% mortality! At this rate we can see that the original life rating of 20,000 hours was extremely conservative, so these products should typically see in excess of 36,000 - 40,000 hours operation before they reach 50% mortality, even in a switched condition. In addition, lumen output is typically still measured within 93% of original, at end of life.
New data is now available from the major lamp manufacturers to address this remarkable performance. Contact The Light Edge for further information.