[Boatanchors] Replacing 866s with 3B28s thread drift to CFLs

[Glen Zook]

The main problem with the life of incandescent bulbs is the fact that those generally sold are rated at 120 volts.  However, most major electric companies these days (in fact for at least the last 2 or 3 decades) now have 125 volts +/- 2 volts as the target voltage.  Virtually all of these run on the "+" side during the warmer months with the air conditioning load.  The higher voltage reduces the life span of the bulb considerably, often as much as a factor of 10, or more.  Using 130 volt bulbs results in considerably long bulb life.

The 130 volt bulbs are available.  Unfortunately, you have to either look close or even ask about them at retail outlets.  The retail outlets don't sell anywhere near as many bulbs when people purchase the 130 volt bulbs so the trend is to make the 130 volt bulbs as difficult to find as possible.  That way the sales of 120 volt bulbs is assured and at a considerably higher rate.

When I was employed by TXU (electric company for almost half the State of Texas) I was on their "speakers bureau".  This was a group that furnished speakers to all sorts of organizations on a variety of subjects.  My usual topics were lightning protection and r.f. grounding.  However, on every speaking engagement someone would ask why their light bulbs did not last very long.  My answer was to obtain 130 volt bulbs.  Several times I would "run into" someone who had been present during one of my presentations who had acquired 130 volt bulbs.  Those persons would always thank me for recommending the 130 volt bulbs.

For years the 130 volt bulbs actually often cost less than the 120 volt bulbs in many places.  But, in recent times, the retailers have realized that they sell considerably less of the 130 volt bulbs and have raised the prices.  The cost of actually producing 130 volt bulbs is basically identical to that of producing 120 volt bulbs.  The only difference is the very slight increase in the cost of the filament since the 130 volt bulb filament is about 8% longer than that of the 120 volt bulb.

At least around this area (Richardson, Texas, on the north side of Dallas), the line voltage rarely drops below 123 volts (at the meter) and usually is in the 125 volts to 127 volts range.  Reducing the voltage on an incandescent bulb by 10% below its rated voltage generally increases the life by at least a factor of 10.  Increasing the voltage over the rating by 10% usually reduces the life of the bulb by at least a factor of 10.  In the "real world", this factor of 10 is a fairly good "rule of thumb" although the actual value can be higher.

Glen, K9STH

Website:  http://k9sth.com


--- On Thu, 12/30/10, D C *Mac* Macdonald <k2gkk at hotmail.com> wrote:

If you want your incandescent lamps to last, simply buy the 130 Volt rated versions. Our house built in 1999 was supplied with such lamps. Some of them are STILL burning after almost 11 years. The "standard" 120V versions do NOT last very long because the mains here in Oklahoma City vary widely over the course of a year. To prevent brownouts, line voltage can run as high as 127 or 128 Volts during the Summer in low use periods.  They can drop down to 105 on really hot days with temperatures at or above 100F.
 
IIRC, operating an incandescent lamp at 10% below its "design" voltage increases its lifespan by at least 100% and maybe longer. I haven't looked at the charts in many years.
 
I think GE published a chart on this many years ago.