prv@briar.philips.com (Paul Veldman) (04/10/90)
In article <28713@cup.portal.com> ISW@cup.portal.com (Isaac S Wingfield) writes: >There's been some recent commentary concerning those screw-base >fluorescent conversion units. Does anybody know: > 1) What is the "incandescent equavalent" light output? None that I've seen > mention it. > 2) What is the economic payback time, including initial purchase? > 3) Do they hum, buzz, or do other antisocial fluorescent type things? > Compact fluorescent lamps basically come in two versions: 1) With a conventional magnetic ballast. 2) With an electronic ballast. ad 1) Compact fluorescent lamps with a conventional magnetic ballast are easily recognized by their high weight. The luminous efficiency of those lamps is normally in the range from 35 to 45 lumen/watt. Incandescent lamps have a typical luminous efficiency of 12 lumen/watt (slightly lower for the long-life versions). Multiplying the power rating of this type of compact lamp by 3 to 3.5 will therefore give you the equivalent incandescent lamp power rating. Compact fluorescent lamps with conventional ballast will generally exhibit the same advantages/disadvantages as normal fluorescent lamps: * The possibility of ballast hum * Slight stroboscopic effect ad 2) Compact fluorescent lamps with an electronic ballast are considerably lighter than their counterparts with a conventional ballast and are generally also more expensive. The lamp is operated at a frequency in the range between 25 and 50 kHz, as opposed to the 60 Hz operation of the conventionally ballasted version. If done correctly, this results in a higher efficiency of the discharge. In addition it is possible to reduce the power dissipation in the ballast. Therefore the luminous efficiency of electronically ballasted compact lamps is normally between 45 and 60 lumen/watt. There should be no hum or buzz, and normally there is no or a reduced stroboscopic effect. Pay-back time -------------- It is relatively simple to calculate your savings over the life time of the lamp, once you know the estimated life time of the compact lamp. This ranges from 3000 to 8000 hr., depending on brand and make, but also on the application. Simply add the initial purchasing price of these lamps to the overall cost of the energy consumed over lifetime, and compare that to the purchasing price of N incandescent lamps (to cover the same time-span) plus the overall cost of the energy consumed by those incandescent lamps over the lifetime of the compact fluorescent lamp. The pay-back time is slightly harder to calculate, although still quite simple. The problem here is, the cost versus time curve for the incandescent lamps is discontinuous every time you have to replace a lamp. But with a couple of iterations you will readily find the answer. CFL_cost(t) = CFL_purch_price + CFL_power_rating*price_per_watthour*t t INC_cost(t) = INC_purch-price*{1+INTEGER(------------)} + INC_lifetime + INC_power_rating*price_per_watthour*t with t in use-hours. The pay back time is the time t for which CFL_cost(t) = INC_cost(t). Factors like heating or air-conditioning can also affect the result. The effect of interest to be paid on the higher initial investment is left as an exercise for the reader ...... :-) Hope this helps =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Try to understand why things || are hardly ever what they seem to be ...... || paul veldman And try even harder next time. || prv@philabs.Philips.Com